A series of gravitational instabilities in a circumnuclear gas disk (CND) are required to trigger gas transport to a central supermassive black hole (SMBH) and ignite Active Galactic Nuclei (AGNs). A test of this scenario is to investigate whether an enhanced molecular gas mass surface density ($Σ_{\rm mol}$) is found in the CND-scale of quasars relative to a comparison sample of inactive galaxies. Here we performed sub-kpc resolution CO(2-1) observations with ALMA of four low-redshift ($z \sim 0.06$), luminous ($\sim 10^{45}$ erg s$^{-1}$) quasars with each matched to a different star-forming galaxy, having similar redshift, stellar mass, and star-formation rate. We detected CO(2-1) emission from all quasars, which show diverse morphologies. Contrary to expectations, $Σ_{\rm mol}$ of the quasar sample, computed from the CO(2-1) luminosity, tends to be smaller than the comparison sample at $r < 500$ pc; there is no systematic enhancement of $Σ_{\rm mol}$ in our quasars. We discuss four possible scenarios that would explain the lower molecular gas content (or CO(2-1) luminosity as an actual observable) at the CND-scale of quasars, i.e., AGN-driven outflows, gas-rich minor mergers, time-delay between the onsets of a starburst-phase and a quasar-phase, and X-ray-dominated region (XDR) effects on the gas chemical abundance and excitation. While not extensively discussed in the literature, XDR effects can have an impact on molecular mass measurements particularly in the vicinity of luminous quasar nuclei; therefore higher resolution molecular gas observations, which are now viable using ALMA, need to be considered.
We present an analysis of observations with the Atacama Large (sub-)Millimetre Array (ALMA) of the 380 GHz water emission line and CO (11-10) emission line from MG J0414+0534, a gravitationally lensed dusty star-forming galaxy that hosts a type 1 quasar. We also present observations at 1.6 GHz with global very long baseline interferometry (VLBI) of the radio source. We confirm the previously reported detection of the 380 GHz water line and that the flux density ratio between the two merging lensed images is reversed with respect to the radio/mm continuum. We further find tentative evidence of …
We present the 0.85-2.5-micron discovery spectrum and multi-epoch photometry of the new high-redshift quasar ULAS J081621.47+213442.6 obtained using the GNIRS spectrograph of the Gemini North and near-infrared wide-field camera of the 4-m UKIRT telescopes. The redshift of ULAS J081621.47+213442.6 measured from the MgII 2799 emission line is z=7.461. The absolute magnitude of the quasar is M1450=-25.33. The black hole mass estimated using the MgII 2799 line and Eddington accretion rate are ~5x10^8Msun and ~0.7. The spectrum of ULAS J081621.47+213442.6 exhibits strong NIII] 1750 emission line of…
Galaxies are believed to experience star formation and black hole driven nuclear activity symbiotically. The symbiosis may be more extreme in the distant universe, as far-infrared photometry with the Herschel Space Observatory has found many cases of ultra-luminous cool dust emission in z>1 radio galaxies and quasars, which could have its origin in the central black hole activity, or in extreme starbursts. We here present strong evidence for an extreme circumnuclear starburst in the z=1.439 quasar 3C298. Our unparalleled 0.18 arcsecond resolution ALMA image at rest-frame 410micrometer waveleng…
While supermassive black holes are known to co-evolve with their host galaxy, the precise nature and origin of this co-evolution is not clear. We here explore the possible connection between star formation and black hole growth in the circumnuclear disk (CND) to probe this connection in the vicinity close to the black hole. We adopt here the circumnuclear disk model developed by Kawakatu & Wada (2008) and Wutschik et al. (2013), and explore both the dependence on the star formation recipe as well as the role of the gravitational field, which can be dominated by the central black hole, the CND …
We have analyzed the frequency and properties of the nuclear activity in a sample of galaxies with circumnuclear rings and spirals (CNRs). This sample was compared with a control sample of galaxies with very similar global properties but without circumnuclear rings. We discuss the relevance of the results in regard to the AGN feeding processes and present the following results: (i) bright companion galaxies seem not to be important for the appearance of CNRs, which appear to be more related to intrinsic properties of the host galaxies or to minor merger processes; (ii) the proportion of strong…
