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we present director's discretionary time multi-frequency observations obtained with the jansky very large array and the very long baseline array (vlba) of the blazar pso j030947.49+271757.31 (hereafter pso j0309+27) at z = 6.10 ± 0.03. the milliarcsecond angular resolution of our vlba observations at 1.5, 5, and 8.4 ghz unveils a bright one-sided jet extended for ∼500 parsecs in projection. this high-z radio-loud active galactic nucleus is resolved into multiple compact sub-components that are embedded in a more diffuse and faint radio emission that enshrouds them in a continuous jet structure. we directly derive limits on some physical parameters from observable quantities such as viewing angle and lorentz and doppler factors. if pso j0309+27 is a genuine blazar, as suggested by its x-ray properties, then we find that its bulk lorentz factor must be relatively low (lower than 5). this value would be in favour of a scenario currently proposed to reconcile the paucity of high-z blazars with current predictions. nevertheless, we cannot exclude that pso j0309+27 is seen under a larger viewing angle, which would imply that the x-ray emission must be enhanced, for example, by inverse compton scattering with the cosmic microwave background. more stringent constraints on the bulk lorentz factor in pso j0309+27 and on these factors in the other high-z blazars are necessary to test whether their properties are intrinsically different from those of the low-z blazar population. | parsec-scale properties of the radio brightest jetted agn at z > 6 |
we report on observations made with the cosmic origins spectrograph (cos) on the hubble space telescope (hst) using background quasi-stellar objects to probe the circum-galactic medium (cgm) around 17 low-redshift galaxies that are undergoing or have recently undergone a strong starburst (the cos-burst program). the sightlines extend out to roughly the virial radius of the galaxy halo. we construct control samples of normal star-forming low-redshift galaxies from the cos/hst archive that match the starbursts in terms of galaxy stellar mass and impact parameter. we find clear evidence that the cgm around the starbursts differs systematically compared to the control galaxies. the lyα, si iii, c iv, and possibly o vi absorption lines are stronger as a function of impact parameter, and the ratios of the equivalent widths of c iv/lyα and si iii/lyα are both higher than in normal star-forming galaxies. we also find that the widths and the velocity offsets (relative to v sys) of the lyα absorption lines are significantly larger in the cgm of the starbursts, implying velocities of the absorbing material that are roughly twice the halo virial velocity. we show that these properties can be understood as a consequence of the interaction between a starburst-driven wind and the preexisting cgm. these results underscore the importance of winds driven from intensely star-forming galaxies in helping drive the evolution of galaxies and the intergalactic medium. they also offer a new probe of the properties of starburst-driven winds and of the cgm itself. | cos-burst: observations of the impact of starburst-driven winds on the properties of the circum-galactic medium |
we present improved results of the measurement of the correlation between galaxies and the intergalactic medium transmission at the end of reionization. we have gathered a sample of 13 spectroscopically confirmed lyman-break galaxies (lbgs) and 21 lyman-α emitters (laes) at angular separations 20 arcsec ≲ θ ≲ 10 arcmin (∼0.1-4 pmpc at z ∼ 6) from the sightlines to eight background z ≳ 6 quasars. we report for the first time the detection of an excess of lyman-α transmission spikes at ∼10-60 cmpc from laes (3.2σ) and lbgs (1.9σ). we interpret the data with an improved model of the galaxy-lyman-α transmission and two-point cross-correlations, which includes the enhanced photoionization due to clustered faint sources, enhanced gas densities around the central bright objects and spatial variations of the mean free path. the observed lae(lbg)-lyman-α transmission spike two-point cross-correlation function (2pccf) constrains the luminosity-averaged escape fraction of all galaxies contributing to reionization to $\langle f_{\rm esc} \rangle _{m_{\rm uv}\lt -12} = 0.14_{-0.05}^{+0.28}\, (0.23_{-0.12}^{+0.46})$ . we investigate if the 2pccf measurement can determine whether bright or faint galaxies are the dominant contributors to reionization. our results show that a contribution from faint galaxies ( $m_{\rm uv} \gt -20 \, (2\sigma)$ ) is necessary to reproduce the observed 2pccf and that reionization might be driven by different sub-populations around lbgs and laes at z ∼ 6. | the role of galaxies and agn in reionizing the igm - iii. igm-galaxy cross-correlations at z ∼ 6 from eight quasar fields with deimos and muse |
we study the first year of the eboss quasar sample in the redshift range 0.9<z<2.2 which includes 68,772 homogeneously selected quasars. we show that the main source of systematics in the evaluation of the correlation function arises from inhomogeneities in the quasar target selection, particularly related to the extinction and depth of the imaging data used for targeting. we propose a weighting scheme that mitigates these systematics. we measure the quasar correlation function and provide the most accurate measurement to date of the quasar bias in this redshift range, bq = 2.45 ± 0.05 at bar z=1.55, together with its evolution with redshift. we use this information to determine the minimum mass of the halo hosting the quasars and the characteristic halo mass, which we find to be both independent of redshift within statistical error. using a recently-measured quasar-luminosity-function we also determine the quasar duty cycle. the size of this first year sample is insufficient to detect any luminosity dependence to quasar clustering and this issue should be further studied with the final ~500,000 eboss quasar sample. | clustering of quasars in sdss-iv eboss: study of potential systematics and bias determination |
we present an intrinsic agn spectral energy distribution (sed) extending from the optical to the submm, derived with a sample of unobscured, optically luminous (νlν,5100 > 1043.5 erg s-1) qsos at z < 0.18 from the palomar green survey. the intrinsic agn sed was computed by removing the contribution from stars using the 11.3 μm polycyclic aromatic hydrocarbon (pah) feature in the qsos' mid-ir spectra; the 1σ uncertainty on the sed ranges between 12 and 45 per cent as a function of wavelength and is a combination of pah flux measurement errors and the uncertainties related to the conversion between pah luminosity and star-forming luminosity. longwards of 20 μm, the shape of the intrinsic agn sed is independent of the agn power indicating that our template should be applicable to all systems hosting luminous agn (νlν, 5100 or l_x(2-10 kev) ≳ 1043.5 erg s-1). we note that for our sample of luminous qsos, the average agn emission is at least as high as, and mostly higher than, the total stellar powered emission at all wavelengths from the optical to the submm. this implies that in many galaxies hosting powerful agn, there is no `safe' broad-band photometric observation (at λ < 1000 μm) which can be used in calculating star formation rates without subtracting the agn contribution. roughly, the agn contribution may be ignored only if the intrinsic agn luminosity at 5100 aa is at least a factor of 4 smaller than the total infrared luminosity (lir, 8-1000 μm) of the galaxy. finally, we examine the implication of our work in statistical studies of star formation in agn host galaxies. | agn are cooler than you think: the intrinsic far-ir emission from qsos |
recent years have brought more precise temperature measurements of the low-density intergalactic medium (igm). these new measurements constrain the processes that heated the igm, such as the reionization of h i and of he ii. we present a semi-analytical model for the thermal history of the igm that follows the photoheating history of primordial gas. our model adopts a multizone approach that, compared to previous models, more accurately captures the inhomogeneous heating and cooling of the igm during patchy reionization. we compare our model with recent temperature measurements spanning z = 1.6-4.8, finding that these measurements are consistent with scenarios in which the he ii was reionized at z = 3-4 by quasars. significantly longer duration or higher redshift he ii reionization scenarios are ruled out by the measurements. for hydrogen reionization, we find that only low-redshift and high-temperature scenarios are excluded. for example, a model in which the igm was heated to 30 000 k when an ionization front passed, and with hydrogen reionization occurring over 6 < z < 9, is ruled out. finally, we place constraints on how much heating could owe to tev blazars, cosmic rays, and other non-standard mechanisms. we find that by z = 2, a maximum of 1 ev of additional heat could be injected per baryon over standard photoheating-only models, with this limit becoming ≲0.5 ev at z > 3. | models of the thermal evolution of the intergalactic medium after reionization |
we present accretion disk size measurements for 15 luminous quasars at 0.7 ≤ z ≤ 1.9 derived from griz light curves from the dark energy survey. we measure the disk sizes with continuum reverberation mapping using two methods, both of which are derived from the expectation that accretion disks have a radial temperature gradient and the continuum emission at a given radius is well described by a single blackbody. in the first method we measure the relative lags between the multiband light curves, which provides the relative time lag between shorter and longer wavelength variations. from this, we are only able to constrain upper limits on disk sizes, as many are consistent with no lag the 2σ level. the second method fits the model parameters for the canonical thin disk directly rather than solving for the individual time lags between the light curves. our measurements demonstrate good agreement with the sizes predicted by this model for accretion rates between 0.3 and 1 times the eddington rate. given our large uncertainties, our measurements are also consistent with disk size measurements from gravitational microlensing studies of strongly lensed quasars, as well as other photometric reverberation mapping results, that find disk sizes that are a factor of a few (∼3) larger than predictions. | quasar accretion disk sizes from continuum reverberation mapping from the dark energy survey |
supermassive black holes (smbhs) are the central engines of luminous quasars and are found in most massive galaxies today. but the recent discoveries of ulas j1120+0641, a 2 × 109 {m}⊙black hole (bh) at z = 7.1, and ulas j1342+0928, a 8.0 × 108 {m}⊙bh at z = 7.5, now push the era of quasar formation up to just 690 myr after the big bang. here we report new cosmological simulations of smbhs with x-rays fully coupled to primordial chemistry and hydrodynamics which show that j1120 and j1342 can form from direct collapse black holes if their growth is fed by cold, dense accretion streams, like those thought to fuel rapid star formation in some galaxies at later epochs. our models reproduce all of the observed properties of j1120: its mass, luminosity, and h ii region as well as star formation rates and metallicities in its host galaxy. they also reproduce the dynamical mass of the innermost 1.5 kpc of its emission region recently measured by alma and j-band magnitudes that are in good agreement with those found by the vista hemisphere survey. | radiation hydrodynamical simulations of the first quasars |
we analyze the stellar growth of brightest cluster galaxies (bcgs) produced by cosmological zoom-in hydrodynamical simulations of the formation of massive galaxy clusters. the evolution of the stellar mass content is studied considering different apertures, and tracking backwards either the main progenitor of the z = 0 bcg or that of the cluster hosting the bcg at z = 0. both methods lead to similar results up to z ≃ 1.5. the simulated bcg masses at z = 0 are in agreement with recent observations. in the redshift interval from z = 1 to 0, we find growth factors 1.3, 1.6 and 3.6 for stellar masses within 30 kpc, 50 kpc and 10 per cent of r500, respectively. the first two factors, and, in general, the mass evolution in this redshift range, are in agreement with most recent observations. the last larger factor is similar to the growth factor obtained by a semi-analytical model (sam). half of the star particles that end up in the inner 50 kpc was typically formed by redshift ∼3.7, while the assembly of half of the bcgs stellar mass occurs on average at lower redshifts ∼1.5. this assembly redshift correlates with the mass attained by the cluster at high z ≳ 1.3, due to the broader range of the progenitor clusters at high-z. the assembly redshift of bcgs decreases with increasing apertures. our results are compatible with the inside-out scenario. simulated bcgs could lack intense enough star formation (sf) at high redshift, while possibly exhibit an excess of residual sf at low redshift. | bcg mass evolution in cosmological hydro-simulations |
direct collapse black holes (dcbh) have been proposed as a solution to the challenge of assembling supermassive black holes by z > 6 to explain the bright quasars observed at this epoch. the formation of a dcbh seed with mbh ∼ 104-5 m⊙ requires a pristine atomic-cooling halo to be illuminated by an external radiation field that is sufficiently strong to entirely suppress h2 cooling in the halo. many previous studies have attempted to constrain the critical specific intensity that is likely required to suppress h2 cooling, denoted as jcrit. however, these studies have typically assumed that the incident external radiation field can be modelled with a blackbody spectrum. under this assumption, it is possible to derive a unique value for jcrit that depends only on the temperature of the blackbody. in this study we consider a more realistic spectral energy distribution (sed) for the external source of radiation that depends entirely on its star formation history and age. the rate of destruction of the species responsible for suppressing molecular hydrogen cooling depends on the detailed shape of the sed. therefore the value of jcrit is tied to the shape of the incident sed of the neighbouring galaxy. we fit a parametric form to the rates of destruction of h2 and h- that permit direct collapse. owing to this, we find that jcrit is not a fixed threshold but can lie anywhere in the range jcrit ∼ 0.5-103, depending on the details of the source stellar population. | new constraints on direct collapse black hole formation in the early universe |
the flat-spectrum radio quasar pks 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 gev with a significance of 25.5σ using the magic telescopes. together with the gravitationally lensed blazar qso b0218+357 (z = 0.944), pks 1441+25 is the most distant very high energy (vhe) blazar detected to date. the observations were triggered by an outburst in 2015 april seen at gev energies with the large area telescope on board fermi. multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. in the band covered by magic, the variability timescale is estimated to be 6.4 ± 1.9 days. modeling the broadband spectral energy distribution with an external compton model, the location of the emitting region is understood as originating in the jet outside the broad-line region (blr) during the period of high activity, while being partially within the blr during the period of low (typical) activity. the observed vhe spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy. | very high energy γ-rays from the universe's middle age: detection of the z = 0.940 blazar pks 1441+25 with magic |
context. as part of the data processing for gaia data release 1 (gaia dr1) a special astrometric solution was computed, the so-called auxiliary quasar solution. this gives positions for selected extragalactic objects, including radio sources in the second realisation of the international celestial reference frame (icrf2) that have optical counterparts bright enough to be observed with gaia. a subset of these positions was used to align the positional reference frame of gaia dr1 with the icrf2. although the auxiliary quasar solution was important for internal validation and calibration purposes, the resulting positions are in general not published in gaia dr1.aims: we describe the properties of the gaia auxiliary quasar solution for a subset of sources matched to icrf2, and compare their optical and radio positions at the sub-mas level.methods: descriptive statistics are used to characterise the optical data for the icrf sources and the optical-radio differences. the most discrepant cases are examined using online resources to find possible alternative explanations than a physical optical-radio offset of the quasars.results: in the auxiliary quasar solution 2191 sources have good optical positions matched to icrf2 sources with high probability. their formal standard errors are better than 0.76 milliarcsec (mas) for 50% of the sources and better than 3.35 mas for 90%. optical magnitudes are obtained in gaia's unfiltered photometric g band. the gaia results for these sources are given as a separate table in gaia dr1. the comparison with the radio positions of the defining sources shows no systematic differences larger than a few tenths of a mas. the fraction of questionable solutions, not readily accounted for by the statistics, is less than 6%. normalised differences have extended tails requiring case-by-case investigations for around 100 sources, but we have not seen any difference indisputably linked to an optical-radio offset in the sources.conclusions: with less than a quarter of the data expected from the nominal mission it has been possible to obtain positions at the sub-mas level for most of the icrf sources having an optical counterpart brighter than 20.5 mag. | gaia data release 1. reference frame and optical properties of icrf sources |
fast radio burst (frb) 190608 was detected by the australian square kilometre array pathfinder (askap) and localized to a spiral galaxy at ${z}_{\mathrm{host}}=0.11778$ in the sloan digital sky survey (sdss) footprint. the burst has a large dispersion measure ( ${\mathrm{dm}}_{\mathrm{frb}}=339.8\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ ) compared to the expected cosmic average at its redshift. it also has a large rotation measure ( ${\mathrm{rm}}_{\mathrm{frb}}=353\,\mathrm{rad}\,{{\rm{m}}}^{-2}$ ) and scattering timescale (τ = 3.3 ms at 1.28 ghz). chittidi et al. perform a detailed analysis of the ultraviolet and optical emission of the host galaxy and estimate the host dm contribution to be $110\pm 37\,{\rm{p}}{\rm{c}}\,{{\rm{c}}{\rm{m}}}^{-3}$ . this work complements theirs and reports the analysis of the optical data of galaxies in the foreground of frb 190608 in order to explore their contributions to the frb signal. together, the two studies delineate an observationally driven, end-to-end study of matter distribution along an frb sightline, the first study of its kind. combining our keck cosmic web imager (kcwi) observations and public sdss data, we estimate the expected cosmic dispersion measure ${\mathrm{dm}}_{\mathrm{cosmic}}$ along the sightline to frb 190608. we first estimate the contribution of hot, ionized gas in intervening virialized halos ( ${\mathrm{dm}}_{\mathrm{halos}}\approx 7\mbox{--}28\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ ). then, using the monte carlo physarum machine methodology, we produce a 3d map of ionized gas in cosmic web filaments and compute the dm contribution from matter outside halos ( ${\mathrm{dm}}_{\mathrm{igm}}\approx 91\mbox{--}126\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ ). this implies that a greater fraction of ionized gas along this sightline is extant outside virialized halos. we also investigate whether the intervening halos can account for the large frb rotation measure and pulse width and conclude that it is implausible. both the pulse broadening and the large faraday rotation likely arise from the progenitor environment or the host galaxy. | disentangling the cosmic web toward frb 190608 |
