We search for high-redshift (z>4.5) X-ray AGNs in the deep central (off-axis angle <5.7') region of the 7 Ms Chandra Deep Field-South X-ray image. We compile an initial candidate sample from direct X-ray detections. We then probe more deeply in the X-ray data by using pre-selected samples with high spatial resolution NIR/MIR (HST 1.6 micron and Spitzer 4.5 micron) and submillimeter (ALMA 850 micron) observations. The combination of the NIR/MIR and submillimeter pre-selections allows us to find X-ray sources with a wide range of dust properties and spectral energy distributions (SEDs). We use the SEDs from the optical to the submillimeter to determine if previous photometric redshifts were plausible. Only five possible z>5 X-ray AGNs are found, all of which might also lie at lower redshifts. If they do lie at high redshifts, then two are Compton-thick AGNs, and three are ALMA 850 micron sources. We find that (i) the number density of X-ray AGNs is dropping rapidly at high redshifts, (ii) the detected AGNs do not contribute significantly to the photoionization at z>5, and (iii) the measured X-ray light density over z=5-10 implies a very low black hole accretion density with very little growth in the black hole mass density in this redshift range.
Offset active galactic nuclei (AGNs) are AGNs that are in ongoing galaxy mergers, which produce kinematic offsets in the AGNs relative to their host galaxies. Offset AGNs are also close relatives of dual AGNs. We conduct a systematic search for offset AGNs in the Sloan Digital Sky Survey, by selecting AGN emission lines that exhibit statistically significant line-of-sight velocity offsets relative to systemic. From a parent sample of 18314 Type 2 AGNs at z<0.21, we identify 351 offset AGN candidates with velocity offsets of 50 km/s < |v| < 410 km/s. When we account for projection effects in th…
We present results of the clustering analysis between active galactic nuclei (AGNs) and galaxies at redshift 0.1-1.0 for investigating properties of galaxies associated with the AGNs, revealing the nature of fueling mechanism of supermassive black holes (SMBHs). We used 8059 SDSS AGNs/QSOs for which virial masses of individual SMBHs were measured, and divided them into four mass groups. Cross-correlation analysis was performed and bias for each mass group was derived. The averaged color and luminosity distributions of galaxies around the AGNs/QSOs were also derived for each mass group. The gal…
A complete catalogue of broad-line AGNs and double-peaked emission lines from MaNGA integral-field spectroscopy of 10K galaxies: stellar population of AGNs, supermassive black holes, and dual AGNs
Using a compiled sample of 34 broad-line active galactic nuclei (AGNs) with measured H$β$ time lags from the reverberation mapping (RM) method and measured bulge stellar velocity dispersions $σ_*$, we calculate the virial factor $f$ by assuming that the RM AGNs intrinsically obey the same $M_{\rm BH}-σ_*$ relation as quiescent galaxies, where $M_{\rm BH}$ is the mass of the supermassive black hole (SMBH). Considering four tracers of the velocity of the broad-line regions (BLRs), i.e., the H$β$ line width or line dispersion from the mean or rms spectrum, there are four kinds of the factor $f$. …
For type-1 active galactic nuclei (AGNs) for which the equatorial scattering is the dominant broad line polarization mechanism, it is possible to measure the supermassive black hole mass by tracing the Keplerian motion across the polarization plane positionangle. So far this method has been used for 30 objects but only for H$α$ emission line. We explore the possibilities this method for determining SMBH masses using polarization in broad emission lines by applying it for the first time to Mg II$λ$2798AA spectral line. We use 3D Monte Carlo radiative transfer code stokes for simultaneous modeli…
The mass measurement of supermassive black holes (SMBHs) is a very complex task. Between several methods for SMBH mass measurements, some of them use the spectral lines, which indicate the motion of the emitting/absorbing material around an SMBH. Mostly there is assumption of virialization of line emitting gas in the region close to SMBHs that is used for their mass measurements. In this paper we will give an overview of methods for the SMBH mass measurements using broad emission spectral lines observed in Type 1 AGNs. First we give the basic idea to use the parameters of broad lines to SMBH m…
