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we present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the seyfert 1 galaxy ngc 5548. this includes 12 years of new unpublished observations (2003 to 2015). we compiled about 1600 hβ spectra and analyzed the long-term spectral variations of the 5100 å continuum and the hβ line. our analysis is based on standard procedures, including the lomb-scargle method, which is known to be rather limited to such heterogeneous data sets, and a new method developed specifically for this project that is more robust and reveals a ∼5700 day periodicity in the continuum light curve, the hβ light curve, and the radial velocity curve of the red wing of the hβ line. the data are consistent with orbital motion inside the broad emission line region of the source. we discuss several possible mechanisms that can explain this periodicity, including orbiting dusty and dust-free clouds, a binary black hole system, tidal disruption events, and the effect of an orbiting star periodically passing through an accretion disk. | evidence for periodicity in 43 year-long monitoring of ngc 5548 |
we present vlt/sinfoni imaging spectroscopy of the rest-frame optical emission lines of warm ionized gas in 33 powerful radio galaxies at redshifts z ≳ 2, which are excellent sites to study the interplay of rapidly accreting active galactic nuclei and the interstellar medium of the host galaxy in the very late formation stages of massive galaxies. our targets span two orders of magnitude in radio size (2-400 kpc) and kinetic jet energy (a few 1046- almost 1048 erg s-1). all sources have complex gas kinematics with broad line widths up to ~1300 km s-1. about half have bipolar velocity fields with offsets up to 1500 km s-1 and are consistent with global back-to-back outflows. the others have complex velocity distributions, often with multiple abrupt velocity jumps far from the nucleus of the galaxy, and are not associated with a major merger in any obvious way. we present several empirical constraints that show why gas kinematics and radio jets seem to be physically related in all galaxies of the sample. the kinetic energy in the gas from large scale bulk and local outflow or turbulent motion corresponds to a few 10-3 to 10-2 of the kinetic energy output of the radio jet. in galaxies with radio jet power ≳ 1047 erg s-1, the kinetic energy in global back-to-back outflows dominates the total energy budget of the gas, suggesting that bulk motion of outflowing gas encompasses the global interstellar medium. this might be facilitated by the strong gas turbulence, as suggested by recent analytical work. we compare our findings with recent hydrodynamic simulations, and discuss the potential consequences for the subsequent evolution of massive galaxies at high redshift. compared with recent models of metal enrichment in high-z agn hosts, we find that the gas-phase metallicities in our galaxies are lower than in most low-z agn, but nonetheless solar or even super-solar, suggesting that the ism we see in these galaxies is very similar to the gas from which massive low-redshift galaxies formed most of their stars. this further highlights that we are seeing these galaxies near the end of their active formation phase. based on observations collected at the very large telescope of eso. program ids 070.a-0545, 070.a-0229, 076.a-0684, 079.a-0617, 081.a-0468, 381.a-0541, 082.a-0825, 083.a-0445. | the sinfoni survey of powerful radio galaxies at z 2: jet-driven agn feedback during the quasar era |
in preparation for the tomography study of the intergalactic medium (igm) by subaru prime focus spectrograph (pfs) survey and other large future telescopes such as tmt/elt/gmt, we present the results of our pilot study on lyα forest and igm tomography statistics using the gadget3-osaka cosmological smoothed particle hydrodynamical simulation. our simulation includes models for star formation and supernova feedback, which enables more realistic cross-correlation studies between galaxies, neutral hydrogen (h i), and metals in circumgalactic and intergalactic medium. we create a light-cone data set at z = 2-3 from our simulations and generate mock lyα forest data. as a first step, in this paper, we focus on the distribution of h i and galaxies, and present statistical results on 1d flux probability distribution function, 1d power spectrum, flux contrast versus impact parameter, and h i-galaxy cross-correlations. our results show overall agreement with current observational data, with some interesting discrepancies on small scales that are due to either feedback effects or varying observational conditions. our simulation shows stronger h i absorption with decreasing transverse distance from galaxies. we find that massive galaxies with m⋆ ≥ 1010 m⊙ contribute strongly to the flux contrast signal, and that lower-mass galaxies with m⋆ ~ 108-1010 m⊙ tend to dilute the flux contrast signal from massive galaxies. on large scales, the average flux contrast smoothly connects to the igm level, supporting the concordance λ cold dark matter model. we also find an increase in the h i absorption toward the center of a protocluster. | probing feedback via igm tomography and the lyα forest with subaru pfs, tmt/elt, and jwst |
the dominant gaseous structure in the galactic halo is the magellanic stream, an extended network of neutral and ionized filaments surrounding the large and small magellanic clouds (lmc/smc), the two most massive satellite galaxies of the milky way. recent observations indicate that the clouds are on their first passage around our galaxy, the stream is made up of gas stripped from both the lmc and the smc, and the majority of this gas is ionized. while it has long been suspected that tidal forces and ram-pressure stripping contributed to the stream's formation, a full understanding of its origins has defied modelers for decades. several recent developments, including the discovery of dwarf galaxies associated with the magellanic group, the high mass of the lmc, the detection of highly ionized gas toward stars in the lmc and the predictions of cosmological simulations all support the existence of a halo of warm ionized gas around the lmc at a temperature of $\sim5\times10^{5}\;\mathrm{k}$. here we show that by including this "magellanic corona" in hydrodynamic simulations of the magellanic clouds falling onto the galaxy, we can simultaneously reproduce the stream and its leading arm. our simulations explain the stream's filamentary structure, spatial extent, radial velocity gradient, and total ionized gas mass. we predict that the magellanic corona will be unambiguously observable via high-ionization absorption lines in the ultraviolet spectra of background quasars lying near the lmc. this prediction is directly testable with the cosmic origins spectrograph on the hubble space telescope. | the magellanic corona as the key to the formation of the magellanic stream. |
context. broad emission lines are the most characteristic features in the spectra of galaxies with an active galactic nucleus (agn). they mostly show either single-peaked or double-peaked profiles and originate from a complex dynamics of the likely discrete clouds moving in a spatially extended region known as the broad line region (blr).aims: in this paper, we present a large grid of results, which is used to test the model based on calculations of the spectral line generic profiles.methods: we followed a non-hydrodynamical single-cloud approach to blr dynamics based on a radiatively dust-driven model. we previously showed in detail that the 2.5d version of the model could provide us with the 3d geometry of the blr.results: we show that the shape of profiles not only depends on the accretion rate of the source, the black hole mass, and the viewing angle, but it is most significantly affected by the adopted dust-to-gas mass ratio regulating the strength of the radiation pressure. we also show that the model can aptly explain the low ionized broad emission lines of the mean spectrum of quasars, such as mgii and hβ.conclusions: the radiatively dust-driving mechanism can appropriately account for the low-ionized part of blr of agns. | radiation pressure on dust explaining the low ionized broad emission lines in active galactic nuclei. dust as an important driver of line shape |
we present an analysis of the metallicity distribution of the dense circumgalactic medium (cgm) of galaxies at 0.1 ≲ z ≲ 1.1 as probed by partial lyman limit systems (pllss, 16.1 < log {n}{{h}{{i}}} < 17.2) and llss (17.2 ≤ log {n}{{h}{{i}}} < 17.7 in our sample). the new h i-selected sample, drawn from our hubble space telescope cos g140l snapshot survey of 61 qsos, has 20 pllss and 10 llss. combined with our previous survey, we have a total of 44 pllss and 11 llss. we find that the metallicity distribution of the pllss is bimodal at z ≲ 1, with a minimum at [x/h] = -1. the low-metallicity peak comprises (57 ± 8)% of the pllss and is centered at [x/h] ≃ -1.87(1.3% solar metallicity), while the high-metallicity peak is centered at [x/h] ≃ -0.32 (48% solar metallicity). although the sample of llss is still small, there is some evidence that the metallicity distributions of the llss and pllss are different, with a far lower fraction of very metal-poor ([x/h] < -1.4) llss than pllss. the fraction of llss with [x/h] < -1 is similar to that found in pllss (∼56%). however, higher h i column density absorbers (log {n}{{h}{{i}}} > 19.0) show a much lower fraction of metal-poor gas; therefore, the metallicity distribution of gas in and around galaxies depends sensitively on n h iat z ≲ 1. we interpret the high-metallicity ([x/h] ≥ -1) pllss and llss as arising in outflows, recycling winds, and tidally stripped gas around galaxies. the low-metallicity pllss and llss imply that the cgm of z ≲ 1 galaxies hosts a substantial mass of cool, dense, low-metallicity gas that may ultimately accrete onto the galaxies. | low-metallicity absorbers account for half of the dense circumgalactic gas at z ≲ 1 |
we study the sizes of galaxies in the epoch of reionization using a sample of ${\sim 100\, 000}$ galaxies from the bluetides cosmological hydrodynamical simulation from z = 7 to 11. we measure the galaxy sizes from stellar mass and luminosity maps, defining the effective radius as the minimum radius that could enclose the pixels containing 50 per cent of the total mass/light in the image. we find an inverse relationship between stellar mass and effective half-mass radius, suggesting that the most massive galaxies are more compact and dense than lower mass galaxies, which have flatter mass distributions. we find a mildly negative relation between intrinsic far-ultraviolet luminosity and size, while we find a positive size-luminosity relation when measured from dust-attenuated images. this suggests that dust is the predominant cause of the observed positive size-luminosity relation, with dust preferentially attenuating bright sightlines resulting in a flatter emission profile and thus larger measured effective radii. we study the size-luminosity relation across the rest-frame ultraviolet and optical, and find that the slope decreases at longer wavelengths; this is a consequence of the relation being caused by dust, which produces less attenuation at longer wavelengths. we find that the far-ultraviolet size-luminosity relation shows mild evolution from z = 7 to 11, and galaxy size evolves with redshift as r ∝ (1 + z)-m, where m = 0.662 ± 0.009. finally, we investigate the sizes of z = 7 quasar host galaxies, and find that while the intrinsic sizes of quasar hosts are small relative to the overall galaxy sample, they have comparable sizes when measured from dust-attenuated images. | the impact of dust on the sizes of galaxies in the epoch of reionization |
we analyse the effect of stochastic torque fluctuations on the orbital evolution and the gravitational wave (gw) emission of gas-embedded sources with intermediate and extreme mass ratios. we show that gas-driven fluctuations imprint additional harmonic content in the gws of the binary system, which we dub dirty waveforms (dws). we find three interesting observational prospects for dws, provided that torque fluctuations do indeed persist beyond the resolution limit of current hydrodynamical simulations. first, dws can produce a significant stochastic gw background, comparable to other gw noise sources. secondly, the energy flux implied by the additional harmonics can cause a detectable secular phase shift in laser interferometer space antenna (lisa) sources, even if the net torque fluctuations vanish when averaged over orbital time-scales. lastly, the dws of moderate-redshift nhz supermassive binaries detectable by pulsar timing arrays (ptas) could be detectable in the mhz range, producing a new type of pta-lisa multiband gravitational source. our results suggest that searching for dws and their effects can potentially be a novel way to probe the heaviest of black holes and the physics of the accretion discs surrounding them. we find these results to be a further confirmation of the many exciting prospects of actively searching for environmental effects within the data stream of future gw detectors. | dirty waveforms: multiband harmonic content of gas-embedded gravitational wave sources |
we present the goals, design, and first results of the muse ultra deep field (mudf) survey, a large programme using the multi unit spectroscopic explorer (muse) instrument at the eso very large telescope. the mudf survey is collecting ≈150 h on-source of integral field optical spectroscopy in a 1.5 × 1.2 arcmin2 region which hosts several astrophysical structures along the line of sight, including two bright z ≈ 3.2 quasars with close separation (≈500 kpc). following the description of the data reduction procedures, we present the analysis of the galaxy environment and gaseous properties of seven groups detected at redshifts 0.5 < z < 1.5, spanning a large dynamic range in halo mass, log (m_h/{m_⊙ }) ≈ 11 - 13.5. for four of the groups, we find associated mg ii absorbers tracing cool gas in high-resolution spectroscopy of the two quasars, including one case of correlated absorption in both sightlines at distance ≈480 kpc. the absorption strength associated with the groups is higher than what has been reported for more isolated galaxies of comparable mass and impact parameters. we do not find evidence for widespread cool gas giving rise to strong absorption within these groups. combining these results with the distribution of neutral and ionized gas seen in emission in lower redshift groups, we conclude that gravitational interactions in the group environment strip gas from the galaxy haloes into the intragroup medium, boosting the cross-section of cool gas and leading to the high fraction of strong mg ii absorbers that we detect. | the muse ultra deep field (mudf). ii. survey design and the gaseous properties of galaxy groups at 0.5 < z < 1.5 |
we present the results of an extensive analysis of the optical, ultraviolet, x-ray, and γ-ray data collected from the observations of the bl lac objects prototype bl lacertae carried out over a period of nearly 13 yr, between 2008 august and 2021 march. the source is characterized by strongly variable emission at all frequencies, often accompanied by spectral changes. in the γ-ray band several prominent flares have been detected, the largest one reaching the flux of fγ(> 196.7 mev) = (4.39 ± 1.01) × 10-6 photon cm-2 s-1. the x-ray spectral variability of the source during the brightest flare on mjd 59128.18 (2020 october 6) was characterized by a softer-when-brighter trend due to a shift of the synchrotron peak to ~1016 hz, well into the hbl domain. the widely changing multiwavelength emission of bl lacertae was systematically investigated by fitting leptonic models that include synchrotron self-compton and external compton components to 511 high-quality and quasi-simultaneous broad-band spectral energy distributions (seds). the majority of selected seds can be adequately fitted within a one-zone model with reasonable parameters. only 46 seds with soft and bright x-ray spectra and when the source was observed in very high energy γ-ray bands can be explained in a two-zone leptonic scenario. the hbl behaviour observed during the brightest x-ray flare is interpreted as due to the emergence of synchrotron emission from freshly accelerated particles in a second emission zone located beyond the broad-line region. | a 13-yr-long broad-band view of bl lac |
we report on quasi-periodic variability found in two blazars included in the steward observatory blazar monitoring data sample: the bl lac object 3c 66a and the flat spectrum radio quasar b2 1633+38. we collect optical photometric and polarimetric data in v and r bands of these sources from different observatories: st. petersburg university, crimean astrophysical observatory, webt-gasp, catalina real-time transient survey, steward observatory, stella robotic observatory, and katzman automatic imaging telescope. in addition, an analysis of the γ-ray light curves from fermi-lat is included. three methods are used to search for any periodic behaviour in the data: the z-transform discrete correlation function, the lomb-scargle periodogram and the weighted wavelet z-transform. we find pieces of evidence of possible quasi-periodic variability in the optical photometric data of both sources with periods of ∼3 yr for 3c 66a and ∼1.9 yr for b2 1633+38, with significances between 3σ and 5σ. only b2 1633+38 shows evidence of this behaviour in the optical polarized data set at a confidence level of 2σ-4σ. this is the first reported evidence of quasi-periodic behaviour in the optical light curve of b2 1633+38. also, a hint of quasi-periodic behaviour is found in the γ-ray light curve of b2 1633+38 with a confidence level ≥2σ, while no periodicity is observed for 3c 66a in this energy range. we propose different jet emission models that could explain the quasi-periodic variability and the differences found between these two sources. | quasi-periodic behaviour in the optical and γ-ray light curves of blazars 3c 66a and b2 1633+38 |
we present the design, methods, and first results of the muse analysis of gas around galaxies (magg) survey, a large programme on the multi-unit spectroscopic explorer (muse) instrument at the very large telescope (vlt), which targets 28 z > 3.2 quasars to investigate the connection between optically thick gas and galaxies at z ∼ 3-4. magg maps the environment of 52 strong absorption line systems at z ≳ 3, providing the first statistical sample of galaxies associated with gas-rich structures in the early universe. in this paper, we study the galaxy population around a very metal poor gas cloud at z ≈ 3.53 towards the quasar j124957.23-015928.8. we detect three lyα emitters within $\lesssim 200~\rm km~s^{-1}$ of the cloud redshift, at projected separations $\lesssim 185~\rm ~kpc$ (physical). the presence of star-forming galaxies near a very metal-poor cloud indicates that metal enrichment is still spatially inhomogeneous at this redshift. based on its very low metallicity and the presence of nearby galaxies, we propose that the most likely scenario for this lyman limit system (lls) is that it lies within a filament which may be accreting on to a nearby galaxy. taken together with the small number of other llss studied with muse, the observations to date show a range of different environments near strong absorption systems. the full magg survey will significantly expand this sample and enable a statistical analysis of the link between gas and galaxies to pin down the origin of these diverse environments at z ≈ 3-4. | muse analysis of gas around galaxies (magg) - i: survey design and the environment of a near pristine gas cloud at z ≈ 3.5 |
pristine, atomically cooled haloes may be the sites of primordial quasar formation because atomic cooling triggers rapid baryon collapse that can create 104-105 m⊙ black hole seeds. however, no numerical simulation has ever followed the collapse of these haloes for the times required to form supermassive stars and direct-collapse black holes (dcbhs). we have now modelled baryon collapse in atomically cooled haloes with a wide range of spin parameters and assembly histories for times that are sufficient for dcbh formation. fragmentation of accretion discs after ~500 kyr is nearly ubiquitous in these haloes and in most cases leads to the formation of binary or multiple supermassive stellar systems. they also confirm that rapid baryon collapse proceeds for the times required for these stars to form dcbhs. our simulations suggest that binary or even multiple dcbh formation was the rule rather than the exception in the primordial universe. | the collapse of atomically cooled primordial haloes - i. high lyman-werner backgrounds |