the cosmic curvature (ωk) is a fundamental parameter for cosmology. in this paper, we propose an improved model-independent method to constrain the cosmic curvature, which is geometrically related to the hubble parameter h(z) and luminosity distance dl(z). using the currently largest h(z) sample from the well-known cosmic chronometers, as well as the luminosity distance dl(z) from the relation between the uv and x-ray luminosities of 1598 quasars and the newly compiled pantheon sample including 1048 sne ia, 31 independent measurements of the cosmic curvature ωk(z) can be expected covering the redshift range of 0.07 < z < 2. our estimation of ωk(z) is fully compatible with flat universe at the current level of observational precision. meanwhile, we find that, for the hubble diagram of 1598 quasars as a new type of standard candle, the spatial curvature is constrained to be ωk = 0.08 ± 0.31. for the latest pantheon sample of sne ia observations, we obtain ωk = - 0.02 ± 0.14. compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieves constraints with competitive precision. more interestingly, it is suggested that the reconstructed curvature ωk is negative in the high-redshift region, which is also consistent with the results from the model-dependent constraints in the literature. such findings are confirmed by our reconstructed evolution of ωk(z), in the framework of a model-independent method of gaussian processes (gp) without assuming a specific form. | model-independent constraints on cosmic curvature: implication from updated hubble diagram of high-redshift standard candles |
hydrostatic equilibrium (hse), where the thermal pressure gradient balances the force of gravity, is tested across a range of simulated eagle haloes from milky way l* haloes (m200≈ 1012m⊙) to cluster scales. clusters (m200≈1014m⊙) reproduce previous results with thermal pressure responsible for ∼90 per cent of the support against gravity, but this fraction drops for group-sized haloes (m200≈ 1013m⊙) and is even lower (40-70 per cent) for l* haloes between 0.1 and 0.3r200. energy from feedback grows relative to the binding energy of a halo towards lower mass resulting in greater deviations from hse. tangential motions comprise the largest deviation from hse in l* haloes indicating that the hot circumgalactic medium (cgm) has significant subcentrifugal rotation and angular momentum spin parameters 2-3 × higher than the dark matter spin parameters. thermal feedback can buoyantly rise to the outer cgm of m200 ≲ 1012m⊙ haloes, both moving baryons beyond r200 and feeding uncorrelated tangential motions. the resulting hot halo density and rotation profiles show promising agreement with x-ray observations of the inner milky way halo, and we discuss future observational prospects to detect spinning hot haloes around other galaxies. acceleration and radial streaming motions also comprise significant deviations from hse, especially net outward accelerations seen in l* and group haloes indicating active feedback. black hole feedback acts in a preventative manner during the later growth of group haloes, applying significant accelerations via shocks that do not feed tangential motions. we argue that hse is a poor assumption for the cgm, especially in the inner regions, and rotating baryonic hot haloes are a critical consideration for analytic models of the cgm. | deviations from hydrostatic equilibrium in the circumgalactic medium: spinning hot haloes and accelerating flows |
modelling reionization often requires significant assumptions about the properties of ionizing sources. here, we infer the total output of hydrogen-ionizing photons (the ionizing emissivity, \dot{n}_\textrm {ion}) at z = 4-14 from current reionization constraints, being maximally agnostic to the properties of ionizing sources. we use a bayesian analysis to fit for a non-parametric form of \dot{n}_\textrm {ion}, allowing us to flexibly explore the entire prior volume. we infer a declining \dot{n}_\textrm {ion} with redshift at z > 6, which can be used as a benchmark for reionization models. model-independent reionization constraints from the cosmic microwave background (cmb) optical depth and ly α and ly β forest dark pixel fraction produce \dot{n}_\textrm {ion} evolution ( d\log _{10}\dot{\mathbf {n}}_{ion}/ dz|_{z=6\rarr 8} = -0.31± 0.35 dex) consistent with the declining uv luminosity density of galaxies, assuming constant ionizing photon escape fraction and efficiency. including measurements from ly α damping of galaxies and quasars produces a more rapid decline: d\log _{10}\dot{\mathbf {n}}_{ion}/ dz|_{z=6\rarr 8} =-0.44± 0.22 dex, steeper than the declining galaxy luminosity density (if extrapolated beyond m_uv≳ -13), and constrains the mid-point of reionization to z = 6.93 ± 0.14. | model-independent constraints on the hydrogen-ionizing emissivity at z > 6 |
galactic outflows of molecular gas are a common occurrence in galaxies and may represent a mechanism by which galaxies self-regulate their growth, redistributing gas that could otherwise have formed stars. we previously presented the first survey of molecular outflows at z > 4 toward a sample of massive, dusty galaxies. here we characterize the physical properties of the molecular outflows discovered in our survey. using low-redshift outflows as a training set, we find agreement at the factor of 2 level between several outflow rate estimates. we find molecular outflow rates of 150-800 ${m}_{\odot }$ yr-1 and infer mass loading factors just below unity. among the high-redshift sources, the molecular mass loading factor shows no strong correlations with any other measured quantity. the outflow energetics are consistent with expectations for momentum-driven winds with star formation as the driving source, with no need for energy-conserving phases. there is no evidence for active galactic nucleus activity in our sample, and while we cannot rule out deeply buried active galactic nuclei, their presence is not required to explain the outflow energetics, in contrast to nearby obscured galaxies with fast outflows. the fraction of the outflowing gas that will escape into the circumgalactic medium (cgm), though highly uncertain, may be as high as 50%. this nevertheless constitutes only a small fraction of the total cool cgm mass based on a comparison to z ∼ 2-3 quasar absorption line studies, but could represent ≳10% of the cgm metal mass. our survey offers the first statistical characterization of molecular outflow properties in the very early universe. | ubiquitous molecular outflows in z > 4 massive, dusty galaxies. ii. momentum-driven winds powered by star formation in the early universe |
quasars show considerable promise as standard candles in a high-redshift window beyond type ia supernovae. recently, risaliti, lusso & collaborators [1-3] have succeeded in producing a high redshift hubble diagram (z ≲ 7) that supports "a trend whereby the hubble diagram of quasars is well reproduced by the standard flat λcdm model up to z ∼ 1.5 - 2, but strong deviations emerge at higher redshifts". this conclusion hinges upon a log polynomial expansion for the luminosity distance. in this note, we demonstrate that this expansion (or "improvements" thereof) typically can only be trusted up to z ∼ 1.5 - 2. as a result, a breakdown in the validity of the expansion may be misinterpreted as a (phantom) deviation from flat λcdm. we further illustrate the problem through mock data examples. | on problems with cosmography in cosmic dark ages |
motivated by evidences favoring a rapid and late hydrogen reionization process completing at z ~ 5.2-5.5 and mainly driven by rare and luminous sources, we have reassessed the estimate of the space density of ultra-luminous qsos at z ~ 5 in the framework of the qubrics survey. a ~ 90% complete sample of 14 spectroscopically confirmed qsos at m 1450 ≤ -28.3 and 4.5 ≤ z ≤ 5.0 has been derived in an area of 12,400 deg2, thanks to multiwavelength selection and gaia astrometry. the space density of z ~ 5 qsos within -29.3 ≤ m 1450 ≤ -28.3 is three times higher than previous determinations. our results suggest a steep bright-end slope for the qso luminosity function at z ~ 5 and a mild redshift evolution of the space density of ultrabright qsos (m 1450 ~ -28.5) at 3 < z < 5.5, in agreement with the redshift evolution of the much fainter active galactic nucleus (agn) population at m 1450 ~ -23. these findings are consistent with a pure density evolution for the agn population at z > 3. adopting our z ~ 4 qso luminosity function and applying a mild density evolution in redshift, a photoionization rate of ${{\rm{\gamma }}}_{\mathrm{hi}}={0.46}_{-0.09}^{+0.17}\times {10}^{-12}\,{{\rm{s}}}^{-1}$ has been obtained at z = 4.75, assuming an escape fraction of ~70% and a steep faint-end slope of the agn luminosity function. the derived photoionization rate is ~50-100% of the ionizing background measured at the end of the reionization epoch, suggesting that agns could play an important role in the cosmological reionization process. | the space density of ultra-luminous qsos at the end of reionization epoch by the qubrics survey and the agn contribution to the hydrogen ionizing background |
we study the connection between ly α emitters (laes) and metal-enriched ionized gas traced by c iv absorption at redshift z ≈ 3-4 in 28 quasar fields with high-resolution spectroscopy from the muse analysis of gas around galaxies survey. in a sample of 220 c iv absorbers, we identify 143 laes connected to c iv gas within a line-of-sight separation $\pm 500\rm \, km\, s^{-1}$, equal to a detection rate of 36 ± 5 per cent once we account for multiple laes connected to the same absorber. the luminosity function of laes associated with absorbers has an ≈2.4 higher normalization than the field. the analysis of the lae-c iv correlation function suggests that metal-enriched gas arises both in the haloes of the laes and from locations not connected to galaxies. c iv absorbers with higher equivalent width are more often associated with laes and c iv systems are twice less likely, especially at low equivalent width, to be found near laes than strong h i absorbers. the covering fraction in groups is up to ≈3 times larger than for isolated galaxies. similar results are found using si iv as tracer of ionized gas. we propose three components to model the gas environment of laes: (i) the circumgalactic medium of galaxies, accounting for the strongest correlations between absorption and emission; (ii) overdense gas filaments connecting galaxies, driving the excess of laes at a few times the virial radius and the modulation of the luminosity and cross-correlation functions for strong absorbers; (iii) an enriched and more diffuse medium, accounting for weaker c iv absorbers farther from galaxies. | muse analysis of gas around galaxies (magg) - v. linking ionized gas traced by c iv and si iv absorbers to ly α emitting galaxies at z ≈ 3.0-4.5 |
we present six new time-delay measurements obtained from rc-band monitoring data acquired at the max planck institute for astrophysics (mpia) 2.2 m telescope at la silla observatory between october 2016 and february 2020. the lensed quasars he 0047-1756, wg 0214-2105, des 0407-5006, 2m 1134-2103, psj 1606-2333, and des 2325-5229 were observed almost daily at high signal-to-noise ratio to obtain high-quality light curves where we can record fast and small-amplitude variations of the quasars. we measured time delays between all pairs of multiple images with only one or two seasons of monitoring with the exception of the time delays relative to image d of psj 1606-2333. the most precise estimate was obtained for the delay between image a and image b of des 0407-5006, where τab = -128.4-3.8+3.5 d (2.8% precision) including systematics due to extrinsic variability in the light curves. for he 0047-1756, we combined our high-cadence data with measurements from decade-long light curves from previous cosmograil campaigns, and reach a precision of 0.9 d on the final measurement. the present work demonstrates the feasibility of measuring time delays in lensed quasars in only one or two seasons, provided high signal-to-noise ratio data are obtained at a cadence close to daily. all light curves presented in this paper 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/cat/j/a+a/642/a193 | tdcosmo. ii. six new time delays in lensed quasars from high-cadence monitoring at the mpia 2.2 m telescope |
aims: the goal of this work is to better understand the correlations between the rest-frame uv/optical variability amplitude of quasi-stellar objects (qsos) and physical quantities such as redshift, luminosity, black hole mass, and eddington ratio. previous analyses of the same type found evidence for correlations between the variability amplitude and these active galactic nucleus (agn) parameters. however, most of the relations exhibit considerable scatter, and the trends obtained by various authors are often contradictory. moreover, the shape of the optical power spectral density (psd) is currently available for only a handful of objects.methods: we searched for scaling relations between the fundamental agn parameters and rest-frame uv/optical variability properties for a sample of ~90 x-ray selected agns covering a wide redshift range from the xmm-cosmos survey, with optical light curves in four bands (gp1, rp1, ip1, zp1) provided by the pan-starrs1 (ps1) medium deep field 04 survey. to estimate the variability amplitude, we used the normalized excess variance (σ2rms) and probed variability on rest-frame timescales of several months and years by calculating σ2rms from different parts of our light curves. in addition, we derived the rest-frame optical psd for our sources using continuous-time autoregressive moving average (carma) models.results: we observe that the excess variance and the psd amplitude are strongly anticorrelated with wavelength, bolometric luminosity, and eddington ratio. there is no evidence for a dependency of the variability amplitude on black hole mass and redshift. these results suggest that the accretion rate is the fundamental physical quantity determining the rest-frame uv/optical variability amplitude of quasars on timescales of months and years. the optical psd of all of our sources is consistent with a broken power law showing a characteristic bend at rest-frame timescales ranging between ~100 and ~300 days. the break timescale exhibits no significant correlation with any of the fundamental agn parameters. the low-frequency slope of the psd is consistent with a value of -1 for most of our objects, whereas the high-frequency slope is characterized by a broad distribution of values between ~-2 and ~-4. these findings unveil significant deviations from the simple damped random walk model that has frequently been used in previous optical variability studies. we find a weak tendency for agns with higher black hole mass to have steeper high-frequency psd slopes. | pan-starrs1 variability of xmm-cosmos agn. ii. physical correlations and power spectrum analysis |
nearly 150 massive black hole binary (mbhb) candidates at sub-pc orbital separations have been reported in recent literature. nevertheless, the definitive detection of even a single such object remains elusive. if at least one of the black holes is accreting, the light emitted from its accretion disc will be lensed by the other black hole for binary orbital inclinations near to the line of sight. this binary self-lensing could provide a unique signature of compact mbhb systems. we show that, for mbhbs with masses in the range 106-1010 m⊙ and with orbital periods less than ∼10 yr, strong lensing events should occur in one to 10s of per cent of mbhb systems that are monitored for an entire orbit. lensing events will last from days for the less massive, shorter period mbhbs to a year for the most massive ∼10 year orbital period mbhbs. at small inclinations of the binary orbit to the line of sight, lensing must occur and will be accompanied by periodicity due to the relativistic doppler boost. flares at the same phase as the otherwise average flux of the doppler modulation would be a smoking gun signature of self-lensing and can be used to constrain binary parameters. for mbhbs with separation ≳100 schwarzschild radii, we show that finite-sized source effects could serve as a probe of mbh accretion disc structure. finally, we stress that our lensing probability estimate implies that ∼10 of the known mbhb candidates identified through quasar periodicity should exhibit strong lensing flares. | periodic self-lensing from accreting massive black hole binaries |
supermassive black hole binaries (smbhbs) are a natural outcome of galaxy mergers and should form frequently in galactic nuclei. sub-parsec binaries can be identified from their bright electromagnetic emission, e.g. active galactic nuclei (agns) with doppler shifted broad emission lines or agn with periodic variability, as well as from the emission of strong gravitational radiation. the most massive binaries (with total mass >108m⊙) emit in the nanohertz band and are targeted by pulsar timing arrays (ptas). here we examine the synergy between electromagnetic and gravitational wave signatures of smbhbs. we connect both signals to the orbital dynamics of the binary and examine the common link between them, laying the foundation for joint multimessenger observations. we find that periodic variability arising from relativistic doppler boost is the most promising electromagnetic signature to connect with gws. we delineate the parameter space (binary total mass/chirp mass versus binary period/gw frequency) for which joint observations are feasible. currently multimessenger detections are possible only for the most massive and nearby galaxies, limited by the sensitivity of ptas. however, we demonstrate that as ptas collect more data in the upcoming years, the overlapping parameter space is expected to expand significantly. | multimessenger time-domain signatures of supermassive black hole binaries |
if primordial black holes (pbhs) formed at the quark-hadron epoch, their mass must be close to the chandrasekhar limit, this also being the characteristic mass of stars. if they provide the dark matter (dm), the collapse fraction must be of order the cosmological baryon-to-photon ratio ∼10-9, which suggests a scenario in which a baryon asymmetry is produced efficiently in the outgoing shock around each pbh and then propagates to the rest of the universe. we suggest that the temperature increase in the shock provides the ingredients for hotspot electroweak baryogenesis. this also explains why baryons and dm have comparable densities, the precise ratio depending on the size of the pbh relative to the cosmological horizon at formation. the observed value of the collapse fraction and baryon asymmetry depends on the amplitude of the curvature fluctuations that generate the pbhs and may be explained by an anthropic selection effect associated with the existence of galaxies. we propose a scenario in which the quantum fluctuations of a light stochastic spectator field during inflation generate large curvature fluctuations in some regions, with the stochasticity of this field providing the basis for the required selection. finally, we identify several observational predictions of our scenario that should be testable within the next few years. in particular, the pbh mass function could extend to sufficiently high masses to explain the black hole coalescences observed by ligo/virgo. | primordial black holes from the qcd epoch: linking dark matter, baryogenesis, and anthropic selection |
observational constraints on the birth and early evolution of massive black holes come from two extreme regimes. at high redshift, quasars signal the rapid growth of billion-solar-mass black holes and indicate that these objects began remarkably heavy and/or accreted mass at rates above the eddington limit. at low redshift, the smallest nuclear black holes known are found in dwarf galaxies and provide the most concrete limits on the mass of black hole seeds. here, we review current observational work in these fields that together are critical for our understanding of the origin of massive black holes in the universe. | observational signatures of high-redshift quasars and local relics of black hole seeds |
