Polar dust has been found to play an important role in the mid-infrared emission of nearby Seyfert nuclei. If and how often polar dust exists among the quasar population is unknown due to the lack of spatially-resolved observations. In this Letter, we report correlations between the prominence of AGN forbidden line emission (commonly associated with the narrow line region) and the dust mid-IR energy output among the archetypal Palomar-Green quasar sample and other bright type-1 AGNs drawn from the SDSS, Spitzer and WISE archives. The AGN mid-IR color differences traced by WISE W2 ($\sim4.6 μm$)$-$W3 ($\sim12 μm$) and W2 ($\sim4.6 μm$)$-$W4 ($\sim22 μm$), and near-IR to mid-IR SEDs constrained with 2MASS, WISE and Spitzer data have clear trends with the relative strength of the forbidden line regions traced by the optical \OIII and mid-IR \OIV emission lines. These observations indicate that, where the lines are strong, a large fraction of the AGN emission at $λ\gtrsim5 μ$m comes from dust in the forbidden line regions. We find that the widely quoted universal AGN template is a result of averaging quasar SEDs with different levels of polar dust emission above the torus output and that the typical intrinsic IR SED of compact torus dust emission alone falls with increasing wavelength past 5 $μ$m (in $νF_ν$). In addition, the association of polar dust with the forbidden lines suggests an alternative to the receding torus hypothesis for the decrease in infrared output with increasing AGN luminosity.
Periodic quasars are candidates for binary supermassive black holes (BSBHs) efficiently emitting low frequency gravitational waves. Recently, $\sim$150 candidates were identified from optical synoptic surveys. However, they may be false positives caused by stochastic quasar variability given the few cycles covered (typically 1.5). To independently test the binary hypothesis, we search for evidence of truncated or gapped circumbinary accretion discs (CBDs) in their spectral energy distributions (SEDs). Our work is motivated by CBD simulations that predict flux deficits as cutoffs from central c…
To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z<0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ~60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: 1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and 2) warm-dust-deficient (WDD) quasars that have similar hot du…
Studying the coupling between the energy output produced by the central quasar and the host galaxy is fundamental to fully understand galaxy evolution. Quasar feedback is indeed supposed to dramatically affect the galaxy properties by depositing large amounts of energy and momentum into the ISM. In order to gain further insights on this process, we study the SEDs of sources at the brightest end of the quasar luminosity function, for which the feedback mechanism is supposed to be at its maximum. We model the rest-frame UV-to-FIR SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.…
We present observed mid-infrared and optical colors and composite spectral energy distributions (SEDs) of type 1 (broad-line) and 2 (narrow-line) quasars selected from Sloan Digital Sky Survey (SDSS) spectroscopy. A significant fraction of powerful quasars are obscured by dust, and are difficult to detect in optical photometric or spectroscopic surveys. However these may be more easily identified on the basis of mid-infrared (MIR) colors and SEDs. Using samples of SDSS type 1 type 2 matched in redshift and [OIII] luminosity, we produce composite rest-frame 0.2-15 micron SEDs based on SDSS, UKI…
We present the Swift optical to X-ray spectral energy distributions (SEDs) of 44 quasars at redshifts z~2 observed by Swift, part of a larger program to establish and characterize the optical through X-ray SEDs of moderate-redshift quasars. Here we outline our analysis approach and present preliminary analysis and results for the first third of the full quasar sample. Not all quasars in the sample are detected in X-rays; all of the X-ray detected objects so far are radio loud. As expected for radio loud objects, they are X-ray bright relative to radio-quiet quasars of comparable optical lumino…
The rest ultraviolet to infrared spectral energy distributions of heavily reddened quasars are "V-shaped" and hot-dust poor
School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学学院）；Centre for Extragalactic Astronomy, Department of Physics, Durham University（杜伦大学物理系河外天文中心）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）
We present the results of an optical spectroscopic survey of a sample of 40 candidate obscured quasars identified on the basis of their mid-infrared emission detected by the Wide-Field Infrared Survey Explorer (WISE). Optical spectra for this survey were obtained using the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT). Our sample was selected with WISE colors characteristic of AGNs, as well as red optical to mid-IR colors indicating that the optical/UV AGN continuum is obscured by dust. We obtain secure redshifts for the majority of the objects that comprise o…
