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in area and depth, the pan-starrs1 (ps1) 3π survey is unique among many-epoch, multi-band surveys and has enormous potential for the all-sky identification of variable sources. ps1 has observed the sky typically seven times in each of its five bands (grizy) over 3.5 years, but unlike sdss, not simultaneously across the bands. here we develop a new approach for quantifying statistical properties of non-simultaneous, sparse, multi-color light curves through light curve structure functions, effectively turning ps1 into a ∼35-epoch survey. we use this approach to estimate variability amplitudes and timescales (ωr , τ) for all point sources brighter than r p1 = 21.5 mag in the survey. with ps1 data on sdss stripe 82 as “ground truth,” we use a random forest classifier to identify qsos and rr lyrae based on their variability and their mean ps1 and wise colors. we find that, aside from the galactic plane, qso and rr lyrae samples of purity ∼75% and completeness ∼92% can be selected. on this basis we have identified a sample of ∼1,000,000 qso candidates, as well as an unprecedentedly large and deep sample of ∼150,000 rr lyrae candidates with distances from ∼10 to ∼120 kpc. within the draco dwarf spheroidal, we demonstrate a distance precision of 6% for rr lyrae candidates. we provide a catalog of all likely variable point sources and likely qsos in ps1, a total of 25.8 × 106 sources. | finding, characterizing, and classifying variable sources in multi-epoch sky surveys: qsos and rr lyrae in ps1 3π data |
cosmograil is a long-term photometric monitoring of gravitationally lensed quasars aimed at implementing refsdal's time-delay method to measure cosmological parameters, in particular h0. given the long and well sampled light curves of strongly lensed quasars, time-delay measurements require numerical techniques whose quality must be assessed. to this end, and also in view of future monitoring programs or surveys such as the lsst, a blind signal processing competition named time delay challenge 1 (tdc1) was held in 2014. the aim of the present paper, which is based on the simulated light curves from the tdc1, is double. first, we test the performance of the time-delay measurement techniques currently used in cosmograil. second, we analyse the quantity and quality of the harvest of time delays obtained from the tdc1 simulations. to achieve these goals, we first discover time delays through a careful inspection of the light curves via a dedicated visual interface. our measurement algorithms can then be applied to the data in an automated way. we show that our techniques have no significant biases, and yield adequate uncertainty estimates resulting in reduced χ2 values between 0.5 and 1.0. we provide estimates for the number and precision of time-delay measurements that can be expected from future time-delay monitoring campaigns as a function of the photometric signal-to-noise ratio and of the true time delay. we make our blind measurements on the tdc1 data publicly available. | cosmograil: the cosmological monitoring of gravitational lenses. xv. assessing the achievability and precision of time-delay measurements |
the lyman-α forest is a powerful probe for cosmology, but it is also strongly impacted by galaxy evolution and baryonic processes such as active galactic nucleus (agn) feedback, which can redistribute mass and energy on large scales. we constrain the signatures of agn feedback on the 1d power spectrum of the lyman-α forest using a series of eight hydro-cosmological simulations performed with the adaptive mesh refinement code ramses. this series starts from the horizon-agn simulation and varies the subgrid parameters for agn feeding, feedback, and stochasticity. these simulations cover the whole plausible range of feedback and feeding parameters according to the resulting galaxy properties. agns globally suppress the lyman-α power at all scales. on large scales, the energy injection and ionization dominate over the supply of gas mass from agn-driven galactic winds, thus suppressing power. on small scales, faster cooling of denser gas mitigates the suppression. this effect increases with decreasing redshift. we provide lower and upper limits of this signature at nine redshifts between z = 4.25 and 2.0, making it possible to account for it at post-processing stage in future work given that running simulations without agn feedback can save considerable amounts of computing resources. ignoring agn feedback in cosmological inference analyses leads to strong biases with 2 per cent shift on σ8 and 1 per cent shift on ns, which represents twice the standards deviation of the current constraints on ns. | the impact of agn feedback on the 1d power spectra from the ly α forest using the horizon-agn suite of simulations |
we describe a multiwavelength program of monitoring of a sample of bright γ-ray blazars, which the boston university (bu) group has being carrying out since june 2007. the program includes monthly monitoring with the very long baseline array at 43 ghz, optical photometric and polarimetric observations, construction and analysis of uv and x-ray light curves obtained with the rossi x-ray timing explorer (rxte) and swift satellites, and construction and analysis of γ-ray light curves based on data provided by the large area telescope of the fermi gamma-ray space telescope. we present general results about the kinematics of parsec-scale radio jets, as well as the connection between γ-ray outbursts and jet events. | the vlba-bu-blazar multi-wavelength monitoring program |
we use the sky-average spectrum measured by edges high-band (90-190 mhz) to constrain parameters of early galaxies independent of the absorption feature at 78 mhz reported by bowman et al. these parameters represent traditional models of cosmic dawn and the epoch of reionization produced with the 21cmfast simulation code. the parameters considered are (1) the uv ionizing efficiency (ζ) (2) minimum halo virial temperature hosting efficient star-forming galaxies ({t}vir}\min ); (3) integrated soft-band x-ray luminosity ({l}{{x}< 2{kev}}/{sfr}); and (4) minimum x-ray energy escaping the first galaxies (e 0), corresponding to a typical h i column density for attenuation through the interstellar medium. the high-band spectrum disfavors high values of {t}vir}\minand ζ, which correspond to signals with late absorption troughs and sharp reionization transitions. it also disfavors intermediate values of {l}{{x}< 2{kev}}/{sfr}, which produce relatively deep and narrow troughs within the band. specifically, we rule out 39.4< {log}}10({l}{{x}< 2{kev}}/{sfr})< 39.8 (95% c.l.). we then combine the edges high-band data with constraints on the electron-scattering optical depth from planck and the hydrogen neutral fraction from high-z quasars. this produces a lower degeneracy between ζ and {t}vir}\minthan that reported by greig & mesinger using the planck and quasar constraints alone. our main result in this combined analysis is the estimate 4.5≤slant {log}}10({t}vir}\min /{{k}})≤slant 5.7 (95% c.l.). we leave the evaluation of 21 cm models using simultaneously data from edges low- and high-band for future work. | results from edges high-band. ii. constraints on parameters of early galaxies |
we investigate the blazar contribution to the cumulative neutrino intensity assuming a generic relationship between neutrino and gamma-ray luminosities, ${l}_{\nu }\propto {({l}_{\mathrm{ph}})}^{{\gamma }_{\mathrm{lw}}}$ l ν ∝ ( l ph ) γ lw . using the gamma-ray luminosity functions for blazars, including flat-spectrum radio quasars (fsrqs) and bl lac objects, as well as the fermi-lat detection efficiency, we estimate contributions from blazars resolved by fermi-lat as well as the unresolved counterpart. combining the existing upper limits from stacking analyses, the cumulative neutrino flux from all blazars (including fermi-lat resolved and unresolved ones) are constrained in the range 0 ≲ γlw ≲ 2.5. we also evaluate the effects of the redshift evolution and the effective local number densities for each class of fsrqs, bl lacs, and all blazars, on which we place another type of constraints on the blazar contribution using the nondetection of high-energy neutrino multiplets. we demonstrate that these two upper limits are complementary, and that the joint consideration of the stacking and multiplet analyses not only supports the argument that blazars are disfavored as the dominant sources of the 100 tev neutrino background, but also extends it by including fermi-lat-unresolved blazars as well, for a more generic luminosity correlation ${l}_{\nu }\propto {({l}_{\mathrm{ph}})}^{{\gamma }_{\mathrm{lw}}}$ l ν ∝ ( l ph ) γ lw . | complementarity of stacking and multiplet constraints on the blazar contribution to the cumulative high-energy neutrino intensity |
gravitational lensing has emerged as a powerful probe of the matter distribution on subgalactic scales, which itself may contain important clues about the fundamental origins and properties of dark matter. broadly speaking, two different approaches have been taken in the literature to map the small-scale structure of the universe using strong lensing, with one focused on measuring the position and mass of a small number of discrete massive subhalos appearing close in projection to lensed images, and the other focused on detecting the collective effect of all the small-scale structures between the lensed source and the observer. in this paper, we follow the latter approach and perform a detailed study of the sensitivity of galaxy-scale gravitational lenses to the ensemble properties of small-scale structure. as in some previous studies, we adopt the language of the substructure power spectrum to characterize the statistical properties of the small-scale density field. we present a comprehensive theory that treats lenses with extended sources as well as those with time-dependent compact sources (such as quasars) in a unified framework for the first time. our approach uses mode functions to provide both computational advantages and insights about couplings between the lens and source. the goal of this paper is to develop the theory and gain the intuition necessary to understand how the sensitivity to the substructure power spectrum depends on the source and lens properties, with the eventual aim of identifying the most promising targets for such studies. | beyond subhalos: probing the collective effect of the universe's small-scale structure with gravitational lensing |
to extend the search for quasars in the epoch of reionization beyond the tip of the luminosity function, we explore point-source candidates at redshift z ∼ 8 in superborg, a compilation of ∼0.4 deg2 archival medium-deep (mf160w ∼ 26.5 abmag, 5σ) parallel infrared (ir) images taken with the hubble space telescope (hst). initial candidates are selected by using the lyman-break technique. we then carefully analyze source morphology, and robustly identify three point sources at z ∼ 8. photometric redshift analysis reveals that they are preferentially fit by extragalactic templates, and we conclude that they are unlikely to be low-z interlopers, including brown dwarfs. a clear irac ch2 flux excess is seen in one of the point sources, which is expected if the source has strong hβ+[o iii] emission with a rest-frame equivalent width of ∼3000 å. deep spectroscopic data taken with keck/mosfire, however, do not reveal lyα emission from the object. in combination with the estimated hβ+[o iii] equivalent width, we place an upper limit on its lyα escape fraction of ${f}_{\mathrm{esc},\mathrm{ly}\alpha }\lesssim 2 \% $ . we estimate the number density of these point sources as ∼1 × 10-6 mpc-3 mag-1 at muv ∼ -23 mag. the final interpretation of our results remains inconclusive: extrapolation from low-z studies of faint quasars suggests that ≳100× survey volume may be required to find one of this luminosity. the james webb space telescope will be able to conclusively determine the nature of our luminous point-source candidates, while the roman space telescope will probe ∼200 times the area of the sky with the same observing time considered in this hst study. * based on observations made with the nasa/esa hubble space telescope, obtained from the data archive at the space telescope science institute. stsci is operated by the association of universities for research in astronomy, inc. under nasa contract nas 5-26555 (doi:10.17909/t9-m7tx-qb86). | superborg: exploration of point sources at z ∼ 8 in hst parallel fields |
we report the discovery and analysis of the most metal-poor damped lyman α (dla) system currently known, based on observations made with the keck hires spectrograph. the metal paucity of this system has only permitted the determination of three element abundances: [c/h] = -3.43 ± 0.06, [o/h] = -3.05 ± 0.05 and [si/h] = -3.21 ± 0.05, as well as an upper limit on the abundance of iron: [fe/h] ≤ -2.81. this dla is among the most carbon-poor environment currently known with detectable metals. by comparing the abundance pattern of this dla to detailed models of metal-free nucleosynthesis, we find that the chemistry of the gas is consistent with the yields of a 20.5 m⊙ metal-free star that ended its life as a core-collapse supernova; the abundances we measure are inconsistent with the yields of pair-instability supernovae. such a tight constraint on the mass of the progenitor population iii star is afforded by the well-determined c/o ratio, which we show depends almost monotonically on the progenitor mass when the kinetic energy of the supernova explosion is eexp ≳ 1.5 × 1051 erg. we find that the dla presented here has just crossed the critical 'transition discriminant' threshold, rendering the dla gas now suitable for low mass star formation. we also discuss the chemistry of this system in the context of recent models that suggest some of the most metal-poor dlas are the precursors of the 'first galaxies', and are the antecedents of the ultrafaint dwarf galaxies. | discovery of the most metal-poor damped lyman-α system |
galaxies located in the environment or along the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of h0 from the time-delay technique. we present the results of a systematic spectroscopic identification of the galaxies in the field of view of the lensed quasar he 0435-1223 using the w. m. keck, gemini and eso-very large telescopes. our new catalogue triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 3 arcmin from the lens. we complement our catalogue with literature data to gather redshifts up to 15 arcmin from the lens, and search for galaxy groups or clusters projected towards he 0435-1223. we confirm that the lens is a member of a small group that includes at least 12 galaxies, and find 8 other group candidates near the line of sight of the lens. the flexion shift, namely the shift of lensed images produced by high-order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. this analysis demonstrates that (i) at most three of the five brightest galaxies projected within 12 arcsec of the lens need to be explicitly used in the lens models, and (ii) the groups can be treated in the lens model as an external tidal field (shear) contribution. | h0licow - ii. spectroscopic survey and galaxy-group identification of the strong gravitational lens system he 0435-1223 |
the lyα forest transmission probability distribution function (pdf) is an established probe of the intergalactic medium (igm) astrophysics, especially the temperature-density relationship of the igm. we measure the transmission pdf from 3393 baryon oscillations spectroscopic survey (boss) quasars from sloan digital sky survey data release 9, and compare with mock spectra that include careful modeling of the noise, continuum, and astrophysical uncertainties. the boss transmission pdfs, measured at langzrang = [2.3, 2.6, 3.0], are compared with pdfs created from mock spectra drawn from a suite of hydrodynamical simulations that sample the igm temperature-density relationship, γ, and temperature at mean density, t 0, where t(δ) = t 0δγ - 1. we find that a significant population of partial lyman-limit systems (llss) with a column-density distribution slope of βplls ~ - 2 are required to explain the data at the low-transmission end of transmission pdf, while uncertainties in the mean lyα forest transmission affect the high-transmission end. after modeling the llss and marginalizing over mean transmission uncertainties, we find that γ = 1.6 best describes the data over our entire redshift range, although constraints on t 0 are affected by systematic uncertainties. within our model framework, isothermal or inverted temperature-density relationships (γ <= 1) are disfavored at a significance of over 4σ, although this could be somewhat weakened by cosmological and astrophysical uncertainties that we did not model. | igm constraints from the sdss-iii/boss dr9 lyα forest transmission probability distribution function |
active galactic nuclei (agn) vary in their brightness across all wavelengths. moreover, longer wavelength ultraviolet-optical continuum light curves appear to be delayed with respect to shorter wavelength light curves. a simple way to model these delays is by assuming thermal reprocessing of a variable point source (a lamp post) by a blackbody accretion disc. we introduce a new method, cream (continuum reprocessed agn markov chain monte carlo), that models continuum variations using this lamp post model. the disc light curves lag the lamp post emission with a time delay distribution sensitive to the disc temperature-radius profile and inclination. we test cream's ability to recover both inclination and product of black hole mass and accretion rate {mdot{m}}, and show that the code is also able to infer the shape of the driving light curve. cream is applied to synthetic light curves expected from 1000 s exposures of a 17th magnitude agn with a 2-m telescope in sloan g and i bands with signal-to-noise ratio (snr) of 500-900 depending on the filter and lunar phase. we also test cream on poorer quality g and i light curves with snr = 100. we find in the high-snr case that cream can recover the accretion disc inclination to within an uncertainty of 5° and an {mdot{m}} to within 0.04 dex. | accretion disc time lag distributions: applying cream to simulated agn light curves |
we investigate the dependence of gas kinematics and column densities in the {{mg}} {{ii}}-absorbing circumgalactic medium on galaxy color, azimuthal angle, and inclination to trace baryon cycle processes. our sample of 30 foreground isolated galaxies at 0.3\lt {z}{{gal}}\lt 1.0, imaged with the hubble space telescope, is probed by background quasars within a projected distance of 20\lt d\lt 110 {{kpc}}. from the high-resolution ({{δ }}v≃ 6.6 km s-1) quasar spectra, we quantify the extent of the absorber velocity structure with pixel-velocity two-point correlation functions. absorbers with the largest velocity dispersions are associated with blue, face-on (i\lt 57^\circ ) galaxies probed along the projected minor axis ({{φ }}≥slant 45^\circ ), while those with the smallest velocity dispersions belong to red, face-on galaxies along the minor axis. the velocity structure is similar for edge-on (i≥slant 57^\circ ) galaxies regardless of galaxy color or azimuthal angle, for red galaxies with azimuthal angle, and for blue and red galaxies probed along the projected major axis ({{φ }}\lt 45^\circ ). the cloud column densities for face-on galaxies and red galaxies are smaller than for edge-on galaxies and blue galaxies, respectively. these results are consistent with biconical outflows along the minor axis for star-forming galaxies and accreting and/or rotating gas, which is most easily observed in edge-on galaxies probed along the major axis. gas entrained in outflows may be fragmented with large velocity dispersions, while gas accreting onto or rotating around galaxies may be more coherent due to large path lengths and smaller velocity dispersions. quiescent galaxies may exhibit little-to-no outflows along the minor axis, while accretion/rotation may exist along the major axis. | magiicat v. orientation of outflows and accretion determine the kinematics and column densities of the circumgalactic medium |