we present the monitoring of the active galactic nuclei continuum and mg ii broad-line emission for the quasar he 0413-4031 (z = 1.38) based on the six-year monitoring by the south african large telescope (salt). we manage to estimate a time-delay of ${302.6}_{-33.1}^{+28.7}$ days in the rest frame of the source using seven different methods: interpolated cross-correlation function, discrete correlation function (dcf), z-transformed dcf, javelin, two estimators of data regularity (von neumann, bartels), and χ2 method. this time-delay is below the value expected from the standard radius-luminosity relation. however, based on the monochromatic luminosity of the source and the spectral energy distribution modeling, we interpret this departure as the shortening of the time-delay due to the higher accretion rate of the source, with the inferred eddington ratio of ∼0.4. the mg ii line luminosity of he 0413-4031 responds to the continuum variability as ${l}_{\mathrm{line}}\propto {l}_{\mathrm{cont}}^{0.43\pm 0.10}$ , which is consistent with the light-travel distance of the location of mg ii emission at rout ∼ 1018 cm. using the data of 10 other quasars, we confirm the radius-luminosity relation for the broad mg ii line, which was previously determined for the broad hβ line for lower-redshift sources. in addition, we detect a general departure of higher-accreting quasars from this relation in analogy to the hβ sample. after the accretion-rate correction of the light-travel distance, the mg ii-based radius-luminosity relation has a small scatter of only 0.10 dex. | time-delay measurement of mg ii broad-line response for the highly accreting quasar he 0413-4031: implications for the mg ii-based radius-luminosity relation |
discrepancies between the observed and model-predicted radio flux ratios are seen in a number of quadruply-lensed quasars. the most favoured interpretation of these anomalies is that cold dark matter (cdm) substructures present in lensing galaxies perturb the lens potentials and alter image magnifications and thus flux ratios. so far no consensus has emerged regarding whether or not the predicted cdm substructure abundance fully accounts for the lensing flux anomaly observations. accurate modelling relies on a realistic lens sample in terms of both the lens environment and internal structures and substructures. in this paper, we construct samples of generalized and specific lens potentials, to which we add (rescaled) subhalo populations from the galaxy-scale aquarius and the cluster-scale phoenix simulation suites. we further investigate the lensing effects from subhaloes of masses several orders of magnitude below the simulation resolution limit. the resulting flux-ratio distributions are compared to the currently best available sample of radio lenses. the observed anomalies in b0128+437, b0712+472 and b1555+375 are more likely to be caused by propagation effects or oversimplified/improper lens modelling, signs of which are already seen in the data. among the quadruple systems that have closely located image triplets/pairs, the anomalous flux ratios of mg0414+0534 can be reproduced by adding cdm subhaloes to its macroscopic lens potential, with a probability of 5-20 per cent; for b0712+472, b1422+231, b1555+375 and b2045+265, these probabilities are only of a few per cent. we hence find that cdm substructures are unlikely to be the whole reason for radio flux anomalies. we discuss other possible effects that might also be at work. | how well can cold dark matter substructures account for the observed radio flux-ratio anomalies |
active galactic nuclei (agn) can vary significantly in their rest-frame optical/uv continuum emission, and with strong associated changes in broad line emission, on much shorter timescales than predicted by standard models of accretion disks around supermassive black holes. most such changing-look or changing-state agn-and at higher luminosities, changing-look quasars (clqs)-have been found via spectroscopic follow-up of known quasars showing strong photometric variability. the time domain spectroscopic survey of the sloan digital sky survey iv (sdss-iv) includes repeat spectroscopy of large numbers of previously known quasars, many selected irrespective of photometric variability, and with spectral epochs separated by months to decades. our visual examination of these repeat spectra for strong broad line variability yielded 61 newly discovered clq candidates. we quantitatively compare spectral epochs to measure changes in continuum and hβ broad line emission, finding 19 clqs, of which 15 are newly recognized. the parent sample includes only broad line quasars, so our study tends to find objects that have dimmed, i.e., turn-off clqs. however, we nevertheless find four turn-on clqs that meet our criteria, albeit with broad lines in both dim and bright states. we study the response of hβ and mg ii emission lines to continuum changes. the eddington ratios of clqs are low, and/or their hβ broad line width is large relative to the overall quasar population. repeat quasar spectroscopy in the upcoming sdss-v black hole mapper program will reveal significant numbers of clqs, enhancing our understanding of the frequency and duty cycle of such strong variability, and the physics and dynamics of the phenomenon. | the time domain spectroscopic survey: changing-look quasar candidates from multi-epoch spectroscopy in sdss-iv |
we characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z ≲ 1 strong lyα forest systems (slfss, absorbers with 15 < log n h i< 16.2). the sample is drawn from our cosmic origins spectrograph (cos) circumgalactic medium compendium (ccc), an ultraviolet survey of h i-selected circumgalactic gas around z ≲ 1 galaxies that targets 261 absorbers with 15 < log n h i< 19. we show that the metallicity probability distribution function of the slfss at z ≲ 1 is unimodal, skewed to low metallicities with a mean and median of [x/h] = -1.47 and -1.18 dex. very metal-poor gas with [x/h] < -1.4 represents about half of the population of absorbers with 15 < log n h i≲ 18, while it is rare at higher n h i . thus, there are important reservoirs of primitive (though not pristine) diffuse ionized gas around z ≲ 1 galaxies. the photoionized gas around z ≲ 1 galaxies is highly inhomogeneous based on the wide range of metallicities observed (-3 ≲ [x/h] ≲ +0.4) and the fact that there are large metallicity variations (factors of 2 to 25) for most of the closely spaced absorbers (δv ≲ 300 km s-1) along the same sightlines. these absorbers show a complex evolution with redshift and h i column density, and we identify subtle cosmic evolution effects that affect the interpretation of metallicity distributions and comparison with other absorber samples. we discuss the physical conditions and cosmic baryon and metal budgets of the ccc absorbers. finally, we compare the ccc results to recent cosmological zoom simulations and explore the origins of the 15 < log n h i< 19 absorbers within the evolution and assembly of galaxies and their environments (eagle) high-resolution simulations. | the cos cgm compendium. iii. metallicity and physical properties of the cool circumgalactic medium at z ≲ 1 |
the cosmic curvature, a fundamental parameter for cosmology could hold deep clues to inflation and cosmic origins. we propose an improved model-independent method to constrain the cosmic curvature by combining the constructed hubble diagram of high-redshift quasars with galactic-scale strong lensing systems expected to be seen by the forthcoming large synoptic survey telescope survey. more specifically, the most recent quasar data are used as a new type of standard candles in the range 0.036 < z < 5.100, whose luminosity distances can be directly derived from the non-linear relation between x-ray and uv luminosities. compared with other methods, the proposed one involving the quasar data achieves constraints with higher precision (δωk ∼ 10-2) at high redshifts (z ∼ 5.0). we also investigate the influence of lens mass distribution in the framework of three types of lens models extensively used in strong lensing studies (sis model, power-law spherical model, and extended power-law lens model), finding the strong correlation between the cosmic curvature and the lens model parameters. when the power-law mass density profile is assumed, the most stringent constraint on the cosmic curvature ωk can be obtained. therefore, the issue of mass density profile in the early-type galaxies is still a critical one that needs to be investigated further. | testing the cosmic curvature at high redshifts: the combination of lsst strong lensing systems and quasars as new standard candles |
the low-frequency array (lofar) long-baseline calibrator survey (lbcs) was conducted between 2014 and 2019 in order to obtain a set of suitable calibrators for the lofar array. in this paper, we present the complete survey, building on the preliminary analysis published in 2016 which covered approximately half the survey area. the final catalogue consists of 30 006 observations of 24 713 sources in the northern sky, selected for a combination of high low-frequency radio flux density and flat spectral index using existing surveys (wenss, nvss, vlss, and msss). approximately one calibrator per square degree, suitable for calibration of ≥200 km baselines is identified by the detection of compact flux density, for declinations north of 30° and away from the galactic plane, with a considerably lower density south of this point due to relative difficulty in selecting flat-spectrum candidate sources in this area of the sky. the catalogue contains indicators of degree of correlated flux on baselines between the dutch core and each of the international stations, involving a maximum baseline length of nearly 2000 km, for all of the observations. use of the vlba calibrator list, together with statistical arguments by comparison with flux densities from lower-resolution catalogues, allow us to establish a rough flux density scale for the lbcs observations, so that lbcs statistics can be used to estimate compact flux densities on scales between 300 mas and 2'', for sources observed in the survey. the survey is used to estimate the phase coherence time of the ionosphere for the lofar international baselines, with median phase coherence times of about 2 min varying by a few tens of percent between theshortest and longest baselines. the lbcs can be used to assess the structures of point sources in lower-resolution surveys, with significant reductions in the degree of coherence in these sources on scales between 2'' and 300 mas. the lbcs survey sources show a greater incidence of compact flux density in quasars than in radio galaxies, consistent with unified schemes of radio sources. comparison with samples of sources from interplanetary scintillation (ips) studies with the murchison widefield array shows consistent patterns of detection of compact structure in sources observed both interferometrically with lofar and using ips. | sub-arcsecond imaging with the international lofar telescope. ii. completion of the lofar long-baseline calibrator survey |
supernova driven winds are often invoked to remove chemically enriched gas from dwarf galaxies to match their low observed metallicities. in such shallow potential wells, outflows may produce massive amounts of enriched halo gas (circumgalactic medium, cgm) and pollute the intergalactic medium (igm). here, we present a survey of the cgm and igm around 18 star-forming field dwarfs with stellar masses of {log} {m}* /{m}⊙ ≈ 8{--}9 at z≈ 0.2. eight of these have cgm probed by quasar absorption spectra at projected distances, d, less than that of the host virial radius, {r}{{h}}. ten are probed in the surrounding igm at d/{r}{{h}}=1{--}3. the absorption measurements include neutral hydrogen, the dominant silicon ions for diffuse cool gas (t ∼ 104 k; si ii, si iii, and si iv), moderately ionized carbon (c iv), and highly ionized oxygen (o vi). metal absorption from the cgm of the dwarfs is less common and ≈ 4× weaker compared to massive star-forming galaxies, though o vi absorption is still common. none of the dwarfs probed at d/{r}{{h}}=1{--}3 have definitive metal-line detections. combining the available silicon ions, we estimate that the cool cgm of the dwarfs accounts for only 2%-6% of the expected silicon budget from the yields of supernovae associated with past star formation. the highly ionized o vi accounts for ≈8% of the oxygen budget. as o vi traces an ion with expected equilibrium ion fractions of ≲0.2, the highly ionized cgm may represent a significant metal reservoir even for dwarfs not expected to maintain gravitationally shock heated hot halos. | the extent of chemically enriched gas around star-forming dwarf galaxies |
feedback from active galactic nuclei (agn) is thought to be key in shaping the life cycle of their host galaxies by regulating star-formation activity. therefore, to understand the impact of agn on star formation, it is essential to trace the molecular gas out of which stars form. in this paper we present the first systematic study of the co properties of agn hosts at z ≈ 2 for a sample of 27 x-ray selected agn spanning two orders of magnitude in agn bolometric luminosity (log lbol / erg s-1 = 44.7 - 46.9) by using alma band 3 observations of the co(3-2) transition (∼1″ angular resolution). to search for evidence of agn feedback on the co properties of the host galaxies, we compared our agn with a sample of inactive (i.e., non-agn) galaxies from the phibss survey with similar redshift, stellar masses, and star-formation rates (sfrs). we used the same co transition as a consistent proxy for the gas mass for the two samples in order to avoid systematics involved when assuming conversion factors (e.g., excitation corrections and αco). by adopting a bayesian approach to take upper limits into account, we analyzed co luminosities as a function of stellar masses and sfrs, as well as the ratio lco(3-2)′/m∗ (a proxy for the gas fraction). the two samples show statistically consistent trends in the lco(3-2)′-lfir and lco(3-2)′-m∗ planes. however, there are indications that agn feature lower co(3-2) luminosities (0.4-0.7 dex) than inactive galaxies at the 2-3σ level when we focus on the subset of parameters where the results are better constrained (i.e., lfir ≈ 1012.2 l⊙ and m* > 1011 m⊙) and on the distribution of the mean log(lco(3-2)′/m∗). therefore, even by conservatively assuming the same excitation factor r31, we would find lower molecular gas masses in agn, and assuming higher r31 would exacerbate this difference. we interpret our result as a hint of the potential effect of agn activity (such as radiation and outflows), which may be able to heat, excite, dissociate, and/or deplete the gas reservoir of the host galaxies. better sfr measurements and deeper co observations for agn as well as larger and more uniformly selected samples of both agn and inactive galaxies are required to confirm whether there is a true difference between the two populations. data 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/cat/j/a+a/646/a96 | super. iv. co(j = 3-2) properties of active galactic nucleus hosts at cosmic noon revealed by alma |
feedback by active galactic nuclei (agns) is often divided into quasar and radio mode, powered by radiation or radio jets, respectively. both are fundamental in galaxy evolution, especially in late-type galaxies, as shown by cosmological simulations and observations of jet-ism (interstellar medium) interactions in these systems. we compare agn feedback by radiation and by collimated jets through a suite of simulations, in which a central agn interacts with a clumpy, fractal galactic disc. we test agns of 1043 and 1046 erg s-1, considering jets perpendicular or parallel to the disc. mechanical jets drive the more powerful outflows, exhibiting stronger mass and momentum coupling with the dense gas, while radiation heats and rarefies the gas more. radiation and perpendicular jets evolve to be quite similar in outflow properties and effect on the cold ism, while inclined jets interact more efficiently with all the disc gas, removing the densest 20 {per cent} in 20 myr, and thereby reducing the amount of cold gas available for star formation. all simulations show small-scale inflows of 0.01-0.1 m⊙ yr-1, which can easily reach down to the bondi radius of the central supermassive black hole (especially for radiation and perpendicular jets), implying that agns modulate their own duty cycle in a feedback/feeding cycle. | agn feedback compared: jets versus radiation |
we present time-delay estimates for the quadruply imaged quasar pg 1115+080. our results are based on almost daily observations for seven months at the eso mpia 2.2 m telescope at la silla observatory, reaching a signal-to-noise ratio of about 1000 per quasar image. in addition, we re-analyze existing light curves from the literature that we complete with an additional three seasons of monitoring with the mercator telescope at la palma observatory. when exploring the possible source of bias we considered the so-called microlensing time delay, a potential source of systematic error so far never directly accounted for in previous time-delay publications. in 15 yr of data on pg 1115+080, we find no strong evidence of microlensing time delay. therefore not accounting for this effect, our time-delay estimates on the individual data sets are in good agreement with each other and with the literature. combining the data sets, we obtain the most precise time-delay estimates to date on pg 1115+080, with δt(ab) = 8.3+1.5-1.6 days (18.7% precision), δt(ac) = 9.9+1.1-1.1 days (11.1%) and δt(bc) = 18.8+1.6-1.6 days (8.5%). turning these time delays into cosmological constraints is done in a companion paper that makes use of ground-based adaptive optics (ao) with the keck telescope. lightcurve data points 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/616/a183 | cosmograil. xvii. time delays for the quadruply imaged quasar pg 1115+080 |
we report detection of a very bright x-ray-uv-optical outburst of oj 287 in 2020 april-june, the second brightest since the beginning of our swift multiyear monitoring in late 2015. it is shown that the outburst is predominantly powered by jet emission. optical-uv-x-rays are closely correlated, and the low-energy part of the xmm-newton spectrum displays an exceptionally soft emission component consistent with a synchrotron origin. a much harder x-ray power-law component (γx = 2.4, still relatively steep when compared to expectations from inverse compton models) is detected out to 70 kev by nustar. we find evidence for reprocessing around the fe region, consistent with an absorption line. if confirmed, it implies matter in outflow at ∼0.1c. the multiyear swift light curve shows multiple episodes of flaring or dipping with a total amplitude of variability of a factor of 10 in x-rays, and 15 in the optical-uv. the 2020 outburst observations are consistent with an after-flare predicted by the binary black hole model of oj 287, where the disc impact of the secondary black hole triggers time-delayed accretion and jet activity of the primary black hole. | the 2020 april-june super-outburst of oj 287 and its long-term multiwavelength light curve with swift: binary supermassive black hole and jet activity |
we present atacama large millimeter/submillimeter array (alma) observations of eight highly excited co ({j_up} > 8) lines and continuum emission in two z ∼ 6 quasars: sdss j231038.88+185519.7 (hereafter j2310), for which co(8-7), co(9-8), and co(17-16) lines have been observed, and ulas j131911.29+095951.4 (j1319), observed in the co(14-13), co(17-16), and co(19-18) lines. the continuum emission of both quasars arises from a compact region (<0.9 kpc). by assuming a modified blackbody law, we estimate dust masses of log(mdust/m⊙) = 8.75 ± 0.07 and log(mdust/m⊙) = 8.8 ± 0.2 and dust temperatures of tdust = 76 ± 3 k and t_dust=66^{+15}_{-10} k, respectively, for j2310 and j1319. only co(8-7) and co(9-8) in j2310 are detected, while 3σ upper limits on luminosities are reported for the other lines of both quasars. the co line luminosities and upper limits measured in j2310 and j1319 are consistent with those observed in local active galactic nuclei and starburst galaxies, and other z ∼ 6 quasars, except for sdss j1148+5251 (j1148), the only quasar at z = 6.4 with a previous co(17-16) line detection. by computing the co spectral line energy distributions normalized to the co(6-5) line and far-infrared luminosities for j2310, j1319, and j1148, we conclude that different gas heating mechanisms (x-ray radiation and/or shocks) may explain the different co luminosities observed in these z ∼ 6 quasar. future {j_up} > 8 co observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-z quasars. | constraints on high-j co emission lines in z ∼ 6 quasars |
