abstract stringlengths 3 192k | title stringlengths 4 857 |
|---|---|
we present the drastic transformation of the x-ray properties of the active galactic nucleus (agn) 1es 1927+654, following a changing-look event. after the optical/ultraviolet outburst the power-law component, produced in the x-ray corona, disappeared, and the spectrum of 1es 1927+65 instead became dominated by a blackbody component (kt ∼ 80-120 ev). this implies that the x-ray corona, ubiquitously found in agns, was destroyed in the event. our dense ∼450 days long x-ray monitoring shows that the source is extremely variable in the x-ray band. on long timescales the source varies up to ∼4 dex in ∼100 days, while on short timescales up to ∼2 dex in ∼8 hr. the luminosity of the source is found to first show a strong dip down to $\sim {10}^{40}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ , and then a constant increase in luminosity to levels exceeding the pre-outburst level ≳300 days after the optical event detection, rising up asymptotically to $\sim 2\times {10}^{44}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ . as the x-ray luminosity of the source increases, the x-ray corona is recreated, and a very steep power-law component (γ ≃ 3) reappears, and dominates the emission for 0.3-2 kev luminosities $\gtrsim {10}^{43.7}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ , ∼300 days after the beginning of the event. we discuss possible origins of this event, and speculate that our observations could be explained by the interaction between the accretion flow and debris from a tidally disrupted star. our results show that changing-look events can be associated with dramatic and rapid transformations of the innermost regions of accreting supermassive black holes. | the destruction and recreation of the x-ray corona in a changing-look active galactic nucleus |
as one paper in a series reporting on a large reverberation mapping campaign of super-eddington accreting massive black holes (seambhs) in active galactic nuclei (agns), we present the results of 10 seambhs monitored spectroscopically during 2015-2017. six of them are observed for the first time, and have generally higher 5100 å luminosities than the seambhs monitored in our campaign from 2012 to 2015; the remaining four are repeat observations to check if their previous lags change. similar to the previous seambhs, the hβ time lags of the newly observed objects are shorter than the values predicted by the canonical r hβ -l 5100 relation of sub-eddington agns, by factors of ∼2-6, depending on the accretion rate. the four previously observed objects have lags consistent with previous measurements. we provide linear regressions for the r hβ -l 5100 relation, solely for the seambh sample and for low-accretion agns. we find that the relative strength of fe ii and the profile of the hβ emission line can be used as proxies of accretion rate, showing that the shortening of hβ lags depends on accretion rates. the recent sdss-rm discovery of shortened hβ lags in agns with low accretion rates provides compelling evidence for retrograde accretion onto the black hole. these evidences show that the canonical r hβ -l 5100 relation holds only in agns with moderate accretion rates. at low accretion rates, it should be revised to include the effects of black hole spin, whereas the accretion rate itself becomes a key factor in the regime of high accretion rates. | supermassive black holes with high accretion rates in active galactic nuclei. ix. 10 new observations of reverberation mapping and shortened hβ lags |
we present atacama large millimeter/submillimeter array (alma) band 7 observations of a remarkably bright galaxy candidate at ${z}_{\mathrm{phot}}={16.7}_{-0.3}^{+1.9}$ (m uv = -21.6), s5-z17-1, identified in james webb space telescope (jwst) early release observation data of stephen's quintet. we do not detect the dust continuum at 866 μm, ruling out the possibility that s5-z17-1 is a low-z dusty starburst with a star formation rate of ≳30 m ⊙ yr-1. we detect a 5.1σ line feature at 338.726 ± 0.007 ghz exactly coinciding with the jwst source position, with a 2% likelihood of the signal being spurious. the most likely line identification would be [o iii]52 μm at z = 16.01 or [c ii]158 μm at z = 4.61, whose line luminosities do not violate the nondetection of the dust continuum in both cases. together with three other z ≳ 11-13 candidate galaxies recently observed with alma, we conduct a joint alma and jwst spectral energy distribution (sed) analysis and find that the high-z solution at z ~ 11-17 is favored in every candidate as a very blue (uv continuum slope of ≃-2.3) and luminous (m uv ≃ [ - 24:-21]) system. still, we find in several candidates that reasonable sed fits (δχ 2 ≲ 4) are reproduced by type ii quasar and/or quiescent galaxy templates with strong emission lines at z ~ 3-5, where such populations predicted from their luminosity functions and ew([o iii]+hβ) distributions are abundant in survey volumes used for the identification of the z ~ 11-17 candidates. while these recent alma observation results have strengthened the likelihood of the high-z solutions, lower-z possibilities are not completely ruled out in several of the z ~ 11-17 candidates, indicating the need to consider the relative surface densities of the lower-z contaminants in the ultra-high-z galaxy search. | alma fir view of ultra-high-redshift galaxy candidates at z 11-17: blue monsters or low-z red interlopers? |
observations of the redshift z=7.085 quasar j1120+0641 have been used to search for variations of the fine structure constant, alpha, over the redshift range 5.5 to 7.1. observations at z=7.1 probe the physics of the universe when it was only 0.8 billion years old. these are the most distant direct measurements of alpha to date and the first measurements made with a near-ir spectrograph. a new ai analysis method has been employed. four measurements from the x-shooter spectrograph on the european southern observatory's very large telescope (vlt) directly constrain any changes in alpha relative to the value measured on earth (alpha_0). the weighted mean strength of the electromagnetic force over this redshift range in this location in the universe is da/a = (alpha_z - alpha_0)/alpha_0 = (-2.18 +/- 7.27) x 10^{-5}, i.e. we find no evidence for a temporal change from the 4 new very high redshift measurements. when the 4 new measurements are combined with a large existing sample of lower redshift measurements, a new limit on possible spatial variation of da/a is marginally preferred over a no-variation model at the 3.7 sigma level. | four direct measurements of the fine-structure constant 13 billion years ago |
the extended baryon oscillation spectroscopic survey (eboss) data release 14 sample includes 80,118 luminous red galaxies (lrgs). by combining these galaxies with the high-redshift tail of the boss galaxy sample, we form a sample of lrgs at an effective redshift z = 0.72, covering an effective volume of 0.9 gpc3. we account for spurious fluctuations caused by targeting and by redshift failures, which were validated on a set of mock catalogs. this analysis is sufficient to provide a 2.5% measurement of spherically averaged baryon acoustic oscillations (bao), {d}v(z=0.72)={2377}-59+61({r}d/{r}d,{fid}) mpc, at 2.8σ of significance. together with the recent quasar-based bao measurement at z = 1.5 and forthcoming emission line galaxy-based measurements, this measurement demonstrates that eboss is fulfilling its remit of extending the range of redshifts covered by such measurements, laying the groundwork for forthcoming surveys such as the dark energy spectroscopic survey and euclid. | the sdss-iv extended baryon oscillation spectroscopic survey: baryon acoustic oscillations at redshift of 0.72 with the dr14 luminous red galaxy sample |
nearly every massive galaxy harbors a supermassive black hole (smbh) in its nucleus. smbh masses are millions to billions of solar mass, and they correlate with properties of spheroids of their host galaxies. while the smbh growth channels, mergers, and gas accretion are well established, their origin remains uncertain: they could have emerged either from massive “seeds” (105-106 m⊙) formed by direct collapse of gas clouds in the early universe or from smaller (100 m⊙) bhs, end products of first stars. the latter channel would leave behind numerous intermediate-mass bhs (imbhs, 102-105 m⊙). although many imbh candidates have been identified, none are accepted as definitive; thus, their very existence is still debated. using data mining in wide-field sky surveys and applying dedicated analysis to archival and follow-up optical spectra, we identified a sample of 305 imbh candidates having masses 3× {10}4 {m}⊙ < {m}bh}< 2× {10}5 {m}⊙ , which reside in galaxy centers and are accreting gas that creates characteristic signatures of a type i active galactic nucleus (agn). we confirmed the agn nature of 10 sources (including five previously known objects that validate our method) by detecting the x-ray emission from their accretion disks, thus defining the first bona fide sample of imbhs in galactic nuclei. all imbh host galaxies possess small bulges and sit on the low-mass extension of the {m}bh}{--}{m}bulge} scaling relation, suggesting that they must have experienced very few if any major mergers over their lifetime. the very existence of nuclear imbhs supports the stellar-mass seed scenario of the massive bh formation. | a population of bona fide intermediate-mass black holes identified as low-luminosity active galactic nuclei |
mergers of galaxies are thought to cause significant gas inflows to the inner parsecs, which can activate rapid accretion on to supermassive black holes (smbhs), giving rise to active galactic nuclei (agn). during a significant fraction of this process, smbhs are predicted to be enshrouded by gas and dust. studying 52 galactic nuclei in infrared-selected local luminous and ultraluminous infrared galaxies in different merger stages in the hard x-ray band, where radiation is less affected by absorption, we find that the amount of material around smbhs increases during the last phases of the merger. we find that the fraction of compton-thick (ct, n h ≥ 1024 cm- 2) agn in late-merger galaxies is higher (f_ ct=65^{+12}_{-13}{per cent}) than in local hard x-ray selected agn (f ct = 27 ± 4 per cent), and that obscuration reaches its maximum when the nuclei of the two merging galaxies are at a projected distance of d12 ≃ 0.4-10.8 kpc (f_ ct=77_{-17}^{+13}{per cent}). we also find that all agn of our sample in late-merger galaxies have n h > 1023 cm- 2, which implies that the obscuring material covers 95^{+4}_{-8}{per cent} of the x-ray source. these observations show that the material is most effectively funnelled from the galactic scale to the inner tens of parsecs during the late stages of galaxy mergers, and that the close environment of smbhs in advanced mergers is richer in gas and dust with respect to that of smbhs in isolated galaxies, and cannot be explained by the classical agn unification model in which the torus is responsible for the obscuration. | growing supermassive black holes in the late stages of galaxy mergers are heavily obscured |
we report on the design and performance of the keck cosmic web imager (kcwi), a general purpose optical integral field spectrograph that has been installed at the nasmyth port of the 10 m keck ii telescope on maunakea, hawaii. the novel design provides blue-optimized seeing-limited imaging from 350-560 nm with configurable spectral resolution from 1000-20,000 in a field of view up to 20″ × 33″. selectable volume phase holographic (vph) gratings and high-performance dielectric, multilayer silver, and enhanced-aluminum coatings provide end-to-end peak efficiency in excess of 45% while accommodating the future addition of a red channel that will extend wavelength coverage to 1 micron. kcwi takes full advantage of the excellent seeing and dark sky above maunakea with an available nod-and-shuffle observing mode. the instrument is optimized for observations of faint, diffuse objects such as the intergalactic medium or cosmic web. in this paper, a detailed description of the instrument design is provided with measured performance results from the laboratory test program and 10 nights of on-sky commissioning during the spring of 2017. the kcwi team is lead by caltech and jpl (project management, design, and implementation) in partnership with the university of california at santa cruz (camera optical and mechanical design) and the w. m. keck observatory (observatory interfaces). | the keck cosmic web imager integral field spectrograph |
a system of 5020 robotic fiber positioners was installed in 2019 on the mayall telescope, at kitt peak national observatory. the robots automatically retarget their optical fibers every 10-20 minutes, each to a precision of several microns, with a reconfiguration time of fewer than 2 minutes. over the next 5 yr, they will enable the newly constructed dark energy spectroscopic instrument (desi) to measure the spectra of 35 million galaxies and quasars. desi will produce the largest 3d map of the universe to date and measure the expansion history of the cosmos. in addition to the 5020 robotic positioners and optical fibers, desi's focal plane system includes six guide cameras, four wave front cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. the system also includes associated structural, thermal, and electrical systems. in all, it contains over 675,000 individual parts. we discuss the design, construction, quality control, and integration of all these components. we include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multiobject, fiber-fed spectrographs. | the robotic multiobject focal plane system of the dark energy spectroscopic instrument (desi) |
context. lbqs 0302−0019 is a blue quasar (qso) at z ∼ 3.3 that hosts powerful outflows and resides in a complex environment consisting of an obscured active galactic nucleus (agn) candidate and multiple companions, all within 30 kpc in projection.aims: we aim to characterise this complex system using jwst nirspec integral field spectrograph (ifs) observations obtained as part of the nirspec ifs gto programme "galaxy assembly with nirspec ifs" (ga-nifs); these data cover the qso rest-frame optical emission lines with a spatial resolution of ∼0.1″ and a sampling of 0.05″ (∼380 pc) over a contiguous sky area of ∼3″ × 3″ (23 × 23 kpc2).methods: we developed a procedure to correct for the spurious oscillations (or "wiggles") in nirspec single-spaxel spectra caused by the spatial under-sampling of the point spread function. we performed a qso-host decomposition with the qdeblend3d tools. we used multi-component kinematic decomposition of the optical emission line profiles to infer the physical properties of the emitting gas in the qso environment.results: the qso-host decomposition allows us to identify both a low- and a high-velocity component. the former possibly traces a warm rotating disk with a dynamical mass mdyn ∼ 1011 m⊙ and a rotation-to-random motion ratio vrot/σ0 ∼ 2. the other kinematic component traces a spatially unresolved ionised outflow with a velocity of ∼1000 km s−1 and an outflow mass rate of ∼104 m⊙ yr−1. we clearly detect eight companion objects close to lbqs 0302−0019. for two of them, we detect a regular velocity field that likely traces rotating gas, and we infer individual dynamical masses of ≈1010 m⊙. another companion shows evidence of gravitational interaction with the qso host. optical line ratios confirm the presence of a second, obscured agn ∼20 kpc from the primary qso; the dual agn dominates the ionisation state of the gas in the entire nirspec field of view.conclusions: this work has unveiled in unprecedented detail the complex environment of lbqs 0302−0019, which includes its host galaxy, a close obscured agn, and nine interacting companions (five of which were previously unknown), all within 30 kpc of the qso. our results support a scenario where mergers can trigger dual agn and can be important drivers of rapid early supermassive black hole growth. jwst/nirspec integrated spectrum of the blue quasar lbqs 0302-0019 is available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/679/a89 | ga-nifs: the ultra-dense, interacting environment of a dual agn at z ∼ 3.3 revealed by jwst/nirspec ifs |
context. as part of the third gaia data release, we present the contributions of the non-stellar and classification modules from the eighth coordination unit (cu8) of the data processing and analysis consortium, which is responsible for the determination of source astrophysical parameters using gaia data. this is the third in a series of three papers describing the work done within cu8 for this release.aims: for each of the five relevant modules from cu8, we summarise their objectives, the methods they employ, their performance, and the results they produce for gaia dr3. we further advise how to use these data products and highlight some limitations.methods: the discrete source classifier (dsc) module provides classification probabilities associated with five types of sources: quasars, galaxies, stars, white dwarfs, and physical binary stars. a subset of these sources are processed by the outlier analysis (oa) module, which performs an unsupervised clustering analysis, and then associates labels with the clusters to complement the dsc classification. the quasi stellar object classifier (qsoc) and the unresolved galaxy classifier (ugc) determine the redshifts of the sources classified as quasar and galaxy by the dsc module. finally, the total galactic extinction (tge) module uses the extinctions of individual stars determined by another cu8 module to determine the asymptotic extinction along all lines of sight for galactic latitudes |b|> 5°. results.gaia dr3 includes 1591 million sources with dsc classifications; 56 million sources to which the oa clustering is applied; 1.4 million sources with redshift estimates from ugc; 6.4 million sources with qsoc redshift; and 3.1 million level 9 healpixes of size 0.013 deg2 where the extinction is evaluated by tge.conclusions: validation shows that results are in good agreement with values from external catalogues; for example 90% of the qsoc redshifts have absolute error lower than 0.1 for sources with empty warning flags, while ugc redshifts have a mean error of 0.008 ± 0.037 if evaluated on a clean set of spectra. an internal validation of the oa results further shows that 30 million sources are located in high confidence regions of the clustering map. | gaia data release 3. apsis. iii. non-stellar content and source classification |