we report the 888 mhz radio detection in the rapid askap continuum survey (racs) of vik j2318−3113, a z = 6.44 quasar. its radio luminosity (1.2 × 1026 w hz−1 at 5 ghz) compared to the optical luminosity (1.8 × 1024 w hz−1 at 4400 å) makes it the most distant radio-loud quasar observed so far, with a radio loudness r ∼ 70 (r = l5 ghz/l4400 å). moreover, the high bolometric luminosity of the source (lbol = 7.4 × 1046 erg s−1) suggests the presence of a supermassive black hole with a high mass (≳6 × 108 m⊙) at a time when the universe was younger than a billion years. combining the new radio data from racs with previous askap observations at the same frequency, we found that the flux density of the source may have varied by a factor of ∼2, which could suggest the presence of a relativistic jet oriented towards the line of sight, that is, a blazar nature. however, currently available radio data do not allow us to firmly characterise the orientation of the source. further radio and x-ray observations are needed. | radio detection of vik j2318−3113, the most distant radio-loud quasar (z = 6.44) |
we analyse near-infrared integral field spectrograph (nifs) observations of the type-2 quasar (qso2) sdss j094521.33+173753.2 to investigate its warm molecular and ionized gas kinematics. this qso2 has a bolometric luminosity of 1045.7 erg s−1 and a redshift of z = 0.128. the k-band spectra provided by nifs cover a range of 1.99-2.40 μm where low ionization (paα and brδ), high ionization ([s xi]λ1.920 μm and [si vi]λ1.963 μm), and warm molecular lines (from h21-0s(5) to 1-0s(1)) are detected, allowing us to study the multi-phase gas kinematics. our analysis reveals gas in ordinary rotation in all the emission lines detected and also outflowing gas in the case of the low and high ionization emission lines. in the case of the nuclear spectrum, which corresponds to a circular aperture of 0.3″ (686 pc) in diameter, the warm molecular lines can be characterized using a single gaussian component of full width at half maximum (fwhm) = 350 − 400 km s−1, while paα, brδ, and [si vi] are best fitted with two blue-shifted gaussian components of fwhm ∼ 800 and 1700 km s−1, in addition to a narrow component of ∼300 km s−1. we interpret the blue-shifted broad components as outflowing gas, which reaches the highest velocities, of up to −840 km s−1, in the south-east direction (pa ∼ 125°), extending up to a distance of ∼3.4 kpc from the nucleus. the ionized outflow has a maximum mass outflow rate of ṁout,max = 42-51 m⊙ yr−1, and its kinetic power represents 0.1% of the quasar bolometric luminosity. very large array (vla) data of j0945 show extended radio emission (pa ∼ 100°) that is aligned with the clumpy emission traced by the narrow component of the ionized lines up to scales of several kiloparsecs, and with the innermost part of the outflow (central ∼0.4″ = 915 pc). beyond that radius, at the edge of the radio jet, the high velocity gas shows a different pa of ∼125°. this might be an indication that the line-emitting gas is being compressed and accelerated by the shocks generated by the radio jet. | warm molecular and ionized gas kinematics in the type-2 quasar j0945+1737 |
we present the discovery of the radio-loud quasar pso j352.4034-15.3373 at z = 5.84 ± 0.02. this quasar is the radio brightest source known, by an order of magnitude, at z ∼ 6 with a flux density in the range of 8-100 mjy from 3 ghz to 230 mhz and a radio loudness parameter r={f}ν ,5{ghz}/{f}ν ,4400\mathringa ≳ 1000. this source provides an unprecedented opportunity to study powerful jets and radio-mode feedback at the highest redshifts, and presents the first real chance to probe deep into the neutral intergalactic medium by detecting 21 cm absorption at the end of cosmic reionization. | a powerful radio-loud quasar at the end of cosmic reionization |
we report the discovery of serenity-18, a galaxy at z ≃ 5.939 for which we could measure the content of molecular gas, m(h2) ≃ 5 × 109 m ⊙, traced by the co(6-5) emission, together with the metal-poor ([fe/h] =-3.08 ± 0.12, [si/h] = -2.86 ± 0.14) gas clump/filament which is possibly feeding its growth. the galaxy has an estimated star formation rate of ≈100 m ⊙ yr-1, implying that it is a typical main sequence galaxy at these redshifts. the metal-poor gas is detected through a damped lyα absorber (dla) observed at a spatial separation of 40 kpc and at the same redshift of serenity-18, along the line of sight to the quasar sdss j2310+1855 (z em ≃ 6.0025). the chemical abundances measured for the damped lyα system are in very good agreement with those measured for other dlas discovered at similar redshifts, indicating an enrichment due to massive popii stars. the galaxy/damped system that we discovered is a direct observational evidence of the assembly of a galaxy at the edge of the reionization epoch. based on alma and eso vlt observations. | witnessing galaxy assembly at the edge of the reionization epoch |
turbulence in the intracluster, intragroup, and circumgalactic medium plays a crucial role in the self-regulated feeding and feedback loop of central supermassive black holes. we dissect the 3d turbulent 'weather' in a high-resolution eulerian simulation of active galactic nucleus (agn) feedback, shown to be consistent with multiple multiwavelength observables of massive galaxies. we carry out post-processing simulations of lagrangian tracers to track the evolution of enstrophy, a proxy of turbulence, and its related sinks and sources. this allows us to isolate in depth the physical processes that determine the evolution of turbulence during the recurring strong and weak agn feedback events, which repeat self-similarly over the gyr evolution. we find that the evolution of enstrophy/turbulence in the gaseous halo is highly dynamic and variable over small temporal and spatial scales, similar to the chaotic weather processes on earth. we observe major correlations between the enstrophy amplification and recurrent agn activity, especially via its kinetic power. while advective and baroclinc motions are always subdominant, stretching motions are the key sources of the amplification of enstrophy, in particular along the jet/cocoon, while rarefactions decrease it throughout the bulk of the volume. this natural self-regulation is able to preserve, as ensemble, the typically observed subsonic turbulence during cosmic time, superposed by recurrent spikes via impulsive anisotropic agn features (wide outflows, bubbles, cocoon shocks). this study facilitates the preparation and interpretation of the thermo-kinematical observations enabled by new revolutionary x-ray integral field unit telescopes, such as xrism and athena. | dissecting the turbulent weather driven by mechanical agn feedback |
we use herschel 70 to 160 μm images to study the size of the far-infrared emitting region in about 400 local galaxies and quasar (qso) hosts. the sample includes normal "main-sequence" star-forming galaxies, as well as infrared luminous galaxies and palomar-green qsos, with different levels and structures of star formation. assuming gaussian spatial distribution of the far-infrared (fir) emission, the excellent stability of the herschel point spread function (psf) enables us to measure sizes well below the psf width, by subtracting widths in quadrature. we derive scalings of fir size and surface brightness of local galaxies with fir luminosity, with distance from the star-forming main-sequence, and with fir color. luminosities lfir~ 1011 l⊙ can be reached with a variety of structures spanning 2 dex in size. ultraluminous lfir≳ 1012 l⊙ galaxies far above the main-sequence inevitably have small re,70~ 0.5 kpc fir emitting regions with large surface brightness, and can be close to optically thick in the fir on average over these regions. compared to these local relations, first alma sizes for the dust emission regions in high redshift galaxies, measured at somewhat longer rest wavelengths, suggest larger sizes at the same ir luminosity. we report a remarkably tight relation with 0.15 dex scatter between fir surface brightness and the ratio of [cii] 158 μm emission and fir emission - the so-called [cii]-deficit is more tightly linked to surface brightness than to fir luminosity or fir color. among 33 z ≤ 0.1 pg qsos with typical lfir/lbol,agn ≈ 0.1, 19 have a measured 70 μm half light radius, with median re,70 = 1.1 kpc. this is consistent with the fir size for galaxies with similar lfir but lacking a qso, in accordance with a scenario where the rest fir emission of these types of qsos is, in most cases, due to host star formation. | the far-infrared emitting region in local galaxies and qsos: size and scaling relations |
we describe a consequence of the eddington bias which occurs when a single astrophysical neutrino event is used to infer the neutrino flux of the source. a trial factor is introduced by the potentially large number of similar sources that remain undetected; if this factor is not accounted for the luminosity of the observed source can be overestimated by several orders of magnitude. based on the resulting unrealistically high neutrino fluxes, associations between high-energy neutrinos and potential counterparts or emission scenarios were rejected in the past. correcting for the bias might justify a reevaluation of these cases. | eddington bias for cosmic neutrino sources |
we constrain the average episodic quasar lifetime (as in steady-state accretion) using two statistics of quasars that are recently turned off (i.e., dimmed by a large factor): (1) the fraction of turned-off quasars in a statistical sample photometrically observed over an extended period (e.g., δt = 20 yr) and (2) the fraction of massive galaxies that show "orphan" broad mg ii emission, argued to be short-lived echoes of recently turned-off quasars. the two statistics constrain the average episodic quasar lifetime to be hundreds to thousands of years. much longer (or shorter) episodic lifetimes are strongly disfavored by these observations. this average episodic lifetime is broadly consistent with the infall timescale (viscous time) in the standard accretion-disk model for quasars, suggesting that quasar episodes are governed by accretion-disk physics rather than by the gas supply on much larger scales. compared with the cumulative quasar lifetime of ~106-108 yr constrained from quasar clustering and massive black hole demographics, our results suggest that there are ~103-105 episodes of quasar accretion during the assembly history of the supermassive black hole. such short episodes should be clustered over intervals of ~104 yr to account for the sizes of ionized narrow-line regions in quasars. our statistical argument also dictates that there will always be a small fraction of extreme variability quasars caught in "state transitions" over multiyear observing windows, despite the much longer episodic lifetime. these transitions could occur in a rather abrupt fashion during non-steady accretion. | extreme variability and episodic lifetime of quasars |
we present a systematic search for periodically varying quasars and supermassive black hole binary (smbhb) candidates in the pan-starrs1 (ps1) medium deep survey’s md09 field. from a color-selected sample of 670 quasars extracted from a multi-band deep-stack catalog of point sources, we locally select variable quasars and look for coherent periods with the lomb-scargle periodogram. three candidates from our sample demonstrate strong variability for more than ∼3 cycles, and their ps1 light curves are well fitted to sinusoidal functions. we test the persistence of the candidates’ apparent periodic variations detected during the 4.2 years of the ps1 survey with archival photometric data from the sdss stripe 82 survey or new monitoring with the large monolithic imager at the discovery channel telescope. none of the three periodic candidates (including pso j334.2028+1.4075) remain persistent over the extended baseline of 7-14 years, corresponding to a detection rate of <1 in 670 quasars in a search area of ≈5 deg2. even though smbhbs should be a common product of the hierarchal growth of galaxies, and periodic variability in smbhbs has been theoretically predicted, a systematic search for such signatures in a large optical survey is strongly limited by its temporal baseline and the “red noise” associated with normal quasar variability. we show that follow-up long-term monitoring (≳5 cycles) is crucial to our search for these systems. | a systematic search for periodically varying quasars in pan-starrs1: an extended baseline test in medium deep survey field md09 |
we use the combined data from the cos-gass and cos-halos surveys to characterize the circum-galactic medium (cgm) surrounding typical low-redshift galaxies in the mass range {m}* ∼ {10}9.5-11.5 {m}⊙ , and over a range of impact parameters extending to just beyond the halo virial radius (r vir). we find the radial scale length of the distributions of the equivalent widths of the lyα and si iii absorbers to be ∼1 and ∼0.4 r vir, respectively. the radial distribution of equivalent widths is relatively uniform for the blue galaxies, but highly patchy (i.e., it has a low covering fraction) for the red galaxies. we also find that the lyα and si iii equivalent widths show significant positive correlations with the specific star formation rate (ssfr) of the galaxy. we find a surprising lack of correlations between the halo mass (virial velocity) and either the velocity dispersions or velocity offsets of the lyα lines. the ratio of the velocity offset to the velocity dispersion for the lyα absorbers has a mean value of ∼4, suggesting that a given line of sight is intersecting a dynamically coherent structure in the cgm, rather than a sea of orbiting clouds. the kinematic properties of the cgm are similar in the blue and red galaxies, although we find that a significantly larger fraction of the blue galaxies have large lyα velocity offsets (>200 km s-1). we show that—if the cgm clouds represent future fuel for star formation—our new results could imply a large drop in the ssfr across the galaxy mass-range we probe. | the properties of the circumgalactic medium in red and blue galaxies: results from the cos-gass+cos-halos surveys |
quasar-driven outflows on galactic scales are a routinely invoked ingredient for galaxy formation models. we report the discovery of ionized gas nebulae surrounding three luminous red quasars at z ~ 0.4 from gemini integral field unit observations. all these nebulae feature unprecedented pairs of "superbubbles" extending ~20 kpc in diameter, and the line-of-sight velocity difference between the red- and blueshifted bubbles reaches up to ~1200 km/s. their spectacular dual-bubble morphology (in analogy to the galactic "fermi bubbles") and their kinematics provide unambiguous evidence for galaxy-wide quasar-driven outflows, in parallel with the quasi-spherical outflows similar in size from luminous type 1 and type 2 quasars at concordant redshift. these bubble pairs manifest themselves as a signpost of the short-lived superbubble "break-out" phase, when the quasar wind drives the bubbles to escape the confinement from the dense environment and plunge into the galactic halo with a high-velocity expansion. unprecedented pairs of superbubbles are caught in red quasars, a signpost of the outflow break-out phase. | discovery of spectacular quasar-driven superbubbles in red quasars |
we study the angular clustering of quaia, a gaia- and unwise-based catalog of over a million quasars with an exceptionally well-defined selection function. with it, we derive cosmology constraints from the amplitude and growth of structure across cosmic time. we divide the sample into two redshift bins, centered at z = 1.0 and z = 2.1, and measure both overdensity auto-correlations and cross-correlations with maps of the cosmic microwave background convergence measured by planck. from these data, and including a prior from measurements of the baryon acoustic oscillations scale, we place constraints on the amplitude of the matter power spectrum σ 8 = 0.766 ± 0.034, and on the matter density parameter ω m= 0.343+0.017 -0.019. these measurements are in reasonable agreement with planck at the ~ 1.4σ level, and are found to be robust with respect to observational and theoretical uncertainties. we find that our slightly lower value of σ 8 is driven by the higher-redshift sample, which favours a low amplitude of matter fluctuations. we present plausible arguments showing that this could be driven by contamination of the cmb lensing map by high-redshift extragalactic foregrounds, which should also affect other cross-correlations with tracers of large-scale structure beyond z ~ 1.5. our constraints are competitive with those from state-of-the-art 3×2-point analyses, but arise from a range of scales and redshifts that is highly complementary to those covered by cosmic shear data and most galaxy clustering samples. this, coupled with the unprecedented combination of volume and redshift precision achieved by quaia, allows us to break the usual degeneracy between ω mand σ 8. | constraining cosmology with the gaia-unwise quasar catalog and cmb lensing: structure growth |
the origin of the radio emission in radio-quiet quasars (rqq) is not established yet. we present new vlba observations at 1.6 and 4.9 ghz of 10 rqq (9 detected), which together with published earlier observations of 8 rqq (5 detected), forms a representative sample of 18 rqq drawn from the palomar-green sample of low z (< 0.5) agn. the spectral slope of the integrated emission extends from very steep (α < -1.98) to strongly inverted (α = +2.18), and the slopes of 9 of the 14 objects are flat (α > -0.5). most objects have an unresolved flat-spectrum core, which coincides with the optical gaia position. the extended emission is generally steep-spectrum, has a low brightness temperature (< 107 k), and is displaced from the optical core (the gaia position) by ~ 5-100 pc. the vlba core flux is tightly correlated with the x-ray flux, and follows a radio to x-ray luminosity relation of log lr/lx ≃ -6, for all objects with a black hole mass log mbh/m⊙ < 8.5. the flatness of the core emission implies a compact source size (≲ 0.1 pc), which likely originates from the accretion disc corona. the mas-scale extended emission is optically thin and of clumpy structure, and is likely produced by an outflow from the center. radio observations at higher frequencies can further test the accretion disc coronal emission interpretation for the core emission in rqq. | the radio emission in radio-quiet quasars: the vlba perspective |
the continued operation of the wide-field infrared survey explorer (wise), combined with several ground-based optical transient surveys (e.g., crts, asas-sn, and ptf), offers an unprecedented opportunity to explore the dust structures in luminous active galactic nuclei (agns). we use these data for a mid-ir dust reverberation mapping (rm) study of 87 archetypal palomar-green quasars at z ≲ 0.5. to cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these data sets and retrieve the dust rm signals have been developed. we find that ∼70% of the sample (with a completeness correction up to 95%) has convincing mid-ir time lags in the wise w1 (∼3.4 μm) and w2 (∼4.5 μm) bands, and they are proportional to the square root of the agn luminosity. combined with previous k-band (∼2.2 μm) rm results in the literature, the inferred dust emission size ratios are {r}k:{r}w1:{r}w2=0.6:1:1.2. under simple assumptions, we put preliminary constraints on the projected dust surface density at these bands and reveal the possibly different torus structures among hot-dust-deficient, warm-dust-deficient, and normal quasars from the reverberation signals. with multi-epoch spitzer data and later wise photometry, we also explore agn ir variability at 10-24 μm over a 5 yr timescale. except for blazars and flat-spectrum radio sources, the majority of agns have typical variation amplitudes at 24 μm of no more than 10% of that in the w1 band, indicating that the dust reverberation signals damp out quickly at longer wavelengths. in particular, steep-spectrum radio quasars also lack strong 24 μm variability, consistent with the unification picture of radio-loud agns. | mid-ir variability and dust reverberation mapping of low-z quasars. i. data, methods, and basic results |