We present an analysis of UV spectra of quasars at intermediate redshifts believed to belong to the extreme Population A (xA), aimed to estimate the chemical abundances of the broad line emitting gas. We follow the approach described in a previous work extending the sample to 42 sources. Our aim is to test the robustness of the analysis carried out previously, as well as to confirm the two most intriguing results of this investigation: evidence of very high solar metallicities, and deviation of the relative abundance of elements with respect to solar values. The basis of our analysis is multi-…
Environment of SDSS quasars at $z=0.4$$-$$1.0$ explored by Subaru HSC
Ehime University（爱媛大学）；Research Center for Space and Cosmic Evolution, Ehime University（爱媛大学宇宙演化研究中心）；Amanogawa Galaxy Astronomy Research Center, Kagoshima University（鹿儿大学银河天文学研究中心）；National Astronomical Observatory of Japan（日本国立天文台）；Department of Advanced Sciences, Faculty of Science and Engineering, Hosei University（法政大学理工学部先进科学系）；School of Science, Kwansei Gakuin University（关西学院大学理学部）；Astronomical Institute, Tohoku University（东北大学天文研究所）；Department of Physical Sciences, Ritsumeikan University（立命馆大学物理科学系）；Academia Sinica Institute of Astronomy and Astrophysics（中央研究院天文及天文物理研究所）
We study the environments of low redshift (z < 0.5) quasars based on a large and homogeneous dataset from the Stripe 82 region of the Sloan Digital Sky Survey (SDSS). We have compared the < 1 Mpc scale envi- ronments of 302 quasars that were resolved in our recent study to those of 288 inactive galaxies with closely matched redshifts. Crucially, the lu- minosities of the inactive galaxies and the quasar host galaxies are also closely matched, unlike in most previous studies. The environmental overdensities were studied by measuring the num- ber density of galaxies within a projected distance o…
As a step toward a comprehensive overview of the infrared diagnostics of the central engines and host galaxies of quasars at low redshift, we present Spitzer Space Telescope spectroscopic (5-40 μm) and photometric (24, 70 and 160 μm) measurements of all Palomar-Green (PG) quasars at z < 0.5 and 2MASS quasars at z < 0.3. We supplement these data with Herschel measurements at 160 μm. The sample is composed of 87 optically selected PG quasars and 52 near-IR selected 2MASS quasars. Here we present the data, measure the prominent spectral features, and separate emission due to star formation from t…
We use Atacama Large Millimeter/submillimeter Array CO(2-1) observations of six low-redshift Palomar-Green quasars to study the distribution and kinematics of the molecular gas of their host galaxies at kpc-scale resolution. While the molecular gas content, molecular gas fraction, and star formation rates are similar to those of nearby massive, star-forming galaxies, the quasar host galaxies possess exceptionally compact, disky molecular gas distributions with a median half-light radius of 1.8 kpc and molecular gas mass surface densities $\gtrsim 22$ $M_\odot$pc$^{-2}$. While the overall veloc…
Understanding the connection between nuclear activity and galaxy environment remains critical in constraining models of galaxy evolution. By exploiting extensive catalogued data from the Galaxy and Mass Assembly (GAMA) survey, we identify a representative sample of 205 quasars at 0.1 < z < 0.35 and establish a comparison sample of galaxies, closely matched to the quasar sample in terms of both stellar mass and redshift. On scales <1 Mpc, the galaxy number counts and group membership of quasars appear entirely consistent with those of the matched galaxy sample. Despite this, we find that quasar…
Dynamical black hole mass measurements in some gas-rich galaxy mergers indicate that they are overmassive relative to their host galaxy properties. Overmassive black holes in these systems present a conflict with the standard progression of galaxy merger - quasar evolution; an alternative explanation is that a nuclear concentration of molecular gas driven inward by the merger is affecting these dynamical black hole mass estimates. We test for the presence of such gas near the two black holes in NGC 6240 using long-baseline ALMA Band 6 observations (beam size 0"06 $\times$ 0"03 or 30 pc$\times$…
We have used optical Integral Field Spectroscopy in order to map the star formation history of the inner kiloparsec of the Post-Starburst Quasar (PSQ) J0330--0532 and to map its gas and stellar kinematics as well as the gas excitation. PSQs are hypothesized to represent a stage in the evolution of galaxies in which the star formation has been recently quenched due to the feedback of the nuclear activity, as suggested by the presence of the post-starburst population at the nucleus. We have found that the old stellar population (age $\ge$ 2.5 Gyr) dominates the flux at 5100 Å in the inner 0.26 k…
