Search

An empirical model is presented that links the demographics of AGN to their ensemble X-ray variability properties. Observations on the incidence of AGN in galaxies are combined with (i) models of the Power Spectrum Density (PSD) of the flux variations of AGN and (ii) parameterisations of the black-hole mass vs stellar-mass scaling relation, to predict the mean excess variance of active black-hole populations in cosmological volumes. We show that the comparison of the model with observational measurements of the ensemble excess variance as a function of X-ray luminosity provides a handle on both the PSD models and the black-hole mass vs stellar mass relation. We find strong evidence against a PSD model that is described by a broken power-law and a constant overall normalisation. Instead our analysis indicates that the amplitude of the PSD depends on the physical properties of the accretion events, such as the Eddington ratio and/or the black hole mass. We also find that current observational measurements of the ensemble excess variance are consistent with the black-hole mass vs stellar mass relation of local spheroids based on dynamically determined black-hole masses. We also discuss future prospects of the proposed approach to jointly constrain the PSD of AGN and the black-hole mass vs stellar mass relation as a function of redshift. The mock AGN catalogue used in the paper is made available. The contents are described in the README file. The code used in the paper is available at https://github.com/ageorgakakis/EnsembleVariability. Full details can be found in the associated paper at https://arxiv.org/abs/2105.08752., The code that uses this data is available at https://github.com/ageorgakakis/EnsembleVariability The paper describing the modeling approach is available at https://arxiv.org/abs/2105.08752, {"references":["https://arxiv.org/abs/2105.08752"]}

This paper presents the construction of the RapidXMM database that is available through the XMM-Newton Science Archive and offers access to upper limits and aperture photometry across the field of view of the XMM-Newton Pointed and Slew Survey observations. The feature of RapidXMM is speed. It enables the fast retrieval of X-ray upper limits and photometry products in three energy bands (0.2-2, 2-12, 0.2-12 keV) for large numbers of input sky positions. This is accomplished using the Hierarchical Equal Area Iso Latitude pixelation of the sphere (HEALPix). The pre-calculated upper-limits and associated X-ray photometry products are reprojected into the HEALPix grid of cells before being ingested into the RapidXMM database. This results in tables of upper limits and aperture photometry within HEALPix cells of size ~3 arcsec (Pointed Observations) and ~6 arcsec (Slew Survey). The database tables are indexed by the unique integer number of the HEALPix cells. This reduces spatial nearest-neighbor queries by sky position to an integer-matching exercise and significantly accelerates the retrieval of results. We describe in detail the processing steps that lead from the science products available in the XMM-Newton archive to a database optimised for sky queries. We also present two simple show-case applications of RapidXMM for scientific studies: searching for variable X-ray sources, and stacking analysis of X-ray faint populations, Comment: 20 pages, 20 figures. This article has been accepted for publication in MNRAS. Published by Oxford University Press on behalf of the Royal Astronomical Society

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2--2.3\,keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3--8\,keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts $z>1$ in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements., 16 pages, 19 figures, accepted by Astronomy & Astrophysics