a minority of the optically selected quasar population are red at optical wavelengths due to the presence of dust along the line of sight. a key focus of many red quasar studies is to understand their relationship with the overall quasar population: are they blue quasars observed at a (slight) inclination angle or do they represent a transitional phase in the evolution of quasars? identifying fundamental differences between red and blue quasars is key to discriminate between these two paradigms. to robustly explore this, we have uniformly selected quasars from the sloan digital sky survey with mid-infrared counterparts, carefully controlling for luminosity and redshift effects. we take a novel approach to distinguish between colour-selected quasars in the redshift range of 0.2 < z < 2.4 by constructing redshift-sensitive g* - i* colour cuts. from cross-matching this sample to the faint images of the radio sky at twenty-centimeters (first) survey, we have found a factor ≈ 3 larger fraction of radio-detected red quasars with respect to that of blue quasars. through a visual inspection of the first images and an assessment of the radio luminosities (rest-frame {l_{1.4 ghz}} and {l_{1.4 ghz}}/{l_{6μ m}}), we find that the radio-detection excess for red quasars is primarily due to compact and radio-faint systems (around the radio-quiet - radio-loud threshold). we show that our results rule out orientation as the origin for the differences between red and blue quasars and argue that they provide broad agreement with an evolutionary model. | fundamental differences in the radio properties of red and blue quasars: evolution strongly favoured over orientation |
we investigate the relation between active galactic nucleus (agn) and star formation (sf) activity at 0.5 < z < 3 by analysing 898 galaxies with x-ray luminous agns (lx > 1044 erg s-1) and a large comparison sample of ~320 000 galaxies without x-ray luminous agns. our samples are selected from a large (11.8 deg2) area in stripe 82 that has multiwavelength (x-ray to far-ir) data. the enormous comoving volume (~0.3 gpc3) at 0.5 < z < 3 minimizes the effects of cosmic variance and captures a large number of massive galaxies (~30 000 galaxies with m* > 1011 m⊙) and x-ray luminous agns. while many galaxy studies discard agn hosts, we fit the sed of galaxies with and without x-ray luminous agns with code investigating galaxy emission and include agn emission templates. we find that without this inclusion, stellar masses and star formation rates (sfrs) in agn host galaxies can be overestimated, on average, by factors of up to ~5 and ~10, respectively. the average sfr of galaxies with x-ray luminous agns is higher by a factor of ~3-10 compared to galaxies without x-ray luminous agns at fixed stellar mass and redshift, suggesting that high sfrs and high agn x-ray luminosities may be fuelled by common mechanisms. the vast majority ($\gt 95 {{\ \rm per\ cent}}$) of galaxies with x-ray luminous agns at z = 0.5-3 do not show quenched sf: this suggests that if agn feedback quenches sf, the associated quenching process takes a significant time to act and the quenched phase sets in after the highly luminous phases of agn activity. | exploring agn and star formation activity of massive galaxies at cosmic noon |
we present a multiwavelength study of seven active galactic nuclei (agn) at spectroscopic redshift >2.5 in the 7 ms chandra deep field south that were selected for their good far-infrared (fir) and submillimeter (submm) detections. our aim is to investigate the possibility that the obscuration observed in the x-rays can be produced by the interstellar medium (ism) of the host galaxy. based on the 7 ms chandra spectra, we measured obscuring column densities nh, x in excess of 7 × 1022 cm-2 and intrinsic x-ray luminosities lx > 1044 erg s-1 for our targets, as well as equivalent widths for the fe kα emission line ewrest ≳ 0.5-1 kev. we built the uv-to-fir spectral energy distributions (seds) by using broadband photometry from the candels and herschel catalogs. by means of an sed decomposition technique, we derived stellar masses (m* ∼ 1011 m⊙), ir luminosities (lir > 1012 l⊙), star formation rates (sfr ∼ 190-1680 m⊙ yr-1) and agn bolometric luminosities (lbol ∼ 1046 erg s-1) for our sample. we used an empirically calibrated relation between gas masses and fir/submm luminosities and derived mgas ∼ 0.8-5.4 × 1010 m⊙. high-resolution (0.3-0.7″) alma data (when available, candels data otherwise) were used to estimate the galaxy size and hence the volume enclosing most of the ism under simple geometrical assumptions. these measurements were then combined to derive the column density associated with the ism of the host, which is on the order of nh, ism ∼ 1023-24 cm-2. the comparison between the ism column densities and those measured from the x-ray spectral analysis shows that they are similar. this suggests that at least at high redshift, significant absorption on kiloparsec scales by the dense ism in the host likely adds to or substitutes that produced by circumnuclear gas on parsec scales (i.e., the torus of unified models). the lack of unobscured agn among our ism-rich targets supports this scenario. | x-ray emission of z > 2.5 active galactic nuclei can be obscured by their host galaxies |
we study the relations between the mass of the central black hole (bh) mbh, the dark matter halo mass mh, and the stellar-to-halo mass fraction f⋆∝m⋆/mh in a sample of 55 nearby galaxies with dynamically measured $m_{\rm bh}\gt 10^6\, {\rm m}_\odot$ and $m_{\rm h}\gt 5\times 10^{11}\, {\rm m}_\odot$. the main improvement with respect to previous studies is that we consider both early- and late-type systems for which mh is determined either from globular cluster dynamics or from spatially resolved rotation curves. independently of their structural properties, galaxies in our sample build a well defined sequence in the mbh-mh-f⋆ space. we find that: (i) mh and mbh strongly correlate with each other and anticorrelate with f⋆; (ii) there is a break in the slope of the mbh-mh relation at mh of $10^{12}\, {\rm m}_\odot$, and in the f⋆-mbh relation at mbh of $\sim 10^7\!-\!10^8\, {\rm m}_\odot$; (iii) at a fixed mbh, galaxies with a larger f⋆ tend to occupy lighter haloes and to have later morphological types. we show that the observed trends can be reproduced by a simple equilibrium model in the λcdm framework where galaxies smoothly accrete dark and baryonic matter at a cosmological rate, having their stellar and bh build-up regulated both by the cooling of the available gas reservoir and by the negative feedback from star formation and active galactic nuclei (agns). feature (ii) arises as the bh population transits from a rapidly accreting phase to a more gentle and self-regulated growth, while scatter in the agn feedback efficiency can account for feature (iii). | a universal relation between the properties of supermassive black holes, galaxies, and dark matter haloes |
we construct the rest-frame 2-10 kev intrinsic x-ray luminosity function (xlf) of active galactic nuclei (agns) from a combination of x-ray surveys from the all-sky swift bat survey to the chandra deep field south. we use ∼3200 agns in our analysis, which covers six orders of magnitude in flux. the inclusion of xmm and chandra cosmos data has allowed us to investigate the detailed behavior of the xlf and evolution. in deriving our xlf, we take into account realistic agn spectrum templates, absorption corrections, and probability density distributions in photometric redshift. we present an analytical expression for the overall behavior of the xlf in terms of the luminosity-dependent density evolution, smoothed two-power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned xlf. we observe a sudden flattening of the low luminosity end slope of the xlf slope at z ≳0.6. detailed structures of the agn downsizing have also been revealed, where the number density curves have two clear breaks at all luminosity classes above log {{l}x}\gt 43. the two-break structure is suggestive of two-phase agn evolution, consisting of major merger triggering and secular processes. | detailed shape and evolutionary behavior of the x-ray luminosity function of active galactic nuclei |
simulations of the formation of large-scale structures predict that dark matter, low density highly ionized gas, and galaxies form 10 to 40 mpc scale filaments. these structures are easily recognized in the distribution of galaxies. here we use lyα absorption lines to study the gas in 30 × 6 mpc filament at cz ∼ 3500 km s-1, defined using a new catalog of nearby (cz < 10,000 km s-1) galaxies, which is complete down to a luminosity of about 0.05 l* for the region of space analyzed here. using hubble space telescope spectra of 24 active galactic nuclei, we sample the gas in this filament. all of our sightlines pass outside the virial radius of any known filament galaxy. within 500 kpc of the filament axis the detection rate is ∼80%, but no detections are seen more than 2.1 mpc from the filament axis. the width of the lyα lines correlates with filament impact parameter and the four blas in our sample occur within 400 kpc of the filament axis, indicating increased temperature and/or turbulence. comparing to simulations, we find that the recent haardt & madau extragalactic ionizing background predicts a factor of 3-5 too few ionizing photons. using a more intense radiation field matches the hydrogen density profile within 2.1 mpc of the filament axis, but the simulations still overpredict the detection rate between 2.1 and 5 mpc from the axis. the baryonic mass inside filament galaxies is 1.4 × 1013 m⊙, while the mass of filament gas outside galaxy halos is found to be 5.2 × {10}13 {m}⊙ . based on observations taken by 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, incorporated, under nasa contract nas5-26555. | nearby galaxy filaments and the ly-alpha forest: confronting simulations and the uv background with observations |
recent observations of the lyα forest show large-scale spatial variations in the intergalactic lyα opacity that grow rapidly with redshift at z\gt 5, far in excess of expectations from empirically motivated models. previous studies have attempted to explain this excess with spatial fluctuations in the ionizing background, but found that this required either extremely rare sources or problematically low values for the mean free path of ionizing photons. here we report that much—or potentially all—of the observed excess likely arises from residual spatial variations in temperature that are an inevitable byproduct of a patchy and extended reionization process. the amplitude of opacity fluctuations generated in this way depends on the timing and duration of reionization. if the entire excess is due to temperature variations alone, the observed fluctuation amplitude favors a late-ending but extended reionization process that was roughly half complete by z∼ 9 and that ended at z∼ 6. in this scenario, the highest opacities occur in regions that reionized earliest, since they have had the most time to cool, while the lowest opacities occur in the warmer regions that reionized most recently. this correspondence potentially opens a new observational window into patchy reionization. | large opacity variations in the high-redshift lyα forest: the signature of relic temperature fluctuations from patchy reionization |
this paper reports the first measurement of the relationship between turbulent velocity and cloud size in the diffuse circumgalactic medium (cgm) in typical galaxy halos at redshift z ≈ 0.4-1. through spectrally resolved absorption profiles of a suite of ionic transitions paired with careful ionization analyses of individual components, cool clumps of size as small as l cl ~ 1 pc and density lower than n h = 10-3 cm-3 are identified in galaxy halos. in addition, comparing the line widths between different elements for kinematically matched components provides robust empirical constraints on the thermal temperature t and the nonthermal motions b nt, independent of the ionization models. on average, b nt is found to increase with l cl following ${b}_{\mathrm{nt}}\propto {l}_{\mathrm{cl}}^{0.3}$ over three decades in spatial scale from l cl ≈ 1 pc to l cl ≈ 1 kpc. attributing the observed b nt to turbulent motions internal to the clumps, the best-fit b nt-l cl relation shows that the turbulence is consistent with kolmogorov at <1 kpc with a roughly constant energy transfer rate per unit mass of ϵ ≈ 0.003 cm2 s-3 and a dissipation timescale of ≲100 myr. no significant difference is found between massive quiescent and star-forming halos in the sample on scales less than 1 kpc. while the inferred ϵ is comparable to what is found in c iv absorbers at high redshift, it is considerably smaller than observed in star-forming gas or in extended line-emitting nebulae around distant quasars. a brief discussion of possible sources to drive the observed turbulence in the cool cgm is presented. | the cosmic ultraviolet baryon survey: empirical characterization of turbulence in the cool circumgalactic medium |
we present jwst/nirspec r ≃ 2700 spectra of four high-redshift quasars: vdes j0020-3653 (z = 6.860), dels j0411-0907 (z = 6.825), uhs j0439+1634 (z = 6.519), and ulas j1342+0928 (z = 7.535). the exquisite data quality, signal-to-noise ratio of 50-200, and large 0.86 μm ≤ λ ≤ 5.5 μm spectral coverage allowed us to identify between 13 and 17 intervening and proximate metal absorption line systems in each quasar spectrum, with a total number of 61 absorption-line systems detected at 2.42 < z < 7.48 including the highest redshift intervening o iλ1302 and mg ii systems at z = 7.37 and z = 7.44. we investigated the evolution of the metal enrichment in the epoch of re-ionisation (eor) at z > 6 and found the following: i) a continued increase in the low-ionisation o i, c ii, and si ii incidence, ii) decreasing high-ionisation c iv and si iv incidence with a transition from predominantly high- to low-ionisation at z ≈ 6.0, and iii) a constant mg ii incidence across all redshifts. the observations support a change in the ionisation state of the intergalactic medium in the eor rather than a change in metallicity. the abundance ratio of [si/o] in five z > 6 absorption systems show enrichment signatures produced by low-mass pop iii pair instability supernovae, and possibly pop iii hypernovae. in the gunn-peterson troughs, we detected transmission spikes where lyα photons can escape. from 22 intervening absorption line systems at z > 5.7, only a single low-ionisation system out of 13 lies within 2000 km s−1 from a spike, while four high-ionisation systems out of nine lie within ∼2000 km s−1 from a spike. most spikes do not have associated metal absorbers close by. this confirms that star-forming galaxies responsible for producing the heavy elements that are transported to the circumgalactic medium via galaxy winds do so in predominantly high-density, neutral environments, while lower density environments are ionised without being polluted by metals at z ≈ 6 − 7. | metal enrichment and evolution in four z > 6.5 quasar sightlines observed with jwst/nirspec |
galaxy mergers produce pairs of supermassive black holes (smbhs), which may be witnessed as dual quasars if both smbhs are rapidly accreting. the kiloparsec (kpc)-scale separation represents a physical regime sufficiently close for merger-induced effects to be important1 yet wide enough to be directly resolvable with the facilities currently available. whereas many kpc-scale, dual active galactic nuclei—the low-luminosity counterparts of quasars—have been observed in low-redshift mergers2, no unambiguous dual quasar is known at cosmic noon (z ≈ 2), the peak of global star formation and quasar activity3,4. here we report multiwavelength observations of sloan digital sky survey (sdss) j0749 + 2255 as a kpc-scale, dual-quasar system hosted by a galaxy merger at cosmic noon (z = 2.17). we discover extended host galaxies associated with the much brighter compact quasar nuclei (separated by 0.46″ or 3.8 kpc) and low-surface-brightness tidal features as evidence for galactic interactions. unlike its low-redshift and low-luminosity counterparts, sdss j0749 + 2255 is hosted by massive compact disk-dominated galaxies. the apparent lack of stellar bulges and the fact that sdss j0749 + 2255 already follows the local smbh mass-host stellar mass relation, suggest that at least some smbhs may have formed before their host stellar bulges. while still at kpc-scale separations where the host-galaxy gravitational potential dominates, the two smbhs may evolve into a gravitationally bound binary system in around 0.22 gyr. | a close quasar pair in a disk-disk galaxy merger at z = 2.17 |
new reverberation mapping (rm) measurements, combined with accurate luminosities and line ratios, provide strong constraints on the location of the line emitting gas in the broad-line region (blr) of active galactic nuclei (agns). in this paper, i present new calculations of radiation pressure and magnetic pressure confined clouds and apply them to a 'generic agn' and to ngc 5548. the new calculations are in good agreement with the observed lags of all broad emission lines, and with the luminosities of ly α, c iv 1549, o vi 1035, and he ii 1640. they are also in reasonable agreement with the luminosities of mg ii 2798 and the 1990 å blend of c iii] and si iii] lines for high-metallicity gas. they explain the changes in time-lag following an increase in continuum luminosity and their dependencies on the inner and outer boundaries of the blr. they also predict very strong balmer and paschen continua with important implications to continuum rm experiments. however, the calculated balmer and paschen line luminosities are too weak, by factors of 2-5. this 'balmer line crisis' was noted in several earlier works and is now confirmed and constrained by rm measurements that were not available in the past. it seems that present photoionization codes that use the escape probability formalism fail to correctly compute the balmer line luminosities in high-density, large optical depth gas. | testing broad-line region models with reverberation mapping |
we report the results of decade-long (2008-2018) γ-ray to 1 ghz radio monitoring of the blazar 3c 279, including gasp/webt, fermi and swift data, as well as polarimetric and spectroscopic data. the x-ray and γ-ray light curves correlate well, with no delay ≳ 3 h, implying general cospatiality of the emission regions. the γ-ray-optical flux-flux relation changes with activity state, ranging from a linear to a more complex dependence. the behaviour of the stokes parameters at optical and radio wavelengths, including 43 ghz very long baseline array images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk lorentz factors close to those needed to explain γ-ray variability on very short time-scales. the mg ii emission line flux in the `blue' and `red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse compton scattering. in the radio bands, we find progressive delays of the most prominent light-curve maxima with decreasing frequency, as expected from the frequency dependence of the τ = 1 surface of synchrotron self-absorption. the global maximum in the 86 ghz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at ∼5 ghz. these tendencies suggest different doppler boosting of stratified radio-emitting zones in the jet. | multiwavelength behaviour of the blazar 3c 279: decade-long study from γ-ray to radio |