In this paper, we investigate the influences of two continuum radiation pressures of the central engines on the black hole mass estimates for 40 active galactic nuclei (AGNs) with high accretion rates. The two continuum radiation pressure forces, usually believed negligible or not considered, are from the free electron Thomson scattering, and the recombination and re-ionization of hydrogen ions that continue to absorb ionizing photons to compensate for the recombination. The masses counteracted by the two radiation pressures $M_{\rm{RP}}$ depend sensitively on the percent of ionized hydrogen i…
Changing-look active galactic nuclei (CL-AGNs) as a new subpopulation challenge some fundamental physics of AGNs because the timescales of the phenomenon can hardly be reconciled with accretion disk models. In this Letter{\textit{}}, we demonstrate the extreme case: close binaries of supermassive black holes (CB-SMBHs) with high eccentricities are able to trigger the CL transition through one orbit. In this scenario, binary black holes build up their own mini-disks by peeling gas off the inner edges of the circumbinary disk during the apastron phase, after which they tidally interact with the …
How Supermassive Blackholes (SMBHs) are spun-up is a key issue of modern astrophysics. As an extension of the study in Wang et al. (2016), we here address the issue by comparing the host galaxy properties of nearby ($z<0.05$) radio-selected Seyfert 2 galaxies. With the two-dimensional bulge+disk decompositions for the SDSS $r$-band images, we identify a dichotomy on various host galaxy properties for the radio-powerful SMBHs. By assuming the radio emission from the jet reflects a high SMBH spin, which stems from the well-known BZ mechanism of jet production, high-mass SMBHs (i.e., $M_{\mathrm{…
Close binaries of supermassive black holes (CB-SMBHs) with separations of $\lesssim 0.1$pc as the final stage of galaxy mergers are sources of low frequency gravitational waves (GW), however, they are still elusive observationally because they are not spatially resolved. Fortunately, reverberation as echoes of broad emission lines to ionizing continuum conveys invaluable information of the dynamics of broad-line regions (BLRs) governed by supermassive black holes in the central regions of active galactic nuclei (AGNs). In this paper, we demonstrate how to composite the hybrid 2-dimensional tra…
Optical polarization signal coming from the innermost part of active galactic nuclei (AGNs) is highly sensitive on the geometry and kinematics of the central engine. Due to the compact size of the AGN central region, which is spatially unresolved with current observing facilities, we rely on spectropolarimetry which can provide us insight in their hidden physics. We model equatorial scattering for various broad line region (BLR) configurations using radiative transfer code STOKES. We analyze the polarization position angle () profiles for four supermassive binary black holes (SMBBHs) models an…
Using different kinds of velocity tracers derived from the broad H$β$ profile (in the mean or rms spectrum) and the corresponding virial factors $f$, the central supermassive black hole (SMBH) masses ($M_{\rm BH}$) are calculated for a compiled sample of 120 reverberation-mapped (RM) AGNs. For its subsample of RM AGNs with measured stellar velocity dispersion ($σ_{\rm \ast}$), the multivariate linear regression technique is used to calibrate the mean value $f$, as well as the variable FWHM-based $f$. It is found that, whether excluding the pseudo-bulges or not, $M_{\rm BH}$ from the H$β$ line …
As one of the series of papers 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 H$β$ time lags of the newly observed objects are shorter than the va…
We review results from cosmic X-ray surveys of active galactic nuclei (AGNs) over the past ~ 15 yr that have dramatically improved our understanding of growing supermassive black holes in the distant universe. First, we discuss the utility of such surveys for AGN investigations and the capabilities of the missions making these surveys, emphasizing Chandra, XMM-Newton, and NuSTAR. Second, we briefly describe the main cosmic X-ray surveys, the essential roles of complementary multiwavelength data, and how AGNs are selected from these surveys. We then review key results from these surveys on the …