we detected a possible quasi-periodic oscillation (qpo) of ∼71 d in the 0.1-300 gev γ-ray fermi-large area telescope light curve of the high-redshift flat spectrum radio quasar b2 1520+31. we identify and confirm that quasi-period by lomb-scargle periodogram and weighted wavelet z-transform analyses. using this qpo period, and assuming it originates from accretion disc fluctuations at the innermost stable circular orbit, we estimate the central supermassive black hole mass to range between ∼5.4 × 109 m⊙ for a non-rotating black hole and ∼3.4 × 1010 m⊙ for a maximally rotating black hole. we briefly discuss other possible radio-loud active galactic nuclei emission models capable of producing a γ-ray qpo of such a period in a blazar. | detection of a quasi-periodic oscillation in γ-ray light curve of the high-redshift blazar b2 1520+31 |
context. high-redshift quasars signpost the early accretion history of the universe. the penetrating nature of x-rays enables a less absorption-biased census of the population of these luminous and persistent sources compared to optical/near-infrared colour selection. the ongoing srg/erosita x-ray all-sky survey offers a unique opportunity to uncover the bright end of the high-z quasar population and probe new regions of colour parameter space.aims: we searched for high-z quasars within the x-ray source population detected in the contiguous ~140 deg2 field observed by erosita during the performance verification phase. with the purpose of demonstrating the unique survey science capabilities of erosita, this field was observed at the depth of the final all-sky survey. the blind x-ray selection of high-redshift sources in a large contiguous, near-uniform survey with a well-understood selection function can be directly translated into constraints on the x-ray luminosity function (xlf), which encodes the luminosity-dependent evolution of accretion through cosmic time.methods: we collected the available spectroscopic information in the efeds field, including the sample of all currently known optically selected z > 5.5 quasars and cross-matched secure legacy dr8 counterparts of erosita-detected x-ray point-like sources with this spectroscopic sample.results: we report the x-ray detection of efedsu j083644.0+005459, an erosita source securely matched to the well-known quasar sdss j083643.85+005453.3 (z = 5.81). the soft x-ray flux of the source derived from erosita is consistent with previous chandra observations. the detection of sdss j083643.85+005453.3 allows us to place the first constraints on the xlf at z > 5.5 based on a secure spectroscopic redshift. compared to extrapolations from lower-redshift observations, this favours a relatively flat slope for the xlf at z ~ 6 beyond l*, the knee in the luminosity function. in addition, we report the detection of the quasar with lofar at 145 mhz and askap at 888 mhz. the reported flux densities confirm a spectral flattening at lower frequencies in the emission of the radio core, indicating that sdss j083643.85+005453.3 could be a (sub-) gigahertz peaked spectrum source. the inferred spectral shape and the parsec-scale radio morphology of sdss j083643.85+005453.3 indicate that it is in an early stage of its evolution into a large-scale radio source or confined in a dense environment. we find no indications for a strong jet contribution to the x-ray emission of the quasar, which is therefore likely to be linked to accretion processes.conclusions: our results indicate that the population of x-ray luminous agns at high redshift may be larger than previously thought. from our xlf constraints, we make the conservative prediction that erosita will detect ~90 x-ray luminous agns at redshifts 5.7 < z < 6.4 in the full-sky survey (de+ru). while subject to different jet physics, both high-redshift quasars detected by erosita so far are radio-loud; a hint at the great potential of combined x-ray and radio surveys for the search of luminous high-redshift quasars. | first constraints on the agn x-ray luminosity function at z 6 from an erosita-detected quasar |
we investigate the infrared (ir) emission of high-redshift (z ∼ 6), highly star-forming ( ${{\rm sfr}\gt 100\,{\rm m}_{\odot }\, {\rm yr}^{-1}}$ ) galaxies, with/without active galactic nuclei (agn), using a suite of cosmological simulations featuring dust radiative transfer. synthetic spectral energy distributions (seds) are used to quantify the relative contribution of stars/agn to dust heating. in dusty (md ≳ 3 × 107 m⊙) galaxies, ≳50-90 per cent of the ultraviolet (uv) radiation is obscured by dust inhomogeneities on scales ≳100 pc. in runs with agn, a clumpy, warm (≈250 k) dust component coexists with a colder (≈60 k) and more diffuse one, heated by stars. warm dust provides up to ${50 {{\ \rm per\ cent}}}$ of the total infrared (ir) luminosity, but only ${\lesssim}0.1 {{\ \rm per\ cent}}$ of the total mass content. the agn boosts the mir flux by 10-100 times with respect to star-forming galaxies, without significantly affecting the far-ir. our simulations successfully reproduce the observed sed of bright (muv ∼ -26) z ∼ 6 quasars, and show that these objects are part of complex, dust-rich merging systems, containing multiple sources (accreting black holes and/or star-forming galaxies) in agreement with recent hst and alma observations. our results show that the proposed origins missions will be able to investigate the mid-ir (mir) properties of dusty star-forming galaxies and to obtain good-quality spectra of bright quasars at z ∼ 6. finally, the mir-to-fir flux ratio of faint (muv ∼ -24) agn is >10 times higher than for normal star-forming galaxies. this implies that combined jwst/origins/alma observations will be crucial to identify faint and/or dust-obscured agn in the distant universe. | infrared emission of z ∼ 6 galaxies: agn imprints |
in this work, we present the first results of the long-term high-cadence spectroscopic monitoring of 15 pg quasars with relatively strong fe ii emission, as a part of a broader reverberation mapping campaign performed using the calar alto observatory's 2.2 m telescope. the v-band, 5100 å continuum, and hβ broad emission line light curves are measured for a set of quasars for periods ranging from dozens to more than a hundred epochs between 2017 may and 2020 july. accurate time lags between the variations of the hβ broad-line fluxes and the optical continuum strength are obtained for all 15 quasars, ranging from ${17.0}_{-3.2}^{+2.5}$?--> 17.0 - 3.2 + 2.5 to ${95.9}_{-23.9}^{+7.1}$?--> 95.9 - 23.9 + 7.1 days in the rest frame. the virial masses of the central supermassive black holes are derived for all 15 quasars, ranging between ${0.50}_{-0.19}^{+0.18}$?--> 0.50 - 0.19 + 0.18 and ${19.17}_{-2.73}^{+2.98}$?--> 19.17 - 2.73 + 2.98 in units of 107m⊙. for 11 of the objects in our sample, this is the first reverberation analysis to be published. of the rest, two objects have been the subject of previous reverberation studies, but we determine time lags for these that are only half as long as those found in the earlier investigations, which had only been able to sample much more sparsely. the remaining two objects have previously been monitored with high sampling rates. our results here are consistent with the earlier findings, in the sense that the time lag and the line width vary inversely, consistent with virialization. | supermassive black holes with high accretion rates in active galactic nuclei. xii. reverberation mapping results for 15 pg quasars from a long-duration high-cadence campaign |
we considered the fourth catalog of gamma-ray point sources produced by the fermi large area telescope (lat) and selected only jetted active galactic nuclei (agn) or sources with no specific classification, but with a low-frequency counterpart. our final list is composed of 2980 gamma-ray point sources. we then searched for optical spectra in all the available literature and publicly available databases, to measure redshifts and to confirm or change the original lat classification. our final list of gamma-ray emitting jetted agn is composed of bl lac objects (40%), flat-spectrum radio quasars (23%), misaligned agn (2.8%), narrow-line seyfert 1, seyfert, and low-ionization nuclear emission-line region galaxies (1.9%). we also found a significant number of objects changing from one type to another, and vice versa (changing-look agn, 1.1%). about 30% of gamma-ray sources still have an ambiguous classification or lack one altogether. | a new sample of gamma-ray emitting jetted active galactic nuclei |
quasar broad emission lines are largely powered by photoionization from the accretion continuum. increased central luminosity will enhance line emissivity in more distant clouds, leading to increased average distance of the broad-line-emitting clouds and decreased averaged line width, which is known as the "breathing" broad-line region. however, different lines breathe differently, and some high-ionization lines, such as c iv, can even show "anti-breathing" where the line broadens when luminosity increases. using multi-year photometric and spectroscopic monitoring data from the sloan digital sky survey reverberation mapping project, we quantify the breathing effect ( ${\rm{\delta }}\mathrm{log}w=\alpha {\rm{\delta }}\mathrm{log}l$ ) of broad hα, hβ, mg ii, c iv, and c iii] for statistical quasar samples over z ≈ 0.1-2.5. we find that hβ displays the most consistent normal breathing expected from the virial relation (α ∼ -0.25), mg ii and hα on average show no breathing (α ∼ 0), and c iv (and similarly c iii] and si iv) mostly shows anti-breathing (α > 0). the anti-breathing of c iv can be well understood by the presence of a non-varying core component in addition to a reverberating broad-base component, which is consistent with earlier findings. the deviation from canonical breathing introduces extra scatter (a luminosity-dependent bias) in single-epoch virial bh mass estimates due to intrinsic quasar variability, which underlies the long-argued caveats of c iv single-epoch masses. using the line dispersion instead of fwhm leads to fewer, albeit still substantial, deviations from canonical breathing in most cases. our results strengthen the need for reverberation mapping to provide reliable quasar bh masses and to quantify the level of variability-induced bias in single-epoch bh masses based on various lines. | the sloan digital sky survey reverberation mapping project: how broad emission line widths change when luminosity changes |
using blazar light curves from the optical all-sky automated survey for supernovae (asas-sn) and the γ-ray fermi-lat telescope, we performed the most extensive statistical correlation study between both bands, using a sample of 1180 blazars. this is almost an order of magnitude larger than other recent studies. blazars represent more than 98 per cent of the agns detected by fermi-lat and are the brightest γ-ray sources in the extragalactic sky. they are essential for studying the physical properties of astrophysical jets from central black holes. however, their γ-ray flare mechanism is not fully understood. multiwavelength correlations help constrain the dominant mechanisms of blazar variability. we search for temporal relationships between optical and γ-ray bands. using a bayesian block decomposition, we detect 1414 optical and 510 γ-ray flares, we find a strong correlation between both bands. among all the flares, we find 321 correlated flares from 133 blazars, and derive an average rest-frame time delay of only 1.1$_{-8.5}^{+7.1}$ d, with no difference between the flat-spectrum radio quasars, bl lacertae-like objects or low, intermediate, and high-synchrotron peaked blazar classes. our time-delay limit rules out the hadronic proton-synchrotron model as the driver for non-orphan flares and suggests a leptonic single-zone model. limiting our search to well-defined light curves and removing 976 potential but unclear 'orphan' flares, we find 191 (13 per cent) and 115 (22 per cent) clear 'orphan' optical and γ-ray flares. the presence of 'orphan' flares in both bands challenges the standard one-zone blazar flare leptonic model and suggests multizone synchrotron sites or a hadronic model for some blazars. | optical/γ-ray blazar flare correlations: understanding the high-energy emission process using asas-sn and fermi light curves |
the recent evidence of a stochastic background of gravitational waves in the nhz band by pulsar timing array (pta) experiments has shed new light on the formation and evolution of massive black hole binaries with masses ∼108- 109m⊙ . the pta data are consistent with a population of such binaries merging efficiently after the coalescence of their galactic hosts, and presenting masses slightly larger than previously expected. this momentous discovery calls for investigating the prospects of detecting the smaller (∼105- 107m⊙) massive black hole binaries targeted by the laser interferometer space antenna (lisa). by using semianalytic models for the formation and evolution of massive black hole binaries calibrated against the pta results, we find that lisa will observe at least a dozen and up to thousands of black hole binaries during its mission duration. the minimum number of detections rises to ∼70 if one excludes models that only marginally reproduce the quasar luminosity function at z =6 . we also assess lisa's parameter estimation capabilities with state-of-the-art waveforms including higher modes and realistic instrumental response, and find that the masses, sky position, and distance will typically be estimated to within, respectively, 1%, 10 sq deg, and 10% for the detected systems (assuming a four-year mission). | implications of the pulsar timing array detections for massive black hole mergers in the lisa band |
recent studies have suggested that red quasars are a phase in quasar evolution when feedback from black hole accretion evacuates obscuring gas from the nucleus of the host galaxy. here, we report a direct link between dust-reddening and molecular outflows in quasars at z ~ 2.5. by examining the dynamics of warm molecular gas in the inner region of galaxies, we find evidence for outflows with velocities 500-1000 km s-1 and time-scales of ≈0.1 myr that are due to ongoing quasar energy output. we infer outflows only in systems where quasar radiation pressure on dust in the vicinity of the black hole is sufficiently large to expel their obscuring gas column densities. this result is in agreement with theoretical models that predict radiative feedback regulates gas in the nuclear regions of galaxies and is a major driving mechanism of galactic-scale outflows of cold gas. our findings suggest that radiative quasar feedback ejects star-forming gas from within nascent stellar bulges at velocities comparable to those seen on larger scales, and that molecules survive in outflows even from the most luminous quasars. | red quasars blow out molecular gas from galaxies during the peak of cosmic star formation |
context. the most highly accreting quasars are of special interest in studies of the physics of active galactic nuclei (agns) and host galaxy evolution. quasars accreting at high rates (l/ledd ∼ 1) hold promise for use as "standard candles": distance indicators detectable at very high redshift. however, their observational properties are still largely unknown.aims: we seek to identify a significant number of extreme accretors. a large sample can clarify the main properties of quasars radiating near l/ledd ∼ 1 (in this paper they are designated as extreme population a quasars or simply as extreme accretors) in the hβ spectral range for redshift ≲0.8.methods: we use selection criteria derived from four-dimensional eigenvector 1 (4de1) studies to identify and analyze spectra for a sample of 334 candidate sources identified from the sdss dr7 database. the source spectra were chosen to show a ratio rfeii between the feii emission blend at λ4570 and hβ, rfeii > 1. composite spectra were analyzed for systematic trends as a function of fe ii strength, line width, and [oiii] strength. we introduced tighter constraints on the signal-to-noise ratio (s/n) and rfeii values that allowed us to isolate sources most likely to be extreme accretors.results: we provide a database of detailed measurements. analysis of the data allows us to confirm that hβ shows a lorentzian function with a full width at half maximum (fwhm) of hβ ≤ 4000 km s-1. we find no evidence for a discontinuity at 2000 km s-1 in the 4de1, which could mean that the sources below this fwhm value do not belong to a different agn class. systematic [oiii] blue shifts, as well as a blueshifted component in hβ are revealed. we interpret the blueshifts as related to the signature of outflowing gas from the quasar central engine. the fwhm of hβ is still affected by the blueshifted emission; however, the effect is non-negligible if the fwhm hβ is used as a "virial broadening estimator" (vbe). we emphasize a strong effect of the viewing angle on hβ broadening, deriving a correction for those sources that shows major disagreement between virial and concordance cosmology luminosity values.conclusions: the relatively large scatter between concordance cosmology and virial luminosity estimates can be reduced (by an order of magnitude) if a correction for orientation effects is included in the fwhm hβ value; outflow and sample definition yield relatively minor effects. tables 1 and 2 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/620/a118 | highly accreting quasars: the sdss low-redshift catalog |
we investigate the multi-wavelength properties of host galaxies of 3701 x-ray-selected active galactic nuclei (agns) out to z ∼ 5 in the chandra-cosmos legacy survey. thanks to the extensive multi-wavelength photometry available in the cosmos field, we derive agn luminosities, host stellar masses, and star formation rates (sfrs) via a multi-component sed fitting technique. type 1 and type 2 agns follow the same intrinsic l 2-10 kev-l 6 μm relation, suggesting that mid-infrared emission is a reasonably good measure of the agn accretion power regardless of obscuration. we find that there is a strong increase in type 1 agn fraction toward higher agn luminosity, possibly due to the fact that type 1 agns tend to be hosted by more massive galaxies. the agn luminosity and sfr are consistent with an increase toward high stellar mass, while the m stellar dependence is weaker toward the high-mass end, which could be interpreted as a consequence of quenching both star formation and agn activity in massive galaxies. agn host galaxies tend to have sfrs that are consistent with normal star-forming galaxies, independent of agn luminosities. we confirm that black hole accretion rate and sfr are correlated up to z ∼ 5, when forming stars. the majority (∼73%) of our agn sample are faint in the far-infrared, implying that the moderate-luminosity agns seem to be still active after the star formation is suppressed. it is not certain whether agn activity plays a role in quenching the star formation. we conclude that both agn activity and star formation might be more fundamentally related to host stellar mass. | multi-wavelength properties of type 1 and type 2 agn host galaxies in the chandra-cosmos legacy survey |
we present the first systematic study of 50 low-redshift (0.66 < z < 1.63) iron low-ionization broad absorption-line quasars (felobalqs) using simbal, which represents a more than five-fold increase in the number of felobalqs with detailed absorption line spectral analyses. we found the outflows have a wide range of ionization parameters, $-4\lesssim \mathrm{log}u\lesssim 1.2$ and densities, $2.8\lesssim \mathrm{log}n\lesssim 8\ [{\mathrm{cm}}^{-3}]$ . the objects in our sample showed felobal gas located at a wide range of distances $0\lesssim \mathrm{log}r\lesssim 4.4$ [pc], although we do not find any evidence for disk winds (with r ≪ 0.01 pc) in our sample. the outflow strength primarily depends on the outflow velocity with faster outflows found in quasars that are luminous or that have flat or redder spectral energy distributions. we found that ~18% of the felobalqs in the sample have the significantly powerful outflows needed for quasar feedback. eight objects showed overlapping troughs in the spectra, and we identified eleven loitering outflow objects, a new class of felobalqs that are characterized by low outflow velocities and high column density winds located $\mathrm{log}r\lesssim 1$ [pc] from the central engine. the felobals in loitering outflows objects do not show properties expected for radiatively driven winds, and these objects may represent a distinct population among felobalqs. we discuss how the potential acceleration mechanisms and the origins of the felobal winds may differ for outflows at different locations in quasars. | the physical properties of low-redshift felobal quasars. i. spectral-synthesis analysis of the broad absorption-line (bal) outflows using simbal |