We aim at characterizing the hot phase of the Circum-Galactic Medium in a large sample of galaxies. We stack X-ray events from the SRG/eROSITA eFEDS survey around central galaxies in the GAMA 9hr field to construct radially projected soft X-ray luminosity profiles as a function of their stellar mass and specific star formation rate. We consider samples of quiescent (star-forming) galaxies in the stellar mass range $2\times 10^{10}$ -- $10^{12}$ M$_\odot$ ($3\times 10^9$ -- $6\times10^{11}$ M$_\odot$). For quiescent galaxies, the X-ray profiles are clearly extended throughout the available mass range; however, the measured profile is likely biased high due to projection effects, as these galaxies tend to live in dense and hot environments. For the most massive star forming samples ($\geq10^{11}$ M$_\odot$), there is a hint of detection of extended emission. For star-forming galaxies with $< 10^{11}$ M$_\odot$ the X-ray stacked profiles are compatible with unresolved sources and consistent with the expected emission from faint Active Galactic Nuclei and X-ray binaries. We measure for the first time the mean relation between average X-ray luminosity and stellar mass separately for quiescent and star-forming galaxies. High-mass ($\geq 10^{11}$ M$_\odot$) star-forming or quiescent galaxies follow the expected scaling of virialized hot haloes, while lower mass star-forming galaxies show a less prominent luminosity and a weaker dependence on stellar mass, consistent with empirical models of the weak AGN population. When comparing our results with state-of-the art numerical simulations, we find an overall consistency on large ($>80$ kpc) scales at masses $\geq 10^{11}$ M$_\odot$, but disagreement on the small scales, where brighter than observed compact cores are predicted. Simulations also do not predict the clear differentiation that we observe between quiescent and star-forming galaxies., Comment: 23 pages, 11 figures, 4 tables, accepted in A&A

VANDELS is an ESO Public Spectroscopic Survey designed to build a sample of high signal to noise, medium resolution spectra of galaxies at redshift between 1 and 6.5. Here we present the final Public Data Release of the VANDELS Survey, comprising 2087 redshift measurements. We give a detailed description of sample selection, observations and data reduction procedures. The final catalogue reaches a target selection completeness of 40% at iAB = 25. The high Signal to Noise ratio of the spectra (above 7 in 80% of the spectra) and the dispersion of 2.5�� allowed us to measure redshifts with high precision, the redshift measurement success rate reaching almost 100%. Together with the redshift catalogue and the reduced spectra, we also provide optical mid-IR photometry and physical parameters derived through SED fitting. The observed galaxy sample comprises both passive and star forming galaxies covering a stellar mass range 8.3< Log(M*/Msolar), 16 pages, 13 figures, accepted for publication in Astronomy & Astrophysics

Context. High-redshift quasars signpost the early accretion history of the Universe. The penetrating nature of X-rays enables a less absorption-biased census of the population of these luminous and persistent sources compared to optical/near-infrared colour selection. The ongoing SRG/eROSITA X-ray all-sky survey offers a unique opportunity to uncover the bright end of the high-z quasar population and probe new regions of colour parameter space. Aims. We searched for high-z quasars within the X-ray source population detected in the contiguous ~140 deg2 field observed by eROSITA during the performance verification phase. With the purpose of demonstrating the unique survey science capabilities of eROSITA, this field was observed at the depth of the final all-sky survey. The blind X-ray selection of high-redshift sources in a large contiguous, near-uniform survey with a well-understood selection function can be directly translated into constraints on the X-ray luminosity function (XLF), which encodes the luminosity-dependent evolution of accretion through cosmic time. Methods. We collected the available spectroscopic information in the eFEDS field, including the sample of all currently known optically selected z > 5.5 quasars and cross-matched secure Legacy DR8 counterparts of eROSITA-detected X-ray point-like sources with this spectroscopic sample. Results. We report the X-ray detection of eFEDSU J083644.0+005459, an eROSITA source securely matched to the well-known quasar SDSS J083643.85+005453.3 (z = 5.81). The soft X-ray flux of the source derived from eROSITA is consistent with previous Chandra observations. The detection of SDSS J083643.85+005453.3 allows us to place the first constraints on the XLF at z > 5.5 based on a secure spectroscopic redshift. Compared to extrapolations from lower-redshift observations, this favours a relatively flat slope for the XLF at z ~ 6 beyond L*, the knee in the luminosity function. In addition, we report the detection of the quasar with LOFAR at 145 MHz and ASKAP at 888 MHz. The reported flux densities confirm a spectral flattening at lower frequencies in the emission of the radio core, indicating that SDSS J083643.85+005453.3 could be a (sub-) gigahertz peaked spectrum source. The inferred spectral shape and the parsec-scale radio morphology of SDSS J083643.85+005453.3 indicate that it is in an early stage of its evolution into a large-scale radio source or confined in a dense environment. We find no indications for a strong jet contribution to the X-ray emission of the quasar, which is therefore likely to be linked to accretion processes. Conclusions. Our results indicate that the population of X-ray luminous AGNs at high redshift may be larger than previously thought. From our XLF constraints, we make the conservative prediction that eROSITA will detect ~90 X-ray luminous AGNs at redshifts 5.7 < z < 6.4 in the full-sky survey (De+RU). While subject to different jet physics, both high-redshift quasars detected by eROSITA so far are radio-loud; a hint at the great potential of combined X-ray and radio surveys for the search of luminous high-redshift quasars.