The triggering mechanism for the most luminous, quasar-like active galactic nuclei (AGN) remains a source of debate, with some studies favouring triggering via galaxy mergers, but others finding little evidence to support this mechanism. Here, we present deep Isaac Newton Telescope/Wide Field Camera imaging observations of a complete sample of 48 optically-selected type 2 quasars $-$ the QSOFEED sample (L$_{\rm [OIII]}>$10$^{8.5}$$L_{\odot}$; $z < 0.14$). Based on visual inspection by eight classifiers, we find clear evidence that galaxy interactions are the dominant triggering mechanism for q…
Gaia GraL X.: The GraL catalogue of gravitationally lensed quasars Matched with \textit{Gaia} data, redshifts, and time delays
Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS（波尔多天体物理学实验室，波尔多大学，法国国家科学研究中心）；Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo（圣保罗大学天文、地球物理与大气科学研究所）；Donald Bren School of Information and Computer Sciences, University of California, Irvine（加州大学尔湾分校唐纳德·布伦信息与计算机科学学院）；CENTRA/SIM, Faculdade de Ciéncias, Universidade de Lisboa（里斯本大学理学院CENTRA/SIM）；Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学，蔚蓝海岸天文台，法国国家科学研究中心，拉格朗日实验室）；Sydney Institute for Astronomy, School of Physics, The University of Sydney（悉尼大学物理学院悉尼天文学研究所）；Center for Astrophysics Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
We present Very Long Baseline Array (VLBA) HI absorption observations of the core region of the powerful radio galaxy Cygnus A. These data show both broad (FWHM = 231 \pm 21 km/s) and narrow (FWHM <30 km/s) velocity width absorption components. The broad velocity absorption shows high opacity on the counter jet, low opacity against the core and no absorption on the jet side. We argue that these results are most naturally explained by a circumnuclear HI absorbing disk orientated roughly perpendicular to the jet axis. We estimate that the HI absorbing gas lies at a radius of ~80 pc has a scale h…
We investigate Extremely Red Quasars (ERQs), a remarkable population of heavily-reddened quasars at redshift z$\sim$2 - 3 that might be caught during a short-lived 'blow-out' phase of quasar/galaxy evolution. We perform a near-IR observational campaign using Keck/NIRSPEC, VLT/X-shooter and Gemini/GNIRS to measure rest-frame optical spectra of 28 ERQs with median infrared luminosity $\langle$log L(erg/s)$\rangle$ $\sim$46.2. They exhibit the broadest and most blue-shifted [OIII] $λ$4959,5007 emission lines ever reported, with widths (w90) ranging between 2053 and 7227 km/s, and maximum outflow …
In a popular scenario for the coevolution of massive black holes and galaxies, major mergers of gas-rich galaxies fuel vigorous star formation and obscured (type 2) quasar activity until energy feedback from the active galactic nucleus clears away the gas and dust to reveal an unobscured (type 1) quasar. Under this scenario, the precursor type 2 quasars should be more gas-rich than their type 1 counterparts, and both types of quasars are expected to be gas-deficient relative to normal, star-forming galaxies of similar stellar mass. We test this evolutionary hypothesis by investigating the infr…
We present X-ray spectral and long-term variability analyses of an unbiased sample of 361 optically selected radio-loud quasars (RLQs) utilizing sensitive serendipitous X-ray data from the Chandra and XMM-Newton archives. The spectral and temporal properties of RLQs are compared with those of radio-quiet quasars (RQQs) matched in $L_\mathrm{2500A}$ and $z$. The median power-law photon index ($Γ$) of RLQs is $1.84^{+0.01}_{-0.01}$, which is close to that of matched RQQs ($1.90^{+0.02}_{-0.01}$). No significant correlations between $Γ$ and radio-loudness, $L_\mathrm{x}/L_\mathrm{x,rqq}$ (the X-r…
We report the results of analysis of the Hbeta emission-line region of a sample of thirty low-redshift (z<1) iron low-ionization broad absorption line quasars (FeLoBALQs). Eleven of these objects are newly classified as FeLoBALQs. A matched sample of 132 unabsorbed quasars was analyzed in parallel. The emission lines showed the well known anticorrelation between the [OIII] and FeII emission (Boroson & Green 1992). Using a summary statistic called E1 to quantify this anticorrelation, we found that while the distribution of E1 for the unabsorbed quasars has a single peak, the FeLoBALQs have a bi…