Are "Changing-Look" Active Galactic Nuclei Special in the Coevolution of Supermassive Black Holes and their Hosts? II. The Case of Changing-Look Narrow-Line Seyfert 1 Galaxies
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理广西重点实验室）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）
We estimated the magnetic field strength at the event horizon for a sample of supermassive black holes (SMBHs) in active galactic nuclei (AGNs). Our estimates were made using the values of the inclination angles of the accretion disk to the line of sight, that we obtained previously from spectropolarimetric observations in the visible spectrum. We also used published values of full width at half maximum (FWHM) of spectral line $H_β$ from broad line region, masses of SMBHs and luminosity of AGNs at 5100 angstrom. In addition we used literature data on the spins of SMBHs obtained from their X-ra…
Some Type-1 active galactic nuclei (AGNs) are showing extremely asymmetric Balmer lines with the broad peak redshifted or blueshifted by thousands of km/s. These AGNs may be good candidates for supermassive binary black holes (SMBBHs). The complex line shapes can be very well due to the complex kinematics of the two broad line regions (BLRs). Therefore another methods should be applied to confirm the SMBBHs. One of them is spectropolarimetry. We rely on numerical modeling of the polarimetry of binary black holes systems since polarimetry is sensitive to geometry, in order to find specific infl…
The coevolution between supermassive black holes (SMBHs) and their host galaxies has been proposed for more than a decade, albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at $z>1$. In this paper, we study the lifetimes of X-ray active galactic nuclei (AGNs) in $UV$-selected red sequence (RS), blue cloud (BC) and green valley (GV) galaxies, finding that AGN accretion activities are most prominent in GV galaxies at $z\sim1.5-2$, compared with RS and BC galaxies. We also compare AGN accretion timescales with typical color transition timesc…
Supermassive Black Holes grow at the center of galaxies in consonance with them. In this review we discuss the mass feeding mechanisms that lead to this growth in Active Galactic Nuclei (AGN), focusing on constraints derived from observations of their environment, from extragalactic down to galactic and nuclear scales. At high AGN luminosities, galaxy mergers and interactions play an important role in AGN triggering and feeding. However, gas chaotic cold accretion (CCA) in galaxy clusters can trigger radiatively inefficient AGNs in brightest cluster galaxies (BCGs). At lower luminosities, mino…
The detection and characterization of supermassive black holes (SMBHs) in local low mass galaxies is crucial to our understanding of the origins of SMBHs. This statement assumes that low mass galaxies have had a relatively quiet cosmic history, so that their black holes have not undergone significant growth and therefore can be treated as relics of the original SMBH seeds. While recent studies have found optical signatures of active galactic nuclei (AGNs) in a growing population of dwarf galaxies, these studies are biased against low metallicity and relatively merger-free galaxies, thus missin…
There is mounting evidence that supermassive black holes form and grow in bulgeless galaxies. However, a robust determination of the fraction of AGNs in bulgeless galaxies, an important constraint to models of supermassive black hole seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for low mass AGNs. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, des…
NEXUS: Spectral Variability of Little Red Dots and Blue Active Galactic Nuclei at $2 \lesssim z \lesssim 6$
University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign（美国国家超级计算应用中心）；Princeton University（普林斯顿大学）；University of Michigan（密歇根大学）
Back to basics: Little Red Dots as galaxies and dust-obscured AGNs in a synthetic NIRCam sky simulated with L-GalaxiesBH
Donostia International Physics Centre (DIPC)（多诺斯蒂亚国际物理中心）；University of the Basque Country UPV/EHU（巴斯克国立大学）；Como Lake Center for AstroPhysics, University of Insubria（因斯布鲁克大学科莫湖天体物理中心）；Dipartimento di Fisica “G. Occhialini”, Università degli Studi di Milano-Bicocca（米兰比可卡大学 G. Occhialini 物理系）；INFN, Sezione di Milano-Bicocca（意大利国家核物理研究所米兰比可卡分部）；Key Laboratory for Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台计算天体物理学重点实验室）；School of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿天文与天体物理研究所）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所（加泰罗尼亚高等研究学院，西班牙国家科研委员会））