we present the first results from the jwst program a spectroscopic survey of biased halos in the reionization era (aspire). this program represents an imaging and spectroscopic survey of 25 reionization-era quasars and their environments by utilizing the unprecedented capabilities of nircam wide field slitless spectroscopy (wfss) mode. aspire will deliver the largest ( $\sim 280\,{\mathrm{arcmin}}^{2}$ ) galaxy redshift survey at 3-4 μm among jwst cycle 1 programs and provide extensive legacy values for studying the formation of the earliest supermassive black holes, the assembly of galaxies, early metal enrichment, and cosmic reionization. in this first aspire paper, we report the discovery of a filamentary structure traced by the luminous quasar j0305-3150 and 10 [o iii] emitters at z = 6.6. this structure has a 3d galaxy overdensity of δ gal = 12.6 over 637 cmpc3, one of the most overdense structures known in the early universe, and could eventually evolve into a massive galaxy cluster. together with existing vlt/muse and alma observations of this field, our jwst observations reveal that j0305-3150 traces a complex environment where both uv-bright and dusty galaxies are present and indicate that the early evolution of galaxies around the quasar is not simultaneous. in addition, we discovered 31 [o iii] emitters in this field at other redshifts, 5.3 < z < 6.7, with half of them situated at z ~ 5.4 and 6.2. this indicates that star-forming galaxies, such as [o iii] emitters, are generally clustered at high redshifts. these discoveries demonstrate the unparalleled redshift survey capabilities of nircam wfss and the potential of the full aspire survey data set. | a spectroscopic survey of biased halos in the reionization era (aspire): jwst reveals a filamentary structure around a z = 6.61 quasar |
we present the results from a full polarization study carried out with the atacama large millimeter/submillimeter array (alma) during the first very long baseline interferometry (vlbi) campaign, which was conducted in 2017 april in the λ3 mm and λ1.3 mm bands, in concert with the global mm-vlbi array (gmva) and the event horizon telescope (eht), respectively. we determine the polarization and faraday properties of all vlbi targets, including sgr a*, m87, and a dozen radio-loud active galactic nuclei (agns), in the two bands at several epochs in a time window of 10 days. we detect high linear polarization fractions (2%-15%) and large rotation measures (rm > 103.3-105.5 rad m-2), confirming the trends of previous agn studies at millimeter wavelengths. we find that blazars are more strongly polarized than other agns in the sample, while exhibiting (on average) order-of-magnitude lower rm values, consistent with the agn viewing angle unification scheme. for sgr a* we report a mean rm of (-4.2 ± 0.3) × 105 rad m-2 at 1.3 mm, consistent with measurements over the past decade and, for the first time, an rm of (-2.1 ± 0.1) × 105 rad m-2 at 3 mm, suggesting that about half of the faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. we also report the first unambiguous measurement of rm toward the m87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from -1.2 to 0.3 × 105 rad m-2 at 3 mm and -4.1 to 1.5 × 105 rad m-2 at 1.3 mm. given this time variability, we argue that, unlike the case of sgr a*, the rm in m87 does not provide an accurate estimate of the mass accretion rate onto the black hole. we put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the eht (on horizon scales) and alma (which observes the combined emission from both components). these measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained vlbi data with the eht and gmva. | polarimetric properties of event horizon telescope targets from alma |
we aim to constrain the evolution of active galactic nuclei (agns) as a function of obscuration using an x-ray-selected sample of ~2000 agns from a multi-tiered survey including the cdfs, aegis-xd, cosmos, and xmm-xxl fields. the spectra of individual x-ray sources are analyzed using a bayesian methodology with a physically realistic model to infer the posterior distribution of the hydrogen column density and intrinsic x-ray luminosity. we develop a novel non-parametric method that allows us to robustly infer the distribution of the agn population in x-ray luminosity, redshift, and obscuring column density, relying only on minimal smoothness assumptions. our analysis properly incorporates uncertainties from low count spectra, photometric redshift measurements, association incompleteness, and the limited sample size. we find that obscured agns with n h > 1022 cm-2 account for {77}+4-5% of the number density and luminosity density of the accretion supermassive black hole population with l x > 1043 erg s-1, averaged over cosmic time. compton-thick agns account for approximately half the number and luminosity density of the obscured population, and {38}+8-7% of the total. we also find evidence that the evolution is obscuration dependent, with the strongest evolution around n h ≈ 1023 cm-2. we highlight this by measuring the obscured fraction in compton-thin agns, which increases toward z ~ 3, where it is 25% higher than the local value. in contrast, the fraction of compton-thick agns is consistent with being constant at ≈35%, independent of redshift and accretion luminosity. we discuss our findings in the context of existing models and conclude that the observed evolution is, to first order, a side effect of anti-hierarchical growth. | obscuration-dependent evolution of active galactic nuclei |
we study the sudden optical and ultraviolet (uv) brightening of 1es 1927+654, which until now was known as a narrow-line active galactic nucleus (agn). 1es 1927+654 was part of the small and peculiar class of “true type-2” agns that lack broad emission lines and line-of-sight obscuration. our high-cadence spectroscopic monitoring captures the appearance of a blue, featureless continuum, followed several weeks later by the appearance of broad balmer emission lines. this timescale is generally consistent with the expected light travel time between the central engine and the broadline emission region in (persistent) broadline agn. hubble space telescope spectroscopy reveals no evidence for broad uv emission lines (e.g., c iv λ1549, c iii] λ1909, mg ii λ2798), probably owing to dust in the broadline emission region. to the best of our knowledge, this is the first case where the lag between the change in continuum and in broadline emission of a “changing look” agn has been temporally resolved. the nature and timescales of the photometric and spectral evolution disfavor both a change in line-of-sight obscuration and a change of the overall rate of gas inflow as driving the drastic spectral transformations seen in this agn. although the peak luminosity and timescales are consistent with those of tidal disruption events seen in inactive galaxies, the spectral properties are not. the x-ray emission displays a markedly different behavior, with frequent flares on timescales of hours to days, and will be presented in a companion publication. | 1es 1927+654: an agn caught changing look on a timescale of months |
we present two large catalogs of active galactic nucleus (agn) candidates identified across 30,093 deg2 of extragalactic sky from the wide-field infrared survey explorer’s allwise data release. both catalogs are selected purely using the wide-field infrared survey explorer (wise) w1 and w2 bands. the r90 catalog consists of 4,543,530 agn candidates with 90% reliability, while the c75 catalog consists of 20,907,127 agn candidates with 75% completeness. these reliability and completeness figures were determined from a detailed analysis of uv- to near-ir spectral energy distributions of ∼ {10}5 sources in the 9 deg2 boötes field. the agn selection criteria are based on those of assef et al. (2013) recalibrated to the allwise data release. we provide a detailed discussion of potential artifacts and excise portions of the sky close to the galactic center, galactic plane, nearby galaxies, and other expected contaminating sources. these catalogs are expected to enable a broad range of science, and we present a few illustrative cases. from the r90 sample, we identify 45 highly variable agns lacking radio counterparts in the first survey. one of these sources, wisea j142846.71+172353.1, is a changing-look quasar at z = 0.104, which has changed from having broad hα to being a narrow-lined agn. we characterize our catalogs by comparing them to large, wide-area agn catalogs in the literature. we identify four rosat x-ray sources that are each matched to three wise-selected agns in the r90 sample within 30″. spectroscopy reveals that one of these systems, 2rxs j150158.6+691029, consists of a triplet of quasars at z = 1.133 ± 0.004, suggestive of a rich group or forming galaxy cluster. | the wise agn catalog |
there have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. pg 1302-102 by graham et al. any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. however, normal quasars - powered by accretion on to a single, supermassive black hole - usually show stochastic variability over a wide range of time-scales. it is therefore important to carefully assess the methods for identifying periodic candidates from among a population dominated by stochastic variability. using a bayesian analysis of the light curve of pg 1302-102, we find that a simple stochastic process is preferred over a sinusoidal variation. we then discuss some of the problems one encounters when searching for rare, strictly periodic signals among a large number of irregularly sampled, stochastic time series, and use simulations of quasar light curves to illustrate these points. from a few thousand simulations of steep spectrum (`red noise') stochastic processes, we find many simulations that display few-cycle periodicity like that seen in pg 1302-102. we emphasize the importance of calibrating the false positive rate when the number of targets in a search is very large. | false periodicities in quasar time-domain surveys |
we develop a new spectral model for the broad-band spectral energy distribution (sed) of active galactic nuclei (agn). this includes an outer standard disc, an inner warm comptonizing region to produce the soft x-ray excess and a hot corona. we tie these together energetically by assuming novikov-thorne emissivity, and use this to define a size scale for the hard x-ray corona as equal to the radius where the remaining accretion energy down to the black hole can power the observed x-ray emission. we test this on three agn with well-defined seds as well as on larger samples to show that the average hard x-ray luminosity is always approximately a few per cent of the eddington luminosity across a large range of eddington ratio. as a consequence, the radial size scale required for gravity to power the x-ray corona has to decrease with increasing eddington fraction. for the first time, we hardwire this into the spectral models, and set the hard x-ray spectral index self-consistently from the ratio of the hard x-ray luminosity to intercepted seed photon luminosity from the disc. this matches the observed correlation of steeper spectral index with increasing eddington ratio, as well as reproducing the observed tight uv/x relation of quasars. we also include the reprocessed emission produced by the hot inner flow illuminating the warm comptonization and standard disc regions and show that this predicts a decreasing amount of optical variability with increasing eddington ratio as observed, though additional processes may also be required to explain the observed optical variability. | a physical model of the broad-band continuum of agn and its implications for the uv/x relation and optical variability |
we investigate black hole-host galaxy scaling relations in cosmological simulations with a self-consistent black hole growth and feedback model. our sub-grid accretion model captures the key scalings governing angular momentum transport by gravitational torques from galactic scales down to parsec scales, while our kinetic feedback implementation enables the injection of outflows with properties chosen to match observed nuclear outflows (star formation-driven winds are not included to isolate the effects of black hole feedback). we show that `quasar mode' feedback can have a large impact on the thermal properties of the intergalactic medium and the growth of galaxies and massive black holes for kinetic feedback efficiencies as low as 0.1 per cent relative to the bolometric luminosity. none the less, our simulations indicate that the black hole-host scaling relations are only weakly dependent on the effects of black hole feedback on galactic scales, since black hole feedback suppresses the growth of galaxies and massive black holes by a similar amount. in contrast, the rate at which gravitational torques feed the central black hole relative to the host galaxy star formation rate governs the slope and normalization of the black hole-host correlations. our results suggest that a common gas supply regulated by gravitational torques is the primary driver of the observed co-evolution of black holes and galaxies. | gravitational torque-driven black hole growth and feedback in cosmological simulations |
massive black hole (mbh) coalescences are powerful sources of low-frequency gravitational waves. to study these events in the cosmological context, we need to trace the large-scale structure and cosmic evolution of a statistical population of galaxies, from dim dwarfs to bright galaxies. to cover such a large range of galaxy masses, we analyse two complementary simulations: horizon-agn with a large volume and low resolution that tracks the high-mass ( $\gt 10^7\, {\rm m_\odot }$ ) mbh population, and newhorizon with a smaller volume but higher resolution that traces the low-mass ( $\lt 10^7\, {\rm m_\odot }$ ) mbh population. while horizon-agn can be used to estimate the rate of inspirals for pulsar timing arrays, newhorizon investigate mbh mergers in a statistical sample of dwarf galaxies for lisa, which is sensitive to low-mass mbhs. we use the same method to analyse the two simulations, post-processing mbh dynamics to account for time delays mostly determined by dynamical friction and stellar hardening. in both simulations, mbhs typically merge long after galaxies do, so that the galaxy morphology at the time of the mbh merger is no longer determined by the structural disturbances engendered by the galaxy merger from which the mbh coalescence has originated. these time delays cause a loss of high-z mbh coalescences, shifting the peak of the mbh merger rate to z ∼ 1-2. this study shows how tracking mbh mergers in low-mass galaxies is crucial to probing the mbh merger rate for lisa and investigate the properties of the host galaxies. | black hole mergers from dwarf to massive galaxies with the newhorizon and horizon-agn simulations |
the radius-luminosity ({r}{{h}β }{--}{l}5100) relationship of active galactic nuclei (agns) established by the reverberation mapping (rm) observations has been widely used as a single-epoch black hole mass estimator in the research of large agn samples. however, the recent rm campaigns discovered that the agns with high-accretion rates show shorter time lags by factors of a few comparing with the predictions from the {r}{{h}β }{--}{l}5100 relationship. the explanation of the shortened time lags has not been finalized yet. we collect eight different single-epoch spectral properties to investigate how the shortening of the time lags correlates with those properties and to determine the origin of the shortened lags. we find that the flux ratio between fe ii and hβ emission lines shows the most prominent correlation, thus confirming that accretion rate is the main driver for the shortened lags. in addition, we establish a new scaling relation including the relative strength of fe ii emission. this new scaling relation can provide less biased estimates of the black hole mass and accretion rate from the single-epoch spectra of agns. | the radius-luminosity relationship depends on optical spectra in active galactic nuclei |
context. the erosita final equatorial depth survey (efeds), observed with erosita ahead of its planned 4-yr all-sky survey, is the largest contiguous-field x-ray survey at present. it yielded a large sample of x-ray sources with very rich multiband photometric and spectroscopic coverage.aims: we present here the efeds active galactic nuclei (agn) catalog and the erosita x-ray spectral properties of the efeds sources.methods: using a bayesian method, we performed a systematic x-ray spectral analysis for all the efeds sources. we adopted multiple spectral models, including single-component power-law or hot-plasma models and double-component models of a power law plus soft excess. we investigated the capacity of erosita x-ray spectra for constraining agn spectral shapes through a detailed analysis of the posterior parameter probability distribution functions. hierarchical bayesian modeling was used to recover the spectral parameter distribution of the sample. the source fluxes and luminosities were measured from the posterior of the spectral fitting.results: the efeds agn catalog (22 079 sources) comprises ~80% of the efeds point sources. despite a large number of faint sources, our spectral fitting provides reasonable measurements of spectral shapes and intrinsic luminosities for a majority of the sources. because of sample selection bias, this agn catalog is dominated by x-ray unobscured sources, with an obscured (lognh > 21.5) fraction of 8%; the power-law emission of the hot corona is also relatively soft, with a typical slope of 2.0. for type-i agn, the x-ray emission is well correlated with the uv emission with the usual anticorrelation between the x-ray to uv spectral slope αox and the uv luminosity. the x-ray spectral properties measured with various models are presented for all the efeds sources. the catalog is available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/661/a5 | the erosita final equatorial-depth survey (efeds). the agn catalog and its x-ray spectral properties |
we report the discovery of a quasar at z = 7.07, which was selected from the deep multi-band imaging data collected by the hyper suprime-cam (hsc) subaru strategic program survey. this quasar, hsc j124353.93+010038.5, has an order of magnitude lower luminosity than do the other known quasars at z > 7. the rest-frame ultraviolet absolute magnitude is m 1450 = -24.13 ± 0.08 mag and the bolometric luminosity is {l}bol} =(1.4+/- 0.1) × {10}46 erg s-1. its spectrum in the optical to near-infrared shows strong emission lines, and shows evidence for a fast gas outflow, as the c iv line is blueshifted and there is indication of broad absorption lines. the mg ii-based black hole mass is {m}bh}=(3.3+/- 2.0)× {10}8{m}⊙ , thus indicating a moderate mass accretion rate with an eddington ratio {λ }edd}=0.34+/- 0.20. it is the first z > 7 quasar with sub-eddington accretion, besides being the third most distant quasar known to date. the luminosity and black hole mass are comparable to, or even lower than, those measured for the majority of low-z quasars discovered by the sloan digital sky survey, and thus this quasar likely represents a z > 7 counterpart to quasars commonly observed in the low-z universe. | discovery of the first low-luminosity quasar at z > 7 |
we have analyzed the parsec-scale jet kinematics of 447 bright radio-loud active active galactic nuclei (agn), based on 15 ghz very long baseline array (vlba) data obtained between 1994 august 31 and 2019 august 4. we present new total intensity and linear polarization maps obtained between 2017 january 1 and 2019 august 4 for 143 of these agn. we tracked 1923 bright features for five or more epochs in 419 jets. the majority (60%) of the well-sampled jet features show either accelerated or nonradial motion. in 47 jets there is at least one nonaccelerating feature with an unusually slow apparent speed. most of the jets show variations of 10°-50° in their inner jet position angle (pa) over time, although the overall distribution has a continuous tail out to 200°. agn with spectral energy distributions peaked at lower frequencies tend to have more variable pas, with bl lac objects being less variable than quasars. the fermi large area telescope (lat) gamma-ray-associated agn also tend to have more variable pas than the non-lat agn in our sample. we attribute these trends to smaller viewing angles for the lower spectral peaked and lat-associated jets. we identified 13 agn where multiple features emerge over decade-long periods at systematically increasing or decreasing pas. since the ejected features do not fill the entire jet cross section, this behavior is indicative of a precessing flow instability near the jet base. although some jets show indications of oscillatory pa evolution, we claim no bona fide cases of periodicity since the fitted periods are comparable to the total vlba time coverage. | monitoring of jets in active galactic nuclei with vlba experiments. xviii. kinematics and inner jet evolution of bright radio-loud active galaxies |