Thermal mid-infrared emission of quasars requires an obscuring structure that can be modeled as a magneto-hydrodynamic wind in which radiation pressure on dust shapes the outflow. We have taken the dusty wind models presented by Keating and collaborators that generated quasar mid-infrared spectral energy distributions (SEDs), and explored their properties (such as geometry, opening angle, and ionic column densities) as a function of Eddington ratio and X-ray weakness. In addition, we present new models with a range of magnetic field strengths and column densities of the dust-free shielding gas…
We analyze the near-infrared to UV data of 16 quasars with redshifts ranging from 0.71 $<$ $z$ $<$ 2.13 to investigate dust extinction properties. The sample presented in this work is obtained from the High $A_V$ Quasar (HAQ) survey. The quasar candidates were selected from the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), and follow-up spectroscopy was carried out at the Nordic Optical Telescope (NOT) and the New Technology Telescope (NTT). To study dust extinction curves intrinsic to the quasars, from the HAQ survey we selected 16 cases where the Small Mage…
We have observed 104 gravitationally-lensed quasars at $z\sim1-4$ with Herschel/SPIRE, the largest such sample ever studied. By targeting gravitational lenses, we probe intrinsic far-infrared (FIR) luminosities and star formation rates (SFRs) more typical of the population than the extremely luminous sources that are otherwise accessible. We detect 72 objects with Herschel/SPIRE and find 66 percent (69 sources) of the sample have spectral energy distributions (SEDs) characteristic of dust emission. For 53 objects with sufficiently constrained SEDs, we find a median effective dust temperature o…
Accretion onto black holes at rates above the Eddington limit has long been discussed in the context of supermassive black hole (SMBH) formation and evolution, providing a possible explanation for the presence of massive quasars at high redshifts (z$\gtrsim$7), as well as having implications for SMBH growth at later epochs. However, it is currently unclear whether such `super-Eddington' accretion occurs in SMBHs at all, how common it is, or whether every SMBH may experience it. In this work, we investigate the observational consequences of a simplistic model for super-Eddington accretion flows…
We recently proposed the equivalent width (EW) of the narrow [OIII]5007Å emission line as an orientation indicator for active galactic nuclei. We tested this method on about $12,300$ optically selected broad line quasars from the SDSS 7th Data Release at redshift $z < 0.8$ and with full width at half-maximum values of broad emission lines (H$α$, H$β$, and MgII) larger than $2000$ km/s. We now examine their spectral energy distributions (SEDs) using broad band photometry from the near-infrared to the ultraviolet to look for variations in the overall shape as a function of the EW[OIII]. We find …
The range of currently proposed active galactic nucleus (AGN) far-infrared templates results in uncertainties in retrieving host galaxy information from infrared observations and also undermines constraints on the outer part of the AGN torus. We discuss how to test and reconcile these templates. Physically, the fraction of the intrinsic AGN IR-processed luminosity compared with that from the central engine should be consistent with the dust-covering factor. In addition, besides reproducing the composite spectral energy distributions (SEDs) of quasars, a correct AGN IR template combined with an…
We analyse a sample of 85 luminous (log(nuLnu(3\um)/erg s-1)>45.5) quasars with restframe ~2-11 \um spectroscopy from AKARI and Spitzer. Their high luminosity allows a direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disk and two blackbodies for the dust emission successfully reproduces the 0.1-10 \um spectral energy distributions (SEDs). Excess emission at 1-2 \um over the best-fitting model suggests that hotter dust is necessary in addition to the ~1200 K blackbody and the disk t…
Obscured AGN at z < 1.5: X-ray to Far-Infrared SEDs and Host Galaxy Morphologies in the GOODS Fields
University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校）；University of Wisconsin - Madison（威斯康星大学麦迪逊分校）；Eureka Scientific（尤里卡科学公司）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；Wuhan University（武汉大学）；Northwestern University（西北大学）；Yale Center for Astronomy and Astrophysics（耶鲁天文学与天体物理学中心）；Physics Department and Yale Center for Astronomy and Astrophysics（耶鲁大学物理系及天文学与天体物理学中心）；Yale University（耶鲁大学）；DiRAC Institute and the Department of Astronomy, University of Washington（华盛顿大学DiRAC研究所及天文学系）
We investigate the attenuation law in $z\sim 6$ quasars by combining cosmological zoom-in hydrodynamical simulations of quasar host galaxies, with multi-frequency radiative transfer calculations. We consider several dust models differing in terms of grain size distributions, dust mass and chemical composition, and compare the resulting synthetic Spectral Energy Distributions (SEDs) with data from bright, early quasars. We show that only dust models with grain size distributions in which small grains ($a < 0.1~μ$m, corresponding to $\approx 60\%$ of the total dust mass) are selectively removed …