We used Transiting Exoplanet Survey Satellite (TESS) data to identify 29 candidate active galactic nuclei (AGNs) through their optical variability. The high-cadence, high-precision TESS light curves present a unique opportunity for the identification of AGNs, including those not selected through other methods. Of the candidates, we found that 18 have either previously been identified as AGNs in the literature or could have been selected based on emission-line diagnostics, mid-IR colors, or X-ray luminosity. AGNs in low-mass galaxies offer a window into supermassive black hole (SMBH) and galaxy…
We determined the spin value of supermassive black hole (SMBH) in active galactic nuclei (AGN) with investigated ultraviolet-to-optical spectral energy distribution, presented in the sample of Shang et al. (2005). The estimates of the spin values have been produced at the base of the standard geometrically thin accretion disk model and with using the results of the polarimetric observations. The polarimetric observations are very important for determining the inclination angle of AGN disk. We presented the results of our determinations of the radiation efficiency of the accretion flow and valu…
We compiled a sample of 73 active galactic nuclei (AGNs) with reverberation mapping (RM) observations from RM campaigns including our ongoing campaign of monitoring super-Eddington accreting massive black holes (SEAMBHs). This sample covers a large range of black hole (BH) mass $(M_{\bullet}=10^{6-9}~M_\odot)$, dimensionless accretion rates $(\dot{\mathscr{M}}=10^{-2.7}-10^{2.7})$ and 5100~Å~luminosity $(L_{5100}=10^{42-46}~\rm erg~s^{-1})$, allowing us to systematically study the AGN variability and their relations with BH mass, accretion rates, and optical luminosity. We employed the damped …
In the sixth of the series of papers reporting on a large reverberation mapping (RM) campaign of active galactic nuclei (AGNs) with high accretion rates, we present velocity-resolved time lags of H$β$ emission lines for nine objects observed in the campaign during 2012$-$2013. In order to correct the line-broadening caused by seeing and instruments before the analysis of velocity-resolved RM, we adopt Richardson-Lucy deconvolution to reconstruct their H$β$ profiles. The validity and effectiveness of the deconvolution are checked out by Monte Carlo simulation. Five among the nine objects show c…
Recent observations show that the metallicity of the broad line region ($Z_{\rm BLR}$) in active galactic nuclei (AGNs) is solar-to-supersolar, which is positively correlated with the mass of supermassive black holes ($M_{\rm BH}$) and does not evolve with redshift up to $z \sim 7$. We revisit the $M_{\rm BH}-Z_{\rm BLR}$ correlation with more AGNs with $M_{\rm BH}\sim 10^{6-8} M_{\odot}$ and find that the positive correlation become flat in low-mass range. It is known that outer part of accretion disks is gravitationally unstable and can fragment into stars. Considering the star formation and…
All cosmological models of structure formation predict the existence of a widespread population of dual supermassive black holes in-spiralling inside their common host galaxy, eventually merging and giving rise to intense gravitational waves. These systems can be identified as dual AGNs at kilo parsec separations, but only very few have been confirmed at z>0.5. The appearance of multiple AGNs at small angular separations can also be due to gravitational lensing of single AGNs, which are themselves very important systems for many astrophysical topics. Here we present a novel technique, dubbed t…
This is the third in a series of papers reporting on a large reverberation-mapping campaign aimed to study the properties of active galactic nuclei (AGNs) with high accretion rates. We present new results on the variability of the optical Fe II emission lines in 10 AGNs observed by the Yunnan Observatory 2.4m telescope during 2012--2013. We detect statistically significant time lags, relative to the AGN continuum, in nine of the sources. This accurate measurement is achieved by using a sophisticated spectral fitting scheme that allows for apparent flux variations of the host galaxy, and severa…