we present two new large-scale datasets aimed at evaluating systems designed to comprehend a natural language query and extract its answer from a large corpus of text. the quasar-s dataset consists of 37000 cloze-style (fill-in-the-gap) queries constructed from definitions of software entity tags on the popular website stack overflow. the posts and comments on the website serve as the background corpus for answering the cloze questions. the quasar-t dataset consists of 43000 open-domain trivia questions and their answers obtained from various internet sources. clueweb09 serves as the background corpus for extracting these answers. we pose these datasets as a challenge for two related subtasks of factoid question answering: (1) searching for relevant pieces of text that include the correct answer to a query, and (2) reading the retrieved text to answer the query. we also describe a retrieval system for extracting relevant sentences and documents from the corpus given a query, and include these in the release for researchers wishing to only focus on (2). we evaluate several baselines on both datasets, ranging from simple heuristics to powerful neural models, and show that these lag behind human performance by 16.4% and 32.1% for quasar-s and -t respectively. the datasets are available at https://github.com/bdhingra/quasar . | quasar: datasets for question answering by search and reading |
the observation of quasars at very high redshift such as pōniuā'ena is a challenge for models of supermassive black hole (smbh) formation. this work presents a study of smbh formation via known physical processes in starburst clusters formed at the onset of the formation of their hosting galaxy. while at the early stages hypermassive starburst clusters reach the luminosities of quasars, once their massive stars die, the ensuing gas accretion from the still forming host galaxy compresses its stellar black hole (bh) component to a compact state overcoming heating from the bh-bh binaries such that the cluster collapses, forming a massive smbh-seed within about a hundred myr. within this scenario, the smbh-spheroid correlation emerges near to exactly. the highest redshift quasars may thus be hypermassive starburst clusters or young ultracompact dwarf galaxies (ucds), being the precursors of the smbhs that form therein within about 200 myr of the first stars. for spheroid masses ${\lesssim }10^{9.6}\, \mathrm{m}_\odot$ , an smbh cannot form and instead only the accumulated nuclear cluster remains. the number evolution of the quasar phases with redshift is calculated and the possible problem of missing quasars at very high redshift is raised. smbh-bearing ucds and the formation of spheroids are discussed critically in view of the high-redshift observations. a possible tension is found between the high star formation rates (sfrs) implied by downsizing and the observed sfrs, which may be alleviated within the igimf theory and if the downsizing times are somewhat longer. | very high redshift quasars and the rapid emergence of supermassive black holes |
galaxy-scale strong gravitational lensing can not only provide a valuable probe of the dark matter distribution of massive galaxies, but also provide valuable cosmological constraints, either by studying the population of strong lenses or by measuring time delays in lensed quasars. due to the rarity of galaxy-scale strongly lensed systems, fast and reliable automated lens finding methods will be essential in the era of large surveys such as large synoptic survey telescope, euclid and wide-field infrared survey telescope. to tackle this challenge, we introduce cmu deeplens, a new fully automated galaxy-galaxy lens finding method based on deep learning. this supervised machine learning approach does not require any tuning after the training step which only requires realistic image simulations of strongly lensed systems. we train and validate our model on a set of 20 000 lsst-like mock observations including a range of lensed systems of various sizes and signal-to-noise ratios (s/n). we find on our simulated data set that for a rejection rate of non-lenses of 99 per cent, a completeness of 90 per cent can be achieved for lenses with einstein radii larger than 1.4 arcsec and s/n larger than 20 on individual g-band lsst exposures. finally, we emphasize the importance of realistically complex simulations for training such machine learning methods by demonstrating that the performance of models of significantly different complexities cannot be distinguished on simpler simulations. we make our code publicly available at https://github.com/mcwilliamscenter/cmudeeplens. | cmu deeplens: deep learning for automatic image-based galaxy-galaxy strong lens finding |
active galactic nuclei (agns) that show strong rest-frame optical/uv variability in their blue continuum and broad line emission are classified as changing-look agn, or at higher luminosities, changing-look quasars (clqs). these surprisingly large and sometimes rapid transitions challenge accepted models of quasar physics and duty cycles, offer several new avenues for study of quasar host galaxies, and open a wider interpretation of the cause of differences between broad and narrow-line agn. to better characterize extreme quasar variability, we present follow-up spectroscopy as part of a comprehensive search for clqs across the full sloan digital sky survey (sdss) footprint using spectroscopically confirmed quasars from the sdss dr7 catalog. our primary selection requires large-amplitude (| {{δ }}g| > 1 mag, | {{δ }}r| > 0.5 mag) variability over any of the available time baselines probed by the sdss and pan-starrs 1 surveys. we employ photometry from the catalina sky survey to verify variability behavior in clq candidates where available, and confirm clqs using optical spectroscopy from the william herschel, mmt, magellan, and palomar telescopes. for our adopted signal-to-noise ratio threshold on variability of broad hβ emission, we find 17 new clqs, yielding a confirmation rate of ≳20%. these candidates are at lower eddington ratio relative to the overall quasar population, which supports a disk-wind model for the broad line region. based on our sample, the clq fraction increases from 10% to roughly half as the continuum flux ratio between repeat spectra at 3420 å increases from 1.5 to 6. we release a catalog of more than 200 highly variable candidates to facilitate future clq searches. | changing-look quasar candidates: first results from follow-up spectroscopy of highly optically variable quasars |
the recent detection of ulasj1342+0928, a bright qso at z = 7.54, provides a powerful probe of the ionization state of the intervening intergalactic medium, potentially allowing us to set strong constraints on the epoch of reionization (eor). here we quantify the presence of ly α damping wing absorption from the eor in the spectrum of ulasj1342+0928. our bayesian framework simultaneously accounts for uncertainties on (i) the intrinsic qso emission (reconstructing the ly α profile from a covariance matrix of emission lines) and (ii) the distribution of h ii regions during reionization (from three different 1.63 gpc3 simulations spanning plausible eor morphologies). our analysis is complementary to the banados et al. discovery and accompanying davies et al. method paper as it focuses solely on the damping wing imprint redward of ly α (1218 < λ < 1230 å) and uses a different methodology for (i) and (ii). we recover weak evidence for damping wing absorption from our intermediate eor model yielding a volume-weighted neutral hydrogen fraction at z = 7.5: \bar{x}_{h i} = 0.21^{+0.17}_{-0.19} (68 per cent). these constraints depend weakly on the eor morphology. our limits are lower than those of the previous two analyses, though they are consistent at ∼ 1-1.5σ. we attribute differences to (i) a lower intrinsic amplitude for our recovered ly α profile and (ii) only considering transmission redward of ly α, reducing the available constraining power but making the results less model-dependent. our results are consistent with previous estimates of the eor history, supporting a moderately extended eor. | constraints on reionization from the z = 7.5 qso ulasj1342+0928 |
images of the linear polarizations of synchrotron radiation around active galactic nuclei (agns) highlight their projected magnetic field lines and provide key data for understanding the physics of accretion and outflow from supermassive black holes. the highest-resolution polarimetric images of agns are produced with very long baseline interferometry (vlbi). because vlbi incompletely samples the fourier transform of the source image, any image reconstruction that fills in unmeasured spatial frequencies will not be unique and reconstruction algorithms are required. in this paper, we explore some extensions of the maximum entropy method (mem) to linear polarimetric vlbi imaging. in contrast to previous work, our polarimetric mem algorithm combines a stokes i imager that only uses bispectrum measurements that are immune to atmospheric phase corruption, with a joint stokes q and u imager that operates on robust polarimetric ratios. we demonstrate the effectiveness of our technique on 7 and 3 mm wavelength quasar observations from the vlba and simulated 1.3 mm event horizon telescope observations of sgr a* and m87. consistent with past studies, we find that polarimetric mem can produce superior resolution compared to the standard clean algorithm, when imaging smooth and compact source distributions. as an imaging framework, mem is highly adaptable, allowing a range of constraints on polarization structure. polarimetric mem is thus an attractive choice for image reconstruction with the eht. | high-resolution linear polarimetric imaging for the event horizon telescope |
we present the evolution of ly$\alpha$ emission derived from 53 galaxies at $z=6.6-13.2$ that are identified by multiple jwst/nirspec spectroscopy programs of ero, ers, go, ddt, and gto. these galaxies fall on the star-formation main sequence and are the typical star-forming galaxies with uv magnitudes of $-22.5\leq m_\mathrm{uv}\leq-17.0$. we find that 15 out of 53 galaxies show ly$\alpha$ emission at the $>3\sigma$ levels, and obtain ly$\alpha$ equivalent width (ew) measurements and stringent $3\sigma$ upper limits for the 15 and 38 galaxies, respectively. confirming that ly$\alpha$ velocity offsets and line widths of our galaxies are comparable with those of low-redshift ly$\alpha$ emitters, we investigate the redshift evolution of the ly$\alpha$ ew. we find that ly$\alpha$ ews statistically decrease towards high redshifts on the ly$\alpha$ ew vs. $m_{\rm uv}$ plane for various probability distributions of the uncertainties. we then evaluate neutral hydrogen fractions $x_{\rm hi}$ with the ly$\alpha$ ew redshift evolution and the cosmic reionization simulation results on the basis of a bayesian inference framework, and obtain $x_{\rm hi}=0.59^{+0.15}_{-0.33}$, $0.81^{+0.09}_{-0.26}$, and $0.99^{+0.01}_{-0.05}$ at $z\sim7$, $8$, and $9-13$, respectively. these moderately large $x_{\rm hi}$ values are consistent with the planck cmb optical depth measurement and previous $x_{\rm hi}$ constraints from galaxy and qso ly$\alpha$ damping wing absorptions, and strongly indicate a late reionization history. such a late reionization history suggests that major sources of reionization would emerge late and be hosted by moderately massive halos in contrast with the widely-accepted picture of abundant low-mass objects for the sources of reionization. | ly$\\alpha$ emission at $z=7-13$: clear ly$\\alpha$ equivalent width evolution indicating the late cosmic reionization history |
the ionizing continuum from active galactic nuclei is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. furthermore, it provides hints on how matter accretes on to supermassive black holes. using hubble space telescope's wide field camera 3, we have constructed the first stacked ultraviolet (rest-frame wavelengths 600-2500 å) spectrum of 53 luminous quasars at z ≃ 2.4, with a state-of-the-art correction for the intervening lyman forest and lyman continuum absorption. the continuum slope (f_ν ∝ ν ^{α _ν }) of the full sample shows a break at ∼912 å with spectral index αν = -0.61 ± 0.01 at λ > 912 å and a softening at shorter wavelengths (αν = -1.70 ± 0.61 at λ ≤ 912 å). our analysis proves that a proper intergalactic medium absorption correction is required to establish the intrinsic continuum emission of quasars. we interpret our average ultraviolet spectrum in the context of photoionization, accretion disc models, and quasar contribution to the ultraviolet background. we find that observed broad line ratios are consistent with those predicted assuming an ionizing slope of αion = -2.0, similar to the observed ionizing spectrum in the same wavelength range. the continuum break and softening are consistent with accretion disc plus x-ray corona models when black hole spin is taken into account. our spectral energy distribution yields a 30 per cent increase to previous estimates of the specific quasar emissivity, such that quasars may contribute significantly to the total specific lyman limit emissivity estimated from the lyα forest at z < 3.2. | the first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from wfc3 |
we present a jwst/mrs spectrum of the quasar j1120+0641 at z=7.0848, the first spectroscopic observation of a reionisation-era quasar in the rest-frame infrared ($0.6<\lambda<3.4\mu$m). in the context of the mysterious fast assembly of the first supermassive black holes at z>7, our observations enable for the first time the detection of hot torus dust, the h$\alpha$ emission line, and the paschen-series broad emission lines in a quasar at z>7. hot torus dust is clearly detected as an upturn in the continuum emission at $\lambda_{\text{rest}}\simeq1.3\mu$m, leading to a black-body temperature of $t=1413.5^{+5.7}_{-7.4}$k. compared to similarly-luminous quasars at 0<z<6, the hot dust in j1120+0641 is somewhat elevated in temperature (top 1%). the temperature is more typical among 6<z<6.5 quasars (top 25%), leading us to postulate a weak evolution in the hot dust temperature at z>6 ($2\sigma$ significance). we measure the black hole mass of j1120+0641 based on the h$\alpha$ balmer line, $m_{\text{bh}}=1.52\pm0.17\cdot 10^9 m_\odot$, which is in good agreement with the previous rest-uv mgii black hole mass measurement. the black hole mass based on the paschen-series lines is also consistent, indicating no significant extinction in the rest-frame uv measurement. the broad h$\alpha$, pa-$\alpha$ and pa-$\beta$ emission lines are consistent with an origin in a common broad-line region (blr) with density log$n_h/\text{cm}^{-3}\geq 12$, ionisation parameter $-7<$log$u<-4$, and extinction e(b-v)$\lesssim 0.1$mag. these blr parameters are consistent with similarly-bright quasars at 0<z<4. overall, we find that both j1120+0641's hot dust torus and hydrogen blr properties show no significant peculiarity when compared to luminous quasars down to z=0. the quasar accretion structures must have therefore assembled very quickly, as they appear fully "mature" less than 760 million years after the big bang. | first rest-frame infrared spectrum of a z>7 quasar: jwst/mrs observations of j1120+0641 |
multiple pulsar timing array (pta) collaborations have recently reported the first detection of gravitational waves (gws) of nanohertz frequencies. the signal is expected to be primarily sourced by inspiralling supermassive black hole binaries (smbhbs) and these first results are broadly consistent with the expected gw spectrum from such a population. curiously, the measured amplitude of the gw background in all announced results is a bit larger than theoretical predictions. in this work, we show that the amplitude of the stochastic gravitational wave background (sgwb) predicted from the present-day abundance of smbhs derived from local scaling relations is significantly smaller than that measured by the ptas. we demonstrate that this difference cannot be accounted for through changes in the merger history of smbhs and that there is an upper limit to the boost to the characteristic strain from multiple merger events, due to the fact that they involve black holes of decreasing masses. if we require the current estimate of the black hole mass density -- equal to the integrated quasar luminosity function through the classic soltan argument -- to be preserved, then the currently measured pta result would imply that the typical total mass of smbhs contributing to the background should be at least $\sim 3 \times 10^{10} m_\odot$, a factor of $\sim 10$ larger than previously predicted. the required space density of such massive black holes corresponds to order $10$ $3 \times 10^{10} m_\odot$ smbhs within the volume accessible by stellar and gas dynamical smbh measurements. by virtue of the gw signal being dominated by the massive end of the smbh distribution, pta measurements offer a unique window into such rare objects and complement existing electromagnetic observations. | where are nanograv's big black holes? |
we present an analysis of a sample of robust high-redshift galaxies selected from the 'blank' fields of the prime extragalactic areas for reionization science (pearls) survey and early release observations (ero) data from jwst with the aim of selecting candidate high-redshift active galactic nuclei (agn). sources were identified from this parent sample using a threefold selection procedure, which includes spectral energy distribution (sed) fitting to identify sources that are best fitted by agn sed templates, a further selection based on the relative performance of agn and non-agn models, and finally morphological fitting to identify compact sources of emission, resulting in a purity-oriented procedure. using this procedure, we identify a sample of nine agn candidates at 6.5 < z < 12, from which we constrain their physical properties as well as measure a lower bound on the agn fraction in this redshift range of 5 ± 1 per cent. as this is an extreme lower limit due to our focus on purity and our seds being calibrated for unobscured type 1 agn, this demonstrates that agn are perhaps quite common at this early epoch. the rest-frame uv colours of our candidate objects suggest that these systems are potentially candidate obese black hole galaxies (obgs). we also investigate chandra and vla maps of these areas from which we calculate detection limits. of note is a z = 11.9 candidate source exhibiting an abrupt morphological shift in the reddest band as compared to bluer bands, indicating a potential merger or an unusually strong outflow. | epochs vii: discovery of high-redshift (6.5 < z < 12) agn candidates in jwst ero and pearls data |