context. galaxy evolution scenarios predict that the feedback of star formation and nuclear activity (agn) can drive the transformation of gas-rich spiral mergers into (ultra) luminous infrared galaxies and, eventually, lead to the build-up of qso/elliptical hosts.aims: we study the role that star formation and agn feedback have in launching and maintaining the molecular outflows in two starburst-dominated advanced mergers, ngc 1614 (dl = 66 mpc) and iras 17208-0014 (dl = 181 mpc), by analyzing the distribution and kinematics of their molecular gas reservoirs. both galaxies present evidence of outflows in other phases of their ism.methods: we used the plateau de bure interferometer (pdbi) to image the co(1-0) and co(2-1) line emissions in ngc 1614 and iras 17208-0014, respectively, with high spatial resolution (0''̣5-1''̣2). the velocity fields of the gas were analyzed and modeled to find the evidence of molecular outflows in these sources and characterize the mass, momentum, and energy of these components.results: while most (≥95%) of the co emission stems from spatially resolved (~2-3 kpc-diameter) rotating disks, we also detect in both mergers the emission from high-velocity line wings that extend up to ±500-700 km s-1, well beyond the estimated virial range associated with rotation and turbulence. the kinematic major axis of the line-wing emission is tilted by ~90° in ngc 1614 and by ~180° in iras 17208-0014 relative to the major axes of their respective rotating disks. these results can be explained by the existence of non-coplanar molecular outflows in both systems: the outflow axis is nearly perpendicular to the rotating disk in ngc 1614, but it is tilted relative to the angular momentum axis of the rotating disk in iras 17208-0014.conclusions: in stark contrast to ngc 1614, where star formation alone can drive its molecular outflow, the mass, energy, and momentum budget requirements of the molecular outflow in iras 17208-0014 can be best accounted for by the existence of a so far undetected (hidden) agn of lagn ~ 7 × 1011 l⊙. the geometry of the molecular outflow in iras 17208-0014 suggests that the outflow is launched by a non-coplanar disk that may be associated with a buried agn in the western nucleus. based on observations carried out with the iram plateau de bure interferometer. iram is supported by insu/cnrs (france), mpg (germany), and ign (spain). | high-resolution imaging of the molecular outflows in two mergers: iras 17208-0014 and ngc 1614 |
the cosmological process of hydrogen (h i) reionization in the intergalactic medium is thought to be driven by uv photons emitted by star-forming galaxies and ionizing active galactic nuclei (agn). the contribution of quasars (qsos) to h i reionization at z > 4 has been traditionally believed to be quite modest. however, this view has been recently challenged by new estimates of a higher faint-end uv luminosity function (lf). to set firmer constraints on the emissivity of agn at z < 6, we here make use of complete x-ray-selected samples including deep chandra and new cosmic evolution survey data, capable to efficiently measure the 1 ryd comoving agn emissivity up to z ∼ 5-6 and down to 5 mag fainter than probed by current optical surveys, without any luminosity extrapolation. we find good agreement between the lognh ≲ 21-22 cm-2 x-ray lf and the optically selected qso lf at all redshifts for m1450 ≤ -23. the full range of the lognh ≲ 21-22 cm-2 lf (m1450 ≤ -17) was then used to quantify the contribution of agn to the critical value of photon budget needed to keep the universe ionized. we find that the contribution of ionizing agn at z = 6 is as small as 1-7 per cent, and very unlikely to be greater than 30 per cent, thus excluding an agn-dominated reionization scenario. | constraining the uv emissivity of agn throughout cosmic time via x-ray surveys |
recent results have suggested that active galactic nuclei (agn) could provide enough photons to reionize the universe. we assess the viability of this scenario using a semi-numerical framework for modelling reionization, to which we add a quasar contribution by constructing a quasar halo occupancy distribution (qhod) based on giallongo et al. observations. assuming a constant qhod, we find that an agn-only model cannot simultaneously match observations of the optical depth τe, neutral fraction and ionizing emissivity. such a model predicts τe too low by ∼2σ relative to planck constraints, and reionizes the universe at z ≲ 5. arbitrarily increasing the agn emissivity to match these results yields a strong mismatch with the observed ionizing emissivity at z ∼ 5. if we instead assume a redshift-independent agn luminosity function yielding an emissivity evolution like that assumed in madau & haardt model, then we can match τe albeit with late reionization; however, such evolution is inconsistent with observations at z ∼ 4-6 and poorly motivated physically. these results arise because agn are more biased towards massive haloes than typical reionizing galaxies, resulting in stronger clustering and later formation times. agn-dominated models produce larger ionizing bubbles that are reflected in ∼×2 more 21 cm power on all scales. a model with equal part galaxies and agn contribution is still (barely) consistent with observations, but could be distinguished using next-generation 21 cm experiments such as hydrogen epoch of reionization array and ska-low. we conclude that, even with recent claims of more faint agn than previously thought, agn are highly unlikely to dominate the ionizing photon budget for reionization. | constraining the contribution of active galactic nuclei to reionization |
gaia’s precision astrometry allows systematic identification of optically selected subkiloparsec dual active galactic nuclei (agns), off-nucleus agns, and small-scale lensed quasars by “varstrometry”—where variability-induced astrometric jitter, i.e., temporal displacements of photocenter in unresolved sources, can be reasonably well detected or constrained. this approach extends systematic searches for small-scale (≳mas) dual and off-nucleus agns to the poorly explored regime between ∼10 pc and ∼1 kpc, with gaia’s full sky coverage and depth to g ∼ 21. we outline the general principles of this method and calculate the expected astrometric signals from the full time series of photocenter measurements and light curves. we demonstrate the feasibility of varstrometry by using gaia data release 2 (dr2) data on a sample of variable pre-main-sequence stars with known close companions. we find that extended host galaxies have a significant impact on the accuracy of astrometric and photometric variability in gaia dr2, a situation to be improved in future gaia releases. using spectroscopically confirmed sloan digital sky survey quasars, we present several examples of candidate subkiloparsec off-nucleus or dual agns selected from gaia dr2. we discuss the merits and limitations of this method and a follow-up strategy for promising candidates. we highlight gaia’s potential of systematically discovering and characterizing the subkiloparsec off-nucleus and dual agn population in the entire optical sky. | varstrometry for off-nucleus and dual subkiloparsec agn (vodka): methodology and initial results with gaia dr2 |
very long baseline interferometry (vlbi) from the ground at millimeter wavelengths can resolve the black hole shadow around two supermassive black holes, sagittarius a∗ and m87. the addition of modest telescopes in space would allow the combined array to produce higher-resolution, higher-fidelity images of these and other sources. this paper explores the potential benefits of adding orbital elements to the event horizon telescope. we reconstruct model images using simulated data from arrays including telescopes in different orbits. we find that an array including one telescope near geostationary orbit and one in a high-inclination medium earth of geosynchronous orbit can successfully produce high-fidelity images capable of resolving shadows as small as 3 μ as in diameter. one such key source, the sombrero galaxy, may be important to address questions regarding why some black holes launch powerful jets while others do not. meanwhile, higher-resolution imaging of the substructure of m87 may clarify how jets are launched in the first place. the extra resolution provided by space vlbi will also improve studies of the collimation of jets from active galactic nuclei. | imaging black holes and jets with a vlbi array including multiple space-based telescopes |
intermediate-mass black holes (imbhs; masses between 100{ and }106 m_{\odot }) historically comprise of an elusive population compared to stellar-mass and supermassive black holes (bhs). recently, imbhs have started to be observed at the centres of low-mass galaxies. we perform cosmological hydrodynamical simulations of (2 h^{-1} mpc)^3 comoving boxes and investigate the growth and feedback of central imbhs in dwarf galaxies (dgs). the earliest bhs appear at z ∼ 18-25 and grow thereafter by accreting gas and by merger with other bhs. we find that, starting from 102 m_{\odot }, it is possible to build up imbhs of a few× 105 - 106 m_{\odot } by z = 5, when the bhs are seeded in haloes less massive than 4 × 107 m_{\odot }. the bh accretion rates increase with time and reach \dot{m}_bh = (0.2 - 0.8) \dot{m}_edd for the massive imbhs by z = 4. the star formation rate density (sfrd) evolution of the dgs (stellar mass 105 - 108 m_{\odot }) has a peak plateau between z = 4 and 6. star formation is quenched between z = 9 and 4. the sfrd is reduced by factors up to 3 when the bhs have grown to a few times 10^5 m_{\odot }. even in the presence of stronger supernova (sn)-driven mass ejection, the bhs continue to grow up to z ∼ 6, sustained by gas inflows driven by galaxy mergers and interactions in a cosmological environment. our conclusions, based on numerical simulation results, support the scenario that early feedback from imbhs in gas-rich dgs at z = 5-8 can potentially solve several anomalies in the dg mass range within the concordance λ cold dark matter (λcdm) cosmological scenario (silk 2017). our results suggest that imbhs at dg centres grow faster than their host galaxies in the early universe, and the resulting bh feedback turns the dgs and the bhs dormant. | intermediate-mass black hole growth and feedback in dwarf galaxies at high redshifts |
heavily obscured, compton thick (ct, nh> 1024 cm-2) active galactic nuclei (agn) may represent an important phase in agn/galaxy co-evolution and are expected to provide a significant contribution to the cosmic x-ray background at its peak. however, unambiguously identifying ct agn beyond the local universe is a challenging task even in the deepest x-ray surveys, and given the expected low spatial density of these sources in the 2-10 kev band, large area surveys are needed to collect sizable samples. through direct x-ray spectra analysis, we selected 39 heavily obscured agn (nh>3 × 1023 cm-2) at bright x-ray fluxes (f2-10 ≳ 10-14 erg s-1 cm-2) in the 2 deg2 xmm-cosmos survey. after selecting ct agn based on the fit of a simple absorbed two power law model to the shallow xmm-newton data, the presence of bona fide ct agn was confirmed in 80% of the sources using deeper chandra data and more complex models. the final sample comprises ten ct agn (six of them also have a detected fe kα line with ew ~ 1 kev), spanning a wide range of redshifts (z ~ 0.1-2.5) and luminosity (l2-10 ~ 1043.5-1045 erg s-1) and is complemented by 29 heavily obscured agn spanning the same redshift and luminosity range. we collected the rich multi-wavelength information available for all these sources, in order to study the distribution of super massive black hole and host properties, such as black hole mass (mbh), eddington ratio (λedd), stellar mass (m∗), specific star formation rate (ssfr) in comparison with a sample of unobscured agn. we find that highly obscured sources tend to have significantly smaller mbh and higher λedd with respect to unobscured sources, while a weaker evolution in m∗ is observed. the ssfr of highly obscured sources is consistent with the one observed in the main sequence of star forming galaxies, at all redshifts. we also present and briefly discuss optical spectra, broadband spectral energy distribution (sed) and morphology for the sample of ten ct agn. both the optical spectra and sed agree with the classification as highly obscured sources: all the available optical spectra are dominated by the stellar component of the host galaxy, and to reproduce the broadband sed, a highly obscured torus component is needed for all the ct sources.exploiting the high resolution hubble-acs images available, we are able to show that these highly obscured sources have a significantly larger merger fraction with respect to other x-ray selected samples of agn. finally we discuss the implications of our findings in the context of agn/galaxy co-evolutionary models, and compare our results with the predictions of x-ray background synthesis models. appendices are available in electronic form at http://www.aanda.org | compton thick agn in the xmm-cosmos survey |
we present the infrared (ir) and x-ray properties of a sample of 33 mid-ir luminous quasars (νl6 μm ≥ 6 × 1044 erg s-1) at redshift z ≈ 1-3, identified through detailed spectral energy distribution analyses of distant star-forming galaxies, using the deepest ir data from spitzer and herschel in the goods-herschel fields. the aim is to constrain the fraction of obscured, and compton-thick (ct, nh > 1.5 × 1024 cm-2) quasars at the peak era of nuclear and star formation activities. despite being very bright in the mid-ir band, ≈30 per cent of these quasars are not detected in the extremely deep 2 and 4 ms chandra x-ray data available in these fields. x-ray spectral analysis of the detected sources reveals that the majority (≈67 per cent) are obscured by column densities nh > 1022 cm-2; this fraction reaches ≈80 per cent when including the x-ray-undetected sources (9 out of 33), which are likely to be the most heavily obscured, ct quasars. we constrain the fraction of ct quasars in our sample to be ≈24-48 per cent, and their space density to be φ = (6.7 ± 2.2) × 10-6 mpc-3. from the investigation of the quasar host galaxies in terms of star formation rates (sfrs) and morphological distortions, as a sign of galaxy mergers/interactions, we do not find any direct relation between sfrs and quasar luminosity or x-ray obscuration. on the other hand, there is tentative evidence that the most heavily obscured quasars have, on average, more disturbed morphologies than the unobscured/moderately obscured quasar hosts, which preferentially live in undisturbed systems. however, the fraction of quasars with disturbed morphology amongst the whole sample is ≈40 per cent, suggesting that galaxy mergers are not the main fuelling mechanism of quasars at z ≈ 2. | mid-infrared luminous quasars in the goods-herschel fields: a large population of heavily obscured, compton-thick quasars at z ≈ 2 |
to study the impact of active galactic nuclei (agn) feedback on their galactic ism, we present magellan long-slit spectroscopy of 12 luminous nearby obscured agn ({l}{bol}∼ {10}45.0-46.5 {erg} {{{s}}}-1, z ∼ 0.1). these objects are selected from a parent sample of spectroscopically identified agn to have high [o iii]λ5007 and wide-field infrared survey explorer mid-ir luminosities and extended emission in the sloan digital sky survey r-band images, suggesting the presence of extended [o iii]λ5007 emission. we find spatially resolved [o iii] emission (2-35 kpc) in 8 out of 12 of these objects. combined with samples of higher luminosity obscured agn, we confirm that the size of the narrow-line region (rnlr) scales with the mid-ir luminosity until the relation flattens at rnlr ∼ 10 kpc. nine out of 12 objects in our sample have regions with broad [o iii] line widths (w80 > 600 km s-1), indicating outflows. we define these regions as the kinematically disturbed region (kdr). the size of the kdr ({r}{kdr}) is typically smaller than rnlr by few kiloparsecs but also correlates strongly with the agn mid-ir luminosity. given the uncertain outflow mass, we derive a loose constraint on the outflow energy efficiency {η }{med}=\dot{e}/{l}{bol}∼ 0.007 % {--}7 % . we find no evidence for an agn luminosity threshold below which outflows are not launched. to explain the sizes, velocity profiles, and high occurrence rates of the outflows in the most luminous agn, we propose a scenario in which energy-conserving outflows are driven by agn episodes with ∼108 year durations. within each episode, the agn is unlikely to be constantly luminous but could flicker on shorter timescales (≲107 yr) with a moderate duty cycle (∼10%). | sizes and kinematics of extended narrow-line regions in luminous obscured agn selected by broadband images |
we use the sherwood-relics suite of hybrid hydrodynamical and radiative transfer simulations to model the effect of inhomogeneous reionization on the 1d power spectrum of the lyman α (lyα) forest transmitted flux at redshifts 4.2 ≤ z ≤ 5. relative to models that assume a homogeneous ultraviolet background, reionization suppresses the power spectrum at small scales, k ~ 0.1 km-1 s, by ~10 per cent because of spatial variations in the thermal broadening kernel and the divergent peculiar velocity field associated with overpressurized intergalactic gas. on larger scales, $k\lt 0.03\rm \, km^{-1}\, s$, the power spectrum is instead enhanced by 10-50 per cent by large-scale spatial variations in the neutral hydrogen fraction. the effect of inhomogeneous reionization must therefore be accounted for in analyses of forthcoming high precision measurements. we provide a correction for the lyα forest power spectrum at 4.1 ≤ z ≤ 5.4 that can be easily applied within other parameter inference frameworks using similar reionization models. we perform a bayesian analysis of mock data to assess the extent of systematic biases that may arise in measurements of the intergalactic medium if ignoring this correction. at the scales probed by current high-resolution lyα forest data at z > 4, $0.006 \le k \le 0.2 \rm \, km^{-1}\, s$, we find inhomogeneous reionization does not introduce any significant bias in thermal parameter recovery for the current measurement uncertainties of ~10 per cent. however, for 5 per cent uncertainties, ~1σ shifts between the estimated and true parameters occur. | the effect of inhomogeneous reionization on the lyman α forest power spectrum at redshift z > 4: implications for thermal parameter recovery |
context. the detection of quasi-periodic oscillations (qpos) in the light curves of active galactic nuclei (agns) can provide insights into the physics of the super-massive black holes (smbhs) powering these systems and could represent a signature of the existence of smbh binaries, setting fundamental constraints on smbh evolution in the universe.aims: the identification of long-term qpos, characterized by periods on the order of several months to years, is particularly challenging and can only be achieved via all-sky monitoring instruments that provide unbiased, continuous light curves of astrophysical objects. the fermi-lat satellite, thanks to its monitoring observing strategy, is an ideal instrument for such a goal. here, we aim to identify qpos in the γ-ray light curves of the brightest agns within the fermi-lat catalog.methods: we analyzed the light curves of the 35 brightest fermi-lat agns, including data from the beginning of the fermi mission (august 2008) to april 2021, with energies from 100 mev to 300 gev. two time binnings were investigated: 7 and 30 days. the search for quasi-periodic features was then performed using the continuous wavelet transform. the significance of the result was tested via monte carlo simulations of artificial light curves with the same power spectral density and probability distribution function as the original light curves. the significances were then corrected for the look-elsewhere effect and provided as post-trials.results: we identified 24 quasars with candidate qpos. several of our candidates coincide with previous claims in the literature, namely: pks 0537−441, s5 0716+714, mrk 421, b2 1520+31, and pks 2247−131. all our candidates are transient. the most significant multi-year qpo, with a period of about 1100 days, was observed in the quasar s5 1044+71. it is reported here for the first time. | quasi-periodic oscillations in the γ-ray light curves of bright active galactic nuclei |