deep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (uv) emission line properties of galaxies at z ∼ 2 - 4.5. here we combine vlt/muse guaranteed time observations of the hubble deep field south, ultra deep field, cosmos, and several quasar fields with other publicly available data from vlt/vimos and vlt/fors2 to construct a catalogue of he ii λ1640 emitters at z ≳ 2. the deepest areas of our muse pointings reach a 3σ line flux limit of 3.1 × 10-19 erg s-1 cm-2. after discarding broad-line active galactic nuclei, we find 13 he ii λ1640 detections from muse with a median muv = -20.1 and 21 tentative he ii λ1640 detections from other public surveys. excluding lyα, all except two galaxies in our sample show at least one other rest-uv emission line, with c iii] λ1907, λ1909 being the most prominent. we use multi-wavelength data available in the hubble legacy fields to derive basic galaxy properties of our sample through spectral energy distribution fitting techniques. taking advantage of the high-quality spectra obtained by muse (∼10 - 30 h of exposure time per pointing), we use photo-ionisation models to study the rest-uv emission line diagnostics of the he ii λ1640 emitters. line ratios of our sample can be reproduced by moderately sub-solar photo-ionisation models, however, we find that including effects of binary stars lead to degeneracies in most free parameters. even after considering extra ionising photons produced by extreme sub-solar metallicity binary stellar models, photo-ionisation models are unable to reproduce rest-frame he ii λ1640 equivalent widths (∼0.2 - 10 å), thus additional mechanisms are necessary in models to match the observed he ii λ1640 properties. | exploring he ii λ1640 emission line properties at z ∼2-4 |
we present accretion disk structure measurements from continuum lags in the sloan digital sky survey reverberation mapping (sdss-rm) project. lags are measured using the javelin software from the first-year sdss-rm g and i photometry, resulting in well-defined lags for 95 quasars, 33 of which have lag s/n > 2σ. we also estimate lags using the iccf software and find consistent results, though with larger uncertainties. accretion disk structure is fit using a markov chain monte carlo approach, parameterizing the measured continuum lags as a function of disk size normalization, wavelength, black hole mass, and luminosity. in contrast with previous observations, our best-fit disk sizes and color profiles are consistent (within 1.5σ) with the shakura & sunyaev analytic solution. we also find that more massive quasars have larger accretion disks, similarly consistent with the analytic accretion disk model. the data are inconclusive on a correlation between disk size and continuum luminosity, with results that are consistent with both no correlation and the shakura & sunyaev expectation. the continuum lag fits have a large excess dispersion, indicating that our measured lag errors are underestimated and/or our best-fit model may be missing the effects of orientation, spin, and/or radiative efficiency. we demonstrate that fitting disk parameters using only the highest-s/n lag measurements biases best-fit disk sizes to be larger than the disk sizes recovered using a bayesian approach on the full sample of well-defined lags. | the sloan digital sky survey reverberation mapping project: accretion disk sizes from continuum lags |
we report the discovery of x-ray emission from cfhqs j142952+544717, the most distant known radio-loud quasar at z = 6.18, on 2019 december 10-11 with the erosita telescope on board the srg satellite during its ongoing all-sky survey. the object was identified by cross-matching an intermediate srg/erosita source catalogue with the pan-starrs1 distant quasar sample at 5.6 < z < 6.7. the measured flux ∼8 × 10-14 erg cm-2 s-1 in the 0.3-2 kev energy band corresponds to an x-ray luminosity of $2.6^{+1.7}_{-1.0}\times 10^{46}$ erg s-1 in the 2-10 kev rest-frame energy band, which renders cfhqs j142952+544717 the most x-ray luminous quasar ever observed at z > 6. combining our x-ray measurements with archival and new photometric measurements in other wavebands (radio to optical), we estimate the bolometric luminosity of this quasar at ∼(2-3) × 1047 erg s-1. assuming eddington limited accretion and isotropic emission, we infer a lower limit on the mass of the supermassive black hole of ∼2 × 109 m⊙. the most salient feature of cfhqs j142952+544717 is its x-ray brightness relative to the optical/uv emission. we argue that it may be linked to its radio-loudness (although the object is not a blazar according to its radio properties), specifically to a contribution of inverse compton scattering of cosmic microwave background photons off relativistic electrons in the jets. if so, cfhqs j142952+544717 might be the tip of the iceberg of high-z quasars with enhanced x-ray emission, and srg/erosita may find many more such objects during its 4-yr all-sky survey. | srg/erosita uncovers the most x-ray luminous quasar at z > 6 |
since the discovery of z ∼ 6 quasars two decades ago, studies of their ly α-transparent proximity zones have largely focused on their utility as a probe of cosmic reionization. but even when in a highly ionized intergalactic medium, these zones provide a rich laboratory for determining the time-scales that govern quasar activity and the concomitant growth of their supermassive black holes. in this work, we use a suite of 1d radiative transfer simulations of quasar proximity zones to explore their time-dependent behaviour for activity time-scales from ∼103 to 108 yr. the sizes of the simulated proximity zones, as quantified by the distance at which the smoothed ly α transmission drops below 10 per cent (denoted rp), are in excellent agreement with observations, with the exception of a handful of particularly small zones that have been attributed to extremely short ≲104 lifetimes. we develop a physically motivated semi-analytic model of proximity zones which captures the bulk of their equilibrium and non-equilibrium behaviour, and use this model to investigate how quasar variability on ≲105 yr time-scales is imprinted on the distribution of observed proximity zone sizes. we show that large variations in the ionizing luminosity of quasars on time-scales of ≲104 yr are disfavoured based on the good agreement between the observed distribution of rp and our model prediction based on `lightbulb' (i.e. steady constant emission) light curves. | time-dependent behaviour of quasar proximity zones at z ∼ 6 |
in this work, we present 8523 pairs of r-band optical photometry observations for the quasar 3c 454.3 made during the period of 2006 october-2018 february on the 70 cm meniscus telescope at abastumani observatory, georgia, to study its intraday variabilities (idvs) and long-term variations, and we have come to the following results. (1) we detected 10 outbursts, a δr = 3.825 mag variation, and some idvs. the idv timescales are from 4.1 to 285 minutes, with the corresponding variability amplitude being a = 2.9%-43.67%. the amplitude increases with idv timescale. (2) the largest variation over a 1 day timescale is δr = 1.38 mag. (3) the idv timescales suggest that the emission sizes are from 8.9 × 1013 cm to 6.20 × 1015 cm, and the magnetic field strengths are b = 0.18-0.79 g. (4) period analysis results show three possible long-term periods, p = 3.04 ± 0.02 yr, p = 1.66 ± 0.06 yr, and p = 1.20 ± 0.03 yr in the optical light curve. we adopted the accretion disk models and the lighthouse models to period p = 3.04 ± 0.02 yr: in the accretion disk models, the binary black holes have masses m = 1.17 × 109 m ⊙ in the lighthouse models, we used two boosted jet flux densities to fit the observational light curve. (5) wwz analysis gives some short-period (high-frequency) signals associated with strong bursts (jd 2,454,302 and jd 2,454,521) with variable frequencies and lasting for the entire observation time span (11.3 yr). | optical photometry of the quasar 3c 454.3 during the period 2006-2018 and the long-term periodicity analysis |
the triggering mechanism for the most luminous, quasar-like active galactic nuclei (agn) remains a source of debate, with some studies favouring triggering via galaxy mergers, but others finding little evidence to support this mechanism. here, we present deep isaac newton telescope/wide field camera imaging observations of a complete sample of 48 optically selected type 2 quasars - the qsofeed sample ($l_{\rm [o\, \small {iii}]}\gt 10^{8.5}\, \mathrm{l}_{\odot }$; z < 0.14). based on visual inspection by eight classifiers, we find clear evidence that galaxy interactions are the dominant triggering mechanism for quasar activity in the local universe, with 65$^{+6}_{-7}$ per cent of the type 2 quasar hosts showing morphological features consistent with galaxy mergers or encounters, compared with only 22$^{+5}_{-4}$ per cent of a stellar-mass- and redshift-matched comparison sample of non-agn galaxies - a 5σ difference. the type 2 quasar hosts are a factor of 3.0$^{+0.5}_{-0.8}$ more likely to be morphologically disturbed than their matched non-agn counterparts, similar to our previous results for powerful 3cr radio agn of comparable [o iii] emission-line luminosity and redshift. in contrast to the idea that quasars are triggered at the peaks of galaxy mergers as the two nuclei coalesce, and only become visible post-coalescence, the majority of morphologically disturbed type 2 quasar sources in our sample are observed in the pre-coalescence phase (61$^{+8}_{-9}$ per cent). we argue that much of the apparent ambiguity that surrounds observational results in this field is a result of differences in the surface brightness depths of the observations, combined with the effects of cosmological surface brightness dimming. | galaxy interactions are the dominant trigger for local type 2 quasars |
we present the second catalog and data release of optical spectral line measurements and active galactic nucleus (agn) demographics of the bat agn spectroscopic survey, which focuses on the swift-bat hard x-ray detected agns. we use spectra from dedicated campaigns and publicly available archives to investigate spectral properties of most of the agns listed in the 70 month swift-bat all-sky catalog; specifically, 743 of the 746 unbeamed and unlensed agns (99.6%). we find a good correspondence between the optical emission line widths and the hydrogen column density distributions using the x-ray spectra, with a clear dichotomy of agn types for n h = 1022 cm-2. based on optical emission-line diagnostics, we show that 48%-75% of bat agns are classified as seyfert, depending on the choice of emission lines used in the diagnostics. the fraction of objects with upper limits on line emission varies from 6% to 20%. roughly 4% of the bat agns have lines too weak to be placed on the most commonly used diagnostic diagram, [o iii]λ5007/hβ versus [n ii]λ6584/hα, despite the high signal-to-noise ratio of their spectra. this value increases to 35% in the [o iii]λ5007/[o ii]λ3727 diagram, owing to difficulties in line detection. compared to optically selected narrow-line agns in the sloan digital sky survey, the bat narrow-line agns have a higher rate of reddening/extinction, with hα/hβ > 5 (~36%), indicating that hard x-ray selection more effectively detects obscured agns from the underlying agn population. finally, we present a subpopulation of agns that feature complex broad lines (34%, 250/743) or double-peaked narrow emission lines (2%, 17/743). | bass. xxiv. the bass dr2 spectroscopic line measurements and agn demographics |
using recent empirical constraints on the dark matter halo-galaxy-supermassive black hole (smbh) connection from z = 0-7, we infer how undermassive, typical, and overmassive smbhs contribute to the quasar luminosity function (qlf) at z = 6. we find that beyond lbol = 5 × 1046 erg s-1, the z = 6 qlf is dominated by smbhs that are at least 0.3 dex above the z = 6 median m•-m* relation. the qlf is dominated by typical smbhs (i.e. within ±0.3 dex around the m•-m* relation) at lbol ≲ 1045 erg s-1. at z ~ 6, the intrinsic m•-m* relation for all smbhs is slightly steeper than the z = 0 scaling, with a similar normalization at $m_* \sim 10^{11} \, \mathrm{m}_\odot$. we also predict the m•-m* relation for z = 6 bright quasars selected by different bolometric luminosity thresholds, finding very good agreement with observations. for quasars with lbol > 3 × 1046 (1048) erg s-1, the scaling relation is shifted upwards by ~0.35 (1.0) dex for 1011m⊙ galaxies. to accurately measure the intrinsic m•-m* relation, it is essential to include fainter quasars with lbol ≲ 1045 erg s-1. at high redshifts, low-luminosity quasars are thus the best targets for understanding typical formation paths for smbhs in galaxies. | trinity ii: the luminosity-dependent bias of the supermassive black hole mass-galaxy mass relation for bright quasars at z = 6 |
in theoretical analyses of ultrafast spin dynamics simulated phenomena are commonly discussed in terms of observables. in this paper we report on possible benefits of complementing such studies by quantum state (qs) measures. these measures quantify specific properties of qss, e.g. distance in hilbert space and mixing. for co/cu heterostructures illuminated by femtosecond laser pulses, we discuss the general behavior of selected measures, but address in particular the degree of perturbation by a laser pulse. it turns out that the measures are especially sensitive to variations of the polarization of a laser pulse and the sample composition. moreover, they are closely linked to magnetization and number of photo-excited electrons. | ultrafast spin dynamics: complementing theoretical analyses by quantum state measures |
flat spectrum radio quasar (fsrq) is the most luminous blazar at the gev energies. in this paper, we probe the photon-axion-like particle (alp) oscillation effect on the latest very-high-energy (vhe) γ-ray observations of the fsrq 4c+21.35 (pks 1222+216). the γ-ray spectra are measured by the collaborations major atmospheric gamma imaging cherenkov telescopes (magic), very energetic radiation imaging telescope array system (veritas), and fermi large area telescope (fermi-lat), which cover two activity vhe flares of 4c+21.35 in 2010 and 2014. we show the spectral energy distributions (seds) of these two phases under the null and alp hypotheses, and set the combined limit on the alp parameter space. the 95% c . l . combined limit set by the fsrq 4c+21.35 observations measured by magic, veritas, and fermi-lat in the ma -gaγ plane is roughly at the photon-alp coupling gaγ ≳ 8 ×10-12gev-1 for the alp mass [ 2 ×10-10ev ≲ma ≲ 2 ×10-8ev ]. compared with the constraint of ngc 1275 set by fermi-lat, no stringent limit result is derived with the photon-alp coupling gaγ from the fsrq 4c+21.35, while this result could slightly broaden the alp mass ma limit at the low-mass region. | probing photon-alp oscillations from the flat spectrum radio quasar 4c+21.35 |
observations of the early universe suggest that reionization was complete by z ∼ 6, however, the exact history of this process is still unknown. one method for measuring the evolution of the neutral fraction throughout this epoch is via observing the lyα damping wings of high-redshift quasars. in order to constrain the neutral fraction from quasar observations, one needs an accurate model of the quasar spectrum around lyα, after the spectrum has been processed by its host galaxy but before it is altered by absorption and damping in the intervening intergalactic medium (igm). in this paper, we present a novel machine learning approach, using artificial neural networks, to reconstruct quasar continua around lyα. our quasar spectra from artificial neural network based predictive regression algorithm(qsanndra) improves the error in this reconstruction compared to the state-of-the-art principal component analysis (pca) based model in the literature by 14.2 per cent on average, and provides an improvement of 6.1 per cent on average when compared to an extension thereof. in comparison with the extended pca model, qsanndra further achieves an improvement of 22.1 per cent and 16.8 per cent when evaluated on low-redshift quasars most similar to the two high-redshift quasars under consideration, ulas j1120+0641 at z = 7.0851 and ulas j1342+0928 at z = 7.5413, respectively. using our more accurate reconstructions of these two z > 7 quasars, we estimate the neutral fraction of the igm using a homogeneous reionization model and find $\bar{x}_\mathrm{h\, \small{i}} = 0.25^{+0.05}_{-0.05}$ at z = 7.0851 and $\bar{x}_\mathrm{h\, \small{i}} = 0.60^{+0.11}_{-0.11}$ at z = 7.5413. our results are consistent with the literature and favour a rapid end to reionization. | reionization history constraints from neural network based predictions of high-redshift quasar continua |
this paper presents a systematic study of the photoionization and thermodynamic properties of the cool circumgalactic medium (cgm) as traced by rest-frame ultraviolet absorption lines around 26 galaxies at redshift z ≲ 1. the study utilizes both high-quality far-ultraviolet and optical spectra of background qsos and deep galaxy redshift surveys to characterize the gas density, temperature, and pressure of individual absorbing components and to resolve their internal non-thermal motions. the derived gas density spans more than three decades, from $\log (n_{\rm h}/{{\rm cm^{-3}}}) \approx -4$ to -1, while the temperature of the gas is confined in a narrow range of log (t/k) ≈ 4.3 ± 0.3. in addition, a weak anticorrelation between gas density and temperature is observed, consistent with the expectation of the gas being in photoionization equilibrium. furthermore, decomposing the observed line widths into thermal and non-thermal contributions reveals that more than 30 per cent of the components at z ≲ 1 exhibit line widths driven by non-thermal motions, in comparison to <20 per cent found at z ≈ 2-3. attributing the observed non-thermal line widths to intra-clump turbulence, we find that massive quenched galaxies on average exhibit higher non-thermal broadening/turbulent energy in their cgm compared to star-forming galaxies at z ≲ 1. finally, strong absorption features from multiple ions covering a wide range of ionization energy (e.g. from mg ii to o iv) can be present simultaneously in a single absorption system with kinematically aligned component structure, but the inferred pressure in different phases may differ by a factor of ≈10. | the cosmic ultraviolet baryon survey (cubs) v: on the thermodynamic properties of the cool circumgalactic medium at z ≲ 1 |
supermassive black holes (smbhs) are a key catalyst of galaxy formation and evolution, leading to an observed correlation between smbh mass mbh and host galaxy velocity dispersion σe. outside the local universe, measurements of mbh are usually only possible for smbhs in an active state: limiting sample size and introducing selection biases. gravitational lensing makes it possible to measure the mass of non-active smbhs. we present models of the $z$ = 0.169 galaxy-scale strong lens abell 1201. a cd galaxy in a galaxy cluster, it has sufficient 'external shear' that a magnified image of a $z$ = 0.451 background galaxy is projected just ~1 kpc from the galaxy centre. using multiband hubble space telescope imaging and the lens modelling software pyautolens, we reconstruct the distribution of mass along this line of sight. bayesian model comparison favours a point mass with mbh = 3.27 ± 2.12 × 1010 m⊙ (3σ confidence limit); an ultramassive black hole. one model gives a comparable bayesian evidence without an smbh; however, we argue this model is nonphysical given its base assumptions. this model still provides an upper limit of mbh ≤ 5.3 × 1010 m⊙, because an smbh above this mass deforms the lensed image ~1 kpc from abell 1201's centre. this builds on previous work using central images to place upper limits on mbh, but is the first to also place a lower limit and without a central image being observed. the success of this method suggests that surveys during the next decade could measure thousands more smbh masses, and any redshift evolution of the mbh-σe relation. results are available at https://github.com/jammy2211/autolens_abell_1201. | abell 1201: detection of an ultramassive black hole in a strong gravitational lens |