we present a detailed characterization of the 849 broad-line quasars from the sloan digital sky survey reverberation mapping (sdss-rm) project. our quasar sample covers a redshift range of 0.1 < z < 4.5 and is flux-limited to i psf < 21.7 without any other cuts on quasar properties. the main sample characterization includes: (1) spectral measurements of the continuum and broad emission lines for individual objects from the coadded first-season spectroscopy in 2014, (2) identification of broad and narrow absorption lines in the spectra, and (3) optical variability properties for continuum and broad lines from multi-epoch spectroscopy. we provide improved systemic redshift estimates for all quasars and demonstrate the effects of the signal-to-noise ratio on the spectral measurements. we compile measured properties for all 849 quasars along with supplemental multi-wavelength data for subsets of our sample from other surveys. the sdss-rm sample probes a diverse range in quasar properties and shows well-detected continuum and broad-line variability for many objects from first-season monitoring data. the compiled properties serve as the benchmark for follow-up work based on sdss-rm data. the spectral fitting tools are made public along with this work. | the sloan digital sky survey reverberation mapping project: sample characterization |
in the current paper, a dark energy (de) model reconstructed from the well‑motivated deceleration parameter (dp) is analyzed. a flat frw universe filled with radiation, dark matter (dm), and dark energy fluids is considered. the free parameters are constrained using measurements from supernovae, hubble, gamma ray bursts, quasars, and baryon acoustic oscillations. the model under study is found to be very supported by observation with respect to λcdm since . besides, a cosmographic analysis is performed showing that the reconstructed model behaves similarly as λcdm does. finally, a diagnostic analysis is performed reporting that the studied model behaves quintessence type at a late time.in the current paper, a dark energy (de) model reconstructed from the well‑motivated deceleration parameter (dp) is analyzed. a flat frw universe filled with radiation, dark matter (dm), and dark energy fluids is considered. the free parameters are constrained using measurements from supernovae, hubble, gamma ray bursts, quasars, and baryon acoustic oscillations. the model under study is found to be very supported by observation with respect to λcdm since . besides, a cosmographic analysis is performed showing that the reconstructed model behaves similarly as λcdm does. finally, a diagnostic analysis is performed reporting that the studied model behaves quintessence type at a late time. | observational constraining study of new deceleration parameters in frw universe |
this paper introduces a novel cosmological model aimed at probing the accelerated expansion of the late universe through a unique parametrization of the deceleration parameter. we aim to constrain key cosmic parameters by integrating recent measurements of the hubble parameter obtained from various observational methods, including cosmic chronometers, type ia supernovae, gamma-ray bursts (grb), quasars, and baryon acoustic oscillations (bao) from recent galaxy surveys. with a redshift range spanning (0.106 < z < 2.33) and incorporating the latest hubble constant measurement from riess in 2022, our analysis yields optimal fit values for the hubble parameter $h_{0}$ and sound horizon $r_{d}$. notably, we uncover an inconsistency in $h_{0}$ values derived from late-time observational measurements, reflecting the well-known $h_{0}$ tension. in terms of $r_{d}$, while there is close agreement between joint analysis and joint analysis with r22, discrepancies arise upon gradual inclusion of bao and bao with r22 datasets. our model demonstrates excellent fit to observed data and aligns well with the standard $\lambda$cdm paradigm at higher redshifts. however, its most intriguing aspect lies in predicting a super-accelerated expansion in the distant future, in contrast to the de sitter phase predicted by $\lambda$cdm. additionally, unique behaviors in the jerk parameter hint at novel dynamics beyond traditional cosmological models. statefinder and $o_{m}$ diagnostics tests were conducted, and comparison using the akaike information criterion indicates neither model can be ruled out based on the latest observational measurements. these findings propose our cosmological model as a compelling alternative to $\lambda$cdm, offering fresh insights into dark energy's nature and the cosmos' future. | addressing the $r_{d}$ tension using late-time observational measurements in a novel deceleration parametrization |
gravitational time delays, observed in strong lens systems where the variable background source is multiply imaged by a massive galaxy in the foreground, provide direct measurements of cosmological distance that are very complementary to other cosmographic probes. the success of the technique depends on the availability and size of a suitable sample of lensed quasars or supernovae, precise measurements of the time delays, accurate modeling of the gravitational potential of the main deflector, and our ability to characterize the distribution of mass along the line of sight to the source. we review the progress made during the last 15 years, during which the first competitive cosmological inferences with time delays were made, and look ahead to the potential of significantly larger lens samples in the near future. | time delay cosmography |
concerted effort is currently ongoing to open up the epoch of reionization (eor) ($z\sim$15-6) for studies with ir and radio telescopes. whereas ir detections have been made of sources (lyman-$\alpha$ emitters, quasars and drop-outs) in this redshift regime in relatively small fields of view, no direct detection of neutral hydrogen, via the redshifted 21-cm line, has yet been established. such a direct detection is expected in the coming years, with ongoing surveys, and could open up the entire universe from $z\sim$6-200 for astrophysical and cosmological studies, opening not only the eor, but also its preceding cosmic dawn ($z\sim$30-15) and possibly even the later phases of the dark ages ($z\sim$200-30). all currently ongoing experiments attempt statistical detections of the 21-cm signal during the eor, with limited signal-to-noise. direct imaging, except maybe on the largest (degree) scales at lower redshifts, as well as higher redshifts will remain out of reach. the square kilometre array(ska) will revolutionize the field, allowing direct imaging of neutral hydrogen from scales of arc-minutes to degrees over most of the redshift range $z\sim$6-28 with ska1-low, and possibly even higher redshifts with the ska2-low. in this ska will be unique, and in parallel provide enormous potential of synergy with other upcoming facilities (e.g. jwst). in this chapter we summarize the physics of 21-cm emission, the different phases the universe is thought to go through, and the observables that the ska can probe, referring where needed to detailed chapters in this volume (abridged). | the cosmic dawn and epoch of reionisation with ska |
we review current understanding of the population of radio galaxies and radio-loud quasars from an observational perspective, focusing on their large-scale structures and dynamics. we discuss the physical conditions in radio galaxies, their fuelling and accretion modes, host galaxies and large-scale environments, and the role(s) they play as engines of feedback in the process of galaxy evolution. finally we briefly summarise other astrophysical uses of radio galaxy populations, including the study of cosmic magnetism and cosmological applications, and discuss future prospects for advancing our understanding of the physics and feedback behaviour of radio galaxies. | radio galaxies and feedback from agn jets |
recently we have shown that high-energy neutrinos above 200 tev detected by icecube are produced within several parsecs in the central regions of radio-bright blazars, that is active galactic nuclei with jets pointing toward us. to independently test this result and extend the analysis to a wider energy range, we use public data for all neutrino energies from seven years of icecube observations. the icecube point-source likelihood map is analyzed against the positions of blazars from a statistically complete sample selected according to their compact radio flux density. the latter analysis delivers a 3.0σ significance, with the combined post-trial significance of both studies being 4.1σ. the correlation is driven by a large number of blazars. together with fainter but physically similar sources not included in the sample, they may explain the entire icecube astrophysical neutrino flux as derived from muon-track analyses. the neutrinos can be produced in interactions of relativistic protons with x-ray self-compton photons in parsec-scale blazar jets. | directional association of tev to pev astrophysical neutrinos with radio blazars |
context. the low frequency array (lofar) is the only radio telescope that is presently capable of high-sensitivity, high-resolution (i.e. < 1 mjy beam−1 and < 15″) observations at ultra-low frequencies (< 100 mhz). to utilise these capabilities, the lofar surveys key science project is undertaking a large survey to cover the entire northern sky with low band antenna (lba) observations.aims: the lofar lba sky survey (lolss) aims to cover the entire northern sky with 3170 pointings in the frequency range between 42 − 66 mhz, at a resolution of 15″ and at a sensitivity of 1 mjy beam−1 (1σ). in this work, we outline the survey strategy, the observational status, and the calibration techniques. we also briefly describe several of our scientific motivations and present the preliminary public data release.methods: the preliminary images were produced using a fully automated pipeline aimed at correcting all direction-independent effects in the data. whilst the direction-dependent effects, such as those from the ionosphere, have not yet been corrected, the images presented in this work are still ten times more sensitive than previous available surveys at these low frequencies.results: the preliminary data release covers 740 deg2 around the hetdex spring field region at an angular resolution of 47″ with a median noise level of 5 mjy beam−1. the images and the catalogue of 25 247 sources have been publicly released. we demonstrate that the system is capable of reaching a root mean square (rms) noise of 1 mjy beam−1 and an angular resolution of 15″ once direction-dependent effects are accounted for.conclusions: lolss will provide the ultra-low-frequency information for hundreds of thousands of radio sources, providing critical spectral information and producing a unique data set that can be used for a wide range of science topics, such as the search for high redshift galaxies and quasars, the study of the magnetosphere of exoplanets, and the detection of the oldest populations of cosmic-rays in galaxies, clusters of galaxies, as well as those produced by active galactic nuclei. table 4 and fig. 11 (fits) are available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or viahttp://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/648/a104 | the lofar lba sky survey. i. survey description and preliminary data release |
we present x-shooter near-ir spectroscopy of a large sample of 38 luminous (m1450 = -29.0 to -24.4) quasars at 5.78 < z < 7.54, which have complementary [c ii]158μm observations from alma. this x-shooter/alma sample provides us with the most comprehensive view of reionization-era quasars to date, allowing us to connect the quasar properties with those of its host galaxy. in this work we introduce the sample, discuss data reduction and spectral fitting, and present an analysis of the broad emission line properties. the measured fe ii/mg ii flux ratio suggests that the broad-line regions of all quasars in the sample are already enriched in iron. we also find the mg ii line to be on average blueshifted with respect to the [c ii] redshift with a median of -391 km s-1. a significant correlation between the mg ii-[c ii]158μm and c iv-[c ii]158μm velocity shifts indicates a common physical origin. furthermore, we frequently detect large c iv-mg ii emission line velocity blueshifts in our sample with a median value of -1848 km s-1. while we find all other broad emission line properties not to be evolving with redshift, the median c iv-mg ii blueshift is much larger than found in low-redshift, luminosity-matched quasars (-800 km s-1). dividing our sample into two redshift bins, we confirm an increase of the average c iv-mg ii blueshift with increasing redshift. future observations of the rest-frame optical spectrum with the james webb space telescope will be instrumental in further constraining the possible evolution of quasar properties in the epoch of reionization. | the x-shooter/alma sample of quasars in the epoch of reionization. i. nir spectral modeling, iron enrichment, and broad emission line properties |
we explore the abundance, spatial distribution, and physical properties of the o vi, o vii, and o viii ions of oxygen in circumgalactic and intergalactic media (the cgm, igm, and whim). we use the tng100 and tng300 large volume cosmological magnetohydrodynamical simulations. modelling the ionization states of simulated oxygen, we find good agreement with observations of the low-redshift o vi column density distribution function (cddf), and present its evolution for all three ions from z = 0 to z = 4. producing mock quasar absorption line spectral surveys, we show that the illustristng simulations are fully consistent with constraints on the o vi content of the cgm from cos-haloes and other low-redshift observations, producing columns as high as observed. we measure the total amount of mass and average column densities of each ion using hundreds of thousands of simulated galaxies spanning 10^{11} < {m}_halo/ m⊙<1015 corresponding to 109 < m⋆/ m⊙<1012 in stellar mass. stacked radial profiles of o vi are computed in 3d number density and 2d projected column density, decomposing into 1-halo and 2-halo terms. relating halo o vi to properties of the central galaxy, we find a correlation between the (g - r) colour of a galaxy and the total amount of o vi in its cgm. in comparison to the cos-haloes finding, this leads to a dichotomy of columns around star-forming versus passive galaxies at fixed stellar (or halo) mass. we demonstrate that this correlation is a direct result of black hole feedback associated with quenching and represents a causal consequence of galactic-scale baryonic feedback impacting the physical state of the circumgalactic medium. | the abundance, distribution, and physical nature of highly ionized oxygen o vi, o vii, and o viii in illustristng |
on 2015 june 16, fermi-lat observed a giant outburst from the flat spectrum radio quasar 3c 279 with a peak >100 mev flux of ∼3.6 × 10-5 photons cm-2 s-1, averaged over orbital period intervals. it is historically the highest γ-ray flux observed from the source, including past egret observations, with the γ-ray isotropic luminosity reaching ∼1049 erg s-1. during the outburst, the fermi spacecraft, which has an orbital period of 95.4 minutes, was operated in a special pointing mode to optimize the exposure for 3c 279. for the first time, significant flux variability at sub-orbital timescales was found in blazar observations by fermi-lat. the source flux variability was resolved down to 2-minute binned timescales, with flux doubling times of less than 5 minutes. the observed minute-scale variability suggests a very compact emission region at hundreds of schwarzschild radii from the central engine in conical jet models. a minimum bulk jet lorentz factor (γ) of 35 is necessary to avoid both internal γ-ray absorption and super-eddington jet power. in the standard external radiation comptonization scenario, γ should be at least 50 to avoid overproducing the synchrotron self-compton component. however, this predicts extremely low magnetization (∼5 × 10-4). equipartition requires γ as high as 120, unless the emitting region is a small fraction of the dissipation region. alternatively, we consider γ rays originating as synchrotron radiation of γ e ∼ 1.6 × 106 electrons, in a magnetic field b ∼ 1.3 kg, accelerated by strong electric fields e ∼ b in the process of magnetoluminescence. at such short distance scales, one cannot immediately exclude the production of γ-rays in hadronic processes. | minute-timescale >100 mev γ-ray variability during the giant outburst of quasar 3c 279 observed by fermi-lat in 2015 june |
relativistic jets are associated with extreme astrophysical phenomena, like the core collapse of massive stars in gamma-ray bursts (grbs) and the accretion on to supermassive black holes in active galactic nuclei. it is generally accepted that these jets are powered electromagnetically, by the magnetized rotation of a central compact object (black hole or neutron star). however, how the jets produce the observed emission and survive the propagation for many orders of magnitude in distance without being disrupted by current-driven instabilities is the subject of active debate. we carry out time-dependent 3d relativistic magnetohydrodynamic (mhd) simulations of relativistic, poynting-flux-dominated jets. the jets are launched self-consistently by the rotation of a strongly magnetized central object. this determines the natural degree of azimuthal magnetic field winding, a crucial factor that controls jet stability. we find that the jets are susceptible to two types of instability: (i) a global, external kink mode that grows on long time-scales. it bodily twists the jet, reducing its propagation velocity. we show analytically that in flat density profiles, like the ones associated with galactic cores, the external mode grows and may stall the jet. in the steep profiles of stellar envelopes the external kink weakens as the jet propagates outward. (ii) a local, internal kink mode that grows over short time-scales and causes small-angle magnetic reconnection and conversion of about half of the jet electromagnetic energy flux into heat. we suggest that internal kink instability is the main dissipation mechanism responsible for powering grb prompt emission. | relativistic mhd simulations of core-collapse grb jets: 3d instabilities and magnetic dissipation |
we examine the connection between the properties of the circumgalactic medium (cgm) and the quenching and morphological evolution of central galaxies in the eagle and illustristng simulations. the simulations yield very different median cgm mass fractions, fcgm, as a function of halo mass, m200, with low-mass haloes being significantly more gas-rich in illustristng than in eagle. nonetheless, in both cases scatter in fcgm at fixed m200 is strongly correlated with the specific star formation rate and the kinematic morphology of central galaxies. the correlations are strongest for ∼l⋆ galaxies, corresponding to the mass scale at which agn feedback becomes efficient. this feedback elevates the cgm cooling time, preventing gas from accreting on to the galaxy to fuel star formation, and thus establishing a preference for quenched, spheroidal galaxies to be hosted by haloes with low fcgm for their mass. in both simulations, fcgm correlates negatively with the host halo's intrinsic concentration, and hence with its binding energy and formation redshift, primarily because early halo formation fosters the rapid early growth of the central black hole (bh). this leads to a lower fcgm at fixed m200 in eagle because the bh reaches high accretion rates sooner, whilst in illustristng it occurs because the central bh reaches the mass threshold at which agn feedback is assumed to switch from thermal to kinetic injection earlier. despite these differences, there is consensus from these state-of-the-art simulations that the expulsion of efficiently cooling gas from the cgm is a crucial step in the quenching and morphological evolution of central galaxies. | the quenching and morphological evolution of central galaxies is facilitated by the feedback-driven expulsion of circumgalactic gas |