the chandra x-ray observatory has discovered dozens of resolved, kiloparsec-scale jets associated with powerful quasars in which the x-ray fluxes are observed to be much higher than the expected level based on the radio-optical synchrotron spectrum. the most popular explanation for the anomalously high and hard x-ray fluxes is that these jets do not decelerate significantly by the kiloparsec scale, but rather remain highly relativistic (lorentz factors {γ }∼ 10). by adopting a small angle to the line of sight, the x-rays can thus be explained by inverse compton upscattering of cosmic microwave background (cmb) photons (ic/cmb), where the observed emission is strongly doppler boosted. using over six years of fermi monitoring data, we show that the expected hard, steady gamma-ray emission implied by the ic/cmb model is not seen in pks 0637-752, the prototype jet for which this model was first proposed. ic/cmb emission is thus ruled out as the source of the x-rays, joining recent results for the jets in 3c 273 (using the same method) and pks 1136-135 (using uv polarization). we further show that the fermi observations give an upper limit of δ \lt 6.5 for the four brightest x-ray knots of pks 0637-752, and derive an updated limit of δ \lt 7.8 for knots a and b1 of 3c 273 (assuming equipartition). finally, we discuss the fact that high levels of synchrotron x-ray emission in a slow jet will unavoidably lead to a level of angle-integrated tev emission which exceeds that of the tev bl lac class. | ruling out ic/cmb x-rays in pks 0637-752 and the implications for tev emission from large-scale quasar jets |
recently, risaliti and lusso [nat. astron. 3, 272 (2019), 10.1038/s41550-018-0657-z] reported new measurements of the expansion rate of the universe by constructing the hubble diagram of 1598 quasars in the redshift range 0.5 <z <5.5 . it is claimed a 4 σ tension with the standard concordance λ cdm concerning both the fractionary matter density ωm 0 and the dark energy equation of state parameter wde standard values. in this work we promote an independent analysis of the same data set using a model-independent estimator for cosmic acceleration. our results corroborate that the source of such tension can be related to the ωm 0 value with a reasonable indication of a higher ωm 0 value (ωm 0≳0.4 ). on the other hand, we find that the role played by wde on the claimed tension is weak. we also discuss the use of this estimator as a "quality tool" to test the robustness of hubble diagrams. we conclude claiming that the quasars data cannot yet be seen as a reliable cosmological tool since they cannot even state the universe experienced an accelerated expansion phase. | is the hubble diagram of quasars in tension with concordance cosmology? |
we present alma band 7 observations at 850 μm of 20 luminous (log l_bol > 46.9 [erg s-1]) unobscured quasars at z ∼ 2. we detect continuum emission for 19/20 quasars. after subtracting an agn contribution, we measure the total far-ir luminosity for 18 quasars, assuming a modified blackbody model, and attribute the emission as indicative of the star formation rate (sfr). our sample can be characterized with a lognormal sfr distribution having a mean of 140 m⊙ yr-1 and a dispersion of 0.5 dex. based on an inference of their stellar masses, the sfrs are similar, in both the mean and dispersion, with star-forming main-sequence galaxies at the equivalent epoch. thus, there is no evidence for a systematic enhancement or suppression (i.e. regulation or quenching) of star formation in the hosts of the most luminous quasars at z ∼ 2. these results are consistent with the magneticum cosmological simulation, while in disagreement with a widely recognized phenomenological model that predicts higher sfrs than observed here based on the high bolometric luminosities of this sample. furthermore, there is only a weak relation between sfr and accretion rate on to their supermassive black holes both for average and individual measurements. we interpret these results as indicative of star formation and quasar accretion being fed from the available gas reservoir(s) in their host with a disconnect due to their different physical sizes, temporal scales, and means of gas processing. | no signs of star formation being regulated in the most luminous quasars at z ∼ 2 with alma |
the flat spectrum radio quasar 3c 279 is known to exhibit pronounced variability in the high-energy (100 mev < e < 100 gev) γ-ray band, which is continuously monitored with fermi-lat. during two periods of high activity in april 2014 and june 2015 target-of-opportunity observations were undertaken with the high energy stereoscopic system (h.e.s.s.) in the very-high-energy (vhe, e > 100 gev) γ-ray domain. while the observation in 2014 provides an upper limit, the observation in 2015 results in a signal with 8.7σ significance above an energy threshold of 66 gev. no vhe variability was detected during the 2015 observations. the vhe photon spectrum is soft and described by a power-law index of 4.2 ± 0.3. the h.e.s.s. data along with a detailed and contemporaneous multiwavelength data set provide constraints on the physical parameters of the emission region. the minimum distance of the emission region from the central black hole was estimated using two plausible geometries of the broad-line region and three potential intrinsic spectra. the emission region is confidently placed at r ≳ 1.7 × 1017 cm from the black hole, that is beyond the assumed distance of the broad-line region. time-dependent leptonic and lepto-hadronic one-zone models were used to describe the evolution of the 2015 flare. neither model can fully reproduce the observations, despite testing various parameter sets. furthermore, the h.e.s.s. data were used to derive constraints on lorentz invariance violation given the large redshift of 3c 279. | constraints on the emission region of 3c 279 during strong flares in 2014 and 2015 through vhe γ-ray observations with h.e.s.s. |
we present results from spectroscopic observations with x-shooter at the very large telescope of seven h2-bearing damped lyman-α systems (dlas) at high redshifts (zabs ∼ 2.5-3). these dlas were originally selected from the presence of strong h2 lines directly seen at the dla redshift in low-resolution low signal-to-noise ratio sdss spectra. we confirm the detection of molecular hydrogen in all of them. we measure the column densities of h i, h2 in various rotational levels, and metal species, and associated dust extinction. the metallicities, obtained from undepleted species, are in the range log z = -0.8 to -0.2. we discuss the chemical enrichment in these clouds and compare their properties with that of other molecular-rich systems selected by other means. in particular, we show that three different methods of pre-selection of h2-bearing dlas in the sdss have their own biases but complement each other mostly in terms of chemical enrichment. we use the rotational excitation of h2 molecules together with the fine-structure energy levels of neutral carbon to constrain the physical conditions in the gas with the help of numerical modelling as well as analytical expressions for the surface density at which atomic to molecular conversion happens. we find that the h2-bearing medium revealed by the studied dlas has typical values for the kinetic temperature, hydrogen density, and uv radiation field of t ∼ 100 k, nh ∼ 100 cm-3, and iuv , respectively, about twice the intensity of the draine field. detailed studies combining different selections should therefore bring important clues to understand the h i-h2 transition at high redshift. | x-shooter observations of strong h2-bearing dlas at high redshift |
in this manuscript, we report a new changing-look qso (clqso) sdss j2241 at z = 0.059. based on the multi-epoch sloan digital sky survey spectra from 2011 to 2017, the flux ratio of broad hα to broad hβ has changed from 7 in 2011 to 2.7 in 2017, leading sdss j2241 with a spectral index αλ ~ -5.21 ± 0.02 (λ < 4000) in 2017 to be, so far, the bluest clqso. based on the sdss spectrum in 2011, the host galaxy contribution with a stellar velocity dispersion of ~86 km s-1 can be well determined, leading to the m-sigma relation expected central black hole (bh) mass of ~3 × 106 m⊙. however, based on properties of the broad hα emission, the virial bh mass is ~108 m⊙, about two magnitudes larger than the mass found through the m-sigma relation. the different bh masses found using different methods indicate that sdss j2241 is one unique clqso. the long-term photometric light curve shows interesting variability that is not expected assuming the damped random walk process commonly applied to active galactic nuclei but probably connected to a central tidal disruption event. furthermore, based on continuum emission properties in 2017 with no dust obscuration, the moving dust clouds scenario alone cannot be preferred to explain the clqso sdss j2241, because the expected intrinsic reddening-corrected continuum emission was unreasonably higher than the unobscured continuum emission in 2017. | the bluest changing-look qso sdss j224113-012108 |
the upcoming radio interferometer square kilometre array (ska) is expected to directly detect the redshifted 21-cm signal from the neutral hydrogen present during the cosmic dawn. temperature fluctuations from x-ray heating of the neutral intergalactic medium can dominate the fluctuations in the 21-cm signal from this time. this heating depends on the abundance, clustering, and properties of the x-ray sources present, which remain highly uncertain. we present a suite of three new large-volume, 349 mpc a side, fully numerical radiative transfer simulations including qso-like sources, extending the work previously presented in ross et al. (2017). the results show that our qsos have a modest contribution to the heating budget, yet significantly impact the 21-cm signal. initially, the power spectrum is boosted on large scales by heating from the biased qso-like sources, before decreasing on all scales. fluctuations from images of the 21-cm signal with resolutions corresponding to ska1-low at the appropriate redshifts are well above the expected noise for deep integrations, indicating that imaging could be feasible for all the x-ray source models considered. the most notable contribution of the qsos is a dramatic increase in non-gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm probability distribution functions. however, in the case of late lyman-α saturation, this non-gaussianity could be dramatically decreased particularly when heating occurs earlier. we conclude that increased non-gaussianity is a promising signature of rare x-ray sources at this time, provided that lyman-α saturation occurs before heating dominates the 21-cm signal. | evaluating the qso contribution to the 21-cm signal from the cosmic dawn |
we report the discovery of six spatially extended (10-100 kpc) line-emitting nebulae in the z ≈ 0.57 galaxy group hosting pks 0405-123, one of the most luminous quasars at z < 1. the discovery is enabled by the multi unit spectroscopic explorer and provides tantalizing evidence connecting large-scale gas streams with nuclear activity on scales of <10 proper kpc (pkpc). one of the nebulae exhibits a narrow, filamentary morphology extending over 50 pkpc toward the quasar with narrow internal velocity dispersion (50 {km} {{{s}}}-1) and is not associated with any detected galaxies, consistent with a cool intragroup medium filament. two of the nebulae are 10 pkpc north and south of the quasar with tidal-arm-like morphologies. these two nebulae, along with a continuum-emitting arm extending 60 pkpc from the quasar, are signatures of interactions that are expected to redistribute angular momentum in the host interstellar medium (ism) to facilitate star formation and quasar fueling in the nucleus. the three remaining nebulae are among the largest and most luminous [o iii] emitting “blobs” known (1400-2400 pkpc2) and correspond both kinematically and morphologically to interacting galaxy pairs in the quasar host group, consistent with arising from stripped ism rather than large-scale quasar outflows. the presence of these large- and small-scale nebulae in the vicinity of a luminous quasar bears significantly on the effect of large-scale environment on galaxy and black hole fueling, providing a natural explanation for the previously known correlation between quasar luminosity and cool circumgalactic medium. | galaxy and quasar fueling caught in the act from the intragroup to the interstellar medium |
we investigate possible factors that drive fast quasar outflows using a sample of 39,249 quasars at median redshift $\langle z \rangle \approx$ 2.17. unique to this study, the quasar redshifts are re-measured based on the mg ii emission line, allowing for exploration of unprecedented outflow velocities (>6000 km/s) while maintaining statistical significance and uniformity. we measure reliable c iv blueshifts for 1178 quasars with velocities >2500 km/s. from those, 255(13) quasars have blueshifts above 4000(6000) km/s, with the highest c iv velocity $\approx$ 7000 km/s. several correlations are observed, where higher c iv blueshifts in general are in quasars with broader, weaker c iv emission profiles, weak he ii emission, larger eddington ratios, and bluer uv continuum slope across the rest-frame uv to near-ir. analysis reveals two primary factors contributing to faster outflows: higher eddington ratios, and softer far-uv continuum (h$\nu$ >24.6 ev). we find supporting evidence that radiative line-driving may generate extreme outflow velocities, influenced by multiple factors as suggested by the aforementioned correlations. this evidence highlights the importance of considering a multi-dimensional parameter space in future studies when analyzing large c iv blueshifts to determine the fundamental causes of outflows. | boss quasar outflows traced by c iv |
we present constraints on the amplitude of local primordial non-gaussianities (png), $f_{\rm nl}$, using the quasar sample in the sloan digital sky survey iv extended baryon oscillation spectroscopic survey data release 16. we analyze the power spectrum monopole, testing for the presence of scale dependent galaxy bias induced by local png. our analysis makes use of optimal redshift weights that maximize the response of the quasar sample to the possible presence of non zero png. we find $-4<f_{\rm nl}<27$ at $68\%$ confidence level, which is among the strongest bounds with large scale structure data. the optimal analysis reduces the error bar by about 10% compared to the standard one, an amount which is smaller than what was expected from a fisher matrix analysis. this, and the reduced improvement over previous releases of the same catalog, suggest the presence of still unknown systematic effects in the data. if the quasars have a lower response to local png, our optimal constraint becomes $-23<f_{\rm nl}<21$ at $68\%$, with an improvement of $30\%$ over standard analyses. we also show how to use the optimal weights to put data-driven priors on the sample's response to local png. | optimal constraints on primordial non-gaussianity with the eboss dr16 quasars in fourier space |
recently, the lyman-$\alpha$ (ly$\alpha$) forest flux auto-correlation function has been shown to be sensitive to the mean free path of hydrogen-ionizing photons, $\lambda_{\text{mfp}}$, for simulations at $z \geq 5.4$. measuring $\lambda_{\text{mfp}}$ at these redshifts will give vital information on the ending of reionization. here we present the first observational measurements of the ly$\alpha$ forest flux auto-correlation functions in ten redshift bins from $5.1 \leq z \leq 6.0$. we use a sample of 35 quasar sightlines at $z > 5.7$ from the extended xqr-30 data set, this data has signal-to-noise ratios of $> 20$ per spectral pixel. we carefully account for systematic errors in continuum reconstruction, instrumentation, and contamination by damped ly$\alpha$ systems. with these measurements, we introduce software tools to generate auto-correlation function measurements from any simulation. for an initial comparison, we show our auto-correlation measurements with simulation models for recently measured $\lambda_{\text{mfp}}$ values and find good agreements. further work in modeling and understanding the covariance matrices of the data is necessary to get robust measurements of $\lambda_{\text{mfp}}$ from this data. | measurements of the $z > 5$ lyman-$\\alpha$ forest flux auto-correlation functions from the extended xqr-30 data set |
a characteristic feature of quasars is the observed non-linear relationship between their monochromatic luminosities at rest-frame 2500 å and 2 kev. this relationship is evident across all redshifts and luminosities and, due to its non-linearity, can be implemented to estimate quasar distances and construct a hubble diagram for quasars. historically, a significant challenge in the cosmological application of this relation has been its high observed dispersion. recent studies have demonstrated that this dispersion can be reduced by excluding biased objects from the sample. nevertheless, the dispersion remains considerable ($\delta \sim 0.20$ dex), especially when compared to the phillips relation for supernovae ia. given the absence of a comprehensive physical model for the relation, it remains unclear how much of the remaining dispersion is intrinsically tied to the relation itself and how much can be attributed to observational factors not addressed by the sample selection and by the choice of x-ray and uv indicators. potential contributing factors include (i) the scatter produced by using x-ray photometric results instead of spectroscopic ones, (ii) the intrinsic variability of quasars, and (iii) the inclination of the accretion disc relative to our line of sight. in this study, we thoroughly examine these three factors and quantify their individual contributions to the observed dispersion. based on our findings, we argue that the intrinsic dispersion of the x-ray/uv luminosity relation is likely below 0.06 dex. we also discuss why high-redshift subsamples can show a significantly lower dispersion than the average one. | quasars as standard candles v. evaluation of a $\\leq$ 0.06 dex intrinsic dispersion in the lx-luv relation |
the flux ratios of gravitationally lensed quasars provide a powerful probe of the nature of dark matter. importantly, these ratios are sensitive to small-scale structure, irrespective of the presence of baryons. this sensitivity may allow us to study the halo mass function even below the scales where galaxies form observable stars. for accurate measurements, it is essential that the quasar's light is emitted from a physical region of the quasar with an angular scale of milli-arcseconds or larger; this minimizes microlensing effects by stars within the deflector. the warm dust region of quasars fits this criterion, as it has parsec-size physical scales and dominates the spectral energy distribution of quasars at wavelengths greater than 10$\mu$m. the jwst mid-infrared instrument (miri) is adept at detecting redshifted light in this wavelength range, offering both the spatial resolution and sensitivity required for accurate gravitational lensing flux ratio measurements. here, we introduce our survey designed to measure the warm dust flux ratios of 31 lensed quasars. we discuss the flux-ratio measurement technique and present results for the first target, des j0405-3308. we find that we can measure the quasar warm dust flux ratios with 3% precision. our simulations suggest that this precision makes it feasible to detect the presence of 10$^7$ m$_\odot$ dark matter halos at cosmological distances. such halos are expected to be completely dark in cold dark matter models. | jwst lensed quasar dark matter survey i: description and first results |