We present a sample of 290 24-micron-selected active galactic nuclei (AGNs) mostly at z ~ 0.3 -- 2.5, within 5.2 square degrees distributed as 25' X 25' fields around each of 30 galaxy clusters in the Local Cluster Substructure Survey (LoCuSS). The sample is nearly complete to 1 mJy at 24 microns, and has a rich multi-wavelength set of ancillary data; 162 are detected by Herschel. We use spectral templates for AGNs, stellar populations, and infrared emission by star forming galaxies to decompose the spectral energy distributions (SEDs) of these AGNs and their host galaxies, and estimate their …
Dual AGNs on 100 kpc Scales from the Million Quasar Catalog
School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿交叉科学研究院）
Varstrometry for Off-nucleus and Dual sub-Kpc AGN (VODKA): Radio Classification of High-Redshift Dual AGN Candidates with the Very Large Array
University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign（国家超级计算应用中心，伊利诺伊大学厄巴纳-香槟分校）；Johns Hopkins University（约翰斯·霍普金斯大学）
A Black-Hole Envelope Interpretation for Cosmological Demographics of Little Red Dots
Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Department of Physics, Graduate School of Science, The University of Tokyo（东京大学理学研究科物理系）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学卡尔·萨根天文与天体物理卡弗里研究所）；The Pennsylvania State University（宾夕法尼亚州立大学）；Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）
It is widely known that in active galactic nuclei (AGNs) and black hole X-ray binaries (BHXBs), there is a tight correlation among their radio luminosity ($L_R$), X-ray luminosity ($L_X$) and BH mass ($\mbh$), the so-called `fundamental plane' (FP) of BH activity. Yet the supporting data are very limited in the $\mbh$ regime between stellar mass (i.e., BHXBs) and 10$^{6.5}$\,\msun\ (namely, the lower bound of supermassive BHs in common AGNs). In this work, we developed a new method to measure the 1.4 GHz flux directly from the images of the VLA FIRST survey, and apply it to the type-1 low-mass…
The near-IR emission in Type 1 AGNs is thought to be dominated by the thermal radiation from dust grains that are heated by the central engine in the UV/optical and are almost at the sublimation temperature. A brightening of the central source can thus further sublimate the innermost dust, leading to an increase in the radius of the near-IR emitting region. Such changes in radius have been indirectly probed by the measurements of the changes in the time lag between the near-IR and UV/optical light variation. Here we report direct evidence for such a receding sublimation region through the near…
Accreting supermassive black holes (SMBHs) can exhibit variable emission across the electromagnetic spectrum and over a broad range of timescales. The variability of active galactic nuclei (AGNs) in the ultraviolet and optical is usually at the few tens of per cent level over timescales of hours to weeks. Recently, rare, more dramatic changes to the emission from accreting SMBHs have been observed, including tidal disruption events, 'changing look' AGNs and other extreme variability objects. The physics behind the 're-ignition', enhancement and 'shut-down' of accretion onto SMBHs is not entire…
From a Chandra sample of active galactic nuclei (AGNs) in nearby galaxies, we find that for low-luminosity AGNs (LLAGNs), either the intrinsic absorption column density, or the fraction of absorbed AGNs, positively scales with the Eddington ratio for $L_{\rm bol}/L_{\rm Edd} \lesssim 10^{-2}$. Such a behavior, along with the softness of the X-ray spectrum at low luminosities, is in good agreement with the picture that they are powered by hot accretion flows surrounding supermassive black holes. Numerical simulations find that outflows are inevitable with hot accretion flows, and the outflow ra…
Supermassive stars with embedded stellar black hole cores: dense assembling star clusters as faint multiple Little Red Dot systems
University of Cambridge（剑桥大学）；Kavli Institute for Cosmology, Cambridge (KICC), University of Cambridge（剑桥大学卡弗里宇宙学研究所）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）
Origins of the UV continuum and Balmer emission lines in Little Red Dots: observational validation of dense gas envelope models enshrouding the AGN
Dunlap Institute for Astronomy and Astrophysics（邓普天文学与天体物理研究所）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学柯夫利天文学与天体物理研究所）；David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学大卫·A·邓普普天文学与天体物理学系）；NRC Herzberg（国家研究委员会赫茨伯格研究所）