understanding how super-massive black holes form and grow in the early universe has become a major challenge1,2 since it was discovered that luminous quasars existed only 700 million years after the big bang3,4. simulations indicate an evolutionary sequence of dust-reddened quasars emerging from heavily dust-obscured starbursts that then transition to unobscured luminous quasars by expelling gas and dust5. although the last phase has been identified out to a redshift of 7.6 (ref. 6), a transitioning quasar has not been found at similar redshifts owing to their faintness at optical and near-infrared wavelengths. here we report observations of an ultraviolet compact object, gnz7q, associated with a dust-enshrouded starburst at a redshift of 7.1899 ± 0.0005. the host galaxy is more luminous in dust emission than any other known object at this epoch, forming 1,600 solar masses of stars per year within a central radius of 480 parsec. a red point source in the far-ultraviolet is identified in deep, high-resolution imaging and slitless spectroscopy. gnz7q is extremely faint in x-rays, which indicates the emergence of a uniquely ultraviolet compact star-forming region or a compton-thick super-eddington black-hole accretion disk at the dusty starburst core. in the latter case, the observed properties are consistent with predictions from cosmological simulations7 and suggest that gnz7q is an antecedent to unobscured luminous quasars at later epochs. | a dusty compact object bridging galaxies and quasars at cosmic dawn |
we present 1-7 ghz high-resolution radio imaging (vla and e-merlin) and spatially resolved ionized gas kinematics for 10 z < 0.2 type 2 `obscured' quasars (log [lagn/erg s-1] ≳ 45) with moderate radio luminosities (log [l_{1.4 ghz}/w hz-1] = 23.3-24.4). these targets were selected to have known ionized outflows based on broad [o iii] emission-line components (full width at half-maximum ≈ 800-1800 km s-1). although `radio-quiet' and not `radio agn' by many traditional criteria, we show that for nine of the targets, star formation likely accounts for ≲10 per cent of the radio emission. we find that ∼80-90 per cent of these nine targets exhibit extended radio structures on 1-25 kpc scales. the quasars' radio morphologies, spectral indices, and position on the radio size-luminosity relationship reveals that these sources are consistent with being low power compact radio galaxies. therefore, we favour radio jets as dominating the radio emission in the majority of these quasars. the radio jets we observe are associated with morphologically and kinematically distinct features in the ionized gas, such as increased turbulence and outflowing bubbles, revealing jet-gas interaction on galactic scales. importantly, such conclusions could not have been drawn from current low-resolution radio surveys such as first. our observations support a scenario where compact radio jets, with modest radio luminosities, are a crucial feedback mechanism for massive galaxies during a quasar phase. | prevalence of radio jets associated with galactic outflows and feedback from quasars |
the gaia galactic survey mission is designed and optimized to obtain astrometry, photometry, and spectroscopy of nearly two billion stars in our galaxy. yet as an all-sky multi-epoch survey, gaia also observes several million extragalactic objects down to a magnitude of g ∼ 21 mag. due to the nature of the gaia onboard-selection algorithms, these are mostly point-source-like objects. using data provided by the satellite, we have identified quasar and galaxy candidates via supervised machine learning methods, and estimate their redshifts using the low resolution bp/rp spectra. we further characterise the surface brightness profiles of host galaxies of quasars and of galaxies from pre-defined input lists. here we give an overview of the processing of extragalactic objects, describe the data products in gaia dr3, and analyse their properties. two integrated tables contain the main results for a high completeness, but low purity (50−70%), set of 6.6 million candidate quasars and 4.8 million candidate galaxies. we provide queries that select purer sub-samples of these containing 1.9 million probable quasars and 2.9 million probable galaxies (both ∼95% purity). we also use high quality bp/rp spectra of 43 thousand high probability quasars over the redshift range 0.05−4.36 to construct a composite quasar spectrum spanning restframe wavelengths from 72−1000 nm. full table 8 is only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/674/a41. | gaia data release 3. the extragalactic content |
the milky way hosts a hot (≈2 × 106 k), diffuse, gaseous halo based on detections of z = 0 o vii and o viii absorption lines in quasar spectra and emission lines in blank-sky spectra. here we improve constraints on the structure of the hot gas halo by fitting a radial model to a much larger sample of o vii and o viii emission line measurements from xmm-newton/epic-mos spectra compared to previous studies (≈650 sightlines). we assume a modified β-model for the halo density distribution and a constant-density local bubble from which we calculate emission to compare with the observations. we find an acceptable fit to the o viii emission line observations with χ 2red (dof) = 1.08 (644) for best-fit parameters of no r_c3β= 1.35 +/- 0.24 cm-3 kpc3β and β = 0.50 ± 0.03 for the hot gas halo and negligible local bubble contribution. the o vii observations yield an unacceptable χ 2red (dof) = 4.69 (645) for similar best-fit parameters, which is likely due to temperature or density variations in the local bubble. the o viii fitting results imply hot gas masses of m(<50 kpc) = 3.8-0.3+0.3 × 109 m⊙and m(<250 kpc) = 4.3-0.8+0.9 × 1010 m⊙ , accounting for lsim50% of the milky way's missing baryons. we also explore our results in the context of optical depth effects in the halo gas, the halo gas cooling properties, temperature and entropy gradients in the halo gas, and the gas metallicity distribution. the combination of absorption and emission line analyses implies a sub-solar gas metallicity that decreases with radius, but that also must be >=0.3 z ⊙ to be consistent with the pulsar dispersion measure toward the large magellanic cloud. | constraining the milky way's hot gas halo with o vii and o viii emission lines |
the bolometric luminosity of active galactic nuclei (agns) is difficult to determine, and various approximations have been used to calibrate it against different observed properties. here, i combine theoretical calculations of optically thick, geometrically thin accretion discs, and observed x-ray properties of agn, to provide new bolometric correction factors (kbol) over a large range of black hole (bh) mass, accretion rate, and spin. this is particularly important in cases where the mass accretion rate cannot be determined from the observed spectral energy distribution, and in cases where luminosity-independent correction factors have been used. simple power-law approximations of kbol are provided for l(5100 å), l(3000 å), l(1400 å), l(2-10 kev), and l(narrow hβ). in all cases, the uncertainties are large mostly due to the unknown bh spin. prior knowledge of the bh mass reduces the uncertainty considerably. | bolometric correction factors for active galactic nuclei |
we characterize the thermal state of the intergalactic medium (igm) in 10 redshift bins in the range 2 ≤ z ≤ 4 with a sample of 103 high-resolution, high s/n ly α forest spectra using four different flux distribution statistics. our measurements are calibrated with mock spectra from a large suite of hydrodynamical simulations post-processed with our thermal igm evolution code cite, finely sampling amplitude, and slope of the expected temperature-density relation. the thermal parameters inferred from our measurements of the flux power spectrum, doppler parameter distribution, as well as wavelet and curvature statistics agree well within their respective errors and all clearly show the peak in temperature and minimum in slope of the temperature density relation expected from he ii reionization. combining our measurements from the different flux statistics gives t0 = (14 750 ± 1322) k for the peak temperature at mean density and a corresponding minimum slope γ = 1.225 ± 0.120. the peak in the temperature evolution occurs around z ≈ 3, in agreement with previous measurements that had suggested the presence of such a peak, albeit with a large scatter. using cite, we also calculate the thermal state of the igm predicted by five widely used (spatially homogeneous) uv-background models. the rather rapid thermal evolution inferred by our measurements is well reproduced by two of the models, if we assume (physically well motivated) non-equilibrium evolution with photoheating rates that are reduced by a moderate factor of ~0.7-0.8. the other three models predict he ii reionization to be more extended with a higher temperature peak occurring somewhat earlier than our measurements suggest. | a consistent and robust measurement of the thermal state of the igm at 2 ≤ z ≤ 4 from a large sample of ly α forest spectra: evidence for late and rapid he ii reionization |
we present a systematic investigation of the circumgalactic medium (cgm) within projected distances d < 160 kpc of luminous red galaxies (lrgs). the sample comprises 16 intermediate-redshift (z = 0.21-0.55) lrgs of stellar mass m_star> 10^{11} m_\odot. combining far-ultraviolet cosmic origin spectrograph spectra from the hubble space telescope and optical echelle spectra from the ground enables a detailed ionization analysis based on resolved component structures of a suite of absorption transitions, including the full h i lyman series and various ionic metal transitions. by comparing the relative abundances of different ions in individually matched components, we show that cool gas (t ∼ 104 k) density and metallicity can vary by more than a factor of 10 in an lrg halo. specifically, metal-poor absorbing components with <1/10 solar metallicity are seen in 50 per cent of the lrg haloes, while gas with solar and super-solar metallicity is also common. these results indicate a complex multiphase structure and poor chemical mixing in these quiescent haloes. we calculate the total surface mass density of cool gas, σcool, by applying the estimated ionization fraction corrections to the observed h i column densities. the radial profile of σcool is best described by a projected einasto profile of slope α = 1 and scale radius rs = 48 kpc. we find that typical lrgs at z ∼ 0.4 contain cool gas mass of \mathit {m_{cool} = (1-2)× 10^{10} m_\odot } at d < 160 kpc (or as much as \mathit {m_{cool} ≈ 4× 10^{10} m_\odot } at d < 500 kpc), comparable to the cool cgm mass of star-forming galaxies. furthermore, we show that high-ionization o vi and low-ionization absorption species exhibit distinct velocity profiles, highlighting their different physical origins. we discuss the implications of our findings for the origin and fate of cool gas in lrg haloes. | characterizing circumgalactic gas around massive ellipticals at z ∼ 0.4 - ii. physical properties and elemental abundances |
we conduct global three-dimensional radiation magnetohydrodynamic simulations of the inner regions of accretion flows around a 5 × 108 m ⊙ black hole, with mass accretion rates reaching 7% and 20% of the eddington value. we choose initial field topologies that result in an inner disk supported by magnetic pressure, with surface density significantly smaller than the values predicted by the standard thin-disk model as well as a much larger disk scale height. the disks do not show any sign of thermal instability over many thermal timescales. more than half of the accretion is driven by radiation viscosity in the optically thin coronal region for the case of the lower accretion rate, while accretion in the optically thick part of the disk is driven by the maxwell and reynolds stresses from turbulence caused by magnetorotational instability. optically thin plasma with gas temperatures ≳108 k is generated only in the inner ≈10 gravitational radii in both simulations, and is more compact in the case of the higher accretion rate. such plasma does not form at larger radii because the surface density increases outward with radius, causing less dissipation outside the photosphere. in contrast to standard thin-disk models, the surface density in our simulations increases with increasing mass accretion rate at each radius. this causes a relatively weaker hot plasma component for the simulation with a higher accretion rate. we suggest that these results may provide a physical mechanism for understanding some of the observed properties of coronae and spectra of active galactic nuclei. | global radiation magnetohydrodynamic simulations of sub-eddington accretion disks around supermassive black holes |
we analyse the clustering of the sloan digital sky survey iv extended baryon oscillation spectroscopic survey data release 14 quasar sample (dr14q). we measure the redshift space distortions using the power-spectrum monopole, quadrupole, and hexadecapole inferred from 148 659 quasars between redshifts 0.8 and 2.2, covering a total sky footprint of 2112.9 deg2. we constrain the logarithmic growth of structure times the amplitude of dark matter density fluctuations, fσ8, and the alcock-paczynski dilation scales that allow constraints to be placed on the angular diameter distance da(z) and the hubble h(z) parameter. at the effective redshift of zeff = 1.52, fσ8(zeff) = 0.420 ± 0.076, h(z_eff)=[162± 12] (r_s^fid/r_s) {km s}^{-1} mpc^{-1}, and d_a(z_eff)=[1.85± 0.11]× 10^3 (r_s/r_s^fid) mpc, where rs is the comoving sound horizon at the baryon drag epoch and the superscript `fid' stands for its fiducial value. the errors take into account the full error budget, including systematics and statistical contributions. these results are in full agreement with the current λ-cold dark matter cosmological model inferred from planck measurements. finally, we compare our measurements with other eboss companion papers and find excellent agreement, demonstrating the consistency and complementarity of the different methods used for analysing the data. | the clustering of the sdss-iv extended baryon oscillation spectroscopic survey dr14 quasar sample: structure growth rate measurement from the anisotropic quasar power spectrum in the redshift range 0.8 < z < 2.2 |
we analyze the parsec-scale jet kinematics from 2007 june to 2018 december of a sample of γ-ray bright blazars monitored roughly monthly with the very long baseline array (vlba) at 43 ghz under the vlba-bu-blazar program. we implement a novel piecewise linear fitting method to derive the kinematics of 521 distinct emission knots from a total of 3705 total intensity images in 22 quasars, 13 bl lacertae objects, and 3 radio galaxies. apparent speeds of these components range from 0.01c to 78c, and 18.6% of knots (other than the "core") are quasi-stationary. one-fifth of moving knots exhibit nonballistic motion, with acceleration along the jet within 5 pc of the core (projected) and deceleration farther out. these accelerations occur mainly at locations coincident with quasi-stationary features. we calculate the physical parameters of 273 knots with statistically significant motion, including their doppler factors, lorentz factors, and viewing angles. we determine the typical values of these parameters for each jet and the average for each subclass of active galactic nuclei. we investigate the variability of the position angle of each jet over the 10 yr of monitoring. the fluctuations in position of the quasi-stationary components in radio galaxies tend to be parallel to the jet, while no directional preference is seen in the components of quasars and bl lacertae objects. we find a connection between γ-ray states of blazars and their parsec-scale jet properties, with blazars with brighter 43 ghz cores typically reaching higher γ-ray maxima during flares. | kinematics of parsec-scale jets of gamma-ray blazars at 43 ghz during 10 yr of the vlba-bu-blazar program |
we use updated hubble parameter and baryon acoustic oscillation data, as well as other lower redshift type ia supernova, mg ii reverberation-measured quasar, quasar angular size, h ii starburst galaxy, and amati-correlated gamma-ray burst data, to jointly constrain cosmological parameters in six cosmological models. the joint analysis provides model-independent determinations of the hubble constant, $h_0=69.7\pm 1.2\, \rm {km \ s^{-1} \ mpc^{-1}}$ and the current non-relativistic matter density parameter, ωm0 = 0.295 ± 0.017. these error bars are factors of 2.2 and 2.3 larger than the corresponding error bars in the flat λcdm model from planck tt,te,ee+lowe + lensing cosmic microwave background anisotropy data. based on the deviance information criterion (dic), the flat λcdm model is most favoured but mild dark energy dynamics and a little spatial curvature are not ruled out. | using lower redshift, non-cmb, data to constrain the hubble constant and other cosmological parameters |
the next two decades are expected to open the door to the first coincident detections of electromagnetic (em) and gravitational-wave (gw) signatures associated with massive black-hole (mbh) binaries heading for coalescence. these detections will launch a new era of multimessenger astrophysics by expanding this growing field to the low-frequency gw regime and will provide an unprecedented understanding of the evolution of mbhs and galaxies. they will also constitute fundamentally new probes of cosmology and would enable unique tests of gravity. the aim of this living review is to provide an introduction to this research topic by presenting a summary of key findings, physical processes and ideas pertaining to em counterparts to mbh mergers as they are known at the time of this writing. we review current observational evidence for close mbh binaries, discuss relevant physical processes and timescales, and summarize the possible em counterparts to gws in the precursor, coalescence, and afterglow stages of a mbh merger. we also describe open questions and discuss future prospects in this dynamic and quick-paced research area. | electromagnetic counterparts to massive black-hole mergers |