we study the dipole signal in the spectral index (x) of the differential number counts using quasars in the catwise2020 catalog of infrared sources. the index is extracted by using the log-likelihood method. we obtain the value $x=1.579 \pm 0.001$ for a quasar sample of 1355352 sources. we extract the dipole signal in this parameter by employing $\chi^{2}$ minimization, assuming a sky model of x up to the quadrupole term. we find that the dipole amplitude |d| is 0.005 \pm 0.002 and dipole direction (l, b) in galactic coordinate system equal to $(201.50^{\circ} \pm 27.87^{\circ}, -29.37^{\circ} \pm 19.86^{\circ})$. the direction of dipole anisotropy is found to be very close to the hemispherical power asymmetry $(l,b)=(221^\circ,-27^{\circ})$ in the cosmic microwave background (cmb). we also obtain a signal of quadrupole anisotropy which is correlated with the ecliptic poles and can be attributed to ecliptic bias.} | probing cosmological principle using the spectral index of quasar flux distribution |
we present a free-form lens model for the multiply lensed quasar in the galaxy cluster sdss j$1004+4112$. our lens model makes minimal assumptions about the distribution of mass in the lens plane. we pay particular attention to the model uncertainties on the predicted time delay, originating from the particular configuration of model variables. taking into account this uncertainty, we obtain a value of the hubble constant of $h_0= 74^{+9}_{-13}$km s$^{-1}$ mpc$^{-1}$, consistent with independent recent estimates. the predicted time delay between the central image e and image c (the first to arrive), is $\delta t_{e-c}=3200\pm 200$ days. future measurements of $\delta t_{e-c}$ will allow to impose a tighter constrain on $h_0$ from this cluster-qso system. | parameter free hubble constant from the quadruply lensed quasar sdss j1004 + 4112 |
the well-studied blazar 3c 279 underwent a giant γ-ray outburst in 2014 march-april. the measured γ-ray flux (1.21 ± 0.10 × 10-5 ph c{{m}-2} {{s}-1} in a 0.1-300 gev energy range) is the highest detected from 3c 279 by the fermi large area telescope. hour-scale γ-ray flux variability is observed, with a flux doubling time as short as 1.19 ± 0.36 hr detected during one flare. the γ-ray spectrum is found to be curved at the peak of the flare, suggesting low probability of detecting very high energy (vhe; e \gt 100 gev) emission, which is further confirmed by the veritas observations. the γ-ray flux increased by more than an order in comparison to a low-activity state and the flare consists of multiple sub-structures having a fast rise and slow decay profile. the flux enhancement is seen in all the wavebands, though at a lesser extent compared to γ-rays. during the flare, a considerable amount of the kinetic jet power gets converted to γ-rays and the jet becomes radiatively efficient. a one-zone leptonic emission model is used to reproduce the flare and we find increase in the bulk lorentz factor as a major cause of the outburst. from the observed fast variability, lack of vhe detection, and the curved γ-ray spectrum, we conclude that the location of the emission region cannot be far out from the broad-line region (blr) and contributions from both blr and torus photons are required to explain the observed γ-ray spectrum. | multi-wavelength observations of 3c 279 during the extremely bright gamma-ray flare in 2014 march-april |
the correlation between the x-ray and uv luminosities observed in quasars, spanning a wide redshift range and holding true for several decades in both spectral bands, suggests the presence of a universal mechanism governing the transfer of energy from the accretion disc to the hot corona. in this study, we leverage x-ray spectroscopic data extracted from the chandra source catalog 2.0 for a sample of over $2000$ quasars from the sloan digital sky survey data release 14 (sdss dr14). our analysis reveals a reduced intrinsic dispersion in the $l_{\rm{x}}-l_{\rm{uv}}$ relation at higher redshifts ($\delta < 0.2$ dex) compared to previous studies relying on photometric data from catalogs. additionally, our findings confirm the stability of this relation up to redshifts of approximately $4.5$. the $l_{\rm{x}}-l_{\rm{uv}}$ relation can also serve as a tool to investigate the physics of accretion by identifying outliers - sources that exhibit a different state of the accretion disc-hot corona system compared to the average population. for instance, x-ray-weak quasars are sources with reduced x-ray emissions due to a radiatively inefficient state of the corona, and their optical properties suggest the presence of a powerful accretion disc wind. the wealth of spectroscopic data available in the csc 2.0-sdss catalogs opens up the opportunity for a more comprehensive exploration of the central engine in agn. | the relation between x-ray and uv emission in quasars |
we study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band (g, r, i, z) light curves in the pan-starrs medium deep fields. as photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. we select 240 quasars with redshifts of z ≈ 1 or z ≈ 0.3 that are relatively emission-line free. the light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. with the code javelin, we detect typical lags of several days in the rest frame between the g band and the riz bands. the detected lags are ∼2-3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in ngc 5548 and microlensing measurements of quasars. the lags in our sample are found to increase with increasing luminosity. furthermore, the increase in lags going from g - r to g - i and then to g - z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. the radial temperature profile in the disk must be different from what is assumed. we also find evidence that the lags decrease with increasing line ratios between ultraviolet fe ii lines and mg ii, which may point to changes in the accretion disk structure at higher metallicity. | detection of time lags between quasar continuum emission bands based on pan-starrs light curves |
a complete census of baryons in the late universe is a long-standing challenge due to the intermediate temperate and rarefied character of the majority of cosmic gas. to gain insight into this problem, we extract measurements of the kinematic sunyaev-zel'dovich (ksz) effect from the cross-correlation of angular redshift fluctuations maps, which contain precise information about the cosmic density and velocity fields, and cosmic microwave background maps high-pass filtered using aperture photometry; we refer to this technique as angular redshift fluctuations (arf)-ksz tomography. remarkably, we detect significant cross-correlation for a wide range of redshifts and filter apertures using 6df galaxies, boss galaxies, and sdss quasars as tracers, yielding a 11σ detection of the ksz effect. we then leverage these measurements to set constraints on the location, density, and abundance of gas inducing the ksz effect, finding that this gas resides outside dark matter haloes, presents densities ranging from 10 to 250 times the cosmic average, and comprises half of cosmic baryons. taken together, these findings indicate that arf-ksz tomography provides a nearly complete census of intergalactic gas from z = 0 to 5. | measuring the evolution of intergalactic gas from z = 0 to 5 using the kinematic sunyaev-zel'dovich effect |
context. qso b0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. the gravitational lensing splits the emitted radiation into two components that are spatially indistinguishable by gamma-ray instruments, but separated by a 10-12 day delay. in july 2014, qso b0218+357 experienced a violent flare observed by the fermi-lat and followed by the magic telescopes.aims: the spectral energy distribution of qso b0218+357 can give information on the energetics of z 1 very high energy gamma-ray sources. moreover the gamma-ray emission can also be used as a probe of the extragalactic background light at z 1.methods: magic performed observations of qso b0218+357 during the expected arrival time of the delayed component of the emission. the magic and fermi-lat observations were accompanied by quasi-simultaneous optical data from the kva telescope and x-ray observations by swift-xrt. we construct a multiwavelength spectral energy distribution of qso b0218+357 and use it to model the source. the gev and sub-tev data obtained by fermi-lat and magic are used to set constraints on the extragalactic background light.results: very high energy gamma-ray emission was detected from the direction of qso b0218+357 by the magic telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray source detected to date. the observed emission spans the energy range from 65 to 175 gev. the combined magic and fermi-lat spectral energy distribution of qso b0218+357 is consistent with current extragalactic background light models. the broadband emission can be modeled in the framework of a two-zone external compton scenario, where the gev emission comes from an emission region in the jet, located outside the broad line region. | detection of very high energy gamma-ray emission from the gravitationally lensed blazar qso b0218+357 with the magic telescopes |
accreting supermassive black holes (smbhs) frequently power jets that interact with the interstellar/circumgalactic medium (ism/cgm), regulating star-formation in the galaxy. highly supersonic jets launched by active galactic nuclei (agn) power a cocoon that confines them and shocks the ambient medium. we build upon the models of narrow conical jets interacting with a smooth ambient medium, to include the effect of dense clouds that are an essential ingredient of a multiphase ism. the key physical ingredient of this model is that the clouds along the supersonic jet-beam strongly decelerate the jet-head, but the subsonic cocoon easily moves around the clouds without much resistance. we propose scalings for important physical quantities -- cocoon pressure, head & cocoon speed, and jet radius. we obtain, for the first time, the analytic condition on clumpiness of the ambient medium for the jet to dissipate within the cocoon and verify it with numerical simulations of conical jets interacting with a uniform ism with embedded spherical clouds. a jet is defined to be dissipated when the cocoon speed exceeds the speed of the jet-head. we compare our models to more sophisticated numerical simulations, direct observations of jet-ism interaction (e.g., quasar j1316+1753), and discuss implications for the fermi/erosita bubbles. our work also motivates effective subgrid models for agn jet feedback in a clumpy ism unresolved by the present generation of cosmological galaxy formation simulations. | dissipation of agn jets in a clumpy interstellar medium |
in theoretical models of galaxy evolution, black hole feedback is a necessary ingredient in order to explain the observed exponential decline in number density of massive galaxies. most contemporary black hole feedback models in cosmological simulations rely on a constant radiative efficiency (usually $\eta \sim 0.1$) at all black hole accretion rates. we present a synthesis model for the spin-dependent radiative efficiencies of three physical accretion rate regimes, i.e. $\eta = \eta(j, \dot{m}_\mathrm{bh})$, for use in large-volume cosmological simulations. the three regimes include: an advection dominated accretion flow ($\dot{m}_\mathrm{bh} < 0.03\,\dot{m}_\mathrm{edd}$), a quasar-like mode ($0.03 < \dot{m}_\mathrm{bh} / \dot{m}_\mathrm{edd} < 0.3$), and a slim disc mode ($\dot{m}_\mathrm{bh} > 0.3\,\dot{m}_\mathrm{edd}$). additionally, we include a large-scale powerful jet at low accretion rates. the black hole feedback model we present is a kinetic model that prescribes mass loadings but could be used in thermal models directly using the radiative efficiency. we implemented our model into the \texttt{simba} galaxy evolution model to determine if it is possible to reproduce galaxy populations successfully, and provide a first calibration for further study. using a $2\times1024^3$ particle cosmological simulation in a $(150\,\mathrm{cmpc})^3$ volume, we found that the model is successful in reproducing the galaxy stellar mass function, black hole mass-stellar mass relationship, and stellar mass-halo mass relationship. our model shines when we extrapolate to the galaxy group and cluster scale as it impressively predicts the observed baryon fraction within massive groups and low-mass clusters. moving forward, this model opens new avenues for exploration of the impact of black hole feedback on galactic environments. | three regimes of black hole feedback |
cosmological simulations of the low-density intergalactic medium exhibit a strikingly tight power-law relation between temperature and density that holds over two decades in density. it is found that this relation should roughly apply δz ∼ 1-2 after a reionization event, and this limiting behaviour has motivated the power-law parameterizations used in most analyses of the ly α forest. this relation has been explained by using equations linearized in the baryonic overdensity (which does not address why a tight power-law relation holds over two decades in density) or by equating the photoheating rate with the cooling rate from cosmological expansion (which we show is incorrect). previous explanations also did not address why recombination cooling and compton cooling off of the cosmic microwave background, which are never negligible, do not alter the character of this relation. we provide an understanding for why a tight power-law relation arises for unshocked gas at all densities for which collisional cooling is unimportant. we also use our results to comment on (1) how quickly fluctuations in temperature redshift away after reionization processes, (2) how much shock heating occurs in the low-density intergalactic medium, and (3) how the temperatures of collapsing gas parcels evolve. | on the intergalactic temperature-density relation |
we examine the 2008-2016 γ-ray and optical light curves of three bright bl lac objects, 0716+714, mrk 421, bl lac, which exhibit large structured variability. we searched for periodicities by using a fully bayesian approach. for two out of three sources investigated, no significant periodic variability was found. in the case of bl lac, we detected a periodicity of 680 days. although the signal related to this is modest, the coincidence of the periods in both gamma and optical bands is indicative of a physical relevance. taking into consideration previous literature results, possibly related γ-ray and optical periodicities of about one year time scale are proposed in four bright γ-ray blazars out of the ten examined in detail. compared with results from periodicity search of optical archives of quasars, the presence of quasi-periodicities in blazars may be more frequent by a large factor. this suggests the intriguing possibility that the basic conditions for their observability are related to the relativistic jet in the observer direction, but the overall picture remains uncertain. | gamma-ray and optical oscillations of 0716+714, mrk 421, and bl lacertae |
we examine the properties of the host galaxies of $z=7$ quasars using the large volume, cosmological hydrodynamical simulation bluetides. we find that the 10 most massive black holes and the 191 quasars in the simulation (with $m_{\textrm{uv,agn}}\lt m_{\textrm{uv,host}}$) are hosted by massive galaxies with stellar masses $\log (m_\ast /\, {\rm m}_{\odot })=10.8\pm 0.2$, and $10.2\pm 0.4$, which have large star formation rates of $513_{-351}^{+1225}\, {\rm m}_{\odot }/\rm {yr}$ and $191_{-120}^{+288}\, {\rm m}_{\odot }/\rm {yr}$, respectively. the hosts of the most massive black holes and quasars in bluetides are generally bulge-dominated, with bulge-to-total mass ratio $b/t\simeq 0.85\pm 0.1$; however, their morphologies are not biased relative to the overall $z=7$ galaxy sample. we find that the hosts of the most massive black holes and quasars are compact, with half-mass radii $r_{0.5}=0.41_{-0.14}^{+0.18}$ kpc and $0.40_{-0.09}^{+0.11}$ kpc, respectively; galaxies with similar masses and luminosities have a wider range of sizes with a larger median value, $r_{0.5}=0.71_{-0.25}^{+0.28}$ kpc. we make mock james webb space telescope (jwst) images of these quasars and their host galaxies. we find that distinguishing the host from the quasar emission will be possible but still challenging with jwst, due to the small sizes of quasar hosts. we find that quasar samples are biased tracers of the intrinsic black hole-stellar mass relation, following a relation that is 0.2 dex higher than that of the full galaxy sample. finally, we find that the most massive black holes and quasars are more likely to be found in denser environments than the typical $m_{\textrm{bh}}\gt 10^{6.5}\, {\rm m}_{\odot }$ black hole, indicating that minor mergers play at least some role in growing black holes in the early universe. | the host galaxies of z = 7 quasars: predictions from the bluetides simulation |
context. icecube has reported a very-high-energy neutrino (icecube-170922a) in a region containing the blazar txs 0506+056. correlated gamma-ray activity has led to the first high-probability association of a high-energy neutrino with an extragalactic source. this blazar has been found to be in a radio outburst during the neutrino event.aims: our goal is to probe the sub-milliarcsecond properties of the radio jet right after the neutrino detection and during the further evolution of the radio outburst.methods: we performed target of opportunity observations at 43 ghz frequency using very long baseline interferometry imaging, corresponding to 7 mm in wavelength, with the very long baseline array two and eight months after the neutrino event.results: we produced two images of the radio jet of txs 0506+056 at 43 ghz with angular resolutions of (0.2 × 1.1) mas and (0.2 × 0.5) mas, respectively. the source shows a compact, high brightness temperature core, albeit not approaching the equipartition limit and a bright and originally very collimated inner jet. beyond approximately 0.5 mas from the millimeter-vlbi core, the jet loses this tight collimation and expands rapidly. during the months after the neutrino event associated with this source, the overall flux density is rising. this flux density increase happens solely within the core. notably, the core expands in size with apparent superluminal velocity during these six months so that the brightness temperature drops by a factor of three despite the strong flux density increase.conclusions: the radio jet of txs 0506+056 shows strong signs of deceleration and/or a spine-sheath structure within the inner 1 mas, corresponding to about 70-140 pc in deprojected distance, from the millimeter-vlbi core. this structure is consistent with theoretical models that attribute the neutrino and gamma-ray production in txs 0506+056 to interactions of electrons and protons in the highly relativistic jet spine with external photons originating from a slower moving jet region. proton loading due to jet-star interactions in the inner host galaxy is suggested as the possible cause of deceleration. | apparent superluminal core expansion and limb brightening in the candidate neutrino blazar txs 0506+056 |
proximity zones of high-redshift quasars are unique probes of supermassive black hole formation, but simultaneously explaining proximity zone sizes and black hole masses has proved to be challenging. we study the robustness of some of the assumptions that are usually made to infer quasar lifetimes from proximity zone sizes. we show that small proximity zones can be readily explained by quasars that vary in brightness with a short duty cycle of fduty ~ 0.1 and short bright periods of ton ~ 104 yr, even for long lifetimes. we further show that reconciling this with black hole mass estimates requires the black hole to continue to grow and accrete during its obscured phase. the consequent obscured fractions of ≳ 0.7 or higher are consistent with low-redshift measurements and models of black hole accretion. such short duty cycles and long obscured phases are also consistent with observations of large proximity zones, thus providing a simple, unified model for proximity zones of all sizes. the large dynamic range of our simulation, and its calibration to the lyman-α forest, allows us to investigate the influence of the large-scale topology of reionization and the quasar's host halo mass on proximity zones. we find that incomplete reionization can impede the growth of proximity zones and make them smaller up to 30 per cent, but the quasar host halo mass only affects proximity zones weakly and indirectly. our work suggests that high-redshift proximity zones can be an effective tool to study quasar variability and black hole growth. | the need for obscured supermassive black hole growth to explain quasar proximity zones in the epoch of reionization |