mildly relativistic shocks that are embedded in colliding magnetohydrodynamic flows are prime sites for relativistic particle acceleration and the production of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars and gamma-ray bursts. the principal energization mechanisms at these shocks are diffusive shock acceleration and shock drift acceleration. in recent work, we had self-consistently coupled shock acceleration and radiation transfer simulations in blazar jets in a basic one-zone scenario. these one-zone models revealed that the observed spectral energy distributions (seds) of blazars strongly constrain the nature of the hydromagnetic turbulence in the shock layer. in this paper, we expand our previous work by including full time dependence and treating two zones, one being the site of acceleration and the other a larger emission zone. this construction is applied to multi-wavelength flares of the flat-spectrum radio quasar (fsrq) 3c 279, fitting snapshot seds and generating light curves that are consistent with observed variability timescales. we also present a generic study for the typical flaring behavior of the bl lac object mrk 501. the model predicts correlated variability across all wavebands, but cross-band time lags depending on the type of blazar (fsrq versus bl lac), as well as distinctive spectral hysteresis patterns in all wavelength bands, from millimeter radio waves to gamma-rays. these evolutionary signatures serve to provide diagnostics on the competition between acceleration and radiative cooling. | multi-wavelength variability signatures of relativistic shocks in blazar jets |
we present a new measurement of the lyα forest power spectrum at 1.8 < z < 3.4 using 74 keck/hires and vlt/uves high-resolution, high-signal-to-noise-ratio quasar spectra. we developed a custom pipeline to measure the power spectrum and its uncertainty, which fully accounts for finite resolution and noise and corrects for the bias induced by masking missing data, damped lyα absorption systems, and metal absorption lines. our measurement results in unprecedented precision on the small-scale modes k> 0.02 {{s}} {{km}}-1, inaccessible to previous sdss/boss analyses. it is well known that these high-k modes are highly sensitive to the thermal state of the intergalactic medium, but contamination by narrow metal lines is a significant concern. we quantify the effect of metals on the small-scale power and find a modest effect on modes with k< 0.1 {{s}} {{km}}-1. as a result, by masking metals and restricting to k< 0.1 {{s}} {{km}}-1, their impact is completely mitigated. we present an end-to-end bayesian forward-modeling framework whereby mock spectra with the same noise, resolution, and masking as our data are generated from lyα forest simulations. these mock spectra are used to build a custom emulator, enabling us to interpolate between a sparse grid of models and perform markov chain monte carlo fits. our results agree well with boss on scales k< 0.02 {{s}} {{km}}-1, where the measurements overlap. the combination of the percent-level low-k precision of boss with our 5%-15% high-k measurements results in a powerful new data set for precisely constraining the thermal history of the intergalactic medium, cosmological parameters, and the nature of dark matter. the power spectra and their covariance matrices are provided as electronic tables. | a new precision measurement of the small-scale line-of-sight power spectrum of the lyα forest |
it has been known for over three decades that the monochromatic x-ray and uv luminosities in quasars are correlated, though non-linearly. this offers the possibility of using high-z quasars as standard candles for cosmological testing. in this paper, we use a recently assembled, high-quality catalogue of 1598 quasars extending all the way to redshift ∼6, to compare the predictions of the rh = ct and lambda cold dark matter (λcdm) cosmologies. in so doing, we affirm that the parameters characterizing the correlation depend only weakly on the chosen cosmology, and that both models account very well for the data. unlike λcdm, however, the rh = ct model has no free parameters for this work, so the bayesian information criterion favours it over λcdm with a relative likelihood of ∼ 88{{ per cent}} versus ∼ 10{{ per cent}}. this result is consistent with the outcome of other comparative tests, many of which have shown that rh = ct is favoured over the standard model based on a diverse range of observations. | cosmological test using the hubble diagram of high-z quasars |
we present and make publicly available the first data release (dr1) of the keck observatory database of ionized absorption toward quasars (kodiaq) survey. the kodiaq survey is aimed at studying galactic and circumgalactic gas in absorption at high redshift, with a focus on highly ionized gas traced by o vi, using the hires spectrograph on the keck i telescope. kodiaq dr1 consists of a fully reduced sample of 170 quasars at 0.29\lt {z}{em}\lt 5.29 observed with hires at high resolution (36,000 ≤ r ≤ 103,000) between 2004 and 2012. dr1 contains 247 spectra available in continuum normalized form, representing a sum total exposure time of ∼1.6 megaseconds. these coadded spectra arise from a total of 567 individual exposures of quasars taken from the keck observatory archive (koa) in raw form and uniformly processed using a publicly available hires data reduction package. dr1 is publicly available to the community, housed as a higher level science product at the koa. we will provide future data releases that make available additional quasars, including those with pre-2004 observations taken with the previous-generation hires detectors. | the first data release of the kodiaq survey |
we report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the sdss-iii baryon oscillation spectroscopic survey (boss). we adopted a methodology similar to that used in the sdss quasar lens search (sqls). in addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ( ≲ 2 arcsec) confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. the newly discovered quasar lens system, sdss j1452+4224 at zs ≈ 4.8 is one of the highest redshift multiply imaged quasars found to date. furthermore, we have over 50 good lens candidates yet to be followed up. owing to the heterogeneous selection of boss quasars, the lens sample presented here does not have a well-defined selection function. | the sdss-iii boss quasar lens survey: discovery of 13 gravitationally lensed quasars |
we present qsfit (quasar spectral fitting package), a new software package to automatically perform the analysis of active galactic nuclei (agns) optical spectra. the software provides luminosity estimates for the agn continuum, the balmer continuum, both optical and ultraviolet iron blended complex, host galaxy and emission lines, as well as width, velocity offset and equivalent width of 20 emission lines. improving on a number of previous studies on agn spectral analysis, qsfit fits all the components simultaneously, using an agn continuum model which extends over the entire available spectrum, and is thus a probe of the actual agn continuum whose estimates are scarcely influenced by localized features (e.g. emission lines) in the spectrum. we used qsfit to analyse 71 251 optical spectra of type 1 agn at z < 2 (obtained by the sloan digital sky survey, sdss) and to produce a publicly available catalogue of agn spectral properties. such catalogue allowed us (for the first time) to estimate the agn continuum slope and the balmer continuum luminosity on a very large sample, and to show that there is no evident correlation between these quantities the redshift. all data in the catalogue, the plots with best-fitting model and residuals, and the idl code we used to perform the analysis, are available on a dedicated website. the whole fitting process is customizable for specific needs, and can be extended to analyse spectra from other data sources. the ultimate purpose of qsfit is to allow astronomers to run standardized recipes to analyse the agn data, in a simple, replicable and shareable way. | qsfit: automatic analysis of optical agn spectra |
we study the multiphase feedback processes in the central ∼3 kpc of the barred seyfert 2 galaxy ngc 5643. we used observations of the cold molecular gas (alma co(2-1) transition) and ionized gas (muse ifu optical emission lines). we studied different regions along the outflow zone, which extends out to ∼2.3 kpc in the same direction (east-west) as the radio jet, as well as nuclear and circumnuclear regions in the host galaxy disk. the co(2-1) line profiles of regions in the outflow and spiral arms show two or more different velocity components: one associated with the host galaxy rotation, and the others with out- or inflowing material. in the outflow region, the [o iii]λ5007 å emission lines have two or more components: the narrow component traces rotation of the gas in the disk, and the others are related to the ionized outflow. the deprojected outflowing velocities of the cold molecular gas (median vcentral ∼ 189 km s-1) are generally lower than those of the outflowing ionized gas, which reach deprojected velocities of up to 750 km s-1 close to the active galactic nucleus (agn), and their spatial profiles follow those of the ionized phase. this suggests that the outflowing molecular gas in the galaxy disk is being entrained by the agn wind. we derive molecular and ionized outflow masses of ∼5.2 × 107 m⊙ (αcogalactic) and 8.5 × 104 m⊙ and molecular and ionized outflow mass rates of ∼51 m⊙ yr-1 (αcogalactic) and 0.14 m⊙ yr-1, respectively. this means that the molecular phase dominates the outflow mass and outflow mass rate, while the kinetic power and momentum of the outflow are similar in both phases. however, the wind momentum loads (ṗout/ṗagn) for the molecular and ionized outflow phases are ∼27-5 (αcogalactic and αcoulirgs) and < 1, which suggests that the molecular phase is not momentum conserving, but the ionized phase most certainly is. the molecular gas content (meast ∼ 1.5 × 107 m⊙; αcogalactic) of the eastern spiral arm is approximately 50-70% of the content of the western one. we interpret this as destruction or clearing of the molecular gas produced by the agn wind impacting in the eastern side of the host galaxy (negative feedback process). the increase in molecular phase momentum implies that part of the kinetic energy from the agn wind is transmitted to the molecular outflow. this suggests that in seyfert-like agn such as ngc 5643, the radiative or quasar and the kinetic or radio agn feedback modes coexist and may shape the host galaxies even at kiloparsec scales through both positive and (mild) negative feedback. | multiphase feedback processes in the sy2 galaxy ngc 5643 |
the first generation of galaxies is expected to form in minihaloes, accreting gas through h2 cooling, and possessing unique properties. although unlikely to be directly detected in uv/infrared surveys, the radiation from these molecular-cooling galaxies (mcgs) could leave an imprint in the 21-cm signal from the cosmic dawn. here, we quantify their detectability with upcoming radio interferometers. we generate mock 21-cm power spectra using a model for both mcgs as well as more massive, atomic-cooling galaxies, allowing both populations to have different properties and scaling relations. the galaxy parameters are chosen so as to be consistent with: (i) high-redshift uv luminosity functions; (ii) the upper limit on the neutral fraction from qso spectra; (iii) the thomson scattering optical depth to the cmb; and (iv) the timing of the recent putative edges detection. the latter implies a significant contribution of mcgs to the cosmic dawn, if confirmed to be cosmological. we then perform bayesian inference on two models including and ignoring mcg contributions. comparing their bayesian evidences, we find a strong preference for the model including mcgs, despite the fact that it has more free parameters. this suggests that if mcgs indeed play a significant role in the cosmic dawn, it should be possible to infer their properties from upcoming 21-cm power spectra. our study illustrates how these observations can discriminate among uncertain galaxy formation models with varying complexities, by maximizing the bayesian evidence. | a tale of two sites - ii. inferring the properties of minihalo-hosted galaxies with upcoming 21-cm interferometers |
context. agn outflows are thought to influence the evolution of their host galaxies and of super massive black holes. our deep multiwavelength campaign on ngc 5548 has revealed a new, unusually strong x-ray obscuration, accompanied by broad uv absorption troughs observed for the first time in this object. the x-ray obscuration caused a dramatic decrease in the incident ionizing flux on the outflow that produces the long-studied narrow uv absorption lines in this agn. the resulting data allowed us to construct a comprehensive physical, spatial, and temporal picture for this enduring agn wind.aims: we aim to determine the distance of the narrow uv outflow components from the central source, their total column-density, and the mechanism responsible for their observed absorption variability.methods: we study the uv spectra acquired during the campaign, as well as from four previous epochs (1998-2011). our main analysis tools are ionic column-density extraction techniques, photoionization models based on the code cloudy, and collisional excitation simulations.results: a simple model based on a fixed total column-density absorber, reacting to changes in ionizing illumination, matches the very different ionization states seen in five spectroscopic epochs spanning 16 years. the main component of the enduring outflow is situated at 3.5 ± 1.1 pc from the central source, and its distance and number density are similar to those of the narrow-emitting-line region in this object. three other components are situated between 5-70 pc and two are farther than 100 pc. the wealth of observational constraints and the anti-correlation between the observed x-ray and uv flux in the 2002 and 2013 epochs make our physical model a leading contender for interpreting trough variability data of quasar outflows.conclusions: this campaign, in combination with prior uv and x-ray data, yields the first simple model that can explain the physical characteristics and the substantial variability observed in an agn outflow. appendix a is available in electronic form at http://www.aanda.org | anatomy of the agn in ngc 5548. ii. the spatial, temporal, and physical nature of the outflow from hst/cos observations |
we report on the search for galaxies in the proximity of two very metal-poor gas clouds at z ∼ 3 towards the quasar q0956+122. with a 5-hour multi-unit spectroscopic explorer (muse) integration in a ∼500 × 500 kpc2 region centred at the quasar position, we achieve a ≥80 per cent complete spectroscopic survey of continuum-detected galaxies with mr ≤ 25 mag and lyα emitters with luminosity llyα ≥ 3 × 1041 erg s- 1. we do not identify galaxies at the redshift of a z ∼ 3.2 lyman limit system (lls) with log z/z⊙ = -3.35 ± 0.05, placing this gas cloud in the intergalactic medium or circumgalactic medium of a galaxy below our sensitivity limits. conversely, we detect five lyα emitters at the redshift of a pristine z ∼ 3.1 lls with log z/z⊙ ≤ -3.8, while ∼0.4 sources were expected given the z ∼ 3 lyα luminosity function. both this high detection rate and the fact that at least three emitters appear aligned in projection with the lls suggest that this pristine cloud is tracing a gas filament that is feeding one or multiple galaxies. our observations uncover two different environments for metal-poor llss, implying a complex link between these absorbers and galaxy haloes, which ongoing muse surveys will soon explore in detail. moreover, in agreement with recent muse observations, we detected a ∼ 90 kpc lyα nebula at the quasar redshift and three lyα emitters reminiscent of a `dark galaxy' population. | muse searches for galaxies near very metal-poor gas clouds at z ∼ 3: new constraints for cold accretion models |
we present a detailed analysis of a large-scale galactic outflow in the circumgalactic medium of a massive ({m}{{h}}∼ {10}12.5 {m}⊙ ), star-forming (∼ 6.9 {m}⊙yr-1), sub-l* (∼ 0.5{l}b*) galaxy at z = 0.39853 that exhibits a wealth of metal-line absorption in the spectra of the background quasar q 0122-003 at an impact parameter of 163 kpc. the galaxy inclination angle (i=63^\circ ) and the azimuthal angle ({{φ }}=73^\circ ) imply that the qso sightline is passing through the projected minor-axis of the galaxy. the absorption system shows a multiphase, multicomponent structure with ultra-strong, wide velocity spread {{o}} {{vi}} ({log}n=15.16+/- 0.04, {{δ }}{v}90 = 419 km s-1) and {{n}} {{v}} ({log}n=14.69+/- 0.07, {{δ }}{v}90 = 285 km s-1) lines that are extremely rare in the literature. the highly ionized absorption components are well explained as arising in a low density (∼ {10}-4.2 cm-3), diffuse (∼10 kpc), cool (∼104 k) photoionized gas with a super-solar metallicity ([{{x}}/{{h}}]≳ 0.3). from the observed narrowness of the lyβ profile, the non-detection of {{s}} {{iv}} absorption, and the presence of strong {{c}} {{iv}} absorption in the low-resolution fos spectrum, we rule out equilibrium/non-equilibrium collisional ionization models. the low-ionization photoionized gas with a density of ∼ {10}-2.5 cm-3 and a metallicity of [{{x}}/{{h}}]≳ -1.4 is possibly tracing recycled halo gas. we estimate an outflow mass of ∼ 2× {10}10 {m}⊙ , a mass-flow rate of ∼ 54 {m}⊙{{yr}}-1, a kinetic luminosity of ∼ 9× {10}41 erg s-1, and a mass loading factor of ∼8 for the outflowing high-ionization gas. these are consistent with the properties of “down-the-barrel” outflows from infrared-luminous starbursts as studied by rupke et al. such powerful, large-scale, metal-rich outflows are the primary means of sufficient mechanical and chemical feedback as invoked in theoretical models of galaxy formation and evolution. | an extreme metallicity, large-scale outflow from a star-forming galaxy at z ~ 0.4 |
most active galactic nuclei (agns) are radio quiet, and the origin of their radio emission is not well understood. one hypothesis is that this radio emission is a byproduct of quasar-driven winds. in this paper, we present the radio properties of 108 extremely red quasars (erqs) at z = 2-4. erqs are among the most luminous quasars (lbol ∼ 1047-48 erg s-1) in the universe, with signatures of extreme (≫1000 km s-1) outflows in their [o iii]λ5007 å emission, making them the best subjects to seek the connection between radio and outflow activities. all erqs but one are unresolved in the radio on ∼10 kpc scales, and the median radio luminosity of erqs is νlν[6 ghz] = 1041.0 erg s-1, in the radio-quiet regime, but 1-2 orders of magnitude higher than that of other quasar samples. the radio spectra are steep, with a mean spectral index <α> = -1.0. in addition, erqs neatly follow the extrapolation of the low-redshift correlation between radio luminosity and the velocity dispersion of [o iii]-emitting ionized gas. uncollimated winds, with a power of one per cent of the bolometric luminosity, can account for all these observations. such winds would interact with and shock the gas around the quasar and in the host galaxy, resulting in acceleration of relativistic particles and the consequent synchrotron emission observed in the radio. our observations support the picture in which erqs are signposts of extremely powerful episodes of quasar feedback, and quasar-driven winds as a contributor of the radio emission in the intermediate regime of radio luminosity νlν = 1039-1042 erg s-1. | winds as the origin of radio emission in z = 2.5 radio-quiet extremely red quasars |