context. understanding the physics and geometry of accretion and ejection around super massive black holes (smbhs) is important to understand the evolution of active galactic nuclei (agn) and therefore of the large scale structures of the universe.aims: we aim at providing a simple, coherent, and global view of the sub-parsec accretion and ejection flow in agn with varying eddington ratio, ṁ, and black hole mass, mbh.methods: we made use of theoretical insights, results of numerical simulations, as well as uv and x-ray observations to review the inner regions of agn by including different accretion and ejection modes, with special emphasis on the role of radiation in driving powerful accretion disk winds from the inner regions around the central smbh.results: we propose five ṁ regimes where the physics of the inner accretion and ejection flow around smbhs is expected to change, and that correspond observationally to quiescent and inactive galaxies; low luminosity agn (llagn); seyferts and mini-broad absorption line quasars (mini-bal qsos); narrow line seyfert 1 galaxies (nls1s) and broad absorption line quasars (bal qsos); and super-eddington sources. we include in this scenario radiation-driven disk winds, which are strong in the high ṁ, large mbh regime, and possibly present but likely weak in the moderate ṁ, small mbh regime.conclusions: a great diversity of the accretion/ejection flows in agn can be explained to a good degree by varying just two fundamental properties: the eddington ratio ṁ and the black hole mass mbh, and by the inclusion of accretion disk winds that can naturally be launched by the radiation emitted from luminous accretion disks. | a global view of the inner accretion and ejection flow around super massive black holes. radiation-driven accretion disk winds in a physical context |
we report the discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9. this is the initial result from the subaru high-z exploration of low-luminosity quasars project, which exploits the exquisite multiband imaging data produced by the subaru hyper suprime-cam (hsc) strategic program survey. the candidate selection is performed by combining several photometric approaches including a bayesian probabilistic algorithm to reject stars and dwarfs. the spectroscopic identification was carried out with the gran telescopio canarias and the subaru telescope for the first 80 deg2 of the survey footprint. the success rate of our photometric selection is quite high, approaching 100% at the brighter magnitudes (z ab < 23.5 mag). our selection also recovered all the known high-z quasars on the hsc images. among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright lyman-break galaxies. the remaining three objects have weak continua and very strong and narrow lyα lines, which may be excited by ultraviolet light from both young stars and quasars. these results indicate that we are starting to see the steep rise of the luminosity function of z ≥ 6 galaxies, compared with that of quasars, at magnitudes fainter than m 1450 ∼ -22 mag or z ab ∼ 24 mag. follow-up studies of the discovered objects as well as further survey observations are ongoing. | subaru high-z exploration of low-luminosity quasars (shellqs). i. discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9 |
we present the active galactic nucleus (agn) catalog and optical spectroscopy for the second data release of the swift bat agn spectroscopic survey (bass dr2). with this dr2 release we provide 1449 optical spectra, of which 1182 are released for the first time, for the 858 hard-x-ray-selected agns in the swift bat 70-month sample. the majority of the spectra (801/1449, 55%) are newly obtained from very large telescope (vlt)/x-shooter or palomar/doublespec. many of the spectra have both higher resolution (r > 2500, n ~ 450) and/or very wide wavelength coverage (3200-10000 å, n ~ 600) that are important for a variety of agn and host galaxy studies. we include newly revised agn counterparts for the full sample and review important issues for population studies, with 47 agn redshifts determined for the first time and 790 black hole mass and accretion rate estimates. this release is spectroscopically complete for all agns (100%, 858/858), with 99.8% having redshift measurements (857/858) and 96% completion in black hole mass estimates of unbeamed agns (722/752). this agn sample represents a unique census of the brightest hard-x-ray-selected agns in the sky, spanning many orders of magnitude in eddington ratio (l/l edd = 10-5-100), black hole mass (m bh = 105-1010 m ⊙), and agn bolometric luminosity (l bol = 1040-1047 erg s-1 ). | bass. xxii. the bass dr2 agn catalog and data |
the existence of massive (1011 solar masses) elliptical galaxies by redshift z ≈ 4 (refs 1, 2, 3; when the universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the universe of less than 1 billion years). surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. the only known galaxies with very high star-formation rates at z > 6 are, with one exception, the host galaxies of quasars, but these galaxies also host accreting supermassive (more than 109 solar masses) black holes, which probably affect the properties of the galaxies. here we report observations of an emission line of singly ionized carbon ([c ii] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. the discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. on the basis of the [c ii] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. these sources are similar to the host galaxies of the quasars in [c ii] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. similar systems have previously been found at lower redshift. we find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations. if they are representative of the bright end of the [c ii] luminosity function, then they can account for the population of massive elliptical galaxies at z ≈ 4 in terms of the density of cosmic space. | rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6 |
we report a new changing-look quasar, wise j105203.55+151929.5 at z = 0.303, found by identifying highly mid-ir-variable quasars in the wide-field infrared survey explorer (wise)/near-earth object wise reactivation (neowise) data stream. compared to multiepoch mid-ir photometry of a large sample of sdss-confirmed quasars, wise j1052+1519 is an extreme photometric outlier, fading by more than a factor of two at 3.4 and 4.6 μm since 2009. swift target-of-opportunity observations in 2017 show even stronger fading in the soft x-rays compared to the rosat detection of this source in 1995, with at least a factor of 15 decrease. we obtained second-epoch spectroscopy with the palomar telescope in 2017 that, when compared with the 2006 archival sdss spectrum, reveals that the broad hβ emission has vanished and that the quasar has become significantly redder. the two most likely interpretations for this dramatic change are source fading or obscuration, where the latter is strongly disfavored by the mid-ir data. we discuss various physical scenarios that could cause such changes in the quasar luminosity over this timescale, and favor changes in the innermost regions of the accretion disk that occur on the thermal and heating/cooling front timescales. we discuss possible physical triggers that could cause these changes, and predict the multiwavelength signatures that could distinguish these physical scenarios. | a mid-ir selected changing-look quasar and physical scenarios for abrupt agn fading |
we present a new method to test the λcdm cosmological model and to estimate cosmological parameters based on the nonlinear relation between the ultraviolet and x-ray luminosities of quasars. we built a data set of 1138 quasars by merging several samples from the literature with x-ray measurements at 2 kev and sdss photometry, which was used to estimate the extinction-corrected 2500 å flux. we obtained three main results: (1) we checked the nonlinear relation between x-ray and uv luminosities in small redshift bins up to z∼ 6, confirming that the relation holds at all redshifts with the same slope; (2) we built a hubble diagram for quasars up to z∼ 6, which is well matched to that of supernovae in the common z = 0-1.4 redshift interval and extends the test of the cosmological model up to z∼ 6; and (3) we showed that this nonlinear relation is a powerful tool for estimating cosmological parameters. using the present data and assuming a λcdm model, we obtain {{{ω }}}m = 0.22{}-0.08+0.10 and {{{ω }}}{{λ }} = 0.92{}-0.30+0.18 ({{{ω }}}m = 0.28 ± 0.04 and {{{ω }}}{{λ }} = 0.73 +/- 0.08 from a joint quasar-sne fit). much more precise measurements will be achieved with future surveys. a few thousand sdss quasars already have serendipitous x-ray observations from chandra or xmm-newton, and at least 100,000 quasars with uv and x-ray data will be made available by the extended roentgen survey with an imaging telescope array all-sky survey in a few years. the euclid, large synoptic survey telescope, and advanced telescope for high energy astrophysics surveys will further increase the sample size to at least several hundred thousand. our simulations show that these samples will provide tight constraints on the cosmological parameters and will allow us to test for possible deviations from the standard model with higher precision than is possible today. | a hubble diagram for quasars |
galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. absorption-line measurements along the lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. the lyman-α transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 104 kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. tracing cosmic hydrogen through its lyman-α emission has been a long-standing goal of observational astrophysics1-3, but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. a new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended lyman-α emission from hydrogen around high-redshift galaxies4,5. such measurements were previously limited to especially favourable systems6-8 or to the use of massive statistical averaging9,10 because of the faintness of this emission. here we report observations of low-surface-brightness lyman-α emission surrounding faint galaxies at redshifts between 3 and 6. we find that the projected sky coverage approaches 100 per cent. the corresponding rate of incidence (the mean number of lyman-α emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars11-14. this similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission. | nearly all the sky is covered by lyman-α emission around high-redshift galaxies |
in the current framework, the standard parametrization of our universe is the so-called lambda cold dark matter (λcdm) model. recently, a ∼4σ tension with the λcdm model was shown to exist via a model-independent parametrization of a hubble diagram of type ia supernovae (sne ia) from the jla survey and quasars. model-independent approaches and independent samples over a wide redshift range are key to testing this tension and any possible systematic errors. here we present an analysis of a combined hubble diagram of sne ia, quasars, and gamma-ray bursts (grbs) to check the agreement of the quasar and grb cosmological parameters at high redshifts (z > 2) and to test the concordance flat λcdm model with improved statistical accuracy. we build a hubble diagram with sne ia, quasars, and grbs, where quasars are standardised through the observed non-linear relation between their ultraviolet and x-ray emission and grbs through the correlation between the spectral peak energy and the isotropic-equivalent radiated energy (the so-called amati relation). we fit the data with cosmographic models consisting of a fourth-order logarithmic polynomial and a fifth-order linear polynomial, and compare the results with the expectations from a flat λcdm model. we confirm the tension between the best-fit cosmographic parameters and the λcdm model at ∼4σ with sne ia and quasars, at ∼2σ with sne ia and grbs, and at > 4σ with the whole sne ia+quasars+grb data set. the completely independent high-redshift hubble diagrams of quasars and grbs are fully consistent with each other, strongly suggesting that the deviation from the standard model is not due to unknown systematic effects but to new physics. | tension with the flat λcdm model from a high-redshift hubble diagram of supernovae, quasars, and gamma-ray bursts |
we present the first version of the automatic learning for the rapid classification of events (alerce) broker light curve classifier. alerce is currently processing the zwicky transient facility (ztf) alert stream, in preparation for the vera c. rubin observatory. the alerce light curve classifier uses variability features computed from the ztf alert stream and colors obtained from allwise and ztf photometry. we apply a balanced random forest algorithm with a two-level scheme where the top level classifies each source as periodic, stochastic, or transient, and the bottom level further resolves each of these hierarchical classes among 15 total classes. this classifier corresponds to the first attempt to classify multiple classes of stochastic variables (including core- and host-dominated active galactic nuclei, blazars, young stellar objects, and cataclysmic variables) in addition to different classes of periodic and transient sources, using real data. we created a labeled set using various public catalogs (such as the catalina surveys and gaia dr2 variable stars catalogs, and the million quasars catalog), and we classify all objects with ≥6 g-band or ≥6 r-band detections in ztf (868,371 sources as of 2020 june 9), providing updated classifications for sources with new alerts every day. for the top level we obtain macro-averaged precision and recall scores of 0.96 and 0.99, respectively, and for the bottom level we obtain macro-averaged precision and recall scores of 0.57 and 0.76, respectively. updated classifications from the light curve classifier can be found at the alerce explorer website (http://alerce.online). | alert classification for the alerce broker system: the light curve classifier |
risaliti and lusso have compiled x-ray and uv flux measurements of 1598 quasars (qsos) in the redshift range 0.036 ≤ z ≤ 5.1003, part of which, z ~ 2.4 - 5.1, is largely cosmologically unprobed. in this paper we use these qso measurements, alone and in conjunction with baryon acoustic oscillation (bao) and hubble parameter [h(z)] measurements, to constrain cosmological parameters in six different cosmological models, each with two different hubble constant priors. in most of these models, given the larger uncertainties, the qso cosmological parameter constraints are mostly consistent with those from the bao + h(z) data. a somewhat significant exception is the non-relativistic matter density parameter ωm0 where qso data favour ωm0 ~ 0.5 - 0.6 in most models. as a result, in joint analyses of qso data with h(z) + bao data the 1d ωm0 distributions shift slightly towards larger values. a joint analysis of the qso + bao + h(z) data is consistent with the current standard model, spatially-flat λcdm, but mildly favours closed spatial hypersurfaces and dynamical dark energy. since the higher ωm0 values favoured by qso data appear to be associated with the z ~ 2 - 5 part of these data, and conflict somewhat with strong indications for ωm0 ~ 0.3 from most z < 2.5 data as well as from the cosmic microwave background anisotropy data at z ~ 1100, in most models, the larger qso data ωm0 is possibly more indicative of an issue with the z ~ 2 - 5 qso data than of an inadequacy of the standard flat λcdm model. | using quasar x-ray and uv flux measurements to constrain cosmological model parameters |
announcing the release v6.4 of the milliquas (million quasars) quasar catalogue which presents all published quasars to 11 december 2019, including sdss-dr16. its totals are 757,991 type-i qsos/agn and approx 1.1m high-confidence (80%+ likelihood) quasar candidates from sdss-based & allwise photometric quasar catalogs, plus all-sky radio/x-ray associated candidates available only here. type-ii and bl lac objects are also included, plus candidates/galaxies with double radio lobes (so calculated), bringing the total count to 1,968,377. gaia-dr2 astrometry is given for most objects. the catalogue is available on its home page and on nasa heasarc. | the million quasars (milliquas) catalogue, v6.4 |
black hole feedback is now a standard component of galaxy formation models. these models predict that the impact of black hole activity on its host galaxy likely peaked at z = 2-3, the epoch of strongest star formation activity and black hole accretion activity in the universe. we used xshooter on the very large telescope to measure rest-frame optical spectra of four z ∼ 2.5 extremely red quasars with infrared luminosities ∼1047 erg s-1. we present the discovery of very broad (full width at half max = 2600-5000 km s-1), strongly blueshifted (by up to 1500 km s-1) [o iii] λ5007 å emission lines in these objects. in a large sample of type 2 and red quasars, [o iii] kinematics are positively correlated with infrared luminosity, and the four objects in our sample are on the extreme end in both [o iii] kinematics and infrared luminosity. we estimate that at least 3 per cent of the bolometric luminosity in these objects is being converted into the kinetic power of the observed wind. photo-ionization estimates suggest that the [o iii] emission might be extended on a few kpc scales, which would suggest that the extreme outflow is affecting the entire host galaxy of the quasar. these sources may be the signposts of the most extreme form of quasar feedback at the peak epoch of galaxy formation, and may represent an active `blow-out' phase of quasar evolution. | discovery of extreme [o iii] λ5007 å outflows in high-redshift red quasars |
we present constraints on masses of active and sterile neutrinos in the context of the λcdmν and λwdm models, respectively. we use the one-dimensional lyα-forest power spectrum from the baryon oscillation spectroscopic survey (boss) of the sloan digital sky survey (sdss-iii) measured by palanque-delabrouille et al. [1], and from the vlt/xshooter legacy survey (xq-100). in this paper, we present our own measurement of the publicly released xq-100 quasar spectra, focusing in particular on an improved determination of the spectrograph resolution that allows us to push to smaller scales than the public release and reach k-modes of 0.070 s km-1. we compare the obtained 1d lyα flux power spectrum to the one measured by irsic et al. [2] to k-modes of 0.057 s km-1. fitting lyα data alone leads to cosmological parameters in excellent agreement with the values derived independently from planck 2015 cosmic microwave background (cmb) data. combining boss and xq-100 lyα power spectra, we constrain the sum of neutrino masses to ∑ mν < 0.8 ev (95% c.l.) including all identified sources of systematic uncertainties. with the addition of cmb data, this bound is tightened to ∑ mν < 0.14 ev (95% c.l.). with their sensitivity to small scales, lyα data are ideal to constrain λwdm models. using xq-100 alone, we issue lower bounds on pure dark matter particles: mx gtrsim 2.08 : kev (95% c.l.) for early decoupled thermal relics, and ms gtrsim 10.2 : kev (95% c.l.) for non-resonantly produced right-handed neutrinos. combining the 1d lyα-forest power spectrum measured by boss and xq-100, we improve the two bounds to mx gtrsim 4.17 : kev and ms gtrsim 25.0 : kev (95% c.l.), slightly more constraining than what was achieved in baur et al. 2015 [3] with boss data alone. the 3 σ bound shows a more significant improvement, increasing from mx gtrsim 2.74 : kev for boss alone to mx gtrsim 3.10 : kev for the combined boss+xq-100 data set. finally, we include in our analysis the first two redshift bins (z = 4.2 and z = 4.6) of the power spectrum measured by viel et al. 2013 [4] with the high-resolution hires/mike spectrographs. the addition of hires/mike power spectrum allows us to further improve the two limits to mx gtrsim 4.65 : kev and ms gtrsim 28.8 : kev (95% c.l.). | constraints on neutrino masses from lyman-alpha forest power spectrum with boss and xq-100 |