we present new 5 ghz very large array observations of a sample of eight active intermediate-mass black holes with masses 104.9 m⊙ < m < 106.1 m⊙ found in galaxies with stellar masses m* < 3 × 109 m⊙. we detected five of the eight sources at high significance. of the detections, four were consistent with a point source, and one (sdss j095418.15+471725.1, with black hole mass m < 105 m⊙) clearly shows extended emission that has a jet morphology. combining our new radio data with the black hole masses and literature x-ray measurements, we put the sources on the fundamental plane of black hole accretion. we find that the extent to which the sources agree with the fundamental plane depends on their star-forming/composite/active galactic nucleus (agn) classification based on optical narrow emission-line ratios. the single star-forming source is inconsistent with the fundamental plane. the three composite sources are consistent, and three of the four agn sources are inconsistent with the fundamental plane. we argue that this inconsistency is genuine and not a result of misattributing star formation to black hole activity. instead, we identify the sources in our sample that have agn-like optical emission-line ratios as not following the fundamental plane and thus caution the use of the fundamental plane to estimate masses without additional constraints, such as radio spectral index, radiative efficiency, or the eddington fraction. | intermediate-mass black holes and the fundamental plane of black hole accretion |
we propose a solution to the problem of accretion disc sizes in active galactic nuclei being larger when measured by reverberation mapping than predicted by theory. considering the disc's exposed-surface thickness profile h(r), our solution invokes a steep rim or rippled structures irradiated by the central lamp-post. we model the continuum lags and the faint and bright disc spectral energy distribution (sed) in the best-studied case ngc 5548 (black hole mass $m_\bullet =7\times 10^7\, \mathrm{m}_\odot$, disc inclination i = 45°). with the lamp-post off, the faint-disc sed fixes a low accretion rate $\dot{m}\simeq 0.0014~\mathrm{m}_\odot \, {\rm yr}^{-1}$ and high prograde black hole spin a• ≃ 0.93, for which $r_{\rm in}=2\, g\, m_\bullet /c^2$ and $l_{\rm disc}=0.25\, \dot{m}\, c^2$. the bright-disc sed then requires a lamp-post luminosity ${l_{\rm lp}}\simeq 5\, \dot{m}\, c^2/(1-a)$ for disc albedo a. reprocessing on the thin disc with t ∝ r-3/4 gives time lags τ ∝ λ4/3 but three times smaller than observed. introducing a steep h(r) rim, or multiple crests, near r ~ 5 light days, reprocessing on the steep centre-facing slope increases temperatures from ~1500 to ~6000 k, and this increases optical lags to match the lag data. most of the disc surface maintains the cooler t ∝ r-3/4 profile that matches the sed. the bright lamp-post may be powered by magnetic links tapping the black hole spin. the steep rim occurs near the disc's dust sublimation radius as in the 'failed disc wind model for broad-line clouds'. lens-thirring torques aligning the disc and black hole spin may also raise a warp and associated waves. in both scenarios, the small density scale height implied by the inferred value of h(r) suggests possible marginal gravitational instability in the disc. | rimmed and rippled accretion disc models to explain agn continuum lags |
we study dual agn host galaxy morphologies at $z=2$ using the astrid simulation, selecting black hole (bh) pairs with small separation ($\delta r<30\rm{kpc}$), high mass ($m_{\text{bh,12}}>10^7m_\odot$), and luminosity ($l_{\text{bol,12}}>10^{43}\rm{erg/s}$). we kinematically decompose (using mordor) $\sim1000$ dual agn hosts into standard components - a `disk' (thin and thick disk, pseudo-bulge) and 'bulge' (bulge and halo) and define disk-dominated galaxies by the disk-to-total $d/t\geq0.5$. in astrid, $60.9\pm2.1\%$ of dual agn hosts (independent of separation) are disk-dominated, with the $d/t$ distribution peaking at $\sim0.7$. notably, hosts of bh pairs have similar morphologies (most either both disk or bulge-dominated). in dual-agn hosts, the $d/t$ increases from $\sim17\% $ at $m_{\rm *}\sim 10^{9} m_{\odot}$ to $ 64\% $ for $m_{\rm *} \sim 10^{11.5} m_{\odot}$, and the pseudo-bulge is the dominant component of the disk fraction at the high mass end. moreover, dual agn hosts exhibit a higher fraction of disk/large pseudo-bulge than single-agn hosts. the disk-to-total ratio is approximately constant with bh mass or agn luminosity. we also create mock images of dual agn host galaxies, employing morphological fitting software statmorph to calculate morphological parameters and compare them with our kinematic decomposition results. around $83.3\pm2.4\%$ of galaxies display disk-like profiles, of which $\sim60.7\pm2.2\%$ are kinematically confirmed as disks. seŕsic indices and half-mass radii of dual agn host galaxies align with observational measurements from hst at $z\sim2$. around $34\%$ are identified as mergers from the $\text{gini}-m_{20}$ relation. we find two dual agn hosted by galaxies that exhibit disk-like seŕsic index $n_{12}<1$ and $(d/t)_{12}>0.5$, which are in remarkable agreement with properties of recently discovered dual quasars in disk galaxies at $z\sim 2$. | z~2 dual agn host galaxies are disky: stellar kinematics in the astrid simulation |
using mock data for the hubble diagrams of type ia supernovae (snia) and quasars (qsos) generated based on the standard model of cosmology, and using the least-squares method based on the markov-chain-monte-carlo (mcmc) algorithm, we first put constraints on the cosmographic parameters in the context of the various model-independent cosmographic methods reconstructed from the taylor 4th and 5th order expansions and the padé (2,2) and (3,2) polynomials of the hubble parameter, respectively. we then reconstruct the distance modulus in the framework of cosmographic methods and calculate the percentage difference between the distance modulus of the cosmographic methods and that of the standard model. the percentage difference is minimized when the padé approximation is used which means that the padé cosmographic method is sufficiently suitable for reconstructing the distance modulus even at high-redshifts. in the next step, using the real observational data for the hubble diagrams of snia, qsos, gamma-ray-bursts (grbs), and observations from baryon acoustic oscillations (bao) in two sets of the low-redshift combination (snia +qsos +grbs +bao ) embracing the redshift range of 0.01 <z <2.26 and the high-redshift combination (snia +qsos +grbs ) which covers a redshift range of 0.01 <z <5.5 , we put observational constraints on the cosmographic parameters of the padé cosmography and also the standard model. our analysis indicates that padé cosmographic approaches do not reveal any cosmographic tension between the standard model and the observational data. we also confirm this result, using the statistical aic criteria. finally, we put the cosmographic method in the redshift-bin data and find a larger value of ωm 0 extracted from s0 parameter compared with those of the q0 parameter and planck-λ cdm values. | can high-redshift hubble diagrams rule out the standard model of cosmology in the context of cosmography? |
synthetic data sets are used in cosmology to test analysis procedures, to verify that systematic errors are well understood and to demonstrate that measurements are unbiased. in this work we describe the methods used to generate synthetic datasets of lyman-$\alpha$ quasar spectra aimed for studies with the dark energy spectroscopic instrument (desi). in particular, we focus on demonstrating that our simulations reproduces important features of real samples, making them suitable to test the analysis methods to be used in desi and to place limits on systematic effects on measurements of baryon acoustic oscillations (bao). we present a set of mocks that reproduce the statistical properties of the desi early data set with good agreement. additionally, we use full survey synthetic data to forecast the bao scale constraining power with desi. | synthetic spectra for lyman-$\\alpha$ forest analysis in the dark energy spectroscopic instrument |
the link between the circumgalactic medium (cgm) and the stellar growth of massive galaxies at high-z depends on the properties of the widespread cold molecular gas. as part of the supercold-cgm survey (survey of protocluster elane revealing co/[c i] in the lyα-detected cgm), we present the radio-loud qso q1228+3128 at z = 2.2218, which is embedded in an enormous lyα nebula. alma+aca observations of co(4-3) reveal both a massive molecular outflow, and a more extended molecular gas reservoir across ~100 kpc in the cgm, each containing a mass of m h2 ~ 4-5 × 1010 m ⊙. the outflow and molecular cgm are aligned spatially, along the direction of an inner radio jet. after reanalysis of lyα data of q1228+3128 from the keck cosmic web imager, we found that the velocity of the extended co agrees with the redshift derived from the lyα nebula and the bulk velocity of the massive outflow. we propose a scenario where the radio source in q1228+3128 is driving the molecular outflow and perhaps also enriching or cooling the cgm. in addition, we found that the extended co emission is nearly perpendicular to the extended lyα nebula spatially, indicating that the two gas phases are not well mixed, and possibly even represent different phenomena (e.g., outflow versus infall). our results provide crucial evidence in support of predicted baryonic recycling processes that drive the early evolution of massive galaxies. | massive molecular outflow and 100 kpc extended cold halo gas in the enormous lyα nebula of qso 1228+3128 |
we use zoom simulations to show how merger-driven disruption of the gas disc in a galaxy provides its central active galactic nucleus (agn) with fuel to drive outflows that entrain and expel a significant fraction of the circumgalactic medium (cgm). this in turn suppresses replenishment of the interstellar medium, causing the galaxy to quench up to several gyr after the merger. we start by performing a zoom simulation of a present-day star-forming disc galaxy with the eagle galaxy formation model. then, we re-simulate the galaxy with controlled changes to its initial conditions, using the genetic modification technique. these modifications either increase or decrease the stellar mass ratio of the galaxy's last significant merger, which occurs at $z$ ≈ 0.74. the halo reaches the same present-day mass in all cases, but changing the mass ratio of the merger yields markedly different galaxy and cgm properties. we find that a merger can unlock rapid growth of the central supermassive black hole if it disrupts the co-rotational motion of gas in the black hole's vicinity. conversely, if a less disruptive merger occurs and gas close to the black hole is not disturbed, the agn does not strongly affect the cgm, and consequently the galaxy continues to form stars. our result illustrates how a unified view of agn feedback, the baryon cycle and the interstellar medium is required to understand how mergers and quenching are connected over long time-scales. | galaxy mergers can initiate quenching by unlocking an agn-driven transformation of the baryon cycle |
quasar accretion-disc outflows might play an important role in galaxy evolution, but they are notoriously difficult to study due to line saturation and blending problems in the ly α forest. we circumvent these problems by constructing median composite spectra of diverse broad absorption lines (bals) and `mini-bals' in sdss-iii boss quasars at redshifts 2.3 ≤ z ≤ 3.5. sorting by c iv λλ1549,1551 absorption-line strength with al iii λλ1855,1863 as an additional indicator of low ionizations (lobals) we find the following: (1) deeper and broader bals are accompanied by weaker he ii λ1640 emission lines, consistent with softer ionizing spectra producing more effective radiative acceleration. (2) p v λλ1118,1128 absorption is present with resolved ∼1:1 depth ratios in all composites from mini-bals to strong bals indicating that line saturation, large total column densities log nh(cm-2) ≳ 22.7, and large ionization parameters log u ≳ -0.5 are common. (3) different observed depths in saturated lines identify inhomogeneous partial covering on spatial scales ≲0.006 pc, where weak/low-abundance transitions like p v form in small high-column density clumps while stronger/broader lines like c iv form in larger regions. (4) excited-state s iv* λ1073 and c iii* λ1176 lines in bal outflows indicate typical densities ne ≳ 3 × 105 cm-3 and maximum radial distances r ≲ 23 pc from the quasars. (5) for reasonable actual distances, the median bal outflow has minimum kinetic energy lk/l ≳ 0.005(r/1.2 pc) sufficient for feedback to galaxy evolution. (6) lobal quasars have the largest median outflow column densities, highest velocities, and weakest he ii λ1640 emission in our study; they appear to be at one extreme in a distribution of quasar properties where softer ionizing spectra drive more powerful outflows. | on the structure and energetics of quasar broad absorption-line outflows |
we perform the first broadband study of mrk421 from radio to tev gamma rays with simultaneous measurements of the x-ray polarization from ixpe. the data were collected within an extensive multiwavelength campaign organized between may and june 2022 using magic, fermi-lat, nustar, xmm-newton, swift, and several optical and radio telescopes to complement ixpe. during the ixpe exposures, the measured 0.2-1 tev flux is close to the quiescent state and ranges from 25% to 50% of the crab nebula without intra-night variability. throughout the campaign, the vhe and x-ray emission are positively correlated at a $4\sigma$ significance level. the ixpe measurements unveil a x-ray polarization degree that is a factor of 2-5 higher than in the optical/radio bands; that implies an energy-stratified jet in which the vhe photons are emitted co-spatially with the x-rays, in the vicinity of a shock front. the june 2022 observations exhibit a rotation of the x-ray polarization angle. despite no simultaneous vhe coverage being available during a large fraction of the swing, the swift-xrt monitoring unveils an x-ray flux increase with a clear spectral hardening. it suggests that flares in high synchrotron peaked blazars can be accompanied by a polarization angle rotation, as observed in some flat spectrum radio quasars. finally, during the polarization angle rotation, nustar data reveal two contiguous spectral hysteresis loops in opposite directions (clockwise and counter-clockwise), implying important changes in the particle acceleration efficiency on $\sim$hour timescales. | first characterization of the emission behavior of mrk421 from radio to vhe gamma rays with simultaneous x-ray polarization measurements |
the legacy survey of space and time (lsst) by the vera c. rubin observatory is expected to discover tens of millions of quasars. a significant fraction of these could be powered by coalescing massive black hole (mbh) binaries, since many quasars are believed to be triggered by mergers. we show that under plausible assumptions about the luminosity functions, lifetimes, and binary fractions of quasars, we expect the full lsst quasar catalogue to contain between 20 and 100 million compact mbh binaries with masses m = 105-9m⊙, redshifts z = 0-6, and orbital periods p = 1-70 d. their light-curves are expected to be distinctly periodic, which can be confidently distinguished from stochastic red-noise variability, because lsst will cover dozens, or even hundreds of cycles. a very small subset of 10-150 ultracompact (p ≲ 1 d) binary quasars among these will, over ~5-15 yr, evolve into the mhz gravitational-wave frequency band and can be detected by lisa. they can therefore be regarded as 'lisa verification binaries', analogous to short-period galactic compact-object binaries. the practical question is how to find these handful of 'needles in the haystack' among the large number of quasars: this will likely require a tailored co-adding analysis optimized for this purpose. | ultra-short-period massive black hole binary candidates in lsst as lisa 'verification binaries' |
we derive the statistical properties of neutral gas at redshifts 0.11 < z < 1.65 from ultraviolet (uv) measurements of quasar ly α absorption lines corresponding to 369 mg ii systems with w^{λ 2796}0 ≥ 0.3 å. in addition to the 41 damped lyman alpha (dla) systems presented in rao et al. (2006), the current dla sample includes 29 newly discovered dlas. formally, this dla sample includes 70 systems with n_{h i}≥ 2× 10^{20} atoms cm-2. we find that the incidence of dlas, or the product of their gas cross-section and their comoving number density, can be described by ndla(z) = (0.027 ± 0.007)(1 + z)(1.682 ± 0.200) over the redshift range of 0 < z < 5. the cosmic mass density of neutral gas can be described by ωdla(z) = (4.77 ± 1.60) × 10-4(1 + z)(0.64 ± 0.27). the low-redshift column density distribution function is well fitted by a power law of the form f (n) ∼ nβ with β = -1.46 ± 0.20. it is consistent with the high redshift as well as z = 0 estimates at the high-column density end but lies between them at the low-column density end. we discuss possible n_{h i} and metallicity bias in mg ii-selected dla samples and show that such biases do not exist in the current data at z < 1.65. thus, at least at z < 1.65, dlas found through mg ii selection statistically represent the true population of dlas. however, we caution that studies of dla metallicities should take into account the relative incidence of dlas with respect to w_0^{λ 2796} (or gas velocity spread) in order to correctly measure the mean neutral-gas cosmic metallicity of the universe. | the statistical properties of neutral gas at z < 1.65 from uv measurements of damped lyman alpha systems |
we present a new model-independent method to determine spatial curvature and to mitigate the circularity problem affecting the use of quasars as distance indicators. cosmic-chronometer measurements are used to construct the curvature-dependent luminosity distance ${d}_{l}^{\mathrm{cal}}({{\rm{\omega }}}_{k},z)$ using a polynomial fit. based on the reconstructed ${d}_{l}^{\mathrm{cal}}({{\rm{\omega }}}_{k},z)$ and the known ultraviolet versus x-ray luminosity correlation of quasars, we simultaneously place limits on the curvature parameter ωk and the parameters characterizing the luminosity correlation function. this model-independent analysis suggests that a mildly closed universe ( ${{\rm{\omega }}}_{k}=-0.918\pm 0.429$ ) is preferred at the 2.1σ level. with the calibrated luminosity correlation, we build a new data set consisting of 1598 quasar distance moduli, and use these calibrated measurements to test and compare the standard λcdm model and the rh = ct universe. both models account for the data very well, though the optimized flat λcdm model has one more free parameter than rh = ct, and is penalized more heavily by the bayes information criterion. we find that rh = ct is slightly favored over λcdm with a likelihood of ∼57.7% versus 42.3%. | model-independent distance calibration and curvature measurement using quasars and cosmic chronometers |
deep observations have detected extended lyα emission nebulae surrounding tens of quasars at redshift 2-6. however, the metallicity of such extended halos is still poorly understood. we perform a detailed analysis on a large sample of 80 quasars at z ∼ 3 based on muse-vlt data. we find clear evidence of extended emission of the uv nebular lines such as c iv λ1549 or he ii λ1640 for about 20% of the sample, while c iii] λ1909 is only marginally detected in a few objects. by stacking the cubes, we detect emission of c iv, he ii, and c iii] out to a radius of about 45 kpc. c iv and he ii show a radial decline much steeper than lyα, while c iii] shows a shallower profile similar to lyα in the inner 45 kpc. we infer that the average metallicity of the circumgalactic gas within the central 30-50 kpc is ∼0.5 solar, or even higher. however, we also find evidence of a component of the lyα halos, which has much weaker metal emission lines relative to lyα. we suggest that the high metallicity of the circumgalactic medium within the central 30-50 kpc is associated with chemical pre-enrichment by past quasar-driven outflows and that there is a more extended component of the circumgalactic medium that has much lower metallicity and is likely associated with near-pristine gas accreted from the intergalactic medium. we show that our observational results are in good agreement with the expectations of the fable zoom-in cosmological simulations. | metal enrichment in the circumgalactic medium and lyα halos around quasars at z ∼ 3 |