[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., This work is based on data from eROSITA, the soft X-ray instrument aboard SRG, a joint Russian-German science mission supported by the Russian Space Agency (Roskosmos), in the interests of the Russian Academy of Sciences represented by its Space Research Institute (IKI), and the Deutsches Zentrum für Luft- und Raumfahrt (DLR). The SRG spacecraft was built by Lav-ochkin Association (NPOL) and its subcontractors, and is operated by NPOL with support from the Max Planck Institute for Extraterrestrial Physics (MPE). The development and construction of the eROSITA X-ray instrument was led by MPE, with contributions from the Dr. Karl Remeis Observatory Bamberg and ECAP (FAU Erlangen-Nuernberg), the University of Hamburg Observatory, the Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute for Astronomy and Astrophysics of the University of Tübingen, with the support of DLR and the Max Planck Society. The Argelander Institute for Astronomy of the University of Bonn and the Ludwig Maximilians Universität Munich also participated in the science preparation for eROSITA. The eROSITA data shown here were processed using the eSASS/NRTA software system developed by the German eROSITA consortium. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website is www.sdss.org SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, Center for Astrophysics | Harvard and Smithsonian (CfA), the Chilean Participation Group, the French Participation Group, Instituto de Astrofısica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, the Korean Participation Group, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatório Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University. The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. This paper makes use of software developed for the Large Synoptic Survey Telescope. We thank the LSST Project for making their code available as free software at http://dm.lsst.org The Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation under Grant No. AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE) and the Los Alamos National Laboratory. Based [in part] on data collected at the Subaru Telescope and retrieved from the HSC data archive system, which is operated by Subaru Telescope and Astronomy Data Center at National Astronomical Observatory of Japan. M.K. acknowledges support by DFG grant KR 3338/4-1. K.I. acknowledges support by the Spanish MICINN under grant PID2019-105510GB-C33/AEI/10.13039/501100011033.

International audience; VANDELS is an ESO Public Spectroscopic Survey designed to build a sample of high-signal-to-noise ratio, medium-resolution spectra of galaxies at redshifts between 1 and 6.5. Here we present the final Public Data Release of the VANDELS Survey, comprising 2087 redshift measurements. We provide a detailed description of sample selection, observations, and data reduction procedures. The final catalogue reaches a target selection completeness of 40% at i AB = 25. The high signal-to-noise ratio of the spectra (above 7 in 80% of the spectra) and the dispersion of 2.5 Å allowed us to measure redshifts with high precision, the redshift measurement success rate reaching almost 100%. Together with the redshift catalogue and the reduced spectra, we also provide optical mid-infrared photometry and physical parameters derived through fitting the spectral energy distribution. The observed galaxy sample comprises both passive and star forming galaxies covering a stellar mass range of 8.3 < Log( M * / M ⊙ ) < 11.7.