the origin of the radio emission in radio-quiet (rq) quasars is not established yet. important hints can be provided by the spectral slope, and its relation to other emission properties. we compiled the highest resolution 5 and 8.4 ghz very large array observations available of the rq optically selected palomar-green (pg) quasars at z < 0.5. we derive the 5-8.4 ghz spectral slope, αr, for 25 of the complete and well-studied sample of 71 rq pg quasars. we find a highly significant correlation of αr with l/ledd, where high l/ledd(>0.3) quasars have a steep slope (αr < -0.5), indicative of an optically thin synchrotron source. in contrast, lower l/ledd(<0.3) quasars generally have a flat slope (αr > -0.5), indicative of a compact optically thick synchrotron source. flat αr quasars also have a low fe ii/hβ line ratio, and a flat soft x-ray slope. the 16 radio loud (rl) pgs do not follow the rq quasar set of correlations, and their αr is set by mbh, suggesting that the radio emission mechanisms in rl and rq quasars are different. a possible interpretation is that high l/ledd rq quasars produce a strong outflow and an associated optically thin synchrotron emission. in lower l/ledd rq quasars, the strong outflow is missing, and only a compact optically thick radio source remains, possibly associated with the accretion disc coronal emission. a systematic study of rq quasars at higher frequencies, and higher resolution, can test whether a compact flat source indeed resides in the cores of all rq quasars, and allows the exploration of its relation with the coronal x-ray emission. | what drives the radio slopes in radio-quiet quasars? |
off-nucleus active galactic nuclei (agn) can be signposts of inspiraling supermassive black holes (smbhs) on galactic scales, or accreting smbhs recoiling after the coalescence of an smbh binary or slingshot from three-body interactions. because of the stochastic variability of agn, the measured photocenter of an unresolved agn-host system will display astrometric jitter that depends on the off-nucleus distance of the agn, the total photometric variability of the system, and the agn-host contrast. here we use the precision astrometry from gaia dr2 to constrain the off-nucleus population of a low-redshift (0.3 < z < 0.8) sample of unobscured broad-line agn drawn from the sloan digital sky survey with significant host contribution and photometric variability. we find that gaia dr2 already provides strong constraints on the projected off-nucleus distance in the sub-kiloparsec regime at these redshifts: 99%, 90%, and 40% of agn must be well centered to <1 kpc, <500 pc, and <100 pc, respectively. limiting the sample to the most variable subset constrains >99% of agn to be well centered below 500 pc. these results suggest that genuine off-nucleus agn (offset by > a few hundred parsecs) must be rare at low redshift. future gaia releases of time series of photocenter and flux measurements, improved treatments for extended sources, and longer baselines will further tighten these constraints, and enable a systematic full-sky search for rare off-nucleus agn on ∼10-1000 pc scales. | varstrometry for off-nucleus and dual sub-kpc agn (vodka): how well centered are low-z agn? |
the 4most cosmology redshift survey (crs) will perform stringent cosmological tests via spectroscopic clustering measurements that will complement the best lensing, cosmic microwave background and other surveys in the southern hemisphere. the combination of carefully selected samples of bright galaxies, luminous red galaxies, emission-line galaxies and quasars, totalling about 8 million objects over the redshift range z = 0.15 to 3.5, will allow definitive tests of gravitational physics. many key science questions will be addressed by combining crs spectra of these targets with data from current or future facilities such as the large synoptic survey telescope, the square kilometre array and the euclid mission. | 4most consortium survey 8: cosmology redshift survey (crs) |
here we present the spectropolarimetric observations of a sample of 30 type 1 active galactic nuclei (agns) and an analysis of the observed polarization in these agns. the observations have been performed with the 6 m telescope of sao ras using the modified scorpio-2 spectropolarimeter. we measured the stokes parameters for the continuum and the broad h α line and obtained the values of polarization degree and the angle of polarization. we found that equatorial scattering is dominant polarization mechanism in the sample that allows us to use the observed polarization in the broad lines for determination of the central black hole (bh) masses and characteristics (the inclination and emissivity) of the broad-line region (blr). we demonstrated that the recently proposed method of afanasiev & popović (2015) for bh mass measurement gives accurate bh masses that are in a good correlation with the stellar velocity dispersion, and consequently, the masses determined by the polarization method can be used with calibration purposes. additionally we found that the blr in the sample of 30 agns has an averaged inclination of 35°±9° (mostly between 20° and 40°) and emissivity α ∼ -0.57 that is more flat than one expected for the classical accretion disc α ∼ -0.75. | spectropolarimetry of seyfert 1 galaxies with equatorial scattering: black hole masses and broad-line region characteristics |
we present a markov chain monte carlo (mcmc)-based parameter estimation package, cosmoreionmc, to jointly constrain cosmological parameters of the lambda cold dark matter (λcdm) model and the astrophysical parameters related to hydrogen reionization. the package is based on a previously developed physically motivated semi-analytical model for reionization, a similar semi-analytical model for computing the global 21 cm signal during the cosmic dawn and using an appropriately modified version of the publicly available camb for computing the cmb anisotropies. these calculations are then coupled to an mcmc ensemble sampler emcee to compute the posterior distributions of the model parameter. the model has 12 free parameters in total: five cosmological and seven related to the stellar populations. we constrain the parameters by matching the theoretical predictions with cmb data from planck, observations related to the quasar absorption spectra, and, for the first time, the global 21 cm signal from edges. we find that incorporating the quasar spectra data in the analysis tightens the bounds on the electron scattering optical depth τ and consequently the normalization as of the primordial matter power spectrum (or equivalently σ8). furthermore, when we include the edges data in the analysis, we find that an early population of metal-free stars with efficient radio emission is necessary to match the absorption amplitude. the cosmoreionmc package should have interesting future applications, e.g. probing non-standard extensions to the λcdm model. | cosmoreionmc: a package for estimating cosmological and astrophysical parameters using cmb, lyman-α absorption, and global 21 cm data |
the epoch of reionization (eor) depends on the complex astrophysics governing the birth and evolution of the first galaxies and structures in the intergalactic medium. eor models rely on cosmic microwave background (cmb) observations, and in particular the large-scale e-mode polarization power spectra (ee ps), to help constrain their highly uncertain parameters. however, rather than directly forward-modelling the ee ps, most eor models are constrained using a summary statistic - the thompson scattering optical depth, τe. compressing cmb observations to τe requires adopting a basis set for the eor history. the common choice is the unphysical, redshift-symmetric hyperbolic tangent (tanh) function, which differs in shape from physical eor models based on hierarchical structure formation. combining public eor and cmb codes, 21cmfast and class, here we quantify how inference using the τe summary statistic impacts the resulting constraints on galaxy properties and eor histories. using the last planck 2018 data release, we show that the marginalized constraints on the eor history are more sensitive to the choice of the basis set (tanh versus physical model) than to the cmb likelihood statistic (τe versus ps). for example, eor histories implied by the growth of structure show a small tail of partial reionization extending to higher redshifts. however, biases in inference using τe are negligible for the planck 2018 data. using eor constraints from high-redshift observations including the quasar dark fraction, galaxy uv luminosity functions, and cmb ee ps, our physical model recovers $\tau _\mathrm{ e} = 0.0569_{-0.0066}^{+0.0081}$ . | reionization inference from the cmb optical depth and e-mode polarization power spectra |
we study the mass assembly and spin evolution of supermassive black holes (bhs) across cosmic time as well as the impact of gravitational recoil on the population of nuclear and wandering bhs (wbhs) by using the semi-analytical model l-galaxies run on top of millennium merger trees. we track spin changes that bhs experience during both coalescence events and gas accretion phases. for the latter, we assume that spin changes are coupled with the bulge assembly. this assumption leads to predictions for the median spin values of z = 0 bhs that depend on whether they are hosted by pseudo-bulges, classical bulges or ellipticals, being $\overline{a} \sim 0.9$ , 0.7 and 0.4, respectively. the outcomes of the model display a good consistency with $z \le 4$ quasar luminosity functions and the $z = 0$ bh mass function, spin values, and bh correlation. regarding the wbhs, we assume that they can originate from both the disruption of satellite galaxies (orphan wbh) and ejections due to gravitational recoils (ejected wbh). the model points to a number density of wbhs that increases with decreasing redshift, although this population is always $\rm {\sim}2\, dex$ smaller than the one of nuclear bhs. at all redshifts, wbhs are typically hosted in $\rm {\it m}_{halo} \gtrsim 10^{13} \, m_{\odot }$ and $\rm {\it m}_{stellar} \gtrsim 10^{10} \, m_{\odot }$ , being orphan wbhs the dominant type. besides, independently of redshift and halo mass, ejected wbhs inhabit the central regions ( ${\lesssim}\rm 0.3{\it r}_{200}$ ) of the host dm halo, while orphan wbh linger at larger scales ( ${\gtrsim}\rm 0.5{\it r}_{200}$ ). finally, we find that gravitational recoils cause a progressive depletion of nuclear bhs with decreasing redshift and stellar mass. moreover, ejection events lead to changes in the predicted local bh-bulge relation, in particular for bhs in pseudo-bulges, for which the relation is flattened at $\rm {\it m}_{bulge} \gt 10^{10.2}\, m_{\odot }$ and the scatter increase up to ${\sim}\rm 3\, dex$ . | from galactic nuclei to the halo outskirts: tracing supermassive black holes across cosmic history and environments |
we have recently used the faint images of the radio sky at twenty-centimeters (first) survey to show that red quasars have fundamentally different radio properties to typical blue quasars: a significant (factor ≈3) enhancement in the radio-detection fraction, which arises from systems around the radio-quiet threshold with compact (<5 arcsec) radio morphologies. to gain greater insight into these physical differences, here we use the dr14 sloan digital sky survey (sdss) and more sensitive, higher resolution radio data from the very large array (vla) stripe 82 (s82) and vla-cosmos 3 ghz (c3ghz) surveys. with the s82 data, we perform morphological analyses at a resolution and depth three times that of the first radio survey, and confirm an enhancement in radio-faint and compact red quasars over typical quasars; we now also find tentative evidence for an enhancement in red quasars with slightly extended radio structures (16-43 kpc at z = 1.5). these analyses are complemented by c3ghz, which is deep enough to detect radio emission from star-formation processes. from our data we find that the radio enhancement from red quasars is due to agn activity on compact scales (≲43 kpc) for radio-intermediate-radio-quiet sources (-5 < $\mathcal {r}$ < -3.4, where $\mathcal {r}$ = $l_{\rm{1.4\,ghz}}/l_{6\mu\text{m}}$ ), which decreases at $\mathcal {r}$ < -5 as the radio emission from star-formation starts to dilute the agn component. overall our results argue against a simple orientation scenario and are consistent with red quasars representing a younger, earlier phase in the overall evolution of quasars. | fundamental differences in the radio properties of red and blue quasars: enhanced compact agn emission in red quasars |
quasars whose broad emission lines show temporal, bulk radial velocity (rv) shifts have been proposed as candidate sub-parsec (sub-pc), binary supermassive black holes (bsbhs). we identified a sample of 16 bsbh candidates based on two-epoch spectroscopy among 52 quasars with significant rv shifts over a few rest-frame years. the candidates showed consistent velocity shifts independently measured from two broad lines (hβ and hα or mg ii) without significant changes in the broad-line profiles. here in the third paper of the series, we present further third- and fourth-epoch spectroscopy for 12 of the 16 candidates for continued rv tests, spanning ∼5-15 yr in the quasars' rest frames. cross-correlation analysis of the broad hβ calibrated against [o iii] λ5007 suggests that five of the 12 quasars remain valid as bsbh candidates. they show broad hβ rv curves that are consistent with binary orbital motion without significant changes in the broad-line profiles. their broad hα (or mg ii) lines display rv shifts that are either consistent with or smaller than those seen in broad hβ. the rv shifts can be explained by an ∼0.05-0.1 pc bsbh with an orbital period of ∼40-130 yr, assuming a mass ratio of 0.5-2 and a circular orbit. however, the parameters are not well constrained given the few epochs that sample only a small portion of the hypothesized binary orbital cycle. the apparent occurrence rate of sub-pc bsbhs is ≲13 ± 5 per cent among all sdss quasars, with no significant difference in the subsets with and without single-epoch broad-line velocity offsets. dedicated long-term spectroscopic monitoring is still needed to further confirm or reject these bsbh candidates. | constraining sub-parsec binary supermassive black holes in quasars with multi-epoch spectroscopy - iii. candidates from continued radial velocity tests |
in this paper, the multiwavelength data from radio to x-ray bands for 2709 blazars in the 4fgl-dr3 catalog are compiled to calculate their spectral energy distributions using a parabolic equation $\mathrm{log}(\nu {f}_{\nu })={p}_{1}{\left(\mathrm{log}\nu -{p}_{2}\right)}^{2}+{p}_{3}$ . some important parameters including spectral curvature (p 1), synchrotron peak frequency (p 2, $\mathrm{log}{\nu }_{{\rm{p}}}$ ), and peak luminosity ( $\mathrm{log}{l}_{{\rm{p}}}$ ) are obtained. based on those parameters, we discussed the classification of blazars using the "bayesian classification" and investigated some mutual correlations. we came to the following results. (1) based on the bayesian classification of synchrotron peak frequencies, the 2709 blazars can be classified into three subclasses, i.e., $\mathrm{log}({\nu }_{{\rm{p}}}/\mathrm{hz})\lt 13.7$ for low synchrotron peak blazars (lsps), $13.7\lt \mathrm{log}({\nu }_{{\rm{p}}}/\mathrm{hz})\lt 14.9$ for intermediate synchrotron peak blazars (isps), and $\mathrm{log}({\nu }_{{\rm{p}}}/\mathrm{hz})\gt 14.9$ for high synchrotron peak blazars (hsps), and there are 820 hsps, 750 isps, and 1139 lsps. (2) the γ-ray emission has the closest relationship with radio emission, followed by optical emission, while the weakest relationship is that with x-ray emission. the γ-ray luminosity is also correlated with the synchrotron peak luminosity. (3) there are strong positive correlations between the curvature (1/∣p 1∣) and the peak frequency ( $\mathrm{log}{\nu }_{{\rm{p}}}$ ) for all subclasses (fsrqs, (high, intermediate, and low) bl lacertae objects). for different subclasses, the correlation slopes are different, which implies that there are different acceleration mechanisms and emission processes for different subclasses of blazars. | the spectral energy distributions for 4fgl blazars |
the vera c. rubin observatory's legacy survey of space and time (lsst) will detect an unprecedentedly large sample of actively accreting supermassive black holes with typical accretion disk (ad) sizes of a few light days. this brings us to face challenges in the reverberation mapping (rm) measurement of ad sizes in active galactic nuclei using interband continuum delays. we examine the effect of lsst cadence strategies on ad rm using our metric agn_timelagmetric. it accounts for redshift, cadence, the magnitude limit, and magnitude corrections for dust extinction. running our metric on different lsst cadence strategies, we produce an atlas of the performance estimations for lsst photometric rm measurements. we provide an upper limit on the estimated number of quasars for which the ad time lag can be computed within 0 < z < 7 using the features of our metric. we forecast that the total counts of such objects will increase as the mean sampling rate of the survey decreases. the ad time lag measurements are expected for >1000 sources in each deep drilling field (ddf; (10 deg2)) in any filter, with the redshift distribution of these sources peaking at z ≈ 1. we find the lsst observation strategies with a good cadence (≲5 days) and a long cumulative season (~9 yr), as proposed for lsst ddf, are favored for the ad size measurement. we create synthetic lsst light curves for the most suitable ddf cadences and determine rm time lags to demonstrate the impact of the best cadences based on the proposed metric. | the lsst era of supermassive black hole accretion disk reverberation mapping |
we present the discovery of pso j083.8371+11.8482, a weak emission line quasar with extreme star formation rate at z = 6.3401. this quasar was selected from pan-starrs1, uhs, and unwise photometric data. gemini/gnirs spectroscopy follow-up indicates a mg ii-based black hole mass of ${m}_{\mathrm{bh}}=\left({2.0}_{-0.4}^{+0.7}\right)\times {10}^{9}$ m⊙ and an eddington ratio of ${l}_{\mathrm{bol}}/{l}_{\mathrm{edd}}={0.5}_{-0.2}^{+0.1}$ , in line with an actively accreting supermassive black hole (smbh) at z ≳ 6. hubble space telescope imaging sets strong constraint on lens boosting, showing no relevant effect on the apparent emission. the quasar is also observed as a pure point source with no additional emission component. the broad-line region (blr) emission is intrinsically weak and not likely caused by an intervening absorber. we found rest-frame equivalent widths of ew ${(\mathrm{ly}\alpha +{\rm{n}}{\rm\small{v}})}_{\mathrm{rest}}=5.7\pm 0.7\,\mathring{\rm a} $ , ew ${({\rm{c}}{\rm\small{iv}})}_{\mathrm{rest}}\leqslant 5.8$ š(3σ upper limit), and ew ${(\mathrm{mg}{\rm\small{ii}})}_{\mathrm{rest}}=8.7\pm 0.7\,\mathring{\rm a} $ . a small proximity zone size ( ${r}_{{\rm{p}}}=1.2\pm 0.4$ pmpc) indicates a lifetime of only ${t}_{{\rm{q}}}={10}^{3.4\pm 0.7}$ years from the last quasar phase ignition. alma shows extended [c ii] emission with a mild velocity gradient. the inferred far-infrared luminosity ( ${l}_{\mathrm{fir}}=(1.2\pm 0.1)\times {10}^{13}\,{l}_{\odot }$ ) is one of the highest among all known quasar hosts at z ≳ 6. dust and [c ii] emissions put a constraint on the star formation rate of sfr = 900- $4900\,{m}_{\odot }\,{\mathrm{yr}}^{-1}$ , similar to that of a hyperluminous infrared galaxy. considering the observed quasar lifetime and blr formation timescale, the weak-line profile in the quasar spectrum is most likely caused by a blr that is not yet fully formed rather than by continuum boosting by gravitational lensing or a soft continuum due to super-eddington accretion. | probing the nature of high-redshift weak emission line quasars: a young quasar with a starburst host galaxy |