we present a hubble space telescope space telescope imaging spectrograph spectrum of asassn-14li, the first rest-frame ultraviolet (uv) spectrum of a tidal disruption flare (tdf). the underlying continuum is well fit by a blackbody with {t}{uv}=3.5× {10}4 k, an order of magnitude smaller than the temperature inferred from x-ray spectra (and significantly more precise than previous efforts based on optical and near-uv photometry). superimposed on this blue continuum, we detect three classes of features: narrow absorption from the milky way (probably a high-velocity cloud), and narrow absorption and broad (∼2000-8000 km s-1) emission lines at or near the systemic host velocity. the absorption lines are blueshifted with respect to the emission lines by δv = -(250-400) km s-1. due both to this velocity offset and the lack of common low-ionization features (mg ii, fe ii), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at x-ray wavelengths. the broad nuclear emission lines display a remarkable abundance pattern: n iii], n iv], and he ii are quite prominent, while the common quasar emission lines of c iii] and mg ii are weak or entirely absent. detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in tdfs, while future uv spectroscopy of asassn-14li would help to confirm (or refute) the previously proposed connection between tdfs and “n-rich” quasars. | an ultraviolet spectrum of the tidal disruption flare asassn-14li |
in the context of the flashlight survey, we obtained deep narrowband images of 15 z ∼ 2 quasars with the gemini multi-object spectrograph on gemini south in an effort to measure lyα emission from circum- and intergalactic gas on scales of hundreds of kpc from the central quasar. we do not detect bright giant lyα nebulae (sb ∼ 10-17 erg s-1 cm-2 arcsec-2 at distances >50 kpc) around any of our sources, although we routinely (≃47%) detect smaller-scale <50 kpc lyα emission at this surface brightness level emerging from either the extended narrow emission line regions powered by the quasars or by star formation in their host galaxies. we stack our 15 deep images to study the average extended lyα surface brightness profile around z ∼ 2 quasars, carefully psf-subtracting the unresolved emission component and paying close attention to sources of systematic error. our analysis, which achieves an unprecedented depth, reveals a surface brightness of sblyα∼ 10-19 erg s-1 cm-2 arcsec-2 at ∼200 kpc, with a 2.3σ detection of lyα emission at sb {}{lyα }=(5.5+/- 3.1)× {10}-20 erg s-1 cm-2 arcsec-2 within an annulus spanning 50 kpc < r < 500 kpc from the quasars. assuming that this lyα emission is powered by fluorescence from highly ionized gas illuminated by the bright central quasar, we deduce an average volume density of n h = 0.6 × 10-2 cm-3 on these large scales. our results are in broad agreement with the densities suggested by cosmological hydrodynamical simulations of massive (m ≃ 1012.5 m ⊙) quasar hosts; however, they indicate that the typical quasars at these redshifts are surrounded by gas that is a factor of ∼100 times less dense than the (∼1 cm-3) gas responsible for the giant bright lyα nebulae around quasars recently discovered by our group. based on observations obtained at the gemini observatory, which is operated by the association of universities for research in astronomy, inc., under a cooperative agreement with the nsf on behalf of the gemini partnership: the national science foundation (united states), the national research council (canada), conicyt (chile), the australian research council (australia), ministério da ciência, tecnologia e inovação (brazil), and ministerio de ciencia, tecnología e innovación productiva (argentina). | the stacked lyα emission profile from the circum-galactic medium of z ∼ 2 quasars |
we combine cosmological hydrodynamic simulations with analytic models to evaluate the role of galaxy-scale gravitational torques on the evolution of massive black holes at the centers of star-forming galaxies. we confirm and extend our earlier results to show that torque-limited growth yields black holes and host galaxies evolving on average along the m bh-m bulge relation from early times down to z = 0 and that convergence onto the scaling relation occurs independent of the initial conditions and with no need for mass averaging through mergers or additional self-regulation processes. smooth accretion dominates the long-term evolution, with black hole mergers with mass ratios gsim 1:5 representing typically a small fraction of the total growth. winds from the accretion disk are required to eject significant mass to suppress black hole growth, but there is no need for coupling this wind to galactic-scale gas to regulate black holes in a nonlinear feedback loop. torque-limited growth yields a close-to-linear < \dot{m}_bh > \propto star formation rate (sfr) relation for the black hole accretion rate averaged over galaxy evolution timescales. however, the sfr-agn connection has significant scatter owing to strong variability of black hole accretion at all resolved timescales. eddington ratios can be described by a broad lognormal distribution with median value evolving roughly as λmsvprop(1 + z)1.9, suggesting a main sequence for black hole growth similar to the cosmic evolution of specific sfrs. our results offer an attractive scenario consistent with available observations in which cosmological gas infall and transport of angular momentum in the galaxy by gravitational instabilities regulate the long-term co-evolution of black holes and star-forming galaxies. | torque-limited growth of massive black holes in galaxies across cosmic time |
we use the observed unresolved cosmic x-ray background (cxrb) in the 0.5-2 kev band and existing upper limits on the 21-cm power spectrum to constrain the high-redshift population of x-ray sources, focusing on their effect on the thermal history of the universe and the cosmic 21-cm signal. because the properties of these sources are poorly constrained, we consider hot gas, x-ray binaries and mini-quasars (i.e. sources with soft or hard x-ray spectra) as possible candidates. we find that (1) the soft-band cxrb sets an upper limit on the x-ray efficiency of sources that existed before the end of reionization, which is one-to-two orders of magnitude higher than typically assumed efficiencies, (2) hard sources are more effective in generating the cxrb than the soft ones, (3) the commonly assumed limit of saturated heating is not valid during the first half of reionization in the case of hard sources, with any allowed value of x-ray efficiency, (4) the maximal allowed x-ray efficiency sets a lower limit on the depth of the absorption trough in the global 21-cm signal and an upper limit on the height of the emission peak, while in the 21-cm power spectrum it sets a minimum amplitude and frequency for the high-redshift peaks, and (5) the existing upper limit on the 21-cm power spectrum sets a lower limit on the x-ray efficiency for each model. when combined with the 21-cm global signal, the cxrb will be useful for breaking degeneracies and helping constrain the nature of high-redshift heating sources. | constraining the redshifted 21-cm signal with the unresolved soft x-ray background |
in these proceedings we describe the weave-qso survey, which will observe around 400,000 high redshift quasars starting in 2018. this survey is part of a broader weave survey to be conducted at the 4.2m william herschel telescope. we will focus on chiefly on the science goals, but will also briefly summarise the target selection methods anticipated and the expected survey plan. understanding the apparent acceleration in the expansion of the universe is one of the key scientific challenges of our time. many experiments have been proposed to study this expansion, using a variety of techniques. here we describe a survey that can measure this acceleration and therefore help elucidate the nature of dark energy: a survey of the lyα forest (and quasar absorption in general) in spectra towards z>2 quasars (qsos). further constraints on neutrino masses and warm dark matter are also anticipated. the same data will also shed light on galaxy formation via study of the properties of inflowing/outflowing gas associated with nearby galaxies and in a cosmic web context. gas properties are sensitive to density, temperature, uv radiation, metallicity and abundance pattern, and so constraint galaxy formation in a variety of ways. weave-qso will study absorbers with a dynamic range spanning more than 8 orders of magnitude in column density, their thermal broadening, and a host of elements and ionization species. a core principal of the weave-qso survey is the targeting of qsos with near 100% efficiency principally through use of the j-pas (r < 23.2) and gaia (r ≲ 20) data. | weave-qso: a massive intergalactic medium survey for the william herschel telescope |
we present detailed image analysis of rest-frame optical images of 235 low-redshift (z ≲ 0.35) type 1 active galactic nuclei (agns) observed with the hubble space telescope. the high-resolution images enable us to perform rigorous two-dimensional image modeling to decouple the luminous central point source from the host galaxy, which, when warranted, is further decomposed into its principal structural components (bulge, bar, and disk). in many cases, care must be taken to account for structural complexities such as spiral arms, tidal features, and overlapping or interacting companion galaxies. we employ fourier modes to characterize the degree of asymmetry of the light distribution of the stars as a quantitative measure of morphological distortion due to interactions or mergers. we examine the dependence of the physical parameters of the host galaxies on the properties of the agns, namely, radio-loudness and the width of the broad emission lines. in accordance with previous studies, narrow-line (hβ fwhm ≤ 2000 km s-1) type 1 agns, in contrast to their broad-line (hβ fwhm > 2000 km s-1) counterparts, are preferentially hosted in later-type, lower-luminosity galaxies, which have a higher incidence of pseudo-bulges, are more frequently barred, and are less morphologically disturbed. this suggests that narrow-line type 1 agns experienced a more quiescent evolutionary history driven primarily by internal secular evolution instead of external dynamical perturbations. the fraction of agn hosts showing merger signatures is larger for more luminous sources. radio-loud agns generally preferentially live in earlier-type (bulge-dominated), more massive hosts, although a minority of them appear to contain a significant disk component. we do not find convincing evidence for enhanced merger signatures in the radio-loud population. based on observations made with the nasa/esa hubble space telescope, obtained from the data archive at the space telescope science institute, which is operated by the association of universities for research in astronomy (aura), inc., under nasa contract nas5-26555. these data are associated with program ar-12133 and ar-12818. | stellar photometric structures of the host galaxies of nearby type 1 active galactic nuclei |
we study the link between supermassive black hole growth and the stellar mass assembly of their host galaxies in the state-of-the-art romulus suite of simulations. the cosmological simulations romulus25 and romulusc employ innovative recipes for the seeding, accretion, and dynamics of black holes in the field and cluster environments, respectively. we find that the black hole accretion rate traces the star formation rate among star-forming galaxies. this result holds for stellar masses between 108 and 1012 solar masses, with a very weak dependence on host halo mass or redshift. the inferred relation between accretion rate and star formation rate does not appear to depend on environment, as no difference is seen in the cluster/proto-cluster volume compared to the field. a model including the star formation rate, the black hole-to-stellar mass ratio, and the cold gas fraction can explain about 70 per cent of all variations in the black hole accretion rate among star-forming galaxies. finally, bearing in mind the limited volume and resolution of these cosmological simulations, we find no evidence for a connection between black hole growth and galaxy mergers, on any time-scale and at any redshift. black holes and their galaxies assemble in tandem in these simulations, regardless of the larger scale intergalactic environment, suggesting that black hole growth simply follows star formation on galactic scales. | tracing black hole and galaxy co-evolution in the romulus simulations |
aims: the aim of this paper is to investigate the claim that stars in the lensing galaxy of a gravitationally lensed quasar system can always account for the observed microlensing of the individual quasar images.methods: a small sample of gravitationally lensed quasar systems was chosen where the quasar images appear to lie on the fringe of the stellar distribution of the lensing galaxy. as with most quasar systems, all the individual quasar images were observed to be microlensed. the surface brightness of the lensing galaxy at the positions of the quasar images was measured from hubble space telescope frames, and converted to stellar surface mass density. the surface density of smoothly distributed dark matter at the image positions was obtained from lensing models of the quasar systems and applied to the stellar surface mass density to give the optical depth to microlensing. this was then used to assess the probability that the stars in the lensing galaxy could be responsible for the observed microlensing. the results were supported by microlensing simulations of the star fields around the quasar images combined with values of convergence and shear from the lensing models.results: taken together, the probability that all the observed microlensing is due to stars was found to be ∼3 × 10-4. errors resulting from the surface brightness measurement, the mass-to-light ratio, and the contribution of the dark matter halo do not significantly affect this result.conclusions: it is argued that the most plausible candidates for the microlenses are primordial black holes, either in the dark matter halos of the lensing galaxies, or more generally distributed along the lines of sight to the quasars. | the signature of primordial black holes in the dark matter halos of galaxies |
we present spatially resolved echelle spectroscopy of an intervening mg ii-fe ii-mg i absorption-line system detected at zabs = 0.73379 towards the giant gravitational arc psz1 g311.65-18.48. the absorbing gas is associated with an inclined disc-like star-forming galaxy, whose major axis is aligned with the two arc-segments reported here. we probe in absorption the galaxy's extended disc continuously, at ≈3 kpc sampling, from its inner region out to 15× the optical radius. we detect strong (w_0^{2796}> 0.3å) coherent absorption along 13 independent positions at impact parameters d = 0-29 kpc on one side of the galaxy, and no absorption at d = 28-57 kpc on the opposite side (all de-lensed distances at zabs). we show that (1) the gas distribution is anisotropic; (2) w_0^{2796}, w_0^{2600}, w_0^{2852}, and the ratio w_0^{2600}/w_0^{2796}, all anticorrelate with d; (3) the w_0^{2796}-d relation is not cuspy and exhibits significantly less scatter than the quasar-absorber statistics; (4) the absorbing gas is co-rotating with the galaxy out to d ≲ 20 kpc, resembling a 'flat' rotation curve, but at d ≳ 20 kpc velocities decline below the expectations from a 3d disc-model extrapolated from the nebular [o ii] emission. these signatures constitute unambiguous evidence for rotating extra-planar diffuse gas, possibly also undergoing enriched accretion at its edge. arguably, we are witnessing some of the long-sought processes of the baryon cycle in a single distant galaxy expected to be representative of such phenomena. | slicing the cool circumgalactic medium along the major axis of a star-forming galaxy at z = 0.7 |
strongly lensed explosive transients such as supernovae, gamma-ray bursts, fast radio bursts, and gravitational waves are very promising tools to determine the hubble constant (h0) in the near future in addition to strongly lensed quasars. in this work, we show that the transient nature of the point source provides an advantage over quasars: the lensed host galaxy can be observed before or after the transient's appearance. therefore, the lens model can be derived from images free of contamination from bright point sources. we quantify this advantage by comparing the precision of a lens model obtained from the same lenses with and without point sources. based on hubble space telescope (hst) wide field camera 3 (wfc3) observations with the same sets of lensing parameters, we simulate realistic mock data sets of 48 quasar lensing systems (i.e. adding agn in the galaxy centre) and 48 galaxy-galaxy lensing systems (assuming the transient source is not visible but the time delay and image positions have been or will be measured). we then model the images and compare the inferences of the lens model parameters and h0. we find that the precision of the lens models (in terms of the deflector mass slope) is better by a factor of 4.1 for the sample without lensed point sources, resulting in an increase of h0 precision by a factor of 2.9. the opportunity to observe the lens systems without the transient point sources provides an additional advantage for time-delay cosmography over lensed quasars. it facilitates the determination of higher signal-to-noise stellar kinematics of the main deflector, and thus its mass density profile, which, in turn plays a key role in breaking the mass-sheet degeneracy and constraining h0. | improved time-delay lens modelling and h0 inference with transient sources |
hot, dust-obscured galaxies, or “hot dogs,” are a rare, dusty, hyperluminous galaxy population discovered by the wise mission. predominantly at redshifts 2-3, they include the most luminous known galaxies in the universe. their high luminosities likely come from accretion onto highly obscured supermassive black holes (smbhs). we have conducted a pilot survey to measure the smbh masses of five z∼ 2 hot dogs via broad hα emission lines, using keck/mosfire and gemini/flamingos-2. we detect broad hα emission in all five hot dogs. we find substantial corresponding smbh masses for these hot dogs (∼ {10}9 {m}⊙ ), and their derived eddington ratios are close to unity. these z∼ 2 hot dogs are the most luminous active galactic nuclei for their bh masses, suggesting that they are accreting at the maximum rates for their bhs. a similar property is found for known z∼ 6 quasars. our results are consistent with scenarios in which hot dogs represent a transitional, high-accretion phase between obscured and unobscured quasars. hot dogs may mark a special evolutionary stage before the red quasar and optical quasar phases, and they may be present at other cosmic epochs. | eddington-limited accretion in z ∼ 2 wise-selected hot, dust-obscured galaxies |