When a flux-limited quasar sample is observed at later times, there will be more dimmed quasars than brightened ones, due to a selection bias induced at the time of sample selection. Quasars are continuously varying and there are more fainter quasars than brighter ones. At the time of selection, even symmetrical variability will result in more quasars with their instantaneous fluxes scattered above the flux limit than those scattered below, leading to an asymmetry in flux changes over time. The same bias would lead to an asymmetry in the ensemble structure function (SF) of the sample such that…
We present the second Multi-Epoch X-ray Serendipitous AGN Sample (MEXSAS2), extracted from the 6th release of the XMM Serendipitous Source Catalogue (XMMSSC-DR6), cross-matched with Sloan Digital Sky Survey quasar catalogues DR7Q and DR12Q. Our sample also includes the available measurements for masses, bolometric luminosities, and Eddington ratios. Analyses of the ensemble structure function and spectral variability are presented, together with their dependences on such parameters. We confirm a decrease of the structure function with the X-ray luminosity, and find a weak dependence on the bla…
Studies of radio-loud (RL) broad absorption line (BAL) quasars indicate that popular orientation-based BAL models fail to account for all observations. Are these results extendable to radio-quiet (RQ) BAL quasars? Comparisons of RL and RQ BAL quasars show that many of their properties are quite similar. Here we extend these analyses to the rest-frame ultraviolet (UV) spectral properties, using a sample of 73 RL and 473 RQ BAL quasars selected from the Sloan Digital Sky Survey (SDSS). Each RQ quasar is individually matched to a RL quasar in both redshift (over the range $1.5 < z < 3.5$) and con…
We present results from 1.4 and 5 GHz observations at matched resolution with the Karl G. Jansky Very Large Array (VLA) of 11 powerful 3C FR II quasars. We examine the 11 quasars along with a sample of 13 narrow-line FR II radio galaxies and find that radio-loud unification largely holds but environmental effects cannot be ignored. The radio core prominence, largest linear size, and axial ratio parameter values indicate that quasars are at relatively smaller angles compared to the radio galaxies and thus probe orientation. Lack of correlation between statistical orientation indicators such as …
We present new 850$μ$m SCUBA-2 observations for a sample of 19 heavily reddened Type-I quasars at redshifts $z\sim$2 with dust extinctions of A$_{\rm{V}} \simeq 2-6$ mag. Three of the 19 quasars are detected at $>$3$σ$ significance corresponding to an 850$μ$m flux-limit of $\gtrsim$4.8 mJy. Assuming the 850$μ$m flux is dominated by dust heating due to star formation, very high star formation rates (SFR) of $\sim$2500-4500 M$_\odot$ yr$^{-1}$ in the quasar host galaxies are inferred. Even when considering a large contribution to the 850$μ$m flux from dust heated by the quasar itself, significan…
We analyse the 2-dimensional distribution and kinematics of the stars as well as molecular and ionised gas in the central few hundred parsecs of 5 active and 5 matched inactive galaxies. The equivalent widths of the Br-gamma line indicate there is no on-going star formation in their nuclei, although recent (terminated) starbursts are possible in the active galaxies. The stellar velocity fields show no signs of non-circular motions, while the 1-0S(1) H_2 kinematics exhibit significant deviations from simple circular rotation. In the active galaxies the H_2 kinematics reveal inflow and outflow s…
We present VLT-SINFONI near infra-red spectra of 26 new heavily reddened quasar candidates selected from the UKIDSS-LAS, VISTA VHS and VIKING imaging surveys. This new sample extends our reddened quasar search to both brighter and fainter luminosities. 25 of the 26 candidates are confirmed to be broad line quasars with redshifts $0.7<z<2.6$ and dust extinctions $0.5<E(B-V)<3.0$. Combining with previously identified samples, we study the H$α$, H$β$ and [OIII] emission line properties in 22 heavily reddened quasars with $L_{bol}\approx 10^{47}$ erg/s and $z>2$. We present the first comparison of…
We report the result of optical identifications of FIRST radio sources with the Hyper Suprime-Cam Subaru Strategic Program survey (HSC-SSP). The positional cross-match within 1" between the FIRST and HSC-SSP catalogs (i ~< 26) produced more than 3600 optical counterparts in the 156 deg^2 of the HSC-SSP field. The matched counterparts account for more than 50% of the FIRST sources in the search field, which substantially exceed previously reported fractions of SDSS counterparts (i ~< 22) of ~30%. Among the matched sample, 9% are optically unresolved sources such as radio-loud quasars. The optic…