the free-streaming of kev-scale particles impacts structure growth on scales that are probed by the lyman-alpha forest of distant quasars. using an unprecedentedly large sample of medium-resolution qso spectra from the ninth data release of sdss, along with a state-of-the-art set of hydrodynamical simulations to model the lyman-alpha forest in the non-linear regime, we issue one of the tightest bounds to date, from ly-α data alone, on pure dark matter particles: mx>4.09 kev (95% cl) for early decoupled thermal relics such as a hypothetical gravitino, and correspondingly ms>24.4 kev (95% cl) for a non-resonantly produced right-handed neutrino. this limit depends on the value on ns, and planck measures a higher value of ns than sdss-iii/boss. our bounds thus change slightly when ly-α data are combined with cmb data from planck 2016. the limits shift to mx>2.96 kev (95% cl) and ms>16.0 kev (95% cl). thanks to sdss-iii data featuring smaller uncertainties and covering a larger redshift range than sdss-i data, our bounds confirm the most stringent results established by previous works and are further at odds with a purely non-resonantly produced sterile neutrino as dark matter. | lyman-alpha forests cool warm dark matter |
gravitational waves (gws) have now been detected from stellar-mass black hole binaries, and the first observations of gws from massive black hole (mbh) binaries are expected within the next decade. pulsar timing arrays (pta), which can measure the years long periods of gws from mbh binaries (mbhbs), have excluded many standard predictions for the amplitude of a stochastic gw background (gwb). we use coevolved populations of mbhs and galaxies from hydrodynamic, cosmological simulations (`illustris') to calculate a predicted gwb. the most advanced predictions so far have included binary hardening mechanisms from individual environmental processes. we present the first calculation including all of the environmental mechanisms expected to be involved: dynamical friction, stellar `loss-cone' scattering, and viscous drag from a circumbinary disc. we find that mbh binary lifetimes are generally multiple gigayears, and only a fraction coalesce by redshift zero. for a variety of parameters, we find all gwb amplitudes to be below the most stringent pta upper limit of a_{yr^{-1}} ≈ 10^{-15}. our fairly conservative fiducial model predicts an amplitude of a_{yr^{-1}} ≈ 0.4× 10^{-15}. at lower frequencies, we find a_{0.1 yr^{-1}} ≈ 1.5× 10^{-15} with spectral indices between -0.4 and -0.6 - significantly flatter than the canonical value of -2/3 due to purely gw-driven evolution. typical mbhbs driving the gwb signal come from redshifts around 0.3, with total masses of a few times 109 m⊙, and in host galaxies with very large stellar masses. even without gwb detections, our results can be connected to observations of dual active galactic nuclei to constrain binary evolution. | massive black hole binary mergers in dynamical galactic environments |
all galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. but because these episodes are brief, quasars are rare objects typically separated by cosmological distances. in a survey for lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. the chance probability of finding a quadruple quasar is estimated to be ∼10-7, implying a physical connection between lyman-α nebulae and the locations of rare protoclusters. our findings imply that the most massive structures in the distant universe have a tremendous supply (≃1011 solar masses) of cool dense (volume density ≃ 1 cm-3) gas, which is in conflict with current cosmological simulations. | quasar quartet embedded in giant nebula reveals rare massive structure in distant universe |
the recent compilation of quasar (qso) x-ray and ultraviolet (uv) flux measurements include qsos that appear to not be standardizable via the x-ray luminosity and uv luminosity (lx-luv) relation and so should not be used to constrain cosmological model parameters. here, we show that the largest of seven sub-samples in this compilation, the sdss-4xmm qsos that contribute about 2/3 of the total qsos, have lx-luv relations that depend on the cosmological model assumed and also on redshift, and is the main cause of the similar problem discovered earlier for the full qso compilation. the second and third biggest sub-samples, the sdss-chandra and xxl qsos that together contribute about 30 per cent of the total qsos, appear standardizable, but provide only weak constraints on cosmological parameters that are not inconsistent with the standard spatially flat λcdm model or with constraints from better-established cosmological probes. | do quasar x-ray and uv flux measurements provide a useful test of cosmological models? |
axion-like particles (alps) are predicted by several beyond the standard model theories, in particular, string theory. in the presence of an external magnetic field perpendicular to the direction of propagation, alps can couple to photons. therefore, if an x-ray source is viewed through a magnetized plasma, such as a luminous quasar in a galaxy cluster, we may expect spectral distortions that are well described by photon-alp oscillations. we present a 571 ks combined high- and low-energy transmission grating chandra observation of the powerful radio-quiet quasar h1821+643, hosted by a cool-core cluster at redshift 0.3. the spectrum is well described by a double power-law continuum and broad+narrow iron line emission typical of type-1 active galactic nuclei (agns), with remaining spectral features ${\lt}2.5{{\ \rm per\ cent}}$. using a cell-based approach to describe the turbulent cluster magnetic field, we compare our spectrum with photon-alp mixing curves for 500 field realizations, assuming that the thermal-to-magnetic pressure ratio β remains constant up to the virial radius. at $99.7{{\ \rm per\ cent}}$ credibility and taking β = 100, we exclude all couplings gaγ > 6.3 × 10-13 gev-1 for most alp masses <10-12 ev. our results are moderately more sensitive to constraining alps than the best previous result from chandra observations of the perseus cluster, albeit with a less constrained field model. we reflect on the promising future of alp studies with bright agns embedded in rich clusters, especially with the upcoming athena mission. | new constraints on light axion-like particles using chandra transmission grating spectroscopy of the powerful cluster-hosted quasar h1821+643 |
the total contribution of diffuse halo gas to the galaxy baryon budget strongly depends on its dominant ionization state. in this paper, we address the physical conditions in the highly ionized circumgalactic medium (cgm) traced by {{o}} {{vi}} absorption lines observed in cos-halos spectra. we analyze the observed ionic column densities, absorption-line widths and relative velocities, along with the ratios of {{n}} {{v}}/{{o}} {{vi}} for 39 fitted voigt profile components of o vi. we compare these quantities with the predictions given by a wide range of ionization models. photoionization models that include only extragalactic uv background radiation are ruled out; conservatively, the upper limits to {{n}} {{v}}/{{o}} {{vi}} and measurements of {n}{{o}{{vi}}} imply unphysically large path lengths ≳100 kpc. furthermore, very broad {{o}} {{vi}} absorption (b > 40 km s-1) is a defining characteristic of the cgm of star-forming l* galaxies. we highlight two possible origins for the bulk of the observed {{o}} {{vi}}: (1) highly structured gas clouds photoionized primarily by local high-energy sources or (2) gas radiatively cooling on large scales behind a supersonic wind. approximately 20% of circumgalactic o vi does not align with any low-ionization state gas within ±50 km s-1 and is found only in halos with {m}{halo} < 1012 {m}⊙ . we suggest that this type of unmatched o vi absorption traces the hot corona itself at a characteristic temperature of {10}5.5 k. we discuss the implications of these very distinct physical origins for the dynamical state, gas cooling rates, and total baryonic content of l* gaseous halos. | the cos-halos survey: origins of the highly ionized circumgalactic medium of star-forming galaxies |
the observed relation between the soft x-ray and the optical-ultraviolet emission in active galactic nuclei (agns) is nonlinear and it is usually parametrized as a dependence between the logarithm of the monochromatic luminosity at 2500 å and at 2 kev. previous investigations have found that the dispersion of this relation is rather high (∼0.35-0.4 in log units), which may be caused by measurement uncertainties, variability, and intrinsic dispersion due to differences in the agn physical properties (e.g., different accretion modes). we show that, once optically selected quasars with homogeneous sed and x-ray detection are selected, and dust reddened and/or gas obscured objects are not included, the measured dispersion drops to significantly lower values (i.e., ∼0.21-0.24 dex). we show that the residual dispersion is due to some extent to variability, and to remaining measurement uncertainties. therefore, the real physical intrinsic dispersion should be \lt 0.21 dex. such a tight relation, valid over four decades in luminosity, must be the manifestation of an intrinsic (and universal) physical relation between the disk, emitting the primary radiation, and the hot electron corona emitting x-rays. | the tight relation between x-ray and ultraviolet luminosity of quasars |
scaling relations between black hole (bh) masses and their host galaxy properties have been studied extensively over the last two decades, and point toward co-evolution of central massive bhs and their hosts. however, these relations remain poorly constrained for bh masses below ∼ {10}6 {m}⊙ . here we present optical and x-ray observations of the dwarf galaxy rgg 118 taken with the magellan echellette spectrograph on the 6.5 m clay telescope and chandra x-ray observatory. based on sloan digital sky survey spectroscopy, rgg 118 was identified as possessing narrow emission line ratios indicative of photoionization partly due to an active galactic nucleus. our higher resolution spectroscopy clearly reveals broad hα emission in the spectrum of rgg 118. using virial bh mass estimate techniques, we calculate a bh mass of ∼50,000 {m}⊙ . we detect a nuclear x-ray point source in rgg 118, suggesting a total accretion powered luminosity of l=4× {10}40 {erg} {{{s}}}-1, and an eddington fraction of ∼1%. the bh in rgg 118 is the smallest ever reported in a galaxy nucleus and we find that it lies on the extrapolation of the {m}{bh}-{σ }* relation to the lowest masses yet. | a ∼50,000 m⊙ solar mass black hole in the nucleus of rgg 118 |
an incremental version of the fourth catalog of active galactic nuclei (agns) detected by the fermi large area telescope is presented. this version (4lac-dr3) derives from the third data release of the 4fgl catalog based on 12 yr of e > 50 mev gamma-ray data, where the spectral parameters, spectral energy distributions (seds), yearly light curves, and associations have been updated for all sources. the new reported agns include 587 blazar candidates and four radio galaxies. we describe the properties of the new sample and outline changes affecting the previously published one. we also introduce two new parameters in this release, namely the peak energy of the sed high-energy component and the corresponding flux. these parameters allow an assessment of the compton dominance, the ratio of the inverse-compton to the synchrotron-peak luminosities, without relying on x-ray data. | the fourth catalog of active galactic nuclei detected by the fermi large area telescope: data release 3 |
quasars (qsos) are extremely luminous active galactic nuclei currently observed up to redshift z = 7.642. as such, they have the potential to be the next rung of the cosmic distance ladder beyond type ia supernovae, if they can reliably be used as cosmological probes. the main issue in adopting qsos as standard candles (similarly to gamma-ray bursts) is the large intrinsic scatter in the relations between their observed properties. this could be overcome by finding correlations among their observables that are intrinsic to the physics of qsos and not artifacts of selection biases and/or redshift evolution. the reliability of these correlations should be verified through well-established statistical tests. the correlation between the ultraviolet and x-ray fluxes developed by risaliti & lusso is one of the most promising relations. we apply a statistical method to correct this relation for redshift evolution and selection biases. remarkably, we recover the the same parameters of the slope and the normalization as risaliti & lusso. our results establish the reliability of this relation, which is intrinsic to the qso properties and not merely an effect of selection biases or redshift evolution. hence, the possibility to standardize qsos as cosmological candles, thereby extending the hubble diagram up to z = 7.54. | quasar standardization: overcoming selection biases and redshift evolution |
in this paper, we use all available baryon acoustic oscillation, hubble parameter, and quasar angular size data to constrain six dark energy cosmological models, both spatially flat and non-flat. depending on the model and data combination considered, these data mildly favour closed spatial hypersurfaces (by as much as 1.7σ) and dark energy dynamics (up to a little over 2σ) over a cosmological constant λ. the data also favour, at 1.8σ to 3.4σ, depending on the model and data combination, a lower hubble constant than what is measured from the local expansion rate. | baryon acoustic oscillation, hubble parameter, and angular size measurement constraints on the hubble constant, dark energy dynamics, and spatial curvature |
the advent of high-angular-resolution ir and submillimeter interferometry allows for spatially resolved observations of the parsec-scale environment of active galactic nuclei (agns), commonly referred to as the “torus.” while molecular lines show the presence of large, massive disks, the ir observations appear to be dominated by a strong polar component that has been interpreted as a dusty wind. this paper aims at using characteristics shared by agns in each of the wavebands and a set of simple physical principles to form a unifying view of these seemingly contradictory observations: dusty molecular gas flows in from galactic scales of ∼100 pc to the subparsec environment via a disk with small to moderate scale height. the hot, inner part of the disk puffs up due to ir radiation pressure and unbinds a large amount of the inflowing gas from the black hole’s gravitational potential, providing the conditions to launch a wind driven by the radiation pressure from the agn. the dusty wind feeds back mass into the galaxy at a rate of the order of ∼0.1-100 m ⊙ yr-1, depending on the agn luminosity and eddington ratio. angle-dependent obscuration as required by agn unification is provided by a combination of disk, wind, and wind-launching region. | redefining the torus: a unifying view of agns in the infrared and submillimeter |
it is well known that reverberation mapping of active galactic nuclei (agns) reveals a relationship between agn luminosity and the size of the broad-line region, and that use of this relationship, combined with the doppler width of the broad emission line, enables an estimate of the mass of the black hole at the center of the active nucleus based on a single spectrum. an unresolved key issue is the choice of parameter used to characterize the line width, either fwhm or line dispersion ${\sigma }_{\mathrm{line}}$ (the square root of the second moment of the line profile). we argue here that use of fwhm introduces a bias, stretching the mass scale such that high masses are overestimated and low masses are underestimated. here we investigate estimation of black hole masses in agns based on individual or "single-epoch" observations, with a particular emphasis in comparing mass estimates based on line dispersion and fwhm. we confirm the recent findings that, in addition to luminosity and line width, a third parameter is required to obtain accurate masses, and that parameter seems to be eddington ratio. we present simplified empirical formulae for estimating black hole masses from the hβ λ4861 and c iv λ1549 emission lines. while the agn continuum luminosity at 5100 å is usually used to predict the hβ reverberation lag, we show that the luminosity of the hβ broad component can be used instead without any loss of precision, thus eliminating the difficulty of accurately accounting for the host-galaxy contribution to the observed luminosity. | the sloan digital sky survey reverberation mapping project: estimating masses of black holes in quasars with single-epoch spectroscopy |
the evolution of galaxies is connected to the growth of supermassive black holes in their centers. during the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar pds 456. this persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. the outflow’s kinetic power larger than 1046 ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution. | black hole feedback in the luminous quasar pds 456 |
studies of rest-frame optical emission in quasars at z > 6 have historically been limited by the wavelengths accessible by ground-based telescopes. the james webb space telescope (jwst) now offers the opportunity to probe this emission deep into the reionization epoch. we report the observations of eight quasars at z > 6.5 using the jwst/nircam wide field slitless spectroscopy as a part of the "a spectroscopic survey of biased halos in the reionization era (aspire)" program. our jwst spectra cover the quasars' emission between rest frame ~4100 and 5100 å. the profiles of these quasars' broad hβ emission lines span a full width at half maximum from 3000 to 6000 km s-1. the hβ-based virial black hole (bh) masses, ranging from 0.6 to 2.1 billion solar masses, are generally consistent with their mg ii-based bh masses. the new measurements based on the more reliable hβ tracer thus confirm the existence of a billion solar-mass bhs in the reionization epoch. in the observed [o iii] λ λ 4960,5008 doublets of these luminous quasars, broad components are more common than narrow core components (≤ 1200 km s-1), and only one quasar shows stronger narrow components than broad. two quasars exhibit significantly broad and blueshifted [o iii] emission, thought to trace galactic-scale outflows, with median velocities of -610 and -1430 km s-1 relative to the [c ii] 158 μm line. all eight quasars show strong optical fe ii emission and follow the eigenvector 1 relations defined by low-redshift quasars. the entire aspire program will eventually cover 25 quasars and provide a statistical sample for the studies of the bhs and quasar spectral properties. | a spectroscopic survey of biased halos in the reionization era (aspire): a first look at the rest-frame optical spectra of z > 6.5 quasars using jwst |