in the coming decade, a new generation of telescopes, including jwst and wfirst, will probe the period of the formation of first galaxies and quasars, and open up the last frontier for structure formation. recent simulations and observations have suggested that these galaxies are strongly clustered (with large-scale bias ≳6), and therefore have significant cosmic variance. in this work, we use bluetides, the largest volume cosmological simulation of galaxy formation, to directly estimate the cosmic variance for current and upcoming surveys. given its resolution and volume, bluetides can probe the bias and cosmic variance of z > 7 galaxies between magnitude muv ∼ -16 and muv ∼ -22 over survey areas ∼0.1 arcmin2 to ∼10 deg2. within this regime, the cosmic variance decreases with survey area/ volume as a power law with exponents between ∼-0.25 and ∼-0.45. for the planned 10 deg2 field of wfirst, the cosmic variance is between $3{{\ \rm per\ cent}}$ and $10{{\ \rm per\ cent}}$ . upcoming jwst medium/ deep surveys with areas up to a ∼ 100 arcmin2 will have cosmic variance ranging from ${\sim}20\,\mathrm{ to}\,50{{\ \rm per\ cent}}$ . lensed surveys have the highest cosmic variance ${\gtrsim}40{{\ \rm per\ cent}}$ ; the cosmic variance of muv ≲ -16 galaxies is ${\lesssim}100{{\ \rm per\ cent}}$ up to z ∼ 11. at higher redshifts such as z ∼ 12 (14), effective volumes of ≳ (8 mpc h-1)3 (≳(12 mpc h-1)3) are required to limit the cosmic variance to within $100{{\ \rm per\ cent}}$ . finally, we find that cosmic variance is larger than poisson variance and forms the dominant component of the overall uncertainty in all current and upcoming surveys. we present our calculations in the form of simple fitting functions and an online cosmic variance calculator (cv_at_cosmic_dawn) that we publicly release. | cosmic variance of z > 7 galaxies: prediction from bluetides |
measurements of the lyα forest based on large numbers of quasar spectra from sky surveys such as sdss/eboss accurately probe the distribution of matter on small scales and thus provide important constraints on several ingredients of the cosmological model. a main summary statistic derived from those measurements is the one-dimensional power spectrum, p1d, of the lyα absorption. however, model predictions for p1d rely on expensive hydrodynamical simulations of the intergalactic medium, which was the limiting factor in previous analyses. datasets from upcoming surveys such as desi will push observational accuracy near the 1%-level and probe even smaller scales. this observational push mandates even more accurate simulations as well as more careful exploration of parameter space. in this work we evaluate the robustness and accuracy of simulations and the statistical framework used to constrain cosmological parameters. we present a comparison between the grid-based simulation code nyx and sph-based code gadget in the context of p1d. in addition, we perform resolution and box-size convergence tests using nyx code. we use a gaussian process emulation scheme to reduce the number of simulations required for exploration of parameter space without sacrificing the model accuracy. we demonstrate the ability to produce unbiased parameter constraints in an end-to-end inference test using mock eboss- and desi-like data, and we advocate for the usage of adaptive sampling schemes as opposed to using a fixed latin hypercube design. | simulating intergalactic gas for desi-like small scale lymanα forest observations |
understanding the fe ii emission from active galactic nuclei (agns) has been a grand challenge for many decades. the rewards from understanding the agn spectra would be immense, involving both quasar classification schemes such as "eigenvector 1" and tracing the chemical evolution of the cosmos. recently, three large fe ii atomic data sets with radiative and electron collisional rates have become available. we have incorporated these into the spectral synthesis code cloudy and examined predictions using a new generation of agn spectral energy distribution (sed), which indicates that the ultraviolet (uv) emission can be quite different depending on the data set utilized. the smyth et al. data set better reproduces the observed fe ii template of the i zw 1 seyfert galaxy in the uv and optical regions, and we adopt these data. we consider both thermal and microturbulent clouds and show that a microturbulence of ≈100 km s-1 reproduces the observed shape and strength of the so-called fe ii "uv bump." comparing our predictions to the observed fe ii template, we derive a typical cloud density of 1011 cm-3 and photon flux of 1020 cm-2 s-1, and show that these largely reproduce the observed fe ii emission in the uv and optical. we calculate the i(fe ii)/i(mg ii) emission-line intensity ratio using our best-fitting model and obtain log(i(fe ii)/i(mg ii)) ∼ 0.7, suggesting many agns have a roughly solar fe/mg abundance ratio. finally, we vary the eddington ratio and sed shape as a step in understanding the eigenvector 1 correlation. | improved fe ii emission-line models for agns using new atomic data sets |
the leading contenders for the seeds of z > 6 quasars are direct-collapse black holes (dcbhs) forming in atomically cooled haloes at z ~ 20. however, the lyman-werner (lw) uv background required to form dcbhs of 105 m⊙ are extreme, about 104 j21, and may have been rare in the early universe. here we investigate the formation of intermediate-mass black holes (imbhs) under moderate lw backgrounds of 100 and 500 j21, which were much more common at early times. these backgrounds allow haloes to grow to a few 106-107 m⊙ and virial temperatures of nearly 104 k before collapsing, but do not completely sterilize them of h2. gas collapse then proceeds via lyα and rapid h2 cooling at rates that are 10-50 times those in normal pop iii star-forming haloes, but less than those in purely atomically cooled haloes. pop iii stars accreting at such rates become blue and hot, and we find that their ionizing uv radiation limits their final masses to 1800-2800 m⊙ at which they later collapse to imbhs. moderate lw backgrounds thus produced imbhs in far greater numbers than dcbhs in the early universe. | radiation hydrodynamical simulations of the birth of intermediate-mass black holes in the first galaxies |
we present the results from 685 mhz observations with the upgraded giant metrewave radio telescope (ugmrt) of 22 quasars belonging to the palomar-green (pg) quasar sample. only four sources reveal extended radio structures on ∼10-30 kpc scales, while the rest are largely a combination of a radio core unresolved at the ugmrt resolution of ∼3-5 arcsec, surrounded by diffuse emission on few kpc to ∼10 kpc scales. a few sources reveal signatures of barely resolved jets and lobes in their spectral index images that are created using the 685 mhz ugmrt data and similar resolution ghz-frequency data from the very large array. on the basis of their position on the radio-ir correlation as well as the spectral index images, we find that the radio emission in the two radio-loud (rl) quasars and nearly one-third of the radio-quiet (rq) quasars is active galactic nucleus (agn) dominated whereas the remaining sources appear to have significant contributions from stellar-related processes along with the agn. while the two rl sources exhibit inverted spectral index in their cores, the rq sources exhibit a range of spectral indices varying from flat to steep (-0.1 $\gtrsim $ αr $\gtrsim $ -1.1) indicating the presence of unresolved jets/lobes or winds. except for a significant correlation between the 685 mhz radio luminosity and the eddington ratio, we do not find strong correlations between other 685 mhz radio properties and black hole (bh) properties in the rq pg sources. this lack of correlations could be explained by the contribution of stellar-related emission, or radio emission from previous agn activity episodes that may not be related to the current bh activity state. | probing the origin of low-frequency radio emission in pg quasars with the ugmrt - i |
active galactic nuclei (agns) have long been observed to "twinkle" (i.e., their brightness varies with time) on timescales from days to years in the uv/optical bands. such agn uv/optical variability is essential for probing the physics of supermassive black holes (smbhs), the accretion disk, and the broad-line region. here, we show that the temperature fluctuations of an agn accretion disk, which is magnetically coupled with the corona, can account for observed high-quality agn optical light curves. we calculate the temperature fluctuations by considering the gas physics of the accreted matter near the smbh. we find that the resulting simulated agn uv/optical light curves share the same statistical properties as the observed ones as long as the dimensionless viscosity parameter α, which is widely believed to be controlled by magnetohydrodynamic (mhd) turbulence in the accretion disk, is about 0.01-0.2. moreover, our model can simultaneously explain the larger-than-expected accretion disk sizes and the dependence of uv/optical variability upon wavelength for ngc 5548. our model also has the potential to explain some other observational facts of agn uv/optical variability, including the timescale-dependent bluer-when-brighter color variability and the dependence of uv/optical variability on agn luminosity and black-hole mass. our results also demonstrate a promising way to infer the black-hole mass, the accretion rate, and the radiative efficiency, thereby facilitating understanding of the gas physics and mhd turbulence near the smbh and its cosmic mass growth history by fitting the agn uv/optical light curves in the era of time-domain astronomy. | corona-heated accretion-disk reprocessing: a physical model to decipher the melody of agn uv/optical twinkling |
the standard model of cosmology, lambda cold dark matter (λcdm), is the simplest model that matches the current observations, but it relies on two hypothetical components, to wit, dark matter and dark energy. future galaxy surveys and cosmic microwave background (cmb) experiments will independently shed light on these components, but a joint analysis that includes cross-correlations will be necessary to extract as much information as possible from the observations. in this paper, we carry out a multiprobe analysis based on pseudo-spectra and test it on publicly available data sets. we use cmb temperature anisotropies and cmb lensing observations from planck as well as the spectroscopic galaxy and quasar samples of sdss-iii/boss, taking advantage of the large areas covered by these surveys. we build a likelihood to simultaneously analyse the auto and cross spectra of cmb lensing and tracer overdensity maps before running markov chain monte carlo to assess the constraining power of the combined analysis. we then add the cmb temperature anisotropies likelihood and obtain constraints on cosmological parameters (h0, ωb, ωc, ln 1010as, ns, and zre) and galaxy biases. we demonstrate that the joint analysis can additionally constrain the total mass of neutrinos σmν as well as the dark energy equation of state w at once (for a total of eight cosmological parameters), which is impossible with either of the data sets considered separately. finally, we discuss limitations of the analysis related to, e.g. the theoretical precision of the models, particularly in the non-linear regime. | cosmological constraints from a joint analysis of cosmic microwave background and spectroscopic tracers of the large-scale structure |
we propose that one of the sources in the recently detected system cr7 by sobral et al. through spectrophotometric measurements at z = 6.6 harbours a direct collapse black hole (dcbh). we argue that the lw radiation field required for direct collapse in source a is provided by sources b and c. by tracing the lw production history and star formation rate over cosmic time for the halo hosting cr7 in a λcdm universe, we demonstrate that a dcbh could have formed at z ∼ 20. the spectrum of source a is well fit by nebular emission from primordial gas around a bh with mbh ∼4.4 × 106 m⊙ accreting at a 40 per cent of the eddington rate, which strongly supports our interpretation of the data. combining these lines of evidence, we argue that cr7 might well be the first dcbh candidate. | detecting direct collapse black holes: making the case for cr7 |
we present multi-wavelength observations and modeling of the exceptionally bright long γ-ray burst grb 160625b. the optical and x-ray data are well fit by synchrotron emission from a collimated blastwave with an opening angle of {θ }j≈ 3\buildrel{\circ}\over{.} 6 and kinetic energy of {e}k≈ 2× {10}51 erg, propagating into a low-density (n≈ 5× {10}-5 cm-3) medium with a uniform profile. the forward shock is sub-dominant in the radio band; instead, the radio emission is dominated by two additional components. the first component is consistent with emission from a reverse shock, indicating an initial lorentz factor of {{{γ }}}0≳ 100 and an ejecta magnetization of {r}b≈ 1{--}100. the second component exhibits peculiar spectral and temporal evolution and is most likely the result of scattering of the radio emission by the turbulent milky way interstellar medium (ism). such scattering is expected in any sufficiently compact extragalactic source and has been seen in grbs before, but the large amplitude and long duration of the variability seen here are qualitatively more similar to extreme scattering events previously observed in quasars, rather than normal interstellar scintillation effects. high-cadence, broadband radio observations of future grbs are needed to fully characterize such effects, which can sensitively probe the properties of the ism and must be taken into account before variability intrinsic to the grb can be interpreted correctly. | a reverse shock and unusual radio properties in grb 160625b |
context. the kids strongly lensed quasar detection project (kids-squad) is aimed at finding as many previously undiscovered gravitational lensed quasars as possible in the kilo degree survey. this is the second paper of this series where we present a new, automatic object-classification method based on the machine learning technique.aims: the main goal of this paper is to build a catalogue of bright extragalactic objects (galaxies and quasars) from the kids data release 4, with minimum stellar contamination and preserving the completeness as much as possible. we show here that this catalogue represents the perfect starting point to search for reliable gravitationally lensed quasar candidates.methods: after testing some of the most used machine learning algorithms, decision-tree-based classifiers, we decided to use catboost, which was specifically trained with the aim of creating a sample of extragalactic sources that is as clean of stars as possible. we discuss the input data, define the training sample for the classifier, give quantitative estimates of its performances, and finally describe the validation results with gaia dr2, allwise, and gama catalogues.results: we built and made available to the scientific community the kids bright extragalactic objects catalogue (kids-bexgo), specifically created to find gravitational lenses but applicable to a wide number of scientific purposes. the kids-bexgo catalogue is made of ≈6 million sources classified as quasars (≈200 000) and galaxies (≈5.7 m) up to r < 22m. to demonstrate the potential of the catalogue in the search for strongly lensed quasars, we selected ≈950 "multiplets": close pairs of quasars or galaxies surrounded by at least one quasar. we present cutouts and coordinates of the 12 most reliable gravitationally lensed quasar candidates. we showed that employing a machine learning method decreases the stellar contaminants within the gravitationally lensed candidates, comparing the current results to the previous ones, presented in the first paper from this series.conclusions: our work presents the first comprehensive identification of bright extragalactic objects in kids dr4 data, which is, for us, the first necessary step towards finding strong gravitational lenses in wide-sky photometric surveys, but has also many other more general astrophysical applications. the kids bright extragalactic objects (kids-bexgo) catalogue is also 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/632/a56 | kids-squad. ii. machine learning selection of bright extragalactic objects to search for new gravitationally lensed quasars |
we use star, galaxy and quasar spectra taken by the sloan digital sky survey to map out the distribution of diffuse interstellar bands (dibs) induced by the milky way. after carefully removing the intrinsic spectral energy distribution of each source, we show that by stacking thousands of spectra, it is possible to measure statistical flux fluctuations at the 10-3 level, detect more than 20 dibs and measure their strength as a function of position on the sky. we create a map of dib absorption covering about 5000 deg2 and measure correlations with various tracers of the interstellar medium: atomic and molecular hydrogen, dust and polycyclic aromatic hydrocarbons (pahs). after recovering known correlations, we show that each dib has a different dependence on atomic and molecular hydrogen: while they are all positively correlated with n_{h i}, they exhibit a range of behaviours with n_{h_2} showing positive, negative or no correlation. we show that a simple parametrization involving only n_{h i} and n_{h_2} applied to all the dibs is sufficient to reproduce a large collection of observational results reported in the literature: it allows us to naturally describe the relations between dib strength and dust reddening (including the so-called skin effect), the related scatter, dib pair-wise correlations and families, the affinity for σ/ζ-type environments and other correlations related to molecules. our approach allows us to characterize dib dependencies in a simple manner and provides us with a metric to characterize the similarity between different dibs. | exploring the diffuse interstellar bands with the sloan digital sky survey |
we present multi-frequency (1-8 ghz) very large array data, combined with visible multiobject spectrograph integral field unit data and hubble space telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with l 1.4 ghz ≈ 5 × 1023 w hz-1 and l agn ≈ 2 × 1045 erg s-1). due to the morphology of its emission-line region, the target (j1430+1339) has been referred to as the "teacup" active galactic nucleus (agn) in the literature. we identify "bubbles" of radio emission that are extended ≈10-12 kpc to both the east and west of the nucleus. the edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. we also show that the "teacup" agn hosts a compact radio structure, located ≈0.8 kpc from the core position, at the base of the eastern bubble. this radio structure is co-spatial with an ionized outflow with an observed velocity of v = -740 km s-1. this is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. the large-scale radio bubbles appear to be inflated by the central agn, which indicates that the agn can also interact with the gas on >~ 10 kpc scales. our study highlights that even when a quasar is formally "radio-quiet" the radio emission can be extremely effective for observing the effects of agn feedback. | storm in a "teacup": a radio-quiet quasar with ≈10 kpc radio-emitting bubbles and extreme gas kinematics |
flat-spectrum radio-loud narrow-line seyfert 1 galaxies (nls1s) are a recently discovered class of γ-ray emitting active galactic nuclei (agn), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. when blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed nls1s. however, the number of known nls1s with the jet viewed at large angles is not enough. therefore, we tried to understand the origin of this deficit. current hypotheses about the nature of parent sources are steep-spectrum radio-loud nls1s, radio-quiet nls1s and disk-hosted radio-galaxies. to test these hypotheses we built three samples of candidate sources plus a control sample, and calculated their black hole mass and eddington ratio using their optical spectra. we then performed a kolmogorov-smirnov statistical test to investigate the compatibility of our different samples with a beamed population. our results indicate that, when the inclination angle increases, a beamed source appears as a steep-spectrum radio-loud nls1, or possibly even as a disk-hosted radio-galaxy with low black hole mass and high eddington ratio. further investigations, involving larger complete samples and observations at radio frequency, are needed to understand the incidence of disk-hosted radio-galaxies in the parent population, and to assess whether radio-quiet nls1s can play a role, as well. appendix a is available in electronic form at http://www.aanda.org | parent population of flat-spectrum radio-loud narrow-line seyfert 1 galaxies |