Complete studies of the radiative processes of thermal emission from the amorphous dust from microwave through far infrared wavebands are presented by taking into account, self-consistently for the first time, the standard two-level systems (TLS) model of amorphous materials. The observed spectral energy distributions (SEDs) for the Perseus molecular cloud (MC) and W43 from microwave through far infrared are fitted with the SEDs calculated with the TLS model of amorphous silicate. We have found that the model SEDs well reproduce the observed properties of the anomalous microwave emission (AME)…
The WISE mission has unveiled a rare population of high-redshift ($z=1-4.6$), dusty, hyper-luminous galaxies, with infrared luminosities $L_{\rm IR} > 10^{13}~L_{\odot}$, and sometimes exceeding $10^{14}~L_{\odot}$. Previous work has shown that their dust temperatures and overall far-IR SEDs are significantly hotter than expected for star-formation. We present here an analysis of the rest-frame optical through mid-IR SEDs for a large sample of these so-called "Hot, Dust-Obscured Galaxies" (Hot DOGs). We find that the SEDs of Hot DOGs are generally well modeled by the combination of a luminous,…
If the disappearance of the broad emission lines observed in changing-look quasars were caused by the obscuration of the quasar core through moving dust clouds in the torus, high linear polarization typical of type 2 quasars would be expected. We measured the polarization of the changing-look quasar J1011+5442 in which the broad emission lines have disappeared between 2003 and 2015. We found a polarization degree compatible with null polarization. This measurement suggests that the observed change of look is not due to a change of obscuration hiding the continuum source and the broad line regi…
We define a quasar-galaxy mixing diagram using the slopes of their spectral energy distributions (SEDs) from 1μm to 3000Å and from 1μm to 3μm in the rest frame. The mixing diagram can easily distinguish among quasar-dominated, galaxy-dominated and reddening-dominated SED shapes. By studying the position of the 413 XMM selected Type 1 AGN in the wide-field "Cosmic Evolution Survey" (COSMOS) in the mixing diagram, we find that a combination of the Elvis et al. (1994, hereafter E94) quasar SED with various contributions from galaxy emission and some dust reddening is remarkably effective in descr…
If the disappearance of the broad emission lines observed in changing-look quasars originates from the obscuration of the quasar core by dusty clouds moving in the torus, high linear optical polarization would be expected in those objects. We then measured the rest-frame UV-blue linear polarization of a sample of 13 changing-look quasars, 7 of them being in a type 1.9-2 state. For all quasars but one the polarization degree is lower than 1%. This suggests that the disappearance of the broad emission lines cannot be attributed to dust obscuration, and supports the scenario in which changes of l…
Most active supermassive black holes (SMBH) in present-day galaxies are underfed and consist of low-luminosity active galactic nuclei (LLAGN). They have multiwavelength broadband spectral energy distributions (SED) dominated by non-thermal processes which are quite different from those of the brighter, more distant quasars. Modelling the observed SEDs of LLAGNs is currently challenging, given the large computational expenses required. In this work, we used machine learning (ML) methods to generate model SEDs and fit sparse observations of LLAGNs. Our ML model consisted of a neural network and …
To understand the impact of active galactic nuclei (AGN) on their host galaxies and large scale environment it is crucial to determine their total radiative power across all wavelengths (i.e., bolometric luminosity). In this contribution we describe how quasar accretion disk spectral energy distribution (SED) templates, parameterized by the black hole (BH) mass, Eddington ratio, and spin can be used to estimate their total radiated luminosity. To estimate the bolometric luminosity of AGN, we integrate the accretion disk SEDs from 1$μ$m to 10keV. Our approach self-consistently covers any gaps i…
We have obtained spectropolarimetric observations of the four images of the gravitationally lensed broad absorption line quasar H1413+117. The polarization of the microlensed image D is significantly different both in the continuum and in the broad lines from the polarization of image A which is essentially unaffected by microlensing. The observations suggest that the continuum is scattered off two regions spatially separated and producing roughly perpendicular polarizations. These results are compatible with a model in which the microlensed polarized continuum comes from a compact region loca…
We present a new analysis of the PG quasar sample based on Spitzer and Herschel observations. (I) Assuming PAH-based star formation luminosities (L_SF) similar to Symeonidis et al. (2016, S16), we find mean and median intrinsic AGN spectral energy distributions (SEDs). These, in the FIR, appear hotter and significantly less luminous than the S16 mean intrinsic AGN SED. The differences are mostly due to our normalization of the individual SEDs, that properly accounts for a small number of very FIR-luminous quasars. Our median, PAH-based SED represents ~ 6% increase on the 1-243 micron luminosit…