We present a measurement of the star formation properties of a uniform sample of mid-IR selected, unobscured and obscured quasars (QSO1s and QSO2s) in the Boötes survey region. We use an spectral energy distribution (SED) analysis for photometric data spanning optical to far-IR wavelengths to decompose AGN and host galaxy components. We find that when compared to a matched sample of QSO1s, the QSO2s have higher far-IR detection fractions, far-IR fluxes and infrared star formation luminosities ($L_{\rm IR}^{\rm SF}$) by a factor of $\sim2$. Correspondingly, we show that the AGN obscured fractio…
Quasar feedback is suspected to play a key role in the evolution of massive galaxies, by removing or reheating gas in quasar host galaxies and thus limiting the amount of star formation. In this paper we continue our investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1) quasars, to determine the morphology and kinematics of ionized gas around these objects, predominantly via observations of the [O III]5007 emission line. We find that ionized gas nebulae extend out to ~13 kpc from the quasar, th…
Recent simulation studies suggest that the supermassive black hole (SMBH) growth in the early universe may precede the prolonged intense star formation within its host galaxy, instead of quasars appearing after the obscured dusty star formation phase. If so, high-redshift quasars with low Eddington ratios ($λ_{\rm Edd}$) would be found in actively star-forming hosts with a star formation rate (SFR) of $>100~M_{\odot}$ yr$^{-1}$. We present the sub-mm observations of IMS J2204+0112, a faint quasar with a quasar bolometric luminosity of $L_{\rm bol}=4.2\times10^{12}~L_{\odot}$ and a low $λ_{\rm …
We study the rest-frame optical properties of 74 luminous (L_bol=10^46.2-48.2 erg/s), 1.5<z<3.5 broad-line quasars with near-IR (JHK) slit spectroscopy. Systemic redshifts based on the peak of the [OIII]5007 line reveal that redshift estimates from the rest-frame UV broad emission lines (mostly MgII) are intrinsically uncertain by ~ 200 km/s (measurement errors accounted for). The overall full-width-at-half-maximum of the narrow [OIII] line is ~ 1000 km/s on average. A significant fraction of the total [OIII] flux (~ 40%) is in a blueshifted wing component with a median velocity offset of ~ 70…
Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only few quasars have been reported at $z > 6.5$ ($<$800 Myr after the Big Bang). In this work, we present six additional $z \gtrsim 6.5$ quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 $z \gtrsim 6.5$ quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of $z\gtrsim$6.5 quasars show large blueshifts of the broad CIV 1549Å$\,$emissio…
Subaru High-$z$ Exploration of Low-luminosity Quasars (SHELLQs). XVII. Black Hole Mass Distribution at $z \sim 6$ Estimated via Spectral Comparison with Low-$z$ Quasars
We present CO(1-0) and CO(3-2) ALMA observations of the molecular gas in PKS 1549-79, as well as mm and VLBI 2.3-GHz continuum observations of its radio jet. PKS 1549-79 is one of the closest young, radio-loud quasars caught in an on-going merger in which the AGN is in the first phases of its evolution. We detect three structures tracing the accretion and the outflow of molecular gas: kpc-scale tails of gas accreting onto PKS 1549-79, a circumnuclear disc (CND) in the inner few hundred parsec, and a very broad (>2300 \kms) component detected in CO(1-0) at the position of the AGN. Thus, in PKS …
This study is focused on the observational measurement of the viewing angle of individual quasars by modeling the broadband quasar spectrum ranging from the infra-red (IR) to the soft X-ray band. Sources are selected from various published catalogs, and their broadband quasi-simultaneous spectral data points were collected and used to model. We started with a COSMOS sample of type-1 sources which have broadband photometric points. Then, to include more data points, we cross-matched the COSMOS with the SDSS DR14 quasar catalog, and eventually, we find 90 sources that have broadband data ranging…
Extremely variable quasars (EVQs) are a population of sources showing large optical photometric variability revealed by time-domain surveys. The physical origin of such extreme variability is yet unclear. In this first paper of a series, we construct the largest-ever sample of 14,012 EVQs using photometric data spanning over $>$ 15 years from SDSS and Pan-STARRS1. We divide them into five sub-samples according to the relative brightness of an EVQ during SDSS spectroscopic observation compared to the mean brightness from photometric observations. Corresponding control samples of normal quasars …