we perform long-term (≈15 years, observed-frame) x-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (agns) in the 6 ms chandra deep field-south survey; the majority are in the redshift range of 0.6-3.1, providing access to penetrating rest-frame x-rays up to ≈10-30 kev. of the 68 sources, 24 are optical spectral type i agns, and the rest (44) are type ii agns. the timescales probed in this work are among the longest for x-ray variability studies of distant agns. photometric analyses reveal widespread photon flux variability: 90% of agns are variable above a 95% confidence level, including many x-ray obscured agns and several optically classified type ii quasars. we characterize the intrinsic x-ray luminosity ({l}{{x}}) and absorption ({n}{{h}}) variability via spectral fitting. most (74%) sources show {l}{{x}} variability; the variability amplitudes are generally smaller for quasars. a compton-thick candidate agn shows variability of its high-energy x-ray flux, indicating the size of reflecting material to be ≲0.3 pc. {l}{{x}} variability is also detected in a broad absorption line quasar. the {n}{{h}} variability amplitude for our sample appears to rise as time separation increases. about 16% of sources show {n}{{h}} variability. one source transitions from an x-ray unobscured to obscured state, while its optical classification remains type i; this behavior indicates the x-ray eclipsing material is not large enough to obscure the whole broad-line region. | long-term x-ray variability of typical active galactic nuclei in the distant universe |
we investigate the presence of extended ionized outflows in 18 luminous type 2 agns (11 quasars and 7 high-luminosity seyfert 2s) at 0.3 < z < 0.6 based on vlt-fors2 spectroscopy. we infer typical lower limits on the radial sizes of the outflows ro ≳ several × 100 pc and upper limits ro ≲ 1-2 kpc. our results are inconsistent with related studies which suggest that large scale (ro ∼ several-15 kpc) are ubiquitous in qso2. we study the possible causes of discrepancy and propose that seeing smearing is the cause of the large inferred sizes. the implications in our understanding of the feedback phenomenon are important since the mass mo (through the density), mass injection skew3dot{m}_o and energy injection dot{e}_o rates of the outflows become highly uncertain. one conclusion seems unavoidable: mo, skew3dot{m}_o and dot{e}_o are modest or low compared with previous estimations. we obtain typically mo ≲ (0.4-22) × 106 m⊙ (median 1.1 × 106 m⊙) assuming n = 1000 cm-3. these are ∼102-104 times lower than values reported in the literature. even under the most favourable assumptions, we obtain \dot{m}_o ≲ 10 m⊙ yr-1 in general, 100-1000 times lower than claimed in related studies. although the uncertainties are large, it is probable that these are lower than typical star-forming rates. in conclusion, no evidence is found supporting that typical outflows can affect the interstellar medium of the host galaxies across spatial scales ≳ 1-2 kpc. | ionized outflows in luminous type 2 agns at z < 0.6: no evidence for significant impact on the host galaxies |
the origin, geometry, and kinematics of the broad-line region (blr) gas in quasars and active galactic nuclei (agn) are uncertain. we demonstrate that clumpy biconical disc winds illuminated by an agn continuum can produce blr-like spectra. we first use a simple toy model to illustrate that disc winds make quite good blr candidates, because they are self-shielded flows and can cover a large portion of the ionizing flux-density (ϕh-nh) plane. we then conduct monte carlo radiative transfer and photoionization calculations, which fully account for self-shielding and multiple scattering in a non-spherical geometry. the emergent model spectra show broad emission lines with equivalent widths and line ratios comparable to those observed in agn, provided that the wind has a volume filling factor of fv ≲ 0.1. similar emission line spectra are produced for a variety of wind geometries (polar or equatorial) and for launch radii that differ by an order of magnitude. the line emission arises almost exclusively from plasma travelling below the escape velocity, implying that `failed winds' are important blr candidates. the behaviour of a line-emitting wind (and possibly any `smooth flow' blr model) is similar to that of the locally optimally emitting cloud model originally proposed by baldwin et al. (1995), except that the gradients in ionization state and temperature are large-scale and continuous, rather than within or between distinct clouds. our models also produce uv absorption lines and x-ray absorption features, and the stratified ionization structure can partially explain the different classes of broad absorption line quasars. | stratified disc wind models for the agn broad-line region: ultraviolet, optical, and x-ray properties |
quasars have long been known as intrinsically variable sources, but the physical mechanism underlying the temporal optical/uv variability is still not well understood. we propose a novel nonparametric method for modeling and forecasting the optical variability of quasars utilizing an ae neural network to gain insight into the underlying processes. the ae is trained with ∼15,000 decade-long quasar light curves obtained by the catalina real-time transient survey selected with negligible flux contamination from the host galaxy. the ae&'s performance in forecasting the temporal flux variation of quasars is superior to that of the damped random walk process. we find a temporal asymmetry in the optical variability and a novel relation—the amplitude of the variability asymmetry decreases as luminosity and/or black hole mass increases—is suggested with the help of autoencoded features. the characteristics of the variability asymmetry are in agreement with those from the self-organized disk instability model, which predicts that the magnitude of the variability asymmetry decreases as the ratio of the diffusion mass to inflow mass in the accretion disk increases. | deep modeling of quasar variability |
we use the sloan digital sky survey (sdss) quasar data release 12 (dr12q), containing nearly 300,000 active galactic nuclei (agns), to calculate the monochromatic luminosities at 5100, 3000, and 1350 å, derived from the broadband extinction-corrected sdss magnitudes. after matching these sources to their counterparts from the sdss quasar data release 7 (dr7q), we find very high correlations between our luminosities and dr7q spectra-based luminosities with minute mean offsets (∼0.01 dex) and dispersions of differences of 0.11, 0.10, and 0.12 dex, respectively, across a luminosity range of 2.5 dex. we then estimate the black hole (bh) masses of the agns using the broad line region radius-disk luminosity relations and the fwhm of the mg ii and c iv emission lines, to provide a catalog of 283,033 virial bh mass estimates (132,451 for mg ii, 213,071 for c iv, and 62,489 for both) along with the estimates of the bolometric luminosity and eddington ratio for 0.1 < z < 5.5 and for roughly a quarter of the sky covered by sdss. the bh mass estimates from mg ii turned out to be closely matched to the ones from dr7q with a dispersion of differences of 0.34 dex across a bh mass range of ∼2 dex. we uncovered a bias in the derived c iv fwhms from dr12q as compared to dr7q, which we correct empirically. the c iv bh mass estimates should be used with caution because the c iv line is known to cause problems in the estimation of bh mass from single-epoch spectra. finally, after the fwhm correction, the agn bh mass estimates from c iv closely match the dr7q ones (with a dispersion of 0.28 dex), and more importantly the mg ii and c iv bh masses agree internally with a mean offset of 0.07 dex and a dispersion of 0.39 dex. | virial black hole mass estimates for 280,000 agns from the sdss broadband photometry and single-epoch spectra |
we used muse adaptive optics data in narrow field mode to study the properties of the ionised gas in mr 2251-178 and pg 1126-041, two nearby (z ≃ 0.06) bright quasars (qsos) hosting sub-pc scale ultra-fast outflows (ufos) detected in the x-ray band. we decomposed the optical emission from diffuse gas into a low- and a high-velocity components. the former is characterised by a clean, regular velocity field and a low (∼80 km s-1) velocity dispersion. it traces regularly rotating gas in pg 1126-041, while in mr 2251-178 it is possibly associated with tidal debris from a recent merger or flyby. the other component is found to be extended up to a few kpc from the nuclei, and shows a high (∼800 km s-1) velocity dispersion and a blue-shifted mean velocity, as is expected from outflows driven by active galactic nuclei (agn). we estimate mass outflow rates up to a few m⊙ yr-1 and kinetic efficiencies lkin/lbol between 1-4 × 10-4, in line with those of galaxies hosting agn of similar luminosities. the momentum rates of these ionised outflows are comparable to those measured for the ufos at sub-pc scales, which is consistent with a momentum-driven wind propagation. pure energy-driven winds are excluded unless about 100× additional momentum is locked in massive molecular winds. in comparing the outflow properties of our sources with those of a small sample of well-studied qsos hosting ufos from the literature, we find that winds seem to systematically lie either in a momentum-driven or an energy-driven regime, indicating that these two theoretical models bracket the physics of agn-driven winds very well. the reduced datacubes 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/644/a15 | galaxy-scale ionised winds driven by ultra-fast outflows in two nearby quasars |
a diverse array of science goals requires accurate flux calibration of observations with the atacama large millimeter/submillimeter array (alma); however, this goal remains challenging due to the stochastic time-variability of the "grid" quasars alma uses for calibration. in this work, we use 343.5 ghz (band 7) alma atacama compact array observations of four bright and stable young stellar objects over seven epochs to independently assess the accuracy of the alma flux calibration and to refine the relative calibration across epochs. the use of these four extra calibrators allows us to achieve an unprecedented relative alma calibration accuracy of ∼3%. on the other hand, when the observatory calibrator catalog is not up to date, the band 7 data calibrated by the alma pipeline may have a flux calibration poorer than the nominal 10%, which can be exacerbated by weather-related phase decorrelation when self-calibration of the science target is either not possible or not attempted. we also uncover a relative flux calibration uncertainty between spectral windows of 0.8%, implying that measuring spectral indices within a single alma band is likely highly uncertain. we thus recommend various methods for science goals requiring high flux accuracy and robust calibration, in particular, the observation of additional calibrators combined with a relative calibration strategy, and observation of solar system objects for high absolute accuracy. | on the accuracy of the alma flux calibration in the time domain and across spectral windows |
improving our understanding of the nuclear properties of high-eddington-ratio (λedd) active galactic nuclei (agn) is necessary since at this regime the radiation pressure is expected to affect the structure and efficiency of the accretion disc-corona system. this may cause departures from the typical nuclear properties of low-λedd agn, which have been largely studied so far. we present here the x-ray spectral analysis of 14 radio-quiet, λedd ≳ 1 agn at 0.4 ≤ z ≤ 0.75, observed with xmm-newton. optical/uv data from simultaneous optical monitor observations have also been considered. these quasars were selected to have relatively high values of black hole mass (mbh ∼ 108 − 8.5 m⊙) and bolometric luminosity (lbol ∼ 1046 erg s−1) in order to complement previous studies of high-λedd agn at lower mbh and lbol. we studied the relation between λedd and other key x-ray spectral parameters, such as the photon index (γ) of the power-law continuum, the x-ray bolometric correction (kbol, x), and the optical/uv-to-x-ray spectral index (αox). our analysis reveals that, despite the homogeneous optical and supermassive black hole accretion properties, the x-ray properties of these high-λedd agn are quite heterogeneous. we indeed measured values of γ between 1.3 and 2.5, at odds with the expectations based on previously reported γ − λedd relations, for which γ ≥ 2 would be a ubiquitous hallmark of agn with λedd ∼ 1. interestingly, we found that ∼30% of the sources are x-ray weak, with an x-ray emission about a factor of ∼10 − 80 fainter than that of typical agn at similar uv luminosities. the x-ray weakness seems to be intrinsic and not due to the presence of absorption along the line of sight to the nucleus. this result may indicate that high-λedd agn commonly undergo periods of intrinsic x-ray weakness. furthermore, results from follow-up monitoring with swift of one of these x-ray weak sources suggest that these periods can last for several years. | x-ray spectroscopic survey of highly accreting agn |
the outstanding mass growth of supermassive black holes (smbhs) at the epoch of reionisation and its relation to the concurrent growth of their host galaxies poses challenges to theoretical models aimed at explaining how these systems formed on short timescales (< 1 gyr). to trace the average evolutionary paths of quasi-stellar objects (qsos) and their host galaxies in the plane of bh mass to host mass (mdyn), we compare the star formation rate (sfr), derived from the accurate estimate of the dust temperature and the dust mass (tdust, mdust) based on infrared and sub-millimeter (sub-mm) spectral energy distribution (sed), with the bh accretion rate, derived from lbol based on x-ray and optical and ultraviolet sed. to this aim, we analysed a deep alma observation of the sub-mm continuum, [cii], and h2o of the z ∼ 6 qso j2310+1855 with a resolution of 900 pc, which enabled a detailed study of dust properties and cold gas kinematics. we performed an accurate sed analysis obtaining a dust temperature of tdust = 71 ± 4 k, dust mass mdust = (4.4 ± 0.7)×108 m⊙, and total far-infrared luminosity of ltir = 2.5−0.5+0.6 × 1013 l⊙. the implied active galactic nuclei (agn) - corrected sfr = 1240−260+310 m⊙ yr−1 is a factor of 2 lower than previously reported for this qso. we measured a gas-to-dust ratio of gdr = 101 ± 20. the dust continuum and [cii] surface brightness profiles are spatially extended out to r ∼ 6.7 kpc and r ∼ 5 kpc, respectively, with half-light radii of 0.9 and 1.1 kpc for the dust and gas, respectively. the derived gas surface density, σgas, and star formation rate density, σsfr, place the j2310+1855 host galaxy above the kennicutt-schmidt relation. we derived a best estimate of the dynamical mass mdyn = 5.2 × 1010 m⊙ within r = 1.7 kpc based on a dynamical model of the system with a rotating disk inclined at i = 25 deg. the toomre parameter profile across the disk is qgas ∼ 3 and implies that the disk is unstable. we found that sfr/mdyn > ṁbh/mbh, suggesting that agn feedback might be efficiently acting to slow down the smbh accretion, while stellar mass assembly is still vigorously taking place in the host galaxy. in addition, we were also able to detect high-velocity emission on the red and blue sides of the [cii] emission line that is not consistent with disk rotation and traces a gaseous outflow. we derived an outflow mass mout = 3.5 × 108 m⊙, and a mass outflow rate in the range ṁout = 1800 − 4500 m⊙ yr−1. the implied ėout ∼ 0.0005 − 0.001 lbol is in agreement with the values observed for ionised winds. for the first time, we mapped a spatially resolved water vapour disk through the h2o v = 0 3(2, 2) − 3(1, 3) emission line detected at νobs = 274.074 ghz, whose kinematic properties and size are broadly consistent with those of the [cii] disk. the luminosity ratio lh2o/ltir = 1.4 × 10−5 is consistent with line excitation by dust-reprocessed star formation in the interstellar medium of the host galaxy. | black hole and host galaxy growth in an isolated z ∼ 6 qso observed with alma |
eight years after the first detection of high-energy astrophysical neutrinos by icecube, we are still almost clueless as regards to their origin, although the case for blazars being neutrino sources is getting stronger. after the first significant association at the $3\!-\!3.5\, \sigma$ level in time and space with icecube neutrinos, i.e. the blazar txs 0506+056 at z = 0.3365, some of us have in fact selected a unique sample of 47 blazars, out of which ~16 could be associated with individual neutrino track events detected by icecube. building upon our recent spectroscopy work on these objects, here we characterize them to determine their real nature and check if they are different from the rest of the blazar population. for the first time we also present a systematic study of the frequency of masquerading bl lacs, i.e. flat-spectrum radio quasars with their broad lines swamped by non-thermal jet emission, in a γ-ray- and icecube-selected sample, finding a fraction >24 per cent and possibly as high as 80 per cent. in terms of their broad-band properties, our sources appear to be indistinguishable from the rest of the blazar population. we also discuss two theoretical scenarios for neutrino emission, one in which neutrinos are produced in interactions of protons with jet photons and one in which the target photons are from the broad-line region. both scenarios can equally account for the neutrino-blazar correlation observed by some of us. future observations with neutrino telescopes and x-ray satellites will test them out. | the spectra of icecube neutrino (sin) candidate sources - ii. source characterization |
we investigate the mass structure of a strong gravitational lens galaxy at z = 0.350, taking advantage of the milliarcsecond (mas) angular resolution of very long baseline interferometric (vlbi) observations. in the first analysis of its kind at this resolution, we jointly infer the lens model parameters and pixellated radio source surface brightness. we consider several lens models of increasing complexity, starting from an elliptical power-law density profile. we extend this model to include angular multipole structures, a separate stellar mass component, additional nearby field galaxies, and/or a generic external potential. we compare these models using their relative bayesian log-evidence (bayes factor). we find strong evidence for angular structure in the lens; our best model is comprised of a power-law profile plus multipole perturbations and external potential, with a bayes factor of +14984 relative to the elliptical power-law model. it is noteworthy that the elliptical power-law mass distribution is a remarkably good fit on its own, with additional model complexity correcting the deflection angles only at the ~5 mas level. we also consider the effects of added complexity in the lens model on time-delay cosmography and flux-ratio analyses. we find that an overly simplistic power-law ellipsoid lens model can bias the measurement of h0 by ~3 per cent and mimic flux ratio anomalies of ~8 per cent. our results demonstrate the power of high-resolution vlbi observations to provide strong constraints on the inner density profiles of lens galaxies. | a lensed radio jet at milliarcsecond resolution i: bayesian comparison of parametric lens models |