The 140 square degree Final Equatorial-Depth Survey (eFEDS) field, observed with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) aboard the Spectrum-Roentgen-Gamma (SRG) mission, provides a first look at the variable eROSITA sky. We analyze the intrinsic X-ray variability of the eFEDS sources, provide X-ray light curves and tables with variability test results in the 0.2-2.3 keV (soft) and 2.3-5.0 keV (hard) bands. respectively. We perform variability tests using the normalized excess variance and maximum amplitude variability methods as performed for the 2RXS catalogue and add results from the Bayesian excess variance and the Bayesian block methods. In total 65 sources have been identified as being significantly variable in the soft band. In the hard band only one source is found to vary significantly. For the most variable sources fits to stellar flare events reveal extreme flare properties. A few highly variable AGN have also been detected. About half of the variable eFEDS sources have been detected at X-rays with eROSITA for the first time. Comparison with 2RXS and XMM observations provide variability information on timescales of years to decades., Comment: To appear on A&A, Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission; 13 pages, 10 figures, accepted June 21, 2021

We look to provide a detailed description of the SPectroscopic IDentification of ERosita Sources (SPIDERS) survey, an SDSS-IV programme aimed at obtaining spectroscopic classification and redshift measurements for complete samples of sufficiently bright X-ray sources. We describe the SPIDERS X-ray Point Source Spectroscopic Catalogue, considering its store of 11,092 observed spectra drawn from a parent sample of 14,759 ROSAT and XMM sources over an area of 5,129 deg$^2$ covered in SDSS-IV by the eBOSS survey. This programme represents the largest systematic spectroscopic observation of an X-ray selected sample. A total of 10,970 (98.9\%) of the observed objects are classified and 10,849 (97.8\%) have secure redshifts. The majority of the spectra (10,070 objects) are active galactic nuclei (AGN), 522 are cluster galaxies, and 294 are stars. The observed AGN redshift distribution is in good agreement with simulations based on empirical models for AGN activation and duty cycle. Forming composite spectra of type 1 AGN as a function of the mass and accretion rate of their black holes reveals systematic differences in the H-beta emission line profiles. This study paves the way for systematic spectroscopic observations of sources that are potentially to be discovered in the upcoming eROSITA survey over a large section of the sky., accepted in A&A Please visit our project page : http://www.mpe.mpg.de/XraySurveys/SPIDERS The catalogs are here : https://data.sdss.org/sas/dr16/eboss/spiders/analysis/VAC_SPIDERS_2RXS_DR16.fits and https://data.sdss.org/sas/dr16/eboss/spiders/analysis/VAC_SPIDERS_XMMSL2_DR16.fits

The statistical distributions of active galactic nuclei (AGN), i.e. accreting supermassive black holes (BHs), in mass, space and time, are controlled by a series of key properties, namely the BH-galaxy scaling relations, Eddington ratio distributions and fraction of active BHs (duty cycle). Shedding light on these properties yields strong constraints on the AGN triggering mechanisms whilst providing a clear baseline to create useful mock catalogues for the planning of large galaxy surveys. We here delineate a robust methodology to create mock AGN catalogs built on top of large N-body dark matter simulations via state-of-the-art semi-empirical models. We show that by using as independent tests the AGN clustering at fixed X-ray luminosity, galaxy stellar mass and BH mass, along with the fraction of AGN in groups and clusters, it is possible to significantly narrow down the choice in the relation between black hole mass and host galaxy stellar mass, the duty cycle, and the average Eddington ratio distribution, delivering well-suited constraints to guide cosmological models for the co-evolution of BHs and galaxies. Avoiding such a step-by-step methodology inevitably leads to strong degeneracies in the final mock catalogs, severely limiting their usefulness in understanding AGN evolution and in survey planning and testing., Comment: Accepted for publication in the Astrophysical Journal

Theoretical models of galaxy evolution suggest that galaxy-wide outflows driven by active galactic nuclei (AGN), one of the so-called AGN-feedback mechanisms, are a fundamental process affecting the bulk of the baryons in the Universe. While the presence of such outflows out to kpc scales is now undisputed, their impact on the star formation, gas content and kinematics of the host galaxy is hotly debated. Here we report on the results from our Large Programme SUPER, which used the Spectrograph for INtegral Field Observations in the Near INfrared (SINFONI) on the Very Large Telescope (VLT) to carry out the first statistically sound high-spatial-resolution investigation of AGN outflows at z ~ 2, covering four orders of magnitude in AGN bolometric luminosity., Published in The Messenger vol. 182, pp. 45-49, March 2021.