Despite the hypothesized similar face-on viewing angles, the infrared emission of type-1 AGNs has diverse spectral energy distribution (SED) shapes that deviate substantially from the well-characterized quasar templates. Motivated by the commonly-seen UV-optical obscuration and the discovery of parsec-scale mid-IR polar dust emission in some nearby AGNs, we develop semi-empirical SED libraries for reddened type-1 AGNs built on the quasar intrinsic templates, assuming low-level extinction caused by an extended distribution of large dust grains. We demonstrate that this model can reproduce the n…
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalogue, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We constrain the form of the far-infrared emission and find 3$σ$-4$σ$ evidence for the thermal Sunyaev-Zel'dovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy $(6.2 \pm 1.7)\times 10^{60}$ erg. This amount of thermal energy is greater th…
We present results from a combined radio polarization and emission line study of five type 2 quasars at $z<0.2$ with the Karl G. Jansky Very Large Array (VLA) B-array at 5 GHz and Hubble Space Telescope (HST) [O III] observations. These five sources are known to exhibit close association between radio structures and ionized gas morphology and kinematics. Four sources (J0945+1737, J1000+1242, J1356+1026 and J1430+1339) show polarization in the current data. J1010+1413 is the unpolarized source in our sample. We detect $0.5-1\%$ fractional polarization in the radio cores and a high fractional po…
We examine the optical photometric and polarimetric variability of the luminous type 1 non-blazar quasar 3C 323.1 (PG 1545+210). Two optical spectro-polarimetric measurements taken during the periods 1996$-$98 and 2003 combined with a $V$-band imaging polarimetric measurement taken in 2002 reveal that (1) as noted in the literature, the polarization of 3C 323.1 is confined only to the continuum emission, that is, the emission from the broad line region is unpolarized; (2) the polarized flux spectra show evidence of a time-variable broad absorption feature in the wavelength range of the Balmer …
Using a sample of $\simeq$144,000 quasars from the Sloan Digital Sky Survey data release 14 we investigate the outflow properties, evident both in absorption and emission, of high-ionization Broad Absorption Line (BAL) and non-BAL quasars with redshifts 1.6 $\lesssim z \leq$ 3.5 and luminosities 45.3 $< \log_{10}(L_{bol}) < $ 48.2 erg s$^{-1}$. Key to the investigation is a continuum and emission-line reconstruction scheme, based on mean-field independent component analysis, that allows the kinematic properties of the CIV$λ$1550 emission line to be compared directly for both non-BAL and BAL qu…
The mid-infrared to ultraviolet (0.1 -- 10 $μm$) spectral energy distribution (SED) shapes of 407 X-ray-selected radio-quiet type 1 AGN in the wide-field ``Cosmic Evolution Survey" (COSMOS) have been studied for signs of evolution. For a sub-sample of 200 radio-quiet quasars with black hole mass estimates and host galaxy corrections, we studied their mean SEDs as a function of a broad range of redshift, bolometric luminosity, black hole mass and Eddington ratio, and compared them with the Elvis et al. (1994, E94) type 1 AGN mean SED. We found that the mean SEDs in each bin are closely similar …
We have measured the optical linear polarization of quasars belonging to Gpc-scale quasar groups at redshift z ~ 1.3. Out of 93 quasars observed, 19 are significantly polarized. We found that quasar polarization vectors are either parallel or perpendicular to the directions of the large-scale structures to which they belong. Statistical tests indicate that the probability that this effect can be attributed to randomly oriented polarization vectors is of the order of 1%. We also found that quasars with polarization perpendicular to the host structure preferentially have large emission line widt…
The infrared spectral energy distributions (SEDs) of $z\gtrsim 5$ quasars can be reproduced by combining a low-metallicity galaxy template with a standard AGN template. The host galaxy is represented by Haro 11, a compact, moderately low metallicity, star-bursting galaxy that shares typical features of high-$z$ galaxies. For the vast majority of $z\gtrsim 5$ quasars, the AGN contribution is well modeled by a standard empirical template with the contamination of star formation in the infrared subtracted. Together, these two templates can separate the contributions from the host galaxy and the A…
Using the Herschel Space Observatory we have observed a representative sample of 87 powerful 3CR sources at redshift z < 1. The far-infrared (FIR, 70-500 micron) photometry is combined with mid-infrared (MIR) photometry from the Wide-Field Infrared Survey Explorer (WISE) and catalogued data to analyse the complete spectral energy distributions (SEDs) of each object from optical to radio wavelength. To disentangle the contributions of different components, the SEDs are fitted with a set of templates to derive the luminosities of host galaxy starlight, dust torus emission powered by active galac…