we use two model-independent methods to constrain the curvature of the universe. in the first method, we study the evolution of the curvature parameter (ωk0) with redshift by using the observations of the hubble parameter and transverse comoving distances obtained from the age of galaxies. secondly, we also use an indirect method based on the mean image separation statistics of gravitationally lensed quasars. the basis of this methodology is that the average image separation of lensed images will show a positive, negative or zero correlation with the source redshift in a closed, open or flat universe respectively. in order to smoothen the datasets used in both the methods, we use a non-parametric method namely, gaussian process (gp). finally from first method we obtain ωk0 = 0.025±0.57 for a presumed flat universe while the cosmic curvature remains constant throughout the redshift region 0 < z < 1.37 which indicates that the universe may be homogeneous. moreover, the combined result from both the methods suggests that the universe is marginally closed. however, a flat universe can be incorporated at 3σ level. | constraining cosmic curvature by using age of galaxies and gravitational lenses |
we discuss the production of ultra-high-energy cosmic-ray (uhecr) nuclei and neutrinos from blazars. we compute the nuclear cascade in the jet for both bl lac objects and flat-spectrum radio quasars (fsrqs), and in the ambient radiation zones for fsrqs as well. by modeling representative spectral energy distributions along the blazar sequence, two distinct regimes are identified, which we call “nuclear survival” (typically found in low-luminosity bl lacs) and “nuclear cascade” (typically found in high-luminosity fsrqs). we quantify how the neutrino and cosmic-ray (cr) emission efficiencies evolve over the blazar sequence, and we demonstrate that neutrinos and crs come from very different object classes. for example, high-frequency-peaked bl lacs (hbls) tend to produce crs, and high-luminosity fsrqs are the more efficient neutrino emitters. this conclusion does not depend on the cr escape mechanism, for which we discuss two alternatives (diffusive and advective escape). finally, the neutrino spectrum from blazars is shown to significantly depend on the injection composition into the jet, especially in the nuclear cascade case: injection compositions heavier than protons lead to reduced neutrino production at the peak, which moves at the same time to lower energies. thus, these sources will exhibit better compatibility with the observed icecube and uhecr data. | neutrinos and ultra-high-energy cosmic-ray nuclei from blazars |
we present our alma cycle 4 measurements of the [c ii] emission line and the underlying far-infrared (fir) continuum emission from four optically low-luminosity (m1450 > -25) quasars at z ≳ 6 discovered by the subaru hyper suprime cam (hsc) survey. the [c ii] line and fir continuum luminosities lie in the ranges l_[c ii] = (3.8-10.2)× 108 l_{⊙} and lfir = (1.2-2.0) × 1011 l_{⊙}, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. we estimate the star formation rates (sfrs) of our targets as ≃ 23-40 m_{⊙} yr-1. their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their sfr or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. the l_[c ii}]}/l_fir ratios of the hosts, ≃ (2.2-8.7) × 10-3, are fully consistent with local star-forming galaxies. using the [c ii] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≃ (1.4-8.2) × 1010 m_{⊙}. by interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ∼ 6, i.e., they appear to be transforming into quiescent galaxies. this is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the hsc ones, are consistent with the local value. the mass ratios of the hsc quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution. | subaru high-z exploration of low-luminosity quasars (shellqs). iii. star formation properties of the host galaxies at z ≳ 6 studied with alma |
we present the technicolor dawn simulations, a suite of cosmological radiation hydrodynamic simulations of the first 1.2 billion yr. by modelling a spatially inhomogeneous ultraviolet background (uvb) on the fly with 24 frequencies and resolving dark matter haloes down to 108 m⊙ within 12 h-1 mpc volumes, our simulations unify observations of the intergalactic and circumgalactic media, galaxies, and reionization into a common framework. the only empirically tuned parameter, the fraction fesc,gal(z) of ionizing photons that escape the interstellar medium, is adjusted to match observations of the lyman-α forest and the cosmic microwave background. with this single calibration, our simulations reproduce the history of reionization; the stellar mass and star formation rate relation of galaxies; the number density and metallicity of damped lyman-α absorbers (dlas) at z ∼ 5; the abundance of weak metal absorbers; the ultraviolet background amplitude; and the lyman-α flux power spectrum at z = 5.4. the galaxy stellar mass and ultraviolet luminosity functions are underproduced by ≤2 ×, suggesting an overly vigorous feedback model. the mean transmission in the lyman-α forest is underproduced at z < 6, indicating tension between measurements of the uvb amplitude and lyman-α transmission. the observed si iv column density distribution is reasonably well reproduced (∼1σ low). by contrast, c iv remains significantly underproduced despite being boosted by an intense >4 ryd uvb. solving this problem by increasing metal yields would overproduce both weak absorbers and dla metallicities. instead, the observed strength of high-ionization emission from high-redshift galaxies and absorption from their environments suggest that the ionizing flux from conventional stellar population models is too soft. | reionization in technicolor |
modern cosmology predicts that a galaxy overdensity (e.g., protocluster) will be associated with a large intergalactic medium gas reservoir, which can be traced by lyα forest absorption. we have undertaken a systematic study of the relation between coherently strong intergalactic lyα absorption systems (coslas), which have the highest optical depth (τ) in the τ distribution, and mass overdensities on the scales of ∼10-20 h -1 comoving mpc. on such large scales, our cosmological simulations show a strong correlation between the effective optical depth (τ eff) of the coslas and the three-dimensional mass overdensity. in spectra with moderate signal-to-noise ratio, however, the profiles of coslas can be confused with individual high column density absorbers. for z > 2.6, where the corresponding lyβ is redshifted to the optical, we have developed a selection technique to distinguish between these two alternatives. we have applied this technique to ∼6000 sight lines provided by sloan digital sky survey iii quasar survey at z = 2.6-3.3 with a continuum-to-noise ratio greater than 8, and we present a sample of five cosla candidates with τ eff on 15 h -1 mpc greater than 4.5× the mean optical depth. at lower redshifts of z < 2.6, where the background quasar density is higher, the overdensity can be traced by intergalactic absorption groups using multiple sight lines with small angular separations. our overdensity searches fully use the current and next generation of lyα forest surveys, which cover a survey volume of >1 (h -1 gpc)3. systems traced by coslas will yield a uniform sample of the most massive overdensities at z > 2 to provide stringent constraints to models of structure formation. | mapping the most massive overdensity through hydrogen (mammoth) i: methodology |
the connection between multifrequency quasar observational and physical parameters related to accretion processes is still open to debate. in the last 20 year, eigenvector 1-based approaches developed since the early papers by boroson and green (1992) and sulentic et al. (2000b) have been proved to be a remarkably powerful tool to investigate this issue, and have led to the definition of a quasar "main sequence". in this paper we perform a cladistic analysis on two samples of 215 and 85 low-z quasars (z ~ 0.7) which were studied in several previous works and which offer a satisfactory coverage of the eigenvector 1-derived main sequence. the data encompass accurate measurements of observational parameters which represents key aspects associated with the structural diversity of quasars. cladistics is able to group sources radiating at higher eddington ratios, as well as to separate radio-quiet (rq) and radio-loud (rl) quasars. the analysis suggests a black hole mass threshold for powerful radio emission and also properly distinguishes core-dominated and lobe-dominated quasars, in accordance with the basic tenet of rl unification schemes. considering that black hole mass provides a sort of "arrow of time" of nuclear activity, a phylogenetic interpretation becomes possible if cladistic trees are rooted on black hole mass: the ontogeny of black holes is represented by their monotonic increase in mass. more massive radio-quiet population b sources at low-z become a more evolved counterpart of population a i.e., wind dominated sources to which the "local" narrow-line seyfert 1s belong. | the phylogeny of quasars and the ontogeny of their central black holes |
we report the results of the strong lensing insights into the dark energy survey (strides) follow-up campaign of the late 2017/early 2018 season. we obtained spectra of 65 lensed quasar candidates with eso faint object spectrograph and camera 2 on the ntt and echellette spectrograph and imager on keck, confirming 10 new lensed quasars and 10 quasar pairs. eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (desj0345-2545, z = 1.68), and one is quadruply imaged (quad: desj0053-2012, z = 3.8). singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from sami on southern astrophysical research telescope or near infrared camera 2 on keck, give total magnifications between 3.2 and 5.6, and einstein radii between 0.49 and 1.97 arcsec. after spectroscopic follow-up, we extract multi-epoch grizy photometry of confirmed lensed quasars and contaminant quasar + star pairs from des data using parametric multiband modelling, and compare variability in each system's components. by measuring the reduced χ2 associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51-70 per cent, with most remaining contaminants being star-forming galaxies. using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete des magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads. | the strong lensing insights into the dark energy survey (strides) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs |
the star formation activity of the host galaxies of active galactic nuclei provides valuable insights into the complex interconnections between black hole growth and galaxy evolution. a major obstacle arises from the difficulty of estimating accurate star formation rates (sfrs) in the presence of a strong active galactic nucleus. analyzing the 1-500 μm spectral energy distributions and high-resolution mid-infrared spectra of low-redshift (z < 0.5) palomar-green quasars with bolometric luminosity of ∼1044.5-1047.5 erg s-1, we find, from comparison with an independent sfr indicator based on [ne ii] 12.81 μm and [ne iii] 15.56 μm, that the torus-subtracted, total infrared (8-1000 μm) emission yields robust sfrs in the range of ∼1-250 m⊙ yr-1. combined with available stellar mass estimates, the vast majority (∼75%-90%) of the quasars lie on or above the main sequence of local star-forming galaxies, including a significant fraction (∼50%-70%) that would qualify as starburst systems. this is further supported by the high star formation efficiencies derived from the gas content inferred from the dust masses. inspection of high-resolution hubble space telescope images reveals a wide diversity of morphological types, including a number of starbursting hosts that have not experienced significant recent dynamical perturbations. the origin of the high star formation efficiency is unknown. | the infrared emission and vigorous star formation of low-redshift quasars |
quark stars are terrestrial laboratories to study fundamental physics at ultrahigh densities and temperatures. in this work, we investigate the internal structure and the physical properties of quark stars (qss) in the rastall gravity. rastall gravity is considered a non-conservative theory of gravity, which is an effective gravity theory at high energy density, e.g., relevant to the early universe and dense, compact objects. we derive the hydrostatic equilibrium structure for qss with the inclusion of anisotropic pressure. more specifically, we find the qs mass-radius relations for the mit bag model. we focus on the model depending on the rastall free parameter η and examine the deviations from the general relativity (gr) counterparts. | the criteria of the anisotropic quark star models in rastall gravity |
several recent simulations of galaxy formation predict two main phases of supermassive black hole (bh) accretion: an early, highly intermittent phase (during which bhs are undermassive relative to local scaling relations), followed by a phase of accelerated growth. we investigate physical factors that drive the transition in bh accretion in cosmological zoom-in simulations from the fire project, ranging from dwarf galaxies to galaxies sufficiently massive to host luminous quasars. the simulations model multichannel stellar feedback, but neglect agn feedback. we show that multiple physical properties, including halo mass, galaxy stellar mass, and depth of the central gravitational potential correlate with accelerated bh fuelling: constant thresholds in these properties are typically crossed within ~0.1 hubble time of accelerated bh fuelling. black hole masses increase sharply when the stellar surface density in the inner 1 kpc crosses a threshold $\sigma^\star _{1\,\rm kpc}\approx 10^{9.5} \, {\rm m_{\odot }}\,{\rm kpc}^{-2}$, a characteristic value above which gravity prevents stellar feedback from ejecting gas, and similar to the value above which galaxies are observed to quench. we further show that accelerated bh growth correlates with the emergence of long-lived thin gas discs, as well as with virialization of the inner circumgalactic medium. the halo mass mhalo ~ 1012 m⊙ and stellar mass m* ~ 1010.5 m⊙ at which bh growth accelerates correspond to ~l⋆ galaxies. the fact that stellar feedback becomes inefficient at ejecting gas from the nucleus above this mass scale may play an important role in explaining why agn feedback appears to be most important in galaxies above l⋆. | stellar feedback-regulated black hole growth: driving factors from nuclear to halo scales |
inspired by the recent remarkable progress in the experimental test of local realism, we report here such a test that achieves an efficiency greater than (78 %)2 for entangled photon pairs separated by 183 m. further utilizing the randomness in cosmic photons from pairs of stars on the opposite sides of the sky for the measurement setting choices, we not only close the locality and detection loopholes simultaneously, but also test the null hypothesis against local hidden variable mechanisms for events that took place 11 years ago (13 orders of magnitude longer than previous experiments). after considering the bias in measurement setting choices, we obtain an upper bound on the p value of 7.87 ×10-4, which clearly indicates the rejection with high confidence of potential local hidden variable models. one may further push the time constraint on local hidden variable mechanisms deep into the cosmic history by taking advantage of the randomness in photon emissions from quasars with large aperture telescopes. | test of local realism into the past without detection and locality loopholes |
observations reveal massive amounts of o vi around star-forming l * galaxies, with covering fractions of near unity extending to the host halo’s virial radius. this o vi absorption is typically kinematically centered upon photoionized gas, with line widths that are suprathermal and kinematically offset from the galaxy. we discuss various scenarios and whether they could result in the observed phenomenology (cooling gas flows, boundary layers, shocks, virialized gas). if collisionally ionized, as we argue is most probable, the o vi observations require that the circumgalactic medium (cgm) of l * galaxies holds nearly all of the associated baryons within a virial radius (∼ {10}11 {m}⊙ ) and hosts massive flows of cooling gas with ≈ 30[{nt}/30 {{cm}}-3 {{k}}] {m}⊙{{yr}}-1, which must be largely prevented from accreting onto the host galaxy. cooling and feedback energetics considerations require 10< {nt}< 100 cm-3 k for the warm and hot halo gases. we argue that virialized gas, boundary layers, hot winds, and shocks are unlikely to directly account for the bulk of the o vi. furthermore, we show that there is a robust constraint on the number density of many of the photoionized ∼ {10}4 {{k}} absorption systems that yields upper bounds in the range n< (0.1-3) × {10}-3(z/0.3) cm-3, suggesting that the dominant pressure in some photoionized clouds is nonthermal. this constraint is in accordance with the low densities inferred from more complex photoionization modeling. the large amount of cooling gas that is inferred could re-form these clouds in a fraction of the halo dynamical time, and it requires much of the feedback energy available from supernovae to be dissipated in the cgm. | implications of the large o vi columns around low-redshift l ∗ galaxies |
by detecting redshift drift in the spectra of the lyman- forest of distant quasars, the sandage-loeb (sl) test directly measures the expansion of the universe, covering the "redshift desert" of . thus this method is definitely an important supplement to the other geometric measurements and will play a crucial role in cosmological constraints. in this paper, we quantify the ability of the sl test signal by a codex-like spectrograph for constraining interacting dark energy. four typical interacting dark energy models are considered: (i) , (ii) , (iii) , and (iv) . the results show that for all the considered interacting dark energy models, relative to the current joint sn bao cmb observations, the constraints on and would be improved by about 60 and 30-40 %, while the constraints on w and would be slightly improved, with a 30-year observation of the sl test. we also explore the impact of the sl test on future joint geometric observations. in this analysis, we take the model with as an example, and we simulate future sn and bao data based on the space-based project wfirst. we find that with the future geometric constraints, the redshift drift observations would help break the geometric degeneracies in a meaningful way, thus the measurement precisions of , , w, and could be substantially improved using future probes. | redshift drift exploration for interacting dark energy |
the quasar mode of active galactic nuclei (agn) in the high-redshift universe is routinely observed in gas-rich galaxies together with large-scale agn-driven winds. it is crucial to understand how photons emitted by the central agn source couple to the ambient interstellar medium to trigger large-scale outflows. by means of radiation-hydrodynamical simulations of idealized galactic discs, we study the coupling of photons with the multiphase galactic gas, and how it varies with gas cloud sizes, and the radiation bands included in the simulations, which are ultraviolet, optical, and infrared (ir). we show how a quasar with a luminosity of 1046 erg s- 1 can drive large-scale winds with velocities of 10^2-10^3 km s^{-1} and mass outflow rates around 103 m⊙ yr- 1 for times of the order of a few million years. ir radiation is necessary to efficiently transfer momentum to the gas via multiscattering on dust in dense clouds. however, ir multiscattering, despite being extremely important at early times, quickly declines as the central gas cloud expands and breaks up, allowing the radiation to escape through low gas density channels. the typical number of multiscattering events for an ir photon is only about a quarter of the mean optical depth from the centre of the cloud. our models account for the observed outflow rates of ∼500-1000 m⊙ yr- 1 and high velocities of ∼ 103 km s- 1, favouring winds that are energy driven via extremely fast nuclear outflows, interpreted here as being ir radiatively driven winds. | outflows driven by quasars in high-redshift galaxies with radiation hydrodynamics |