the statistics of galactic-scale quasar pairs can elucidate our understanding of the dynamical evolution of supermassive black hole (smbh) pairs, the duty cycles of quasar activity in mergers, or even the nature of dark matter, but they have been challenging to measure at cosmic noon, the prime epoch of massive galaxy and smbh formation. here we measure a double quasar fraction of ~6.2 ± 0.5 × 10-4 integrated over ~0.″3-3″ separations (projected physical separations of ~3-30 kpc at z ~ 2) in luminous (l bol > 1045.8 erg s-1) unobscured quasars at 1.5 < z < 3.5 using gaia edr3-resolved pairs around sdss dr16 quasars. the measurement was based on a sample of 60 gaia-resolved double quasars (out of 487 gaia pairs dominated by quasar+star superpositions) at these separations, corrected for pair completeness in gaia, which we quantify as functions of pair separation, magnitude of the primary, and magnitude contrast. the double quasar fraction increases toward smaller separations by a factor of ~5 over these scales. the division between physical quasar pairs and lensed quasars in our sample is currently unknown, requiring dedicated follow-up observations (in particular, deep, subarcsecond-resolution ir imaging for the closest pairs). intriguingly, at this point, the observed pair statistics are in rough agreement with theoretical predictions both for the lensed quasar population in mock catalogs and for dual quasars in cosmological hydrodynamic simulations. upcoming wide-field imaging/spectroscopic space missions such as euclid, csst, and roman, combined with targeted follow-up observations, will conclusively measure the abundances and host galaxy properties of galactic-scale quasar pairs, offset agns, and subarcsecond lensed quasars across cosmic time. | statistics of galactic-scale quasar pairs at cosmic noon |
the study of the properties of galaxies in the first billion years after the big bang is one of the major topics of current astrophysics. optical and near-infrared spectroscopy of the afterglows of long gamma-ray bursts (grbs) provides a powerful diagnostic tool to probe the interstellar medium (ism) of their host galaxies and foreground absorbers, even up to the highest redshifts. we analyze the vlt/x-shooter afterglow spectrum of grb 210905a, triggered by the neil gehrels swift observatory, and detect neutral hydrogen, low-ionization, high-ionization, and fine-structure absorption lines from a complex system at z = 6.3118, which we associate with the grb host galaxy. we use them to study the ism properties of the host system, revealing the metallicity, kinematics, and chemical abundance pattern of its gas along the grb line of sight. we also detect absorption lines from at least two foreground absorbers at z = 5.7390 and z = 2.8296. the total metallicity of the z ∼ 6.3 system is [m/h]tot = −1.72 ± 0.13, after correcting for dust depletion and taking α-element enhancement into account, as suggested by our analysis. this is consistent with the values found for the other two grbs at z ∼ 6 with spectroscopic data showing metal absorption lines (grb 050904 and grb 130606a), and it is at the higher end of the metallicity distribution of quasar damped lyman-α systems (qso-dlas) extrapolated to such a high redshift. in addition, we determine the overall amount of dust and dust-to-metal mass ratio (dtm) ([zn/fe]fit = 0.33 ± 0.09 and dtm = 0.18 ± 0.03). we find indications of nucleosynthesis due to massive stars and, for some of the components of the gas clouds, we find evidence of peculiar nucleosynthesis, with an overabundance of aluminum (as also found for grb 130606a). from the analysis of fine-structure lines, we determine distances of several kiloparsecs for the low-ionization gas clouds closest to the grb. those are farther distances than usually found for grb host absorption systems, possibly due to the very high number of ionizing photons produced by the grb that could ionize the line of sight up to several hundreds of parsecs. using the hst/f140w image of the grb field, we show the grb host galaxy (with a possible afterglow contamination) as well as multiple objects within 2″ from the grb position. we discuss the galaxy structure and kinematics that could explain our observations, also taking into account a tentative detection of lyman-α emission at z = 6.3449 (∼1200 km s−1 from the grb redshift in velocity space), and the observational properties of lyman-α emitters at very high redshift. this study shows the amazing potential of grbs to access detailed information on the properties (metal enrichment, gas kinematic, dust content, nucleosynthesis...) of very high-redshift galaxies, independently of the galaxy luminosity. deep spectroscopic observations with vlt/muse and jwst will offer the unique possibility of combining the information presented in this paper with the properties of the ionized gas, with the goal of better understanding how galaxies in the reionization era form and evolve. based on observations carried out under eso prog. id 106.21t6.010 and id 106.21t6.015 (pi: n. tanvir) with the x-shooter spectrograph installed at the cassegrain focus of the very large telescope (vlt), unit 3 - melipal, operated by the european southern observatory (eso) on cerro paranal, chile. partly based on observations with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by the association of universities for research in astronomy (aura). this observation is primarily associated with proposal go 16918, pi: n. tanvir. | dissecting the interstellar medium of a z = 6.3 galaxy. x-shooter spectroscopy and hst imaging of the afterglow and environment of the swift grb 210905a |
recent x-ray observations have revealed remarkable correlations between the masses of central supermassive black holes (smbhs) and the x-ray properties of the hot atmospheres permeating their host galaxies, thereby indicating the crucial role of the atmospheric gas in tracing smbh growth in the high-mass regime. we examine this topic theoretically using the illustristng cosmological simulations and provide insights to the nature of this smbh - gaseous halo connection. by carrying out a mock x-ray analysis for a mass-selected sample of tng100 simulated galaxies at $z$ = 0, we inspect the relationship between the masses of smbhs and the hot gas temperatures and luminosities at various spatial and halo scales - from galactic (∼re) to group/cluster scales (∼r500c). we find strong smbh-x-ray correlations mostly in quenched galaxies and find that the correlations become stronger and tighter at larger radii. critically, the x-ray temperature (kbtx) at large radii (r ≳ 5re) traces the smbh mass with a remarkably small scatter (∼0.2 dex). the relations emerging from illustristng are broadly consistent with those obtained from recent x-ray observations. overall, our analysis suggests that, within the framework of illustristng, the present-time mbh-kbtx correlations at the high-mass end (mbh ≳ 108m⊙) are fundamentally a reflection of the smbh mass-halo mass relation, which at such high masses is set by the hierarchical assembly of structures. the exact form, locus, and scatter of those scaling relations are, however, sensitive to feedback processes such as those driven by star formation and smbh activity. | correlations between supermassive black holes and hot gas atmospheres in illustristng and x-ray observations |
using moderate-resolution optical spectra from 58 background lyman-break galaxies and quasars at z∼ 2.3{{{--}}}3 within a 11.‧5 × 13.‧5 area of the cosmos field (∼ 1200 {{deg}}-2 projected area density or ∼ 2.4 {h}-1mpc mean transverse separation), we reconstruct a 3d tomographic map of the foreground lyα forest absorption at 2.2 < z < 2.5 with an effective smoothing scale of {ɛ }{{3d}}≈ 2.5 {h}-1mpc comoving. comparing with 61 coeval galaxies with spectroscopic redshifts in the same volume, we find that the galaxy positions are clearly biased toward regions with enhanced intergalactic medium (igm) absorption in the tomographic map. we find an extended igm overdensity with deep absorption troughs at z = 2.45 associated with a recently discovered galaxy protocluster at the same redshift. based on simulations matched to our data, we estimate the enclosed dark matter mass within this igm overdensity to be {m}{{dm}}(z=2.45)=(1.1+/- 0.6)× {10}14 {h}-1m⊙ , and argue based on this mass and absorption strength that it will form at least one z ∼ 0 galaxy cluster with m(z=0)=(3+/- 1.5)× {10}14 {h}-1{m}⊙ , although its elongated nature suggests that it will likely collapse into two separate clusters. we also point out a compact overdensity of six mosdef galaxies at z = 2.30 within a r∼ 1 {h}-1mpc radius and δz ∼ 0.006, which does not appear to have a large associated igm overdensity. these results demonstrate the potential of lyα forest tomography on larger volumes to study galaxy properties as a function of environment, as well as revealing the large-scale igm overdensities associated with protoclusters or other features of large-scale structure. | shadow of a colossus: a z = 2.44 galaxy protocluster detected in 3d lyα forest tomographic mapping of the cosmos field |
we analyze differences in positions of active galactic nuclei (agns) between gaia data release 2 and very long baseline interferometry (vlbi) and compare the significant vlbi-to-gaia offsets in more than 1000 objects with their jet directions. remarkably at least three-fourths of the significant offsets are confirmed to occur downstream or upstream of the jet representing a genuine astrophysical effect. introducing redshift and gaia color into analysis can help distinguish between the contribution of the host galaxy, jet, and accretion disk emission. we find that strong optical jet emission at least 20-50 pc long is required to explain the gaia positions located downstream from vlbi ones. offsets in the upstream direction of up to 2 mas are at least partly due to the dominant impact of the accretion disk on the gaia coordinates and by the effects of the parsec-scale radio jet. the host galaxy was found not to play an important role in the detected offsets. bl lacertae object and seyfert 2 galaxies are observationally confirmed to have a relatively weak disk and consequently downstream offsets. the disk emission drives upstream offsets in a significant fraction of quasars and seyfert 1 galaxies when it dominates over the jet in the optical band. the observed behavior of the different agn classes is consistent with the unified scheme assuming varying contribution of the obscuring dusty torus and jet beaming. | dissecting the agn disk-jet system with joint vlbi-gaia analysis |
based on constraints from big bang nucleosynthesis and the cosmic microwave background, the baryon content of the high-redshift universe can be precisely determined. however, at low redshift, about one-third of the baryons remain unaccounted for, which poses the long-standing missing baryon problem. the missing baryons are believed to reside in large-scale filaments in the form of warm-hot intergalactic medium (whim). in this work, we employ a novel stacking approach to explore the hot phases of the whim. specifically, we utilize the 470 ks chandra letg data of the luminous quasar, h 1821+643, along with previous measurements of uv absorption line systems and spectroscopic redshift measurements of galaxies toward the quasar’s sightline. we repeatedly blueshift and stack the x-ray spectrum of the quasar corresponding to the redshifts of the 17 absorption line systems. thus, we obtain a stacked spectrum with 8.0 ms total exposure, which allows us to probe x-ray absorption lines with unparalleled sensitivity. based on the stacked data, we detect an o vii absorption line that exhibits a gaussian line profile and is statistically significant at the 3.3σ level. since the redshifts of the uv absorption line systems were known a priori, this is the first definitive detection of an x-ray absorption line originating from the whim. the equivalent width of the o vii line is (4.1 ± 1.3) må, which corresponds to an o vii column density of (1.4+/- 0.4)× {10}15 {cm}}-2. we constrain the absorbing gas to have a density of {n}{{h}}=(1-2)× {10}-6 {cm}}-3 for a single whim filament. we derive {{{ω }}}{{b}}({{o}} {{vii}})=(0.0023+/- 0.0007){≤ft[{f}{{o}{{vii}}}z/{z}⊙ \right]}-1 for the cosmological mass density of o vii, assuming that all 17 systems contribute equally. | detection of the missing baryons toward the sightline of h1821+643 |
we investigate the large-scale structure of lyα emission intensity in the universe at redshifts z = 2-3.5 using cross-correlation techniques. our lyα emission samples are spectra of boss luminous red galaxies from data release 12 with the best-fitting model galaxies subtracted. we cross-correlate the residual flux in these spectra with boss quasars, and detect a positive signal on scales 1∼ 15 h^{-1} mpc. we identify and remove a source of contamination not previously accounted for, due to the effects of quasar clustering on cross-fibre light. corrected, our quasar - lyα emission cross-correlation is 50 per cent lower than that seen by croft et al. for dr10, but still significant. because only {∼ }3{{ per cent}} of space is within 15 h^{-1} mpc of a quasar, the result does not fully explore the global large-scale structure of lyα emission. to do this, we cross-correlate with the lyα forest. we find no signal in this case. the 95 per cent upper limit on the global lyα mean surface brightness from lyα emission - lyα forest cross-correlation is < μ _{α } > < 1.2 × 10^{-22} erg s^{-1} cm^{-2} å^{-1} arcsec^{-2}. this null result rules out the scenario where the observed quasar - lyα emission cross-correlation is primarily due to the large-scale structure of star-forming galaxies. taken in combination, our results suggest that lyα emitting galaxies contribute, but quasars dominate within 15 h^{-1} mpc. a simple model for lyα emission from quasars based on hydrodynamic simulations reproduces both the observed forest - lyα emission and quasar - lyα emission signals. the latter is also consistent with extrapolation of observations of fluorescent emission from smaller scales r<1 h^{-1} mpc. | intensity mapping with sdss/boss lyman-α emission, quasars, and their lyman-α forest |
in this paper, we present the long-term optical spectral monitoring of a changing-look active galactic nucleus (agn), ngc 3516, covering 22 yr (from 1996 to 2018). we explore a variability in the broad lines and continuum, finding that the continuum is changing by more than a factor of 2, while the broad lines are varying by more than a factor of 10. the minimum of activity is observed in 2014, when the broad lines almost disappeared. we confirm that ngc 3516 is a changing-look agn, and the absorption seen in the ultraviolet and x-ray may indicate that there is an obscuring region that is responsible for this. the line profiles are also changing. the mean profiles of the broad hα and hβ lines show a shoulder-like structure in the wings, and an enhanced peak, which could indicate a complex broad-line region. the rms profiles of both lines seem to have the same shape and width, of around 4200 km s-1, indicating practically the same kinematics in the hα and hβ emitting regions. measured time-lags between the continuum and hα and hβ broad-line variability are ∼15 and 17 d, respectively. in combination with the broad-line width, these measurements allow us to estimate the central black hole mass of ngc 3516. we find that the black hole mass is (4.73 ± 1.40) × 107m⊙ which is in agreement with previous estimates. | long-term optical spectral monitoring of a changing-look active galactic nucleus ngc 3516 - i. continuum and broad-line flux variability |
aims: the co-evolution of galaxies and supermassive black holes (smbhs) requires that some sort of feedback mechanism is operating during the active galactic nuclei (agn) phases. agn driven winds are the most likely candidates for such feedback mechanism, but direct observational evidence of their existence and of their effects on the host galaxies are still scarce and their physical origin is still hotly debated.methods: x-shooter observations of a sample of x-ray selected, obscured quasars at z ~ 1.5, selected on the basis of their observed red colors and x-ray-to-optical flux ratio, have shown the presence of outflowing ionized gas identified by broad [oiii] emission lines in 6 out of 8 objects, confirming the efficiency of the selection criteria. here we present slit-resolved spectroscopy for the two brightest sources, xid2028 and xid5321, to study the complex emission and absorption line kinematics.results: we detect outflow extended out to ~10 kpc from the central black hole, both as blueshifted and redshifted emission. interestingly, we also detect kpc scale outflows in the [oii] emission lines and in the neutral gas component, traced by the sodium d and magnesium absorption lines, confirming that a substantial amount of the outflowing mass is in the form of neutral gas.conclusions: the measured gas velocities and the outflow kinetic powers, inferred under reasonable assumptions on the geometry and physical properties of these two systems, favor an agn origin for the observed winds. | galaxy-wide outflows in z ~ 1.5 luminous obscured quasars revealed through near-ir slit-resolved spectroscopy |
we report a bimodality in the azimuthal angle (φ) distribution of gas around galaxies traced by o vi absorption. we present the mean φ probability distribution function of 29 hubble space telescope-imaged o vi absorbing (ew > 0.1 å) and 24 non-absorbing (ew < 0.1 å) isolated galaxies (0.08 \lt z \lt 0.67) within ∼200 kpc of background quasars. we show that equivalent width (ew) is anti-correlated with impact parameter and o vi covering fraction decreases from 80% within 50 kpc to 33% at 200 kpc. the presence of o vi absorption is azimuthally dependent and occurs between ±10°-20° of the galaxy projected major axis and within ±30° of the projected minor axis. we find higher ews along the projected minor axis with weaker ews along the project major axis. highly inclined galaxies have the lowest covering fractions due to minimized outflow/inflow cross-section geometry. absorbing galaxies also have bluer colors while non-absorbers have redder colors, suggesting that star formation is a key driver in the o vi detection rate. o vi surrounding blue galaxies exists primarily along the projected minor axis with wide opening angles while o vi surrounding red galaxies exists primarily along the projected major axis with smaller opening angles, which may explain why absorption around red galaxies is less frequently detected. our results are consistent with a circumgalactic medium (cgm) originating from major axis-fed inflows/recycled gas and from minor axis-driven outflows. non-detected o vi occurs between φ = 20°-60°, suggesting that o vi is not mixed throughout the cgm and remains confined within the outflows and the disk-plane. we find low o vi covering fractions within +/- 10^\circ of the projected major axis, suggesting that cool dense gas resides in a narrow planer geometry surrounded by diffuse o vi gas. | the azimuthal dependence of outflows and accretion detected using o vi absorption |
multiwavelength surveys covering large sky volumes are necessary to obtain an accurate census of rare objects such as high-luminosity and/or high-redshift active galactic nuclei (agns). stripe 82x is a 31.3 x-ray survey with chandra and xmm-newton observations overlapping the legacy sloan digital sky survey stripe 82 field, which has a rich investment of multiwavelength coverage from the ultraviolet to the radio. the wide-area nature of this survey presents new challenges for photometric redshifts for agns compared to previous work on narrow-deep fields because it probes different populations of objects that need to be identified and represented in the library of templates. here we present an updated x-ray plus multiwavelength matched catalog, including spitzer counterparts, and estimated photometric redshifts for 5961 (96% of a total of 6181) x-ray sources that have a normalized median absolute deviation, σnmad=0.06, and an outlier fraction, η = 13.7%. the populations found in this survey and the template libraries used for photometric redshifts provide important guiding principles for upcoming large-area surveys such as erosita and 3xmm (in x-ray) and the large synoptic survey telescope (optical). | agn populations in large-volume x-ray surveys: photometric redshifts and population types found in the stripe 82x survey |