black hole accretion discs can produce powerful outflowing plasma (disc winds), seen as blue-shifted absorption lines in stellar and supermassive systems. these winds in quasars have an essential role in controlling galaxy formation across cosmic time, but there is no consensus on how these are physically launched. a single unique observation of a stellar-mass black hole gro j1655-40 was used to argue that magnetic driving was the only viable mechanism and motivated unified models of magnetic winds in both binaries and quasars. the alternative, x-ray heating (thermal-radiative wind), was ruled out for the low observed luminosity by the high wind density estimated from an absorption line of a metastable level of fe xxii. here, we reanalyse these data using a photoionization code that includes cascades from radiative excitation as well as collisions in populating the metastable level. the cascade reduces the inferred wind density by more than an order of magnitude. the derived column is also optically thick, so the source is intrinsically more luminous than observed. we show that a thermal-radiative wind model calculated from a radiation hydrodynamic simulation matches well with the data. we revisit the previous magnetic wind solution and show that this is also optically thick, leading to a larger source luminosity. however, unlike the thermal-radiative wind, it struggles to reproduce the overall ion population at the required density. these results remove the requirement for a magnetic wind in these data and remove the basis of the self-similar unified magnetic wind models extrapolated to quasar outflows. | what powers the wind from the black hole accretion disc in gro j1655-40? |
we ask how the inclusion of various physical heating processes due to the metal content of gas affects the evolution of central massive galaxies and compute a suite of cosmological hydrodynamical simulations that follow these systems and their supermassive black holes. we use a smoothed particle hydrodynamics code with a pressure-entropy formulation and a more accurate treatment of the metal production, turbulent diffusion, and cooling rate based on individual element abundances. the feedback models include (1) active galactic nucleus (agn) feedback via high-velocity broad absorption line winds and compton/photoionization heating; (2) stellar feedback from multiple processes, including powerful winds from supernovae, stellar winds from young massive stars, and agb stars, as well as radiative heating within str\ddot{{{o}}}mgren spheres; and (3) additional heating effects due to the presence of metals, including grain photoelectric heating and metallicity-dependent x-ray heating by nearby accreting black holes and from the cosmic x-ray background. with a suite of zoom-in simulations of 30 halos with {m}{vir}∼ {10}12.0-13.4, we show that energy and momentum budgeted from all feedback effects generate realistic galaxy properties. we explore the detailed role of each feedback model with three additional sets of simulations with varying input physics. we show that the metal-induced heating reduces the fraction of accreted stellar material but overall has a relatively minor effect on the massive central galaxies. the inclusion of agn feedback significantly improves the ability of our simulations to yield realistic gas and stellar properties of massive galaxies with a reasonable accreted star fraction from other galaxies. | physics of galactic metals: evolutionary effects due to production, distribution, feedback, and interaction with black holes |
we use the soux sample of ~700 active galactic nucleus (agn) to form average optical-ultraviolet (uv)-x-rays spectral energy distributions (seds) on a two-dimensional (2d) grid of mbh and l2500. we compare these with the predictions of a new agn sed model, qsosed, which includes prescriptions for both hot and warm comptonization regions as well as an outer standard disc. this predicts the overall sed fairly well for 7.5 < log(mbh/m⊙) < 9.0 over a wide range in l/ledd, but at higher masses the outer disc spectra in the model are far too cool to match the data. we create optical-uv composites from the entire sloan digital sky survey sample and use these to show that the mismatch is due to there being no significant change in spectral shape of the optical-uv continuum across several decades of mbh at constant luminosity. we show for the first time that this cannot be matched by standard disc models with high black hole spin. these apparently fit, but are not self-consistent as they do not include the general relativistic effects for the emission to reach the observer. at high spin, increased gravitational redshift compensates for almost all of the higher temperature emission from the smaller inner disc radii. the data do not match the predictions made by any current accretion flow model. either the disc is completely covered by a warm comptonization layer whose properties change systematically with l/ledd, or the accretion flow structure is fundamentally different to that of the standard disc models. | the soux agn sample: optical/uv/x-ray seds and the nature of the disc |
the standard λ cold dark matter (λcdm) model is recently reported to deviate from the high-redshift hubble diagram of type ia supernovae (sne) and quasars (qsos) at ~4σ confidence level. in this work, we combine the page approximation (a nearly model-independent parametrization) and a high-quality qso sample to search for the origins of the deviation. by visualizing the λcdm model and the marginalized 3σ constraints of sne+qsos into the page space, we confirm that the sne+qso constraints in both flat and non-flat page cases are in remarkable tension with the standard λcdm cosmology. next, we investigate the tension from the perspective of redshift-evolution effects. we find that the qso correlation coefficient γ calibrated by sne+low-z qsos and sne+high-z qsos shows ~2.7σ and ~4σ tensions in flat and non-flat universes, respectively. the tensions for intrinsic dispersion δ between different data sets are found to be >4σ in both flat and non-flat cases. these results indicate that the qso luminosity correlation suffers from significant redshift evolution and non-universal intrinsic dispersion. using a redshift-dependence correlation to build qso hubble diagram could lead to biases. thus, the ~4σ deviation from the standard λcdm probably originates from the redshift-evolution effects and non-universal dispersion of the qso luminosity correlation rather than new physics. | redshift evolution and non-universal dispersion of quasar luminosity correlation |
we study the rest-frame optical properties of 74 luminous (lbol=1046.2-48.2 erg s-1), 1.5< z< 3.5 broad-line quasars with near-ir (jhk) slit spectroscopy. systemic redshifts based on the peak of the [o iii] λ5007 line reveal that redshift estimates from the rest-frame uv broad emission lines (mostly mg ii) are intrinsically uncertain by ∼ 200 km s-1 (measurement errors accounted for). the overall full-width-at-half-maximum of the narrow [o iii] line is ∼ 1000 km s-1 on average. a significant fraction of the total [o iii] flux (∼40%) is in a blueshifted wing component with a median velocity offset of ∼ 700 km s-1, indicative of ionized outflows within a few kpc from the nucleus; we do not find evidence of significant [o iii] flux beyond ∼ 10 kpc in our slit spectroscopy. the [o iii] line is noticeably more asymmetric and weaker than that in typical less luminous low-z quasars. however, when matched in quasar continuum luminosity, low-z quasars have similar [o iii] profiles and strengths as these high-z systems. therefore the exceptionally large width and blueshifted wing, and the relatively weak strength of [o iii] in high-z luminous quasars are mostly a luminosity effect rather than redshift evolution. the hβ-[o iii] region of these high-z quasars displays a similar spectral diversity and eigenvector 1 correlations with anti-correlated [o iii] and optical fe ii strengths, as seen in low-z quasars; but the average broad hβ width is larger by 25% than typical low-z quasars, indicating more massive black holes in these high-z systems. these results highlight the importance of understanding [o iii] in the general context of quasar parameter space in order to understand quasar feedback in the form of [o iii] outflows. the calibrated one-dimensional near-ir spectra are made publicly available, along with a composite spectrum. | rest-frame optical properties of luminous 1.5 < z < 3.5 quasars: the hβ-[o iii] region |
celestial objects exhibit a wide range of variability in brightness at different wavebands. surprisingly, the most common methods for characterizing time series in statistics - parametric autoregressive modeling - is rarely used to interpret astronomical light curves. we review standard arma, arima and arfima (autoregressive moving average fractionally integrated) models that treat short-memory autocorrelation, long-memory 1/f^a `red noise', and nonstationary trends. though designed for evenly spaced time series, moderately irregular cadences can be treated as evenly-spaced time series with missing data. fitting algorithms are efficient and software implementations are widely available. we apply arima models to light curves of four variable stars, discussing their effectiveness for different temporal characteristics. a variety of extensions to arima are outlined, with emphasis on recently developed continuous-time models like carma and carfima designed for irregularly spaced time series. strengths and weakness of arima-type modeling for astronomical data analysis and astrophysical insights are reviewed. | autoregressive times series methods for time domain astronomy |
enormous lyα nebulae (elane) represent the extrema of lyα nebulosities. they have detected extents of >200 kpc in lyα and lyα luminosities >1044 erg s-1. the elan population is an ideal laboratory to study the interactions between galaxies and the intergalactic/circumgalactic medium (igm/cgm) given their brightness and sizes. the current sample size of elane is still very small, and the few z ≈ 2 elane discovered to date are all associated with local overdensities of active galactic nuclei (agns). inspired by these results, we have initiated a survey of elane associated with quasi-stellar object (qso) pairs using the palomar and keck cosmic web imagers (pcwi/kcwi). in this letter, we present our first result: the discovery of elan0101+0201 associated with a qso pair at z = 2.45. our pcwi discovery data shows that, above a 2σ surface brightness of 1.2 × 10-17 erg s-1 cm-2 arcsec-2, the end-to-end size of elan0101+0201 is ≳232 kpc. we have conducted follow-up observations using kcwi, resolving multiple lyα emitting sources within the rectangular field of view of ≈130 × 165 projected kpc2, and obtaining their emission line profiles at high signal-to-noise ratios (s/ns). combining both kcwi and pcwi, our observations confirm that elan0101+0201 resides in an extremely overdense environment. our observations further support that a large amount of cool (t ∼ 104 k) gas could exist in massive halos (m ≳1013 m ⊙) at z ≈ 2. future observations on a larger sample of similar systems will provide statistics of how cool gas is distributed in massive overdensities at high redshift and strongly constrain the evolution of the intracluster medium. | keck/palomar cosmic web imagers reveal an enormous lyα nebula in an extremely overdense quasi-stellar object pair field at z = 2.45 |
relativistic effects in clustering observations have been shown to introduce scale-dependent corrections to the galaxy overdensity field on large scales, which may hamper the detection of primordial non-gaussianity fnl through the scale-dependent halo bias. the amplitude of relativistic corrections depends not only on the cosmological background expansion, but also on the redshift evolution and sensitivity to the luminosity threshold of the tracer population being examined, as parametrized by the evolution bias be and magnification bias s. in this work, we propagate luminosity function measurements from the extended baryon oscillation spectroscopic survey (eboss) to be and s for the quasar (qso) sample, and thereby derive constraints on relativistic corrections to its power spectrum multipoles. although one could mitigate the impact on the fnl signature by adjusting the redshift range or the luminosity threshold of the tracer sample being considered, we suggest that, for future surveys probing large cosmic volumes, relativistic corrections should be forward modelled from the tracer luminosity function including its uncertainties. this will be important to quasar clustering measurements on scales $k \sim 10^{-3}\, h\, {\rm mpc}^{-1}$ in upcoming surveys such as the dark energy spectroscopic instrument (desi), where relativistic corrections can overwhelm the expected fnl signature at low redshifts z ≲ 1 and become comparable to fnl ≃ 1 in the power spectrum quadrupole at redshifts z ≳ 2.5. | impact of relativistic effects on the primordial non-gaussianity signature in the large-scale clustering of quasars |
until recently, determining the rotational properties of galaxies in the early universe (z> 4, universe age < 1.5 gyr) was impractical, with the exception of a few strongly lensed systems. combining the high resolution and sensitivity of alma at (sub-)millimeter wavelengths with the typically high strength of the [c ii] 158 μm emission line from galaxies and long-developed dynamical modeling tools raises the possibility of characterizing the gas dynamics in both extreme starburst galaxies and normal star-forming disk galaxies at z∼ 4{--}7. using a procedure centered around gipsy’s rotcur task, we have fit tilted ring models to some of the best available alma [c ii] data of a small set of galaxies: the ms galaxies hz9 and hz10, the damped lyα absorber host galaxy alma j0817+1351, the submm galaxies aztec/c159 and cosmos j1000+0234, and the quasar host galaxy ulas j1319+0950. this procedure directly derives rotation curves and dynamical masses as functions of radius for each object. in one case, we present evidence for a dark matter halo of { o }({10}11) {m}⊙ . we present an analysis of the possible velocity dispersions of two sources based on matching simulated observations to the integrated [c ii] line profiles. finally, we test the effects of observation resolution and sensitivity on our results. while the conclusions remain limited at the resolution and signal-to-noise ratios of these observations, the results demonstrate the viability of the modeling tools at high redshift, and the exciting potential for detailed dynamical analysis of the earliest galaxies, as alma achieves full observational capabilities. | dynamical characterization of galaxies at z ∼ 4-6 via tilted ring fitting to alma [c ii] observations |
the existence of axionlike particles (alps) is predicted by many extensions of the standard model of elementary particles and in particular by theories of superstrings and superbranes. alps are very light, neutral, pseudoscalar bosons which are supposed to interact with two photons. they can play an important role in high-energy astrophysics. basically, in certain circumstances, alps substantially enhance the photon survival probability pγ →γ(e ) of a beam emitted by a far-away source through the mechanism of photon-alp oscillations (e denotes the energy). but in order for this to work, an external magnetic field b must be present. in several cases, b is modeled as a domainlike network with "sharp edges": all domains have the same size ldom (set by the b coherence length) and the same strength b , but the direction of b changes randomly and abruptly from one domain to the next. while this model has repeatedly been used since it greatly simplifies the calculations, it is obviously a highly mathematical idealization wherein the components of b are discontinuous across the edges (whence the name sharp edges). it is therefore highly desirable to go a step further and to find out what happens when the edges are smoothed out, namely when the abrupt change of b is replaced by a smooth one. moreover, this step becomes compelling when the photon-alp oscillation length losc turns out to be comparable to—or smaller than—ldom, because in this case, the photon survival probability pγ →γ(e ) critically depends on the domain shape. finally, it would be more realistic to have ldom randomly changing within a given range, since it looks rather unlikely that the coherence length of b should be the same everywhere, especially when its source is sufficiently extended. in the present paper, we propose a smoothed out version of the previous domainlike structure of b which incorporates the above changes, and we work out its implications. even in the present case, we are able to solve analytically and exactly the propagation equation of a monochromatic photon/alp beam of energy e inside a single smoothed out domain, thereby ultimately evaluating the corresponding photon survival probability pγ →γ(e ) exactly. this fact has the great advantage to drastically shorten the computation time in the applications involving computer simulations as compared to a numerical solution of the beam propagation equation. actually, it turns out that the condition losc≲ldom takes place when a photon/alp beam of either very low e or very large e —both in the gamma-ray band—crosses a variety of astronomical objects, like radio lobes of flat spectrum radio quasars, spiral galaxies, starburst galaxies, elliptical galaxies, and extragalactic space. thus, the use of our model becomes compelling in all these instances, since the sharp edges model would yield unphysical results. the case of extragalactic space is of particular importance in view of the new generation of gamma-ray observatories like cta, hawc, gamma-400, lhaaso, and taiga-hiscore, since in such a situation losc≲ldom occurs for e ≳o (40 tev ) with a large uncertainty, depending on the choice of the model parameters (we shall come back to this fundamental issue in a subsequent paper). | behavior of axionlike particles in smoothed out domainlike magnetic fields |
theory suggests that there are two primary modes of accretion through which dark-matter halos acquire the gas to form and fuel galaxies: hot- and cold-flow accretion. in cold-flow accretion, gas streams along cosmic web filaments to the centre of the halo, allowing for the efficient delivery of star-forming fuel. recently, two quasar-illuminated h i lyman ɑ (lyα)-emitting objects were reported to have properties of cold, rotating structures1,2. however, the spatial and spectral resolution available was insufficient to constrain the radial flows associated with connecting filaments. with the keck cosmic web imager (kcwi)3, we now have eight times the spatial resolution, permitting the detection of these inspiralling flows. to detect these inflows, we introduce a suite of models that incorporate zonal radial flows, demonstrate their performance on a numerical simulation that exhibits cold-flow accretion, and show that they are an excellent match to kcwi velocity maps of two lyα emitters observed around high-redshift quasars. these multi-filament inflow models kinematically isolate zones of radial inflow that correspond to extended filamentary emission. the derived gas flux and inflow path is sufficient to fuel the inferred central galaxy star-formation rate and angular momentum. thus, our kinematic emission maps provide strong evidence that the inflow of gas from the cosmic web is building galaxies at the peak of star formation. | multi-filament gas inflows fuelling young star-forming galaxies |
observations of the emission from spatially extended cold gas around bright high-redshift quasars (qsos) reveal surprisingly large velocity widths exceeding 2000 km s- 1, out to projected distances as large as 30 kpc. the high-velocity widths have been interpreted as the signature of powerful agn-driven outflows. naively, these findings appear in tension with hydrodynamic models in which agn-driven outflows are energy-driven and thus very hot with typical temperatures t ≳ 106-7 k. using the moving-mesh code arepo, we perform `zoom-in' cosmological simulations of a z ∼ 6 qso and its environment, following black hole growth and feedback via energy-driven outflows. in the simulations, the qso host galaxy is surrounded by a clumpy circumgalactic medium pre-enriched with metals due to supernovae-driven galactic outflows. as a result, part of the agn-driven hot outflowing gas can cool radiatively, leading to large amounts ( ≳ 109 m⊙) of cold gas comoving with the hot bipolar outflow. this results in velocity widths of spatially extended cold gas similar to those observed. we caution, however, that gas inflows, random motions in the deep potential well of the qso host galaxy and cooling of supernovae-driven winds contribute significantly to the large velocity width of the cold gas in the simulations, complicating the interpretation of observational data. | fast cold gas in hot agn outflows. |
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