Hot, Photoionized X-ray Gas in Two Luminous Type 2 Quasars: Chandra-HST Evidence for a Wind-Driven Sequence
NASA Goddard Space Flight Center（NASA戈达德太空飞行中心）；The Catholic University of America（天主教大学）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森天体物理中心）；INAF Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Eureka Scientific, Inc.（尤里卡科学公司）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；Dipartimento di Fisica, Università di Trento（特伦托大学物理系）；Naval Research Laboratory（海军研究实验室）；AURA for ESA（欧洲空间局美国天文研究联盟）
We present a photometrical and morphological multicolor study of the properties of low redshift (z<0.3) quasar hosts based on a large and homogeneous dataset of quasars derived from the Sloan Digital Sky Survey (DR7). We used quasars that were imaged in the SDSS Stripe82 that is up to 2 mag deeper than standard Sloan images. This sample is part of a larger dataset of ~400 quasars at z<0.5 for which both the host galaxies and their galaxy environments were studied (Falomo et al. 2014,Karhunen et al. 2014). For 52 quasars we undertake a study of the color of the host galaxies and of their close …
Quasars may have played a key role in limiting the stellar mass of massive galaxies. Identifying those quasars in the process of removing star formation fuel from their hosts is an exciting ongoing challenge in extragalactic astronomy. In this paper we present X-ray observations of eleven extremely red quasars (ERQs) with $L_{\rm bol}\sim 10^{47}$ erg s$^{-1}$ at $z=1.5-3.2$ with evidence for high-velocity ($v > 1000$ km s$^{-1}$) [OIII]$λ$5007Å outflows. X-rays allow us to directly probe circumnuclear obscuration and to measure the instantaneous accretion luminosity. We detect ten out of elev…
We present near-IR spectroscopy of 22 luminous low-ionization broad absorption line quasars (LoBAL QSOs) at redshift 1.3<z<2.5, with 12 objects at z~1.5 and 10 at z~2.3. The spectra cover the rest-frame H$α$ and H$β$ line regions, allowing us to obtain robust black hole mass estimates based on the broad H$α$ line. We use these data, augmented by a lower-redshift sample from the Sloan Digital Sky Survey, to test the proposed youth scenario for LoBALs, which suggests that LoBALs constitute an early short-lived evolutionary stage of quasar activity, by probing for any difference in their masses, …
The most frequently proposed model for the origin of quasars holds that the high accretion rates seen in luminous active galactic nuclei are primarily triggered during major mergers between gas-rich galaxies. While plausible for decades, this model has only begun to be tested with statistical rigor in the past few years. Here we report on a Hubble Space Telescope study to test this hypothesis for $z=2$ quasars with high super-massive black hole masses ($M_\mathrm{BH}=10^9-10^{10}~M_\odot{}$), which dominate cosmic black hole growth at this redshift. We compare Wide Field Camera 3 $F160W$ (rest…
We present X-SHOOTER near-infrared spectroscopy of a large sample of 38 luminous ($M_{1450}=-29.0$ to $-24.4$) quasars at $5.78<z<7.54$, which have complementary CII 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 FeII/MgII flux ratio suggests that the broad line regions of all q…
We present the results of a model-independent investigation of the rest-frame UV spectra from a comprehensive sample of $394$ quasars in the redshift range $1.5\leq z \leq 7.5$. We fit the main Broad Emission Lines (BELs) in the rest-frame range $1280 \textÅ \leq λ\leq 3000 \textÅ$ (O I, C II, Si IV, C III, C IV and Mg II) with a lightly-supervised spline fitting technique. Redshifts are derived from the peaks of each fitted BEL and used to compute relative velocity shifts. We show that our method gives unbiased velocity shifts and is insensitive to spectral resolution and instrumental paramet…
We study the radio properties of moderately obscured quasars over a range of redshifts to understand the role of radio activity in accretion using the Jansky Very Large Array (JVLA) at 6.0GHz and 1.4GHz. Our z~2.5 sample consists of optically-selected obscured quasar candidates, all of which are radio-quiet, with typical radio luminosities of $νL_ν$[1.4 GHz] < $10^{40}$ erg s$^{-1}$. Only a single source is individually detected in our deep (rms~10 $μ$Jy) exposures. This population would not be identified by radio-based selection methods used for distinguishing dusty star-forming galaxies and …