despite the hypothesized similar face-on viewing angles, the infrared emission of type-1 active galactic nuclei (agns) has diverse spectral energy distribution (sed) shapes that deviate substantially from the well-characterized quasar templates. motivated by the commonly seen uv-optical obscuration and the discovery of parsec-scale mid-ir polar dust emission in some nearby agns, we develop semi-empirical sed libraries for reddened type-1 agns built on quasar intrinsic templates, assuming low-level extinction caused by an extended distribution of large dust grains. we demonstrate that this model can reproduce the nuclear uv to ir sed and the strong mid-ir polar dust emission of ngc 3783, the type-1 agn with the most relevant and robust observational constraints. in addition, we compile 64 low-z seyfert-1 nuclei with negligible mid-ir star formation contamination and satisfactorily fit the individual ir seds as well as the composite uv to mid-ir composite seds. given the success of these fits, we characterize the possible infrared sed of agn polar dust emission and utilize a simple but effective strategy to infer its prevalence among type-1 agns. the seds of high-z peculiar agns, including the extremely red quasars, mid-ir warm-excess agns, and hot dust-obscured galaxies, can be also reproduced by our model. these results indicate that the ir seds of most agns, regardless of redshift or luminosity, arise from similar circumnuclear torus properties but differ mainly due to the optical depths of extended obscuring dust components. ). | polar dust, nuclear obscuration, and ir sed diversity in type-1 agns |
the quasar lifetime t q is one of the most fundamental quantities for understanding quasar evolution and the growth of supermassive black holes (smbhs), but remains uncertain by several orders of magnitude. in a recent study we uncovered a population of very young quasars (t q ≲ 104-105 yr), based on the sizes of their proximity zones, which are regions of enhanced lyα forest transmission near the quasar resulting from its own ionizing radiation. the presence of such young objects poses significant challenges to models of smbh formation, which already struggle to explain the existence of smbhs (∼109 m ⊙) at such early cosmic epochs. we conduct the first comprehensive spectroscopic study of the youngest quasar known, sdss j1335+3533 at z = 5.9012, whose lifetime is t q = 103.0±0.8 yr (95% confidence). a careful search of our deep optical and near-infrared spectra for h i and metal absorption lines allows us to convincingly exclude the possibility that its small proximity zone results from an associated absorption system rather than a short lifetime. from the mg ii emission line we measure a black hole mass {m}bh}=({4.13}-3.02+10.54)× {10}9 {m}⊙ , implying an eddington ratio of {0.30}-0.22+0.77—comparable to other co-eval quasars of similar luminosity. the only possible anomaly associated with sdss j1335+3533's youth are its weak emission lines, but larger samples are needed to shed light on the potential causality. we discuss the implications of short lifetimes for various smbh growth and formation scenarios, and argue that future observations of young quasars with the james webb space telescope could distinguish between them. | first spectroscopic study of a young quasar |
in this paper, we use multi-frequency angular size measurements of 58 intermediate-luminosity quasars reaching the redshifts z∼ 3 and demonstrate that they can be used as standard rulers for cosmological inference. our results indicate that, for the majority of radio-sources in our sample their angular sizes are inversely proportional to the observing frequency. from the physical point of view it means that opacity of the jet is governed by pure synchrotron self-absorption, i.e. external absorption does not play any significant role in the observed angular sizes at least up to 43 ghz. therefore, we use the value of the intrinsic metric size of compact milliarcsecond radio quasars derived in a cosmology independent manner from survey conducted at 2 ghz and rescale it properly according to predictions of the conical jet model. this approach turns out to work well and produce quite stringent constraints on the matter density parameter ω _m in the flat λ cdm model and dvali-gabadadze-porrati braneworld model. the results presented in this paper pave the way for the follow up engaging multi-frequency vlbi observations of more compact radio quasars with higher sensitivity and angular resolution. | cosmological investigation of multi-frequency vlbi observations of ultra-compact structure in z∼ 3 radio quasars |
measurements of the physical properties of accretion disks in active galactic nuclei are important for better understanding the growth and evolution of supermassive black holes. we present the accretion disk sizes of 22 quasars from continuum reverberation mapping with data from the dark energy survey (des) standard-star fields and the supernova c fields. we construct continuum light curves with the griz photometry that span five seasons of des observations. these data sample the time variability of the quasars with a cadence as short as 1 day, which corresponds to a rest-frame cadence that is a factor of a few higher than most previous work. we derive time lags between bands with both javelin and the interpolated cross-correlation function method and fit for accretion disk sizes using the javelin thin-disk model. these new measurements include disks around black holes with masses as small as ∼107 m⊙, which have equivalent sizes at 2500 å as small as ∼0.1 lt-day in the rest frame. we find that most objects have accretion disk sizes consistent with the prediction of the standard thin-disk model when we take disk variability into account. we have also simulated the expected yield of accretion disk measurements under various observational scenarios for the large synoptic survey telescope deep drilling fields. we find that the number of disk measurements would increase significantly if the default cadence is changed from 3 days to 2 days or 1 day. | quasar accretion disk sizes from continuum reverberation mapping in the des standard-star fields |
we investigate the relationship between black hole accretion and star formation in a sample of 453 z ≈ 0.3 type 1 active galactic nuclei (agns). we use available co observations to demonstrate that the combination of nebular dust extinction and metallicity provides reliable estimates of the molecular gas mass even for the host galaxies of type 1 agns. consistent with other similar but significantly smaller samples, we reaffirm the notion that powerful agns have comparable gas content as nearby star-forming galaxies and that agn feedback does not deplete the host of cold gas instantaneously. we demonstrate that while the strong correlation between star formation rate and black hole accretion rate is in part driven by the mutual dependence of these parameters on molecular gas mass, the star formation rate and black hole accretion rate are still weakly correlated after removing the dependence of star formation rate on molecular gas mass. this, together with a positive correlation between star formation efficiency and black hole accretion rate, may be interpreted as evidence for positive agn feedback. | black hole accretion correlates with star formation rate and star formation efficiency in nearby luminous type 1 active galaxies |
we have carried out a search for optically visible post-asymptotic giant branch (post-agb) stars in the large magellanic cloud (lmc). first, we selected candidates with a mid-ir excess and then obtained their optical spectra. we disentangled contaminants with unique spectra such as m stars, c stars, planetary nebulae, quasi-stellar objects and background galaxies. subsequently, we performed a detailed spectroscopic analysis of the remaining candidates to estimate their stellar parameters such as effective temperature, surface gravity (log g), metallicity ([fe/h]), reddening and their luminosities. this resulted in a sample of 35 likely post-agb candidates with late-g to late-a spectral types, low log g, and [fe/h] < -0.5. furthermore, our study confirmed the existence of the dusty post-red giant branch (post-rgb) stars, discovered previously in our small magellanic cloud survey, by revealing 119 such objects in the lmc. these objects have mid-ir excesses and stellar parameters (teff, log g, [fe/h]) similar to those of post-agb stars except that their luminosities (< 2500 l⊙), and hence masses and radii, are lower. these post-rgb stars are likely to be products of binary interaction on the rgb. the post-agb and post-rgb objects show spectral energy distribution properties similar to the galactic post-agb stars, where some have a surrounding circumstellar shell, while some others have a surrounding stable disc similar to the galactic post-agb binaries. this study also resulted in a new sample of 162 young stellar objects, identified based on a robust log g criterion. other interesting outcomes include objects with an uv continuum and an emission line spectrum; luminous supergiants; hot main-sequence stars; and 15 b[e] star candidates, 12 of which are newly discovered in this study. | optically visible post-agb stars, post-rgb stars and young stellar objects in the large magellanic cloud |
we present n-body simulations, including post-newtonian dynamics, of dense clusters of low-mass stars harbouring central black holes (bhs) with initial masses of 50, 300, and 2000 m⊙. the models are evolved with the n-body code bifrost to investigate the possible formation and growth of massive bhs by the tidal capture of stars and tidal disruption events (tdes). we model star-bh tidal interactions using a velocity-dependent drag force, which causes orbital energy and angular momentum loss near the bh. about ~20-30 per cent of the stars within the spheres of influence of the black holes form bahcall-wolf cusps and prevent the systems from core collapse. within the first 40 myr of evolution, the systems experience 500-1300 tdes, depending on the initial cluster structure. most (>95 per cent) of the tdes originate from stars in the bahcall-wolf cusp. we derive an analytical formula for the tde rate as a function of the central bh mass, density, and velocity dispersion of the clusters ($\dot{n}_{\mathrm{tde}} \propto m\mathrm{_{bh}}\rho \sigma ^{-3}$). we find that tdes can lead a 300 m⊙ bh to reach $\sim 7000 \, \mathrm{{m}_{\odot }}$ within a gyr. this indicates that tdes can drive the formation and growth of massive bhs in sufficiently dense environments, which might be present in the central regions of nuclear star clusters. | the growth of intermediate mass black holes through tidal captures and tidal disruption events |
aims: the sinfoni survey for unveiling the physics and effect of radiative feedback (super) was designed to conduct a blind search for agn-driven outflows on x-ray-selected agns at redshift z ∼ 2 with high (∼2 kpc) spatial resolution, and to correlate them with the properties of their host galaxy and central black hole. the main aims of this paper are: (a) to derive reliable estimates for the masses of the black holes and accretion rates for the type-1 agns in this survey; and (b) to characterise the properties of the agn-driven winds in the broad line region (blr).methods: we analysed rest-frame optical and uv spectra of 21 type-1 agns. we used hα, hβ, and mgii line profiles to estimate the masses of the black holes. we used the blueshift of the civ line profile to trace the presence of winds in the blr.results: we find that the hα and hβ line widths are strongly correlated, as is the line continuum luminosity at 5100 å with hα line luminosity, resulting in a well-defined correlation between black hole masses estimated from hα and hβ. using these lines, we estimate that the black hole masses for our objects are in the range log (mbh/m⊙) = 8.4-10.8 and are accreting at λedd = 0.04-1.3. furthermore, we confirm the well-known finding that the civ line width does not correlate with the balmer lines and the peak of the line profile is blueshifted with respect to the [oiii]-based systemic redshift. these findings support the idea that the civ line is tracing outflowing gas in the blr for which we estimated velocities up to ∼4700 km s-1. we confirm the strong dependence of the blr wind velocity on the uv-to-x-ray continuum slope, the bolometric luminosity, and eddington ratio. we infer blr mass outflow rates in the range 0.005-3 m⊙ yr-1, revealing a correlation with the bolometric luminosity consistent with that observed for ionised winds in the narrow line region (nlr), and x-ray winds detected in local agns, and kinetic power ∼10-7 - 10-4 × lbol. the coupling efficiencies predicted by agn-feedback models are much higher than the values reported for the blr winds in the super sample; although it should be noted that only a fraction of the energy injected by the agn into the surrounding medium is expected to become kinetic power in the outflow. finally, we find an anti-correlation between the equivalent width of the [oiii] line and the civ velocity shift, and a positive correlation between this latter parameter and [oiii] outflow velocity. these findings, for the first time in an unbiased sample of agns at z ∼ 2, support a scenario where blr winds are connected to galaxy-scale detected outflows, and are therefore capable of affecting the gas in the nlr located at kiloparsec scale distances. | super. iii. broad line region properties of agns at z ∼ 2 |
context. damped lyman-α (dla) absorption-line systems at the redshifts of gamma-ray burst (grb) afterglows offer a unique way to probe the physical conditions within star-forming galaxies in the early universe.aims: here we built up a large sample of 22 grbs at redshifts z > 2 observed with vlt/x-shooter in order to determine the abundances of hydrogen, metals, dust, and molecular species. this allows us to study the metallicity and dust depletion effects in the neutral interstellar medium at high redshift and to answer the question of whether (and why) there might be a lack of h2 in grb-dlas.methods: we developed new methods based on the bayesian inference package, pymc, to fit absorption lines and measure the column densities of different metal species as well as atomic and molecular hydrogen. the derived relative abundances are used to fit dust depletion sequences and determine the dust-to-metals ratio and the host-galaxy intrinsic visual extinction. additionally, we searched for the absorption signatures of vibrationally-excited h2 and carbon monoxide.results: we find that there is no lack of h2-bearing grb-dlas. we detect absorption lines from molecular hydrogen in 6 out of 22 grb afterglow spectra, with molecular fractions ranging between f ≃ 5 × 10-5 and f ≃ 0.04, and claim tentative detections in three additional cases. for the remainder of the sample, we measure, depending on s/n, spectral coverage and instrumental resolution, more or less stringent upper limits. the grb-dlas in our sample have on average low metallicities, [x/h]¯ ≈ -1.3, comparable to the population of extremely-strong qso-dlas (log n(h i) > 21.5). furthermore, h2-bearing grb-dlas are found to be associated with significant dust extinction, av > 0.1 mag, and dust-to-metals ratios dtm > 0.4, confirming the importance of dust grains for the production of molecules. all these systems exhibit neutral hydrogen column densities log n(h i) > 21.7. the overall fraction of h2 detections in grb-dlas is ≥ 27% (41% including tentative detections), which is three to four times larger than in the general qso-dla population. for 2 < z < 4, and considering column densities log n(h i) > 21.7, the h2 detection fraction is 60-80% in grb-dlas and in extremely strong qso-dlas. this is likely due to the fact that both grb- and qso-dlas with high neutral hydrogen column densities are probed by sight-lines with small impact parameters, indicating that the absorbing gas is associated with the inner regions of the absorbing galaxy, where the gas pressure is higher and the conversion of h i to h2 takes place. in the case of grb hosts, this diffuse molecular gas is located at distances ≳ 500 pc from the grb and hence is unrelated to the star-forming region where the event occurred. | evidence for diffuse molecular gas and dust in the hearts of gamma-ray burst host galaxies. unveiling the nature of high-redshift damped lyman-α systems |
we derive updated constraints on the integrated sachs-wolfe (isw) effect through cross-correlation of the cosmic microwave background with galaxy surveys. we improve with respect to similar previous analyses in several ways. first, we use the most recent versions of extragalactic object catalogs, sdss dr12 photometric redshift (photo-z ) and 2mass photo-z data sets, as well as those employed earlier for isw, sdss qso photo-z and nvss samples. second, we use for the first time the wise × supercosmos catalog, which allows us to perform an all-sky analysis of the isw up to z ∼0.4 . third, thanks to the use of photo-z s , we separate each data set into different redshift bins, deriving the cross-correlation in each bin. this last step leads to a significant improvement in sensitivity. we remove cross-correlation between catalogs using masks which mutually exclude common regions of the sky. we use two methods to quantify the significance of the isw effect. in the first one, we fix the cosmological model, derive linear galaxy biases of the catalogs, and then evaluate the significance of the isw using a single parameter. in the second approach we perform a global fit of the isw and of the galaxy biases varying the cosmological model. we find significances of the isw in the range 4.7 - 5.0 σ thus reaching, for the first time in such an analysis, the threshold of 5 σ . without the redshift tomography we find a significance of ∼4.0 σ , which shows the importance of the binning method. finally we use the isw data to infer constraints on the dark energy redshift evolution and equation of state. we find that the redshift range covered by the catalogs is still not optimal to derive strong constraints, although this goal will be likely reached using future datasets such as from euclid, lsst, and ska. | updated tomographic analysis of the integrated sachs-wolfe effect and implications for dark energy |
galaxy haloes appear to be missing a large fraction of their baryons, most probably hiding in the circumgalactic medium (cgm), a diffuse component within the dark matter halo that extends far from the inner regions of the galaxies. a powerful tool to study the cgm gas is offered by absorption lines in the spectra of background quasars. here, we present optical (muse) and mm (alma) observations of the field of the quasar q1130-1449 which includes a log [n(h i)/cm-2] = 21.71 ± 0.07 absorber at z = 0.313. ground-based vlt/muse 3d spectroscopy shows 11 galaxies at the redshift of the absorber down to a limiting sfr > 0.01 m⊙ yr-1 (covering emission lines of [o ii], hβ, [o iii], [n ii], and h α), 7 of which are new discoveries. in particular, we report a new emitter with a smaller impact parameter to the quasar line of sight (b = 10.6 kpc) than the galaxies detected so far. three of the objects are also detected in co(1-0) in our alma observations indicating long depletion time-scales for the molecular gas and kinematics consistent with the ionized gas. we infer from dedicated numerical cosmological ramses zoom-in simulations that the physical properties of these objects qualitatively resemble a small group environment, possibly part of a filamentary structure. based on metallicity and velocity arguments, we conclude that the neutral gas traced in absorption is only partly related to these emitting galaxies while a larger fraction is likely the signature of gas with surface brightness almost four orders of magnitude fainter that current detection limits. together, these findings challenge a picture where strong-n(h i) quasar absorbers are associated with a single bright galaxy and favour a scenario where the h i gas probed in absorption is related to far more complex galaxy structures. | multiphase circumgalactic medium probed with muse and alma |