following the recent discovery of x-ray quasi-periodic eruptions (qpes) coming from the nucleus of the galaxy gsn 069, here we report on the detection of qpes in the active galaxy named rx j1301.9+2747. qpes are rapid and recurrent increases of the x-ray count-rate by more than one order of magnitude with respect to a stable quiescent level. during a xmm-newton observation lasting 48 ks that was performed on 30 and 31 may 2019, three strong qpes lasting about half an hour each were detected in the light curves of rx j1301.9+2747. the first two qpes are separated by a longer recurrence time (about 20 ks) compared to the second and third (about 13 ks). this pattern is consistent with the alternating long-short recurrence times of the gsn 069 qpes, although the difference between the consecutive recurrence times is significantly smaller in gsn 069. longer x-ray observations will better clarify the temporal pattern of the qpes in rx j1301.9+2747 and will allow a detailed comparison with gsn 069 to be performed. the x-ray spectral properties of qpes in the two sources are remarkably similar, with qpes representing fast transitions from a relatively cold and likely disk-dominated state to a state that is characterized by a warmer emission similar to the so-called soft x-ray excess, a component that is almost ubiquitously seen in the x-ray spectra of unobscured, radiatively efficient active galaxies. previous x-ray observations of rx j1301.9+2747 in 2000 and 2009 strongly suggest that qpes have been present for at least the past 18.5 yr. the detection of qpes from a second galactic nucleus after gsn 069 rules out contamination by a galactic source in both cases, such that qpes ought to be considered a novel extragalactic phenomenon associated with accreting supermassive black holes. | x-ray quasi-periodic eruptions from the galactic nucleus of rx j1301.9+2747 |
we present alma detections of the [c ii] 158 μm emission line and the underlying far-infrared (fir) continuum of three quasars at 6.6 < z < 6.9 selected from the viking survey. the [c ii] line fluxes range between 1.6 and 3.4 jy km s-1 ([c ii] luminosities ∼(1.9-3.9) × 109 l⊙). we measure continuum flux densities of 0.56-3.29 mjy around 158 μm (rest frame), with implied fir luminosities of (0.6-7.5) × 1012 l⊙ and dust masses md = (0.7-24) × 108 m⊙. in one quasar we derive a dust temperature of {30}-9+12 k from the continuum slope, below the canonical value of 47 k. assuming that the [c ii] and continuum emission are powered by star formation, we find star formation rates from 100 to 1600 m⊙ yr-1 based on local scaling relations. the l[c ii]/lfir ratios in the quasar hosts span a wide range from (0.3-4.6) × 10-3, including one quasar with a ratio that is consistent with local star-forming galaxies. we find that the strength of the l[c ii] and 158 μm continuum emission in z ≳ 6 quasar hosts correlates with the quasar’s bolometric luminosity. in one quasar, the [c ii] line is significantly redshifted by ∼1700 km s-1 with respect to the mg ii broad emission line. comparing to values in the literature, we find that, on average, the mg ii is blueshifted by 480 km s-1 (with a standard deviation of 630 km s-1) with respect to the host galaxy redshift, i.e., one of our quasars is an extreme outlier. through modeling we can rule out a flat rotation curve for our brightest [c ii] emitter. finally, we find that the ratio of black hole mass to host galaxy (dynamical) mass is higher by a factor of 3-4 (with significant scatter) than local relations. | bright [c ii] and dust emission in three z > 6.6 quasar host galaxies observed by alma |
we combine results from deep alma observations of massive (m* > 1010 m⊙) galaxies at different redshifts to show that the column density of their interstellar medium (ism) rapidly increases toward early cosmic epochs. our analysis includes objects from the aspecs and alpine large programs, as well as individual observations of z ∼ 6 quasar hosts. when accounting for non-detections and correcting for selection effects, we find that the median surface density of the ism of the massive galaxy population evolves as ∼(1 + z)3.3. this means that the ism column density toward the nucleus of a z > 3 galaxy is typically > 100 times larger than locally, and it may reach values as high as compton-thick at z ≳ 6. remarkably, the median ism column density is on the same order of what is measured from x-ray observations of large active galactic nucleus (agn) samples already at z ≳ 2. we have developed a simple analytic model for the spatial distribution of ism clouds within galaxies, and estimate the total covering factor toward active nuclei when obscuration by ism clouds on the host scale is added to that of parsec-scale circumnuclear material (the so-called torus). the model includes clouds with a distribution of sizes, masses, and surface densities, and also allows for an evolution of the characteristic cloud surface density with redshift, σc, * ∝ (1 + z)γ. we show that, for γ = 2, such a model successfully reproduces the increase in the obscured agn fraction with redshift that is commonly observed in deep x-ray surveys, both when different absorption thresholds and agn luminosities are considered. our results suggest that 80-90% of supermassive black holes in the early universe (z > 6 − 8) are hidden to our view, primarily by the ism in their hosts. we finally discuss the implications of our results and how they can be tested observationally with current and forthcoming facilities (e.g., vlt, e-elt, alma, and jwst) and with next-generation x-ray imaging satellites. by extrapolating the observed x-ray nebulae around local agn to the environments of supermassive black holes at high redshifts, we find ≲1″ nebulae impose stringent design constraints on the spatial resolution of any future x-ray imaging great observatory in the coming decades. | supermassive black holes at high redshift are expected to be obscured by their massive host galaxies' interstellar medium |
we improve the dynamical black hole (bh) mass estimates in three nearby low-mass early-type galaxies: ngc 205, ngc 5102, and ngc 5206. we use new hubble space telescope (hst)/stis spectroscopy to fit the star formation histories of the nuclei in these galaxies, and use these measurements to create local color-mass-to-light ratio (m/l) relations. we then create new mass models from hst imaging and combined with adaptive optics kinematics, we use jeans dynamical models to constrain their bh masses. the masses of the central bhs in ngc 5102 and ngc 5206 are both below one million solar masses and are consistent with our previous estimates, {9.12}-1.53+1.84× {10}5 m ⊙ and {6.31}-2.74+1.06× {10}5 m ⊙ (3σ errors), respectively. however, for ngc 205, the improved models suggest the presence of a bh for the first time, with a best-fit mass of {6.8}-6.7+95.6× {10}3 m ⊙ (3σ errors). this is the least massive central bh mass in a galaxy detected using any method. we discuss the possible systematic errors of this measurement in detail. using this bh mass, the existing upper limits of both x-ray, and radio emissions in the nucleus of ngc 205 suggest an accretion rate ≲10-5 of the eddington rate. we also discuss the color-m/l eff relations in our nuclei and find that the slopes of these vary significantly between nuclei. nuclei with significant young stellar populations have steeper color-m/l eff relations than some previously published galaxy color-m/l eff relations. | improved dynamical constraints on the masses of the central black holes in nearby low-mass early-type galactic nuclei and the first black hole determination for ngc 205 |
we compute synthetic, rest-frame optical and ultraviolet (uv) emission-line properties of galaxy populations at redshifts from z ≈ 0 to = 8 in a full cosmological framework. we achieve this by coupling, in post-processing, the cosmological illustristng simulations with new-generation nebular-emission models, accounting for line emission from young stars, post-asymptotic giant branch (pagb) stars, accreting black holes (bhs) and, for the first time, fast radiative shocks. the optical emission-line properties of simulated galaxies dominated by different ionizing sources in our models are largely consistent with those expected from classical diagnostic diagrams and reflect the observed increase in [o iii]/hβ at fixed [n ii]/hα and the evolution of the hα, [o iii]λ5007, and [o ii] λ3727 luminosity functions from z ≈ 0 to ~ 2. at higher redshift, we find that the emission-line galaxy population is dominated by star-forming and active galaxies, with negligible fractions of shock- and pagb-dominated galaxies. we highlight 10 uv-diagnostic diagrams able to robustly identify the dominant ionizing sources in high-redshift galaxies. we also compute the evolution of several optical- and uv-line-luminosity functions from z = 4 to 7, and the number of galaxies expected to be detectable per field of view in deep, medium-resolution spectroscopic observations with the nirspec instrument on board the jwst. we find that 2-h-long exposures are sufficient to achieve unbiased censuses of hα and [o iii]λ5007 emitters, while at least 5 h are required for hβ, and even 10 h will detect only progressively smaller fractions of [o ii] λ3727, o iii] λ1663, c iii] λ1908, c iv λ1550, [n ii]λ6584, si iii] λ1888, and he ii λ1640 emitters, especially in the presence of dust. | emission-line properties of illustristng galaxies: from local diagnostic diagrams to high-redshift predictions for jwst |
we introduce a series of 20 cosmological hydrodynamical simulations of l* (m200 = 1011.7-1012.3 m⊙) and group-sized (m200 = 1012.7-1013.3 m⊙) haloes run with the model used for the eagle project, which additionally includes a non-equilibrium ionization and cooling module that follows 136 ions. the simulations reproduce the observed correlation, revealed by cos-halos at z ∼ 0.2, between {o {vi}} column density at impact parameters b < 150 kpc and the specific star formation rate (ssfr ≡ sfr/m*) of the central galaxy at z ∼ 0.2. we find that the column density of circumgalactic {o {vi}} is maximal in the haloes associated with l* galaxies, because their virial temperatures are close to the temperature at which the ionization fraction of {o {vi}} peaks (t ∼ 105.5 k). the higher virial temperature of group haloes (>106 k) promotes oxygen to higher ionization states, suppressing the {o {vi}} column density. the observed n_{o {vi}}-ssfr correlation therefore does not imply a causal link, but reflects the changing characteristic ionization state of oxygen as halo mass is increased. in spite of the mass dependence of the oxygen ionization state, the most abundant circumgalactic oxygen ion in both l* and group haloes is {o vii}; {o {vi}} accounts for only 0.1 per cent of the oxygen in group haloes and 0.9-1.3 per cent with l* haloes. nonetheless, the metals traced by {o {vi}} absorbers represent a fossil record of the feedback history of galaxies over a hubble time; their characteristic epoch of ejection corresponds to z > 1 and much of the ejected metal mass resides beyond the virial radius of galaxies. for both l* and group galaxies, more of the oxygen produced and released by stars in the circumgalactic medium (within twice the virial radius) than in the stars and interstellar medium of the galaxy. | bimodality of low-redshift circumgalactic o vi in non-equilibrium eagle zoom simulations |
we present new synthesis models of the extragalactic background light (ebl) from far infra-red (fir) to tev γ-rays, with an emphasis on the extreme ultraviolet (uv) background that is responsible for the observed ionization and thermal state of the intergalactic medium across the cosmic time. our models use updated values of the star formation rate density and dust attenuation in galaxies, qso emissivity, and the distribution of h {i} gas in the intergalactic medium. two of the most uncertain parameters in these models, the escape fraction of h {i} ionizing photons from galaxies and the spectral energy distribution (sed) of qsos, are determined to be consistent with the latest measurements of h {i} and he {ii} photoionization rates, the he {ii} lyman-α effective optical depths, various constraints on h {i} and he {ii} reionization history, and many measurements of the local ebl from soft x-rays till γ-rays. we calculate the ebl from fir to tev γ-rays by using fir emissivities from our previous work and constructing an average sed of high-energy emitting qsos, i.e, type-2 qsos and blazars. for public use, we also provide the ebl models obtained using different qso seds at extreme-uv energies over a wide range of redshifts. these can be used to quantify uncertainties in the parameters derived from photoionization models and numerical simulations originating from the allowed variations in the uv background radiation. | new synthesis models of consistent extragalactic background light over cosmic time |
warm dark matter has recently become increasingly constrained by observational inferences about the low-mass end of the subhalo mass function, which would be suppressed by dark matter free streaming in the early universe. in this work, we point out that a constraint can be placed on ultralight bosonic dark matter (often referred to as "fuzzy dark matter") based on similar considerations. recent limits on warm dark matter from strong gravitational lensing of quasars and from fluctuations in stellar streams separately translate to a lower limit of ∼2.1 ×10-21 ev on the mass of an ultralight boson comprising all dark matter. these limits are complementary to constraints on ultralight dark matter from the lyman-α forest and are subject to a completely different set of assumptions and systematic uncertainties. taken together, these probes strongly suggest that dark matter with a mass ∼10-22 ev is not a viable way to reconcile differences between cold dark matter simulations and observations of structure on small scales. | subhalo mass function and ultralight bosonic dark matter |
we use six different cosmological models to study the recently released compilation of x-ray and uv flux measurements of 2038 quasars (qsos) which span the redshift range 0.009 ≤ z ≤ 7.5413. we find, for the full qso data set, that the parameters of the x-ray and uv luminosities lx-luv relation used to standardize these qsos depend on the cosmological model used to determine these parameters, i.e. it appears that the full qso data set includes qsos that are not standardized and so cannot be used for the purpose of constraining cosmological parameters. subsets of the qso data, restricted to redshifts z ≲ 1.5-1.7 obey the lx-luv relation in a cosmological-model-independent manner, and so can be used to constrain cosmological parameters. the cosmological constraints from these lower z, smaller qso data subsets are mostly consistent with, but significantly weaker than, those that follow from baryon acoustic oscillation and hubble parameter measurements. | determining the range of validity of quasar x-ray and uv flux measurements for constraining cosmological model parameters |
we publicly release a new sample of 34 medium resolution quasar spectra at 5.77 ≤ z em ≤ 6.54 observed with the echellette spectrograph and imager on the keck telescope. this quasar sample represents an ideal laboratory to study the intergalactic medium (igm) during the end stages of the epoch of reionization, and constrain the timing and morphology of the phase transition. for a subset of 23 of our highest signal-to-noise ratio spectra (s/n > 7, per 10 km s-1 pixel), we present a new measurement of the lyα forest opacity spanning the redshift range 4.8 ≲ z ≲ 6.3. we carefully eliminate spectral regions that could be causing biases in our measurements due to additional transmitted flux in the proximity zone of the quasars, or extra absorption caused by strong intervening absorption systems along the line of sight. we compare the observed evolution of the igm opacity with redshift to predictions from a hydrodynamical simulation with uniform ultraviolet background (uvb) radiation, as well as two semi-numerical patchy reionization models, one with a fluctuating uvb and another with a fluctuating temperature field. our measurements show a steep rise in opacity at z ≳ 5.0 and an increased scatter and thus support the picture of a spatially inhomogeneous reionization process, consistent with previous work. however, we measure significantly higher optical depths at 5.3 ≲ z ≲ 5.7 than previous studies, which reduces the contrast between the highest opacity gunn-peterson troughs and the average opacity trend of the igm, which may relieve some of the previously noted tension between these measurements and reionization models. | the opacity of the intergalactic medium measured along quasar sightlines at z ∼ 6 |
past observations of quasar host galaxies at z> 6 have found cold gas and star formation on compact scales of a few kiloparsecs. we present new high sensitivity iram plateau de bure interferometer follow-up observations of the [c ii] 158 μm emission line and far-infrared (fir) continuum in the host galaxy of sdss j1148+5251, a luminous quasar at redshift 6.4189. we find that a large portion of the gas traced by [c ii] is at high velocities, up to ~1400 km s-1relative to the systemic velocity, confirming the presence of a major outflow as indicated by previous observations. the outflow has a complex morphology and reaches a maximum projected radius of ≃30 kpc. the extreme spatial extent of the outflow allows us, for the first time in an external galaxy, to estimate mass-loss rate, kinetic power, and momentum rate of the outflow as a function of the projected distance from the nucleus and the dynamical time scale. these trends reveal multiple outflow events during the past 100 myr, although the bulk of the mass, energy, and momentum appear to have been released more recently within the past ~20 myr. surprisingly, we discover that the quiescent gas at systemic velocity is also extremely extended. more specifically, we find that, while 30% of the [c ii] within v ∈(-200, 200) km s-1 traces a compact component that is not resolved by our observations, 70% of the [c ii] emission in this velocity range is extended with a projected full width at half maximum (fwhm) size of 17.4 ± 1.4 kpc. we detect fir continuum emission associated with both the compact and the extended [c ii] components, although the extended fir emission has a fwhm of 11 ± 3 kpc, thus smaller than the extended [c ii] source. overall, our results indicate that the cold gas traced by [c ii] is distributed up to r ~ 30 kpc in the host galaxy of sdss j1148+5251. a large amount of extended [c ii] is likely to be associated with star formation occurring on large scales, but the [c ii] source extends well beyond the fir continuum, and additional multi-wavelength observations are needed in order to clarify the origin of this very extended [c ii] . appendices are available in electronic form at http://www.aanda.org | very extended cold gas, star formation and outflows in the halo of a bright quasar at z > 6 |
we present evidence that txs 0506+056, the first plausible non-stellar neutrino source, despite appearances, is not a blazar of the bl lac type but is instead a masquerading bl lac, i.e. intrinsically a flat-spectrum radio quasar with hidden broad lines and a standard accretion disc. this reclassification is based on: (1) its radio and o ii luminosities; (2) its emission line ratios; (3) its eddington ratio. we also point out that the synchrotron peak frequency of txs 0506+056 is more than two orders of magnitude larger than expected by the so-called `blazar sequence', a scenario which has been assumed by some theoretical models predicting neutrino (and cosmic ray) emission from blazars. finally, we comment on the theoretical implications this reclassification has on the location of the γ-ray emitting region and our understanding of neutrino emission in blazars. | txs 0506+056, the first cosmic neutrino source, is not a bl lac |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.