context. over the past few years, on several occasions, large, continuous rotations of the electric vector position angle (evpa) of linearly polarized optical emission from blazars have been reported. these events are often coincident with high energy γ-ray flares and they have attracted considerable attention, since they could allow us to probe the magnetic field structure in the γ-ray emitting region of the jet. the flat-spectrum radio quasar 3c 279 is one of the most prominent examples showing this behaviour.aims: our goal is to study the observed evpa rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability.methods: we have combined multiple data sets of r-band photometry and optical polarimetry measurements of 3c 279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008-2012. several large evpa rotations are identified in the data. we introduce a quantitative measure for the evpa curve smoothness, which is then used to test a set of simple random walk polarization variability models against the data.results: 3c 279 shows different polarization variation characteristics during an optical low-flux state and a flaring state. the polarization variation during the flaring state, especially the smooth ~360° rotation of the evpa in mid-2011, is not consistent with the tested stochastic processes.conclusions: we conclude that, during the two different optical flux states, two different processes govern polarization variation, which is possibly a stochastic process during the low-brightness state and a deterministic process during the flaring activity. the measured and processed optical polarization and r-band photometry data are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/590/a10 | polarization angle swings in blazars: the case of 3c 279 |
the qubrics (quasars as bright beacons for cosmology in the southern hemisphere) survey aims at constructing a sample of the brightest quasars with $z \lower.5ex\hbox{$\,\, \buildrel\gt \over \sim \,\,$}2.5$, observable with facilities in the southern hemisphere. qubrics makes use of the available optical and ir wide-field surveys in the south and of machine learning techniques to produce thousands of bright quasar candidates of which only a few hundred have been confirmed with follow-up spectroscopy. taking advantage of the recent gaia data release 3, which contains 220 million low-resolution spectra, and of a newly developed spectral energy distribution fitting technique, designed to combine the photometric information with the gaia spectroscopy, it has been possible to measure 1672 new secure redshifts of qubrics candidates, with a typical uncertainty of σz = 0.02. this significant progress of qubrics brings it closer to (one of) its primary goals: providing a sample of bright quasars at redshift 2.5 < z < 5 to perform the sandage test of the cosmological redshift drift. a golden sample of seven quasars is presented that makes it possible to carry out this experiment in about 1500 h of observation in 25 yr, using the andes spectrograph at the 39m elt, a significant improvement with respect to previous estimates. | spectroscopy of qubrics quasar candidates: 1672 new redshifts and a golden sample for the sandage test of the redshift drift |
the flat-spectrum radio quasar cta 102 experienced a prolonged state of enhanced activity across the entire observed electromagnetic spectrum during 2016-2017, most pronounced during a major outburst between 2016 december and 2017 may. fermi-lat observed a flux of (2.2 ± 0.2) × 10-5 photons cm-2 s-1 at energies above 100 mev on 2017 april 19 during a single orbit. we report here the detection of significant (4.7σ) flux variations down to timescales of ∼5 minutes during this orbit. the measured variability timescale is much shorter than the light-travel time across the central black hole (∼70 minutes) indicating a very compact emission region within the jet, similar to that seen in ic 310, mrk 501, or pks 1222+21 from magic observations. this short-timescale variability is unexpected since the γ-ray spectrum shows no sign of attenuation due to pair creation in interactions with photons from the broad emission line region, and therefore must be assumed to originate far from the black hole. the observed fast variability could either indicate the dissipation of magnetic islands or protons in a collimated beam from the base of the jet encountering the turbulent plasma at the end of the magnetic nozzle. | short-timescale γ-ray variability in cta 102 |
the specifics of how galaxies form from, and are fuelled by, gas from the intergalactic medium remain uncertain. hydrodynamic simulations suggest that `cold accretion flows'--relatively cool (temperatures of the order of 104 kelvin), unshocked gas streaming along filaments of the cosmic web into dark-matter halos--are important. these flows are thought to deposit gas and angular momentum into the circumgalactic medium, creating disk- or ring-like structures that eventually coalesce into galaxies that form at filamentary intersections. recently, a large and luminous filament, consistent with such a cold accretion flow, was discovered near the quasi-stellar object qso um287 at redshift 2.279 using narrow-band imaging. unfortunately, imaging is not sufficient to constrain the physical characteristics of the filament, to determine its kinematics, to explain how it is linked to nearby sources, or to account for its unusual brightness, more than a factor of ten above what is expected for a filament. here we report a two-dimensional spectroscopic investigation of the emitting structure. we find that the brightest emission region is an extended rotating hydrogen disk with a velocity profile that is characteristic of gas in a dark-matter halo with a mass of 1013 solar masses. this giant protogalactic disk appears to be connected to a quiescent filament that may extend beyond the virial radius of the halo. the geometry is strongly suggestive of a cold accretion flow. | a giant protogalactic disk linked to the cosmic web |
upcoming ultrahigh power lasers at 10 pw level will make it possible to experimentally explore electron-positron (e-e+) pair cascades and subsequent relativistic e-e+ jets formation, which are supposed to occur in extreme astrophysical environments, such as black holes, pulsars, quasars and gamma-ray bursts. in the latter case it is a long-standing question as to how the relativistic jets are formed and what their temperatures and compositions are. here we report simulation results of pair cascades in two counter-propagating qed-strong laser fields. a scaling of qed cascade growth with laser intensity is found, showing clear cascade saturation above threshold intensity of 1024 w/cm2. qed cascade saturation leads to pair plasma cooling and longitudinal compression along the laser axis, resulting in the subsequent formation of relativistic dense e-e+ jets along transverse directions. such laser-driven qed cascade saturation may open up the opportunity to study energetic astrophysical phenomena in laboratory. | qed cascade saturation in extreme high fields |
recent measurements of the parameters of the concordance cosmology model ($\lambda$cdm) done in the low-redshift universe with supernovae ia/cepheids, and in the distant universe done with cosmic microwave background (cmb) imply different values for the hubble constant (67.4 $\pm$ 0.5 km s$^{-1}$ mpc$^{-1}$ from planck vs 74.03 $\pm$ 1.42 km s$^{-1}$ mpc$^{-1}$, riess et al. 2019). this hubble constant tension implies that either the systematic errors are underestimated, or the $\lambda$cdm does not represent well the observed expansion of the universe. since quasars - active galactic nuclei - can be observed in the nearby universe up to redshift z $\sim$ 7.5, they are suitable to estimate the cosmological properties in a large redshift range. our group develops two methods based on the observations of quasars in the late universe up to redshift z$\sim $4.5, with the objective to determine the expansion rate of the universe. these methods do not yet provide an independent measurement of the hubble constant since they do not have firm absolute calibration but they allow to test the $\lambda$cdm model, and so far no departures from this model were found. | dark energy constraintsfrom quasar observations |
we proposed a model-independent method to constrain cosmological parameters using the distance sum rule of the friedmann-lemaître-robertson-walker metric by combining the time delay distances and the comoving distances through a multi-messenger approach. the time delay distances are measured from lensed gravitational wave (gw) signals together with their corresponding electromagnetic wave (em) counterparts, while the comoving distances are obtained from a parameterized fitting approach with independent supernova observations. with a series of simulations based on the einstein telescope, large synoptic survey telescope, and the dark energy survey, we find that only 10 lensed gw+em systems can achieve the constraining power comparable to and even stronger than 300 lensed quasar systems due to the more precise time delay from lensed gw signals. specifically, the cosmological parameters can be constrained to k={0.01}-0.05+0.05 and {h}0={69.7}-0.35+0.35 (1σ).5 our results show that more precise time delay measurements could provide more stringent cosmological parameter values, and lensed gw+em systems therefore can be applied as a powerful tool in the future precision cosmology. | constraining cosmological parameters in the flrw metric with lensed gw+em signals |
theoretical models of galaxy formation suggest that the presence of an active galactic nucleus (agn) is required to regulate the growth of its host galaxy through feedback mechanisms, produced by, for example, agn-driven outflows. although many observational studies have revealed that such outflows are common both at low and high redshift, a comprehensive picture is still missing. in particular, the peak epoch of galaxy assembly (1 < z < 3) has been poorly explored so far, and current observations in this redshift range are mostly limited to targets with high chances to be in an outflowing phase. this paper introduces super (a sinfoni survey for unveiling the physics and effect of radiative feedback), an ongoing eso's vlt/sinfoni large programme. super will perform the first systematic investigation of ionized outflows in a sizeable and blindly-selected sample of 39 x-ray agn at z ∼ 2, which reaches high spatial resolutions (∼2 kpc) thanks to the adaptive optics-assisted ifs observations. the outflow morphology and star formation in the host galaxy will be mapped through the broad component of [o iii]λ5007 and the narrow component of hα emission lines. the main aim of our survey is to infer the impact of outflows on the on-going star formation and to link the outflow properties to a number of agn and host galaxy properties. we describe here the survey characteristics and goals, as well as the selection of the target sample. moreover, we present a full characterization of its multi-wavelength properties: we measure, via spectral energy distribution fitting of uv-to-fir photometry, stellar masses (4 × 109 - 2 × 1011 m⊙), star formation rates (25 - 680 m⊙ yr-1) and agn bolometric luminosities (2 × 1044 - 8 × 1047 erg s-1), along with obscuring column densities (up to 2 × 1024 cm-2) and luminosities in the hard 2 - 10 kev band (2 × 1043 - 6 × 1045 erg s-1) derived through x-ray spectral analysis. finally, we classify our agn as jetted or non-jetted according to their radio and fir emission. full table b.1 is only available in electronic form at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/620/a82 | super. i. toward an unbiased study of ionized outflows in z ∼ 2 active galactic nuclei: survey overview and sample characterization |
using parallaxes from gaia data release 2 (gaia dr2), we estimate the distance to the globular clusters 47 tuc and ngc 362, taking advantage of the background stars in the small magellanic cloud and quasars to account for various parallax systematics. we found the parallax to be dependent on the gaia dr2 g-band apparent magnitude for stars with 13 < g < 18, where brighter stars have a lower parallax zero point than fainter stars. the distance to 47 tuc was found to be 4.45 ± 0.01 ± 0.12 kpc, and for ngc 362 8.54 ± 0.20 ± 0.44 kpc, with random and systematic errors listed, respectively. this is the first time a precise distance measurement directly using parallaxes has been determined for either of these two globular clusters. | distances to the globular clusters 47 tucanae and ngc 362 using gaia dr2 parallaxes |
we report the discovery, spectroscopic confirmation, and first lens models of the first, strongly lensed quasars from a combined search in wise and gaia-dr1 over the des footprint. their einstein radii span a range between ≈2.0 arcsec and ≈0.4 arcsec. two of these (wgd2038-4008, ra = 20:38:02.65, dec. = -40:08:14.64; wgd2021-4115, ra = 20:21:39.45, dec. = -41:15:57.11) also have confirmed deflector redshifts. the four-image lens wgd2038-4008, with source and deflector redshifts s = 0.777 ± 0.001 and zl = 0.230 ± 0.002, respectively, has a deflector with radius reff ≈ 3.4 arcsec, stellar mass log (m_{⋆}/m_{⊙})=11.64^{+0.20}_{-0.43}, and extended isophotal shape variation. simple lens models yield einstein radii re = (1.30 ± 0.04) arcsec, axis ratio q = 0.75 ± 0.1 (compatible with that of the starlight) and considerable shear-ellipticity degeneracies. the two-image lens wgd2021-4115 has zs = 1.390 ± 0.001 and zl = 0.335 ± 0.002, and einstein radius re = (1.1 ± 0.1) arcsec, but higher-resolution imaging is needed to accurately separate the deflector and faint quasar image. analogous lens model degeneracies hold for the other six lenses (j0146-1133, j0150-4041, j0235-2433, j0245-0556, j0259-2338, and j0508-2748) shown in this paper. | des meets gaia: discovery of strongly lensed quasars from a multiplet search |
we review the reports of possible year-long quasi-periodicities of bl lac objects in the γ-ray and optical bands, and present a homogeneous time analysis of the light curves of pks2155-304, pg1553+113, and bl lac. based on results from a survey covering the entire fermi γ-ray sky we have estimated the fraction of possible quasi-periodic bl lac objects. we compared the cyclical behaviour in bl lac objects with that derived from the search of possible optical periodicities in quasars, and find that at z ≲ 1 the cosmic density of quasi-periodic bl lac objects is larger than that of quasi-periodic quasars. if the bl lac quasi-periodicities were due to a supermassive binary black hole (sbbh) scenario, there could be a tension with the upper limits on the gravitational wave background measured by the pulsar timing array. the argument clearly indicates the difficulties of generally associating quasi-periodicities of bl lac objects with sbbhs. | quasi-periodicities of bl lacertae objects |
we present the discovery of two z > 6 quasars, selected as i-band dropouts in the very large telescope survey telescope atlas survey. our first quasar has redshift, z = 6.31 ± 0.03, z-band magnitude, zab = 19.63 ± 0.08 and rest frame 1450 å absolute magnitude, m1450 = -27.8 ± 0.2, making it the joint second most luminous quasar known at z > 6. the second quasar has z = 6.02 ± 0.03, zab = 19.54 ± 0.08 and m1450 = -27.0 ± 0.1. we also recover a z = 5.86 quasar discovered by venemans et al., in preparation. to select our quasars, we use a new 3d colour space, combining the atlas optical colours with mid-infrared data from the wide-field infrared survey explorer. we use iab - zab colour to exclude main-sequence stars, galaxies and lower redshift quasars, w1 - w2 to exclude l dwarfs and zab - w2 to exclude t dwarfs. a restrictive set of colour cuts returns only our three high redshift quasars and no contaminants, albeit with a sample completeness of ∼50 per cent. we discuss how our 3d colour space can be used to reject the majority of contaminants from samples of bright 5.7 < z < 6.3 quasars, replacing follow-up near-infrared photometry, whilst retaining high completeness. | two bright z > 6 quasars from vst atlas and a new method of optical plus mid-infrared colour selection. |
high-redshift quasars are believed to reside in highly biased regions of the universe, where black hole growth is sustained by an enhanced number of mergers and by being at the intersection of filaments bringing fresh gas. this assumption should be supported by an enhancement of the number counts of galaxies in the field of view of quasars. while the current observations of quasar environments do not lead to a consensus on a possible excess of galaxies, the future missions jwst, wfirst, and euclid will provide new insights on quasar environments, and will substantially increase the number of study-cases. we are in a crucial period, where we need to both understand the current observations and predict how upcoming missions will improve our understanding of bh environments. using the large-scale simulation horizon-agn, we find that statistically the most massive bhs reside in environments with the largest galaxy number counts. however, we find a large variance in galaxy number counts, and some massive bhs do not show enhanced counts in their neighbourhood. interestingly, some massive bhs have a very close galaxy companion but no further enhancement at larger scales, in agreement with recent observations. we find that agn feedback in the surrounding galaxies is able to decrease their luminosity and stellar mass, and therefore to make them unobservable when using restrictive galaxy selection criteria. radiation from the quasars can spread over large distances, which could affect the formation history of surrounding galaxies, but a careful analysis of these processes requires radiative transfer simulations. | the diverse galaxy counts in the environment of high-redshift massive black holes in horizon-agn |
accretion states, which are universally observed in stellar mass black holes in x-ray binaries, might be expected in active galactic nuclei (agn). this is the case at low luminosities, when the jet-corona coupling dominates the energy output in both populations. previous attempts to extend this framework to a wider agn population have been extremely challenging due to heavy hydrogen absorption of the accretion disc continuum and starlight contamination from the host galaxies. we present the luminosity-excitation diagram (led), based on the [o iv]25.9 μm and [ne ii]12.8 μm mid-infrared nebular line fluxes. this tool enables to probe the accretion disc contribution to the ionizing continuum. when applied to a sample of 167 nearby agn, the led recovers the characteristic q-shaped morphology outlined by individual x-ray binaries during a typical accretion episode, allowing us to tentatively identify the main accretion states. the soft state would include broad-line seyferts and about half of the seyfert 2 population, showing highly excited gas and radio-quiet cores consistent with disc-dominated nuclei, in agreement with previous studies. the hard state mostly includes low-luminosity agn ($\lesssim 10^{-3}\, \rm {l_{edd}}$) characterized by low-excitation radio-loud nuclei and a negligible disc contribution. the remaining half of seyfert 2 nuclei and the bright liners show low excitation at high accretion luminosities and could be identified with the bright hard and intermediate states. their hosts show ongoing star formation in the central kiloparsecs. we discuss the above scenario, its potential links with the galaxy evolution picture, and the possible presence of accretion state transitions in agn, as suggested by the growing population of changing-look quasars. | x-ray binary accretion states in active galactic nuclei? sensing the accretion disc of supermassive black holes with mid-infrared nebular lines |
we present a comprehensive analysis of all xmm-newton spectra of oj 287 spanning 15 yr of x-ray spectroscopy of this bright blazar. we also report the latest results from our dedicated swift uvot and xrt monitoring of oj 287, which started in 2015, along with all earlier public swift data since 2005. during this time interval, oj 287 was caught in extreme minima and outburst states. its x-ray spectrum is highly variable and encompasses all states seen in blazars from very flat to exceptionally steep. the spectrum can be decomposed into three spectral components: inverse compton (ic) emission dominant at low-state, supersoft synchrotron emission that becomes increasingly dominant as oj 287 brightens, and an intermediately-soft (γx = 2.2) additional component seen at outburst. this last component extends beyond 10 kev and plausibly represents either a second synchrotron/ic component and/or a temporary disc corona of the primary supermassive black hole (smbh). our 2018 xmm-newton observation, quasi-simultaneous with the event horizon telescope observation of oj 287, is well described by a two-component model with a hard ic component of γx = 1.5 and a soft synchrotron component. low-state spectra limit any long-lived accretion disc/corona contribution in x-rays to a very low value of lx/ledd < 5.6 × 10-4 (for mbh, primary = 1.8 × 1010 m⊙). some implications for the binary smbh model of oj 287 are discussed. | x-ray spectral components of the blazar and binary black hole candidate oj 287 (2005-2020) |
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