The infrared properties of blazars can be studied from the statistical point of view with the help of sky surveys, like that provided by the Wide-field Infrared Survey Explorer (WISE) and the Two Micron All Sky Survey (2MASS). However, these sources are known for their strong and unpredictable variability, which can be monitored for a handful of objects only. In this paper we consider the 28 blazars (14 BL Lac objects and 14 flat-spectrum radio quasars, FSRQs) that are regularly monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) since 2007. They show…
Kinematic Stratification in Extremely Red Quasars Revealed by JWST
The Johns Hopkins University（约翰斯·霍普金斯大学）；Florida Gulf Coast University（佛罗里达海湾海岸大学）；California Institute of Technology（加州理工学院）；University of California, Riverside（加利福尼亚大学河滨分校）；University of California, San Diego（加利福尼亚大学圣地亚哥分校）；University of Maryland, College Park（马里兰大学帕克分校）；Zentrum für Astronomie der Universität Heidelberg（海德堡大学天文中心）
We present the mean spectral energy distribution (SED) of a sample of optically selected quasars (QSOs) at redshifts of $1 \le z \le 5$. To derive it, we exploit photometric information from SDSS, UKIDSS, and WISE surveys in combination with a stacking analysis of \textit{Herschel}, \textit{AKARI}, and \textit{Planck} maps at the location of the QSOs. The near-UV and optical parts of the reconstructed mean rest-frame SED are similar to those found in other studies. However, the SED shows an excess at 1-2 $μ$m (when compared to the aforementioned SEDs normalized in the near-UV) and a prominent …
We present the results of a 21-cm HI survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Robert C. Byrd Green Bank Telescope (GBT). These remnants were selected from the Quasar/ULIRG Evolution Study (QUEST) sample of ultraluminous infrared galaxies (ULIRGs; L$_{8-1000 μm} > 10^{12}$ L$_\odot$) and quasars; our targets are all bolometrically dominated by active galactic nuclei (AGN) and sample the later phases of the proposed ULIRG-to-quasar evolutionary sequence. We find the prevalence of HI absorption (emission) to be 100% (29%) in ULIRGs with HI detections, 10…
Polarized emission from a quasar is produced by wavelength-independent electron scattering surrounding its accretion disc, and thus avoid the contamination from its host galaxy and reveal the intrinsic emission spectrum of the accretion disc. Ultra-violet (UV) emission from a quasar is normally free from the contamination from its host galaxy. Polarization fraction of the quasar's disc emission can therefore be determined by comparing total UV emission with polarized visible to near-infrared (NIR) emission; and the resulting continuum spectrum from UV to infrared can reveal the theoretically e…
We present combined $\approx 14-37~\rm ks$ Chandra observations of seven $z = 1.6-2.7$ broad absorption line (BAL) quasars selected from the Large Bright Quasar Survey (LBQS). These seven objects are high-ionization BAL (HiBAL) quasars, and they were undetected in the Chandra hard band ($2-8$ keV) in previous observations. The stacking analyses of previous Chandra observations suggested that these seven objects likely contain some candidates for intrinsically X-ray weak BAL quasars. With the new Chandra observations, six targets are detected. We calculate their effective power-law photon indic…
We conducted the first multi-frequency polarimetric imaging of four broad absorption line (BAL) quasars using Very Long Baseline Array at milli-arcsecond resolutions to investigate the inclination of the non-thermal jet and test the hypothesis that radio sources in BAL quasars are still young. Among these four sources, J0928+446, J1018+0530, and J1405+4056 show one-sided structures in parsec scales, and polarized emission detected in the core. These characteristics are consistent with those of blazars. We set constraints on viewing angles to $<$66 deg for these jets, in the framework of a Dopp…
A handful of active galactic nuclei (AGN) have shown strong spectral variations in the optical band between epochs that are years apart. The appearance or disappearance of broad emission lines in their spectra completely changes their classification. Since their nucleus orientation cannot change in such short timescales another physical interpretation has to be found. Several scenarios are competing to explain their changing-look nature and, for the first time, we conduct polarized radiative transfer Monte Carlo simulations for all the models. We demonstrate that all interpretations have disti…
We present UV/optical spectropolarimetric modelling of the phenomenologically-based structure for quasars proposed by Elvis (2000). In this first paper of a series, we explore the continuum polarisation emerging from radiatively accelerated and bent winds that were vertically launched from the accretion disc in an active galactic nucleus (AGN). We simulate the radiative transfer occurring in Thomson scattering and dust extinction media over a range of morphological parameters and optical depths of the wind. We demonstrate that the wind geometry proposed by Elvis with a phenomenologically-deriv…