the magnifications of compact-source lenses are extremely sensitive to the presence of low-mass dark matter haloes along the entire sightline from the source to the observer. traditionally, the study of dark matter structure in compact-source strong gravitational lenses has been limited to radio-loud systems, as the radio emission is extended and thus unaffected by microlensing which can mimic the signal of dark matter structure. an alternate approach is to measure quasar nuclear-narrow-line emission, which is free from microlensing and present in virtually all quasar lenses. in this paper, we double the number of systems which can be used for gravitational lensing analyses by presenting measurements of narrow-line emission from a sample of eight quadruply imaged quasar lens systems, wgd j0405-3308, hs 0810+2554, rx j0911+0551, sdss j1330+1810, ps j1606-2333, wfi 2026-4536, wfi 2033-4723, and wgd j2038-4008. we describe our updated grism spectral modelling pipeline, which we use to measure narrow-line fluxes with uncertainties of 2-10 per cent, presented here. we fit the lensed image positions with smooth mass models and demonstrate that these models fail to produce the observed distribution of image fluxes over the entire sample of lenses. furthermore, typical deviations are larger than those expected from macromodel uncertainties. this discrepancy indicates the presence of perturbations caused by small-scale dark matter structure. the interpretation of this result in terms of dark matter models is presented in a companion paper. | double dark matter vision: twice the number of compact-source lenses with narrow-line lensing and the wfc3 grism |
we present an analysis of the evolution of the lyman-series forest into the epoch of reionization using cosmological radiative transfer simulations in a scenario where reionization ends late. we explore models with different mid-points of reionization and gas temperatures. we find that once the simulations have been calibrated to match the mean flux of the observed lyman-α (ly α) forest at 4 < z < 6, they also naturally reproduce the distribution of effective optical depths of the lyman-β (ly β) forest in this redshift range. we note that the tail of the largest optical depths that is most challenging to match corresponds to the long absorption trough of ulas j0148+0600, which we have previously shown to be rare in our simulations. we consider the evolution of the lyman-series forest out to higher redshifts, and show that future observations of the ly β forest at z > 6 will discriminate between different reionization histories. the evolution of the ly α and ly γ forests are less promising as a tool for pushing studies of reionization to higher redshifts due to the stronger saturation and foreground contamination, respectively. | constraining the second half of reionization with the ly β forest |
reverberation mapping (rm) of active galactic nuclei (agns) has been used over the past three decades to determine agn broad-line region (blr) sizes and central black hole masses, and their relations with the agn luminosity. until recently, the sample of objects with rm data was limited to low-luminosity agns (lopt ≲ 1046 erg s-1) and low redshifts (z ≲ 0.5). here we present results from an rm project of some of the most luminous and highest-redshift quasars that have been mapped to date. the study is based on almost 20 years of photometric monitoring of 11 quasars, 6 of which were monitored spectrophotometrically for 13 yr. this is the longest rm project carried out so far on this type of agns. we successfully measure a time lag between the c iv λ 1549 broad emission line and the quasar continuum in three objects, and measure a c iii] λ 1909 lag in one quasar. together with recently published data on c iv rm, the blr size is found to scale as the square root of the uv luminosity over eight orders of magnitude in agn luminosity. there is a significant scatter in the relation, part of which may be intrinsic to the agns. although the c iv line is probably less well suited than balmer lines for determination of the mass of the black hole, virial masses are tentatively computed, and in spite of a large scatter, we find that the mass of the black hole scales as the square root of the uv luminosity. | taking a long look: a two-decade reverberation mapping study of high-luminosity quasars |
we present the discovery of a molecular cloud at zabs ≈ 2.5255 along the line of sight to the quasar sdss j 000015.17+004833.3. we use a high-resolution spectrum obtained with the ultraviolet and visual echelle spectrograph together with a deep multi-wavelength medium-resolution spectrum obtained with x-shooter (both on the very large telescope) to perform a detailed analysis of the absorption lines from ionic, neutral atomic and molecular species in different excitation levels, as well as the broad-band dust extinction. we find that the absorber classifies as a damped lyman-α system (dla) with log n(h i) (cm-2) = 20.8 ± 0.1. the dla has super-solar metallicity (z ~ 2.5 z⊙, albeit to within a factor of two to three) with a depletion pattern typical of cold gas and an overall molecular fraction f = 2n(h2)/(2n(h2) + n(h i)) ~ 50%. this is the highest f-value observed to date in a high-z intervening system. most of the molecular hydrogen arises from a clearly identified narrow (b ~ 0.7km s-1), cold component in which carbon monoxide molecules are also found, with log n(co)≈ 15. with the help of the spectral synthesis code cloudy, we study the chemical and physical conditions in the cold gas. we find that the line of sight probes the gas deep after the h i-to-h2 transition in a ~4-5 pc-size cloud with volumic density nh ~ 80 cm-3 and temperature of only 50 k. our model suggests that the presence of small dust grains (down to about 0.001 μm) and high cosmic ray ionisation rate (ζh ~ a few times 10-15 s-1) are needed to explain the observed atomic and molecular abundances. the presence of small grains is also in agreement with the observed steep extinction curve that also features a 2175 å bump. interestingly, the chemical and physical properties of this cloud are very similar to what is seen in diffuse molecular regions of the nearby perseus complex, despite the former being observed when the universe was only 2.5 gyr old. the high excitation temperature of co rotational levels towards j0000+0048 betrays however the higher temperature of the cosmic microwave background. using the derived physical conditions, we correct for a small contribution (0.3 k) of collisional excitation and obtain tcmb(z = 2.53) ≈ 9.6 k, in perfect agreement with the predicted adiabatic cooling of the universe. based on observations collected at the european organisation for astronomical research in the southern hemisphere under eso programmes 093.a-0126(a), 096.a-0354(a) and 096.a-0924(b). | discovery of a perseus-like cloud in the early universe. h i-to-h2 transition, carbon monoxide and small dust grains at zabs≈ 2.53 towards the quasar j0000+0048 |
we measure the 1d ly α power spectrum p1d from keck observatory database of ionized absorption toward quasars (kodiaq), the spectral quasar absorption database (squad), and xq-100 quasars using the optimal quadratic estimator. we combine kodiaq and squad at the spectrum level, but perform a separate xq-100 estimation to control its large resolution corrections in check. our final analysis measures p1d at scales k < 0.1 s km-1 between redshifts $z$ = 2.0-4.6 using 538 quasars. this sample provides the largest number of high-resolution, high-s/n observations; and combined with the power of optimal estimator it provides exceptional precision at small scales. these small-scale modes (k ≳ 0.02 s km-1), unavailable in sloan digital sky survey and dark energy spectroscopic instrument analyses, are sensitive to the thermal state and reionization history of the intergalactic medium, as well as the nature of dark matter. as an example, a simple fisher forecast analysis estimates that our results can improve small-scale cut-off sensitivity by more than a factor of 2. | optimal 1d ly α forest power spectrum estimation - ii. kodiaq, squad, and xq-100 |
we have been spectroscopically monitoring 88 quasars selected to have broad hβ emission lines offset from their systemic redshift by thousands of km s-1. by analogy with single-lined spectroscopic binary stars, we consider these quasars to be candidates for hosting supermassive black hole binaries (sbhbs). in this work, we present new radial velocity measurements, typically three to four per object over a time period of up to 12 yr in the observer's frame. in 29/88 of the sbhb candidates, no variability of the shape of the broad hβ profile is observed, which allows us to make reliable measurements of radial velocity changes. among these, we identify three objects that have displayed systematic and monotonic velocity changes by several hundred km s-1 and are prime targets for further monitoring. because the periods of the hypothetical binaries are expected to be long, we cannot hope to observe many orbital cycles during our lifetimes. instead, we seek to evaluate the credentials of the sbhb candidates by attempting to rule out the sbhb hypothesis. in this spirit, we present a method for placing a lower limit on the period, and thus the mass, of the sbhbs under the assumption that the velocity changes we observe are due to orbital motion. given the duration of our monitoring campaign and the uncertainties in the radial velocities, we were able to place a lower limit on the total mass in the range 4.7 × 104-3.8 × 108 m⊙, which does not yet allow us to rule out the sbhb hypothesis for any candidates. | a large systematic search for close supermassive binary and rapidly recoiling black holes - iii. radial velocity variations |
context. feedback from active galactic nuclei (agn) is thought to play an important role in quenching star formation in galaxies. however, the efficiency with which agn dissipate their radiative energy into the ambient medium remains strongly debated.aims: enormous observational efforts have been made to constrain the energetics of agn feedback by mapping the kinematics of the ionized gas on kpc scale. we study how the observed kinematics and inferred energetics are affected by beam smearing of a bright unresolved narrow-line region (nlr) due to seeing.methods: we re-analyse optical integral-field spectroscopy of a sample of twelve luminous unobscured quasi-stellar objects (qsos) (0.4 <z< 0.7) previously presented in the literature. the point-spread function (psf) for the observations is directly obtained from the light distribution of the broad hβ line component. therefore, we are able to compare the ionized gas kinematics and derived energetics of the total, truly spatially extended, and unresolved [o iii] emission.results: we find that the spatially resolved [o iii] line width on kpc scales is significantly narrower than the one before psf deblending. the extended nlrs (enlrs) appear intrinsically offset from the qso position or more elongated which can be interpreted in favour of a conical outflow on large scales while a spherical geometry cannot be ruled out for the unresolved nlr. we find that the kinetic power at 5 kpc distance based on a spherical model is reduced by two orders of magnitude for a conical outflow and one order of magnitude for the unresolved nlr after psf deblending. this reduced kinetic power corresponds to only 0.01-0.1 per cent of the bolometric agn luminosity. this is smaller than the 5-10% feedback efficiency required by some cosmological simulations to reproduce the massive galaxy population. the injected momentum fluxes are close or below the simple radiation-pressure limit lbol/c for the conical outflow model for the nlr and enlr when beam smearing is considered.conclusions: integral-field spectroscopy is a powerful tool to investigate the energetics of agn outflows, but the impact of beam smearing has to be taken into account in the high contrast regime of qsos. for the majority of observations in the literature, this has not been addressed carefully so that the incidence and energetics of presumed kpc-scale agn-driven outflows still remain an unsolved issue, from an observational perspective. | large-scale outflows in luminous qsos revisited. the impact of beam smearing on agn feedback efficiencies |
we present gas kinematics based on the [o iii]λ5007 line and their connection to galaxy gravitational potential, active galactic nucleus (agn) energetics, and star formation, using a large sample of ∼110,000 agns and star-forming (sf) galaxies at z < 0.3. gas and stellar velocity dispersions are comparable to each other in sf galaxies, indicating that the ionized gas kinematics can be accounted by the gravitational potential of host galaxies. in contrast, agns clearly show non-gravitational kinematics, which is comparable to or stronger than the virial motion caused by the gravitational potential. the [o iii] velocity-velocity dispersion (vvd) diagram dramatically expands toward high values as a function of agn luminosity, implying that the outflows are agn-driven, while sf galaxies do not show such a trend. we find that the fraction of agns with a signature of outflow kinematics, steeply increases with agn luminosity and eddington ratio. in particular, the majority of luminous agns presents strong non-gravitational kinematics in the [o iii] profile. agns with strong outflow signatures show on average similar specific star formation rates (ssfrs) to those of star-forming galaxies. in contrast, agns with weak or no outflows have an order of magnitude lower ssfrs, suggesting that agns with current strong outflows do now show any negative agn feedback and that it may take dynamical time to impact on star formation over galactic scales. | delayed or no feedback? gas outflows in type 2 agns. iii. |
we identify a strong lyα damping wing profile in the spectrum of the quasar p183+05 at z = 6.4386. given the detection of several narrow metal absorption lines at z = 6.40392, the most likely explanation for the absorption profile is that it is due to a damped lyα system. however, in order to match the data a contribution of an intergalactic medium 5%-38% neutral or additional weaker absorbers near the quasar is also required. the absorption system presented here is the most distant damped lyα system currently known. we estimate an h i column density of 1020.68±0.25 cm-2, metallicity [o/h] = -2.92 ± 0.32, and relative chemical abundances of a system consistent with a low-mass galaxy during the first gyr of the universe. this object is among the most metal-poor damped lyα systems known and, even though it is observed only ∼850 myr after the big bang, its relative abundances do not show signatures of chemical enrichment by population iii stars. | a metal-poor damped lyα system at redshift 6.4 |
if the electroweak higgs vacuum expectation value v in early universe is ~ 1 % higher than its present value v0=246 gev, the 7li puzzle in bbn and the cmb/λcdm tension with late-universe measurements on hubble parameter are mitigated. we propose a model of an axion coupled to the higgs field, named "axi-higgs", with its mass ma ~ 10-30 - 10-29 ev and decay constant fa ~ 1017 - 1018 gev, to achieve this goal. the axion initial value aini yields an initial δ vini/v0 ~ 0.01 throughout the bbn-recombination epoch and a percent level contribution to the total matter density today. because of its very large de broglie wavelength, this axion matter density ωa suppresses the matter power spectrum, alleviating the cmb/λcdm s8/σ8 tension with the weak-lensing data. it also explains the recently reported isotropic cosmic birefringence by its coupling with photons. adding the axion (m ~ 10-22ev) in the fuzzy dark matter model to the axi-higgs model allows bigger δ vrec and ωa to address the hubble and s8/σ8 tensions simultaneously. the model predicts that δ v may be detected by the spectral measurements of quasars, while its oscillation may be observed in the atomic clock measurements. | axi-higgs cosmology |
we present a new hubble space telescope cosmic origins spectrograph (cos) absorption-line survey to study halo gas around 16 luminous red galaxies (lrgs) at z = 0.21-0.55. the lrgs are selected uniformly with stellar mass m_star>10^{11} m_{⊙} and no prior knowledge of the presence/absence of any absorption features. based on observations of the full lyman series, we obtain accurate measurements of neutral hydrogen column density n(h i) and find that high-n(h i) gas is common in these massive quiescent haloes with a median of < log n(h i)> = 16.6 at projected distances d ≲ 160 kpc. we measure a mean covering fraction of optically thick gas with log n(h i)≳ 17.2 of < κ > _lls=0.44^{+0.12}_{-0.11} at d ≲ 160 kpc and < κ > _lls=0.71^{+0.11}_{-0.20} at d ≲ 100 kpc. the line-of-sight velocity separations between the h i absorbing gas and lrgs are characterized by a mean and dispersion of < v_{gas-gal}> =29 km s-1 and σ _{< v_{gas-gal}> }=171 km s-1. combining cos far-ultraviolet and ground-based echelle spectra provides an expanded spectral coverage for multiple ionic transitions, from low-ionization mgii and si ii, to intermediate-ionization siiii and c iii, and to high-ionization o vi absorption lines. we find that intermediate ions probed by c iii and si iii are the most prominent uv metal lines in lrg haloes with a mean covering fraction of < κ (c iii)> _{0.1}=0.75^{+0.08}_{-0.13} for wr(977) ⩾ 0.1 å at d < 160 kpc, comparable to what is seen for c iii in l* and sub-l* star-forming and red galaxies but exceeding mg ii or o vi in quiescent halos. the cos-lrg survey shows that massive quiescent haloes contain widespread chemically enriched cool gas and that little distinction between lrg and star-forming haloes is found in their hi and c iii content. | characterizing circumgalactic gas around massive ellipticals at z ∼ 0.4 - i. initial results |
we use the eagle (evolution and assembly of galaxies and their environments) cosmological simulation to study the distribution of baryons, and far-ultraviolet (o vi), extreme-ultraviolet (ne viii), and x-ray (o vii, o viii, ne ix, and fe xvii) line absorbers, around galaxies and haloes of mass $\,{m}_{\rm {200c}}= 10^{11}$-$10^{14.5} \, \rm {m}_{\odot}$ at redshift 0.1. eagle predicts that the circumgalactic medium (cgm) contains more metals than the interstellar medium across halo masses. the ions we study here trace the warm-hot, volume-filling phase of the cgm, but are biased towards temperatures corresponding to the collisional ionization peak for each ion, and towards high metallicities. gas well within the virial radius is mostly collisionally ionized, but around and beyond this radius, and for o vi, photoionization becomes significant. when presenting observables, we work with column densities, but quantify their relation with equivalent widths by analysing virtual spectra. virial-temperature collisional ionization equilibrium ion fractions are good predictors of column density trends with halo mass, but underestimate the diversity of ions in haloes. halo gas dominates the highest column density absorption for x-ray lines, but lower density gas contributes to strong uv absorption lines from o vi and ne viii. of the o vii (o viii) absorbers detectable in an athena x-ifu blind survey, we find that 41 (56) per cent arise from haloes with $\,{m}_{\rm {200c}}= 10^{12.0}{-}10^{13.5} \, \rm {m}_{\odot}$. we predict that the x-ifu will detect o vii (o viii) in 77 (46) per cent of the sightlines passing $\,{m}_{\star }= 10^{10.5}{-}10^{11.0} \, \rm {m}_{\odot}$ galaxies within $100 \, \rm {pkpc}$ (59 (82) per cent for $\,{m}_{\star }\gt 10^{11.0} \, \rm {m}_{\odot}$). hence, the x-ifu will probe covering fractions comparable to those detected with the cosmic origins spectrograph for o vi. | the warm-hot circumgalactic medium around eagle-simulation galaxies and its detection prospects with x-ray and uv line absorption |
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