In November 2019, eROSITA on board of SRG observatory started to map the entire sky in X-rays. After the 4-year survey program, it will reach flux limits about 25 times deeper than ROSAT. During the SRG Performance Verification phase, eROSITA observed a contiguous 140 deg$^2$ area of the sky down to the final depth of the eROSITA all-sky survey ("eROSITA Final Equatorial-Depth Survey": eFEDS), with the goal of obtaining a census of the X-ray emitting populations (stars, compact objects, galaxies, clusters of galaxies, AGN) that will be discovered over the entire sky. This paper presents the identification of the counterparts to the point-sources detected in eFEDS in the Main and Hard samples described in Brunner et al 2021, and their multi-wavelength properties, including redshift. For the identification of the counterparts we combined the results from two independent methods (NWAY and ASTROMATCH), trained on the multi-wavelength properties of a sample of 23k XMM-Newton sources detected in the DESI Legacy Imaging Survey DR8. Then spectroscopic redshifts and photometry from ancillary surveys are collated for the computation of photometric redshifts. The eFEDS sources with a reliable counterparts are 24774/27369 (90.5\%) in the Main sample and 231/246 (93.9\%) in the Hard sample, including 2514 (3) sources for which a second counterpart is equally likely. [abridged] This paper is accompanying the eROSITA early data release of all the observations performed during the performance and verification phase. Together with the catalogs of primary and secondary counterparts to the Main and Hard samples of the eFEDS survey this paper releases their multi-wavelength properties and redshifts., Comment: Accepted by A&A for the Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission. NOTE: Paper completely revised wrt the first version submitted to arXiv. Revised catalogs available via https://erosita.mpe.mpg.de/edr/eROSITAObservations/Catalogues/

The eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) satellite has started to detect new X-ray sources over the full sky at an unprecedented rate. Understanding the performance and selection function of the source detection is important for the subsequent scientific analysis of the eROSITA catalogs. Through simulations, we test and optimize the eROSITA source detection procedures, and we characterize the detected catalog quantitatively. Taking the eROSITA Final Equatorial-Depth Survey (eFEDS) as an example, we ran extensive photon-event simulations based on our best knowledge of the instrument characteristics, the background spectrum, and the population of astronomical X-ray sources. We introduce a method of analyzing source detection completeness, purity, and efficiency based on the origin of each photon. According to the source detection efficiency measured in the simulation, we chose a two-pronged strategy to build eROSITA X-ray catalogs, creating a main catalog using only the most sensitive band (0.2-2.3 keV) and an independent hard-band-selected catalog using multiband detection in a range up to 5 keV. Because our mock data are highly representative of the real eFEDS data, we used the mock catalogs to measure the completeness and purity of the eFEDS catalogs as a function of multiple parameters, such as detection likelihood, flux, and luminosity. These measurements provide a basis for choosing the eFEDS catalog selection thresholds. The mock catalogs (available with this paper) can be used to construct the selection function of active galactic nuclei and galaxy clusters. A direct comparison of the output and input mock catalogs also gives rise to a correction curve that converts the raw point-source flux distribution into the intrinsic number counts distribution., Comment: Accepted by A&A for the Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission

We map the co-eval growth of galaxies and their central supermassive black holes in detail by measuring the incidence of Active Galactic Nuclei (AGN) in galaxies as a function of star formation rate (SFR) and redshift (to z~4). We combine large galaxy samples with deep Chandra X-ray imaging to measure the probability distribution of specific black hole accretion rates (LX relative to stellar mass) and derive robust AGN fractions and average specific accretion rates. First, we consider galaxies along the main sequence of star formation. We find a linear correlation between the average SFR and both the AGN fraction and average specific accretion rate across a wide range in stellar mass ($M_* \sim 10^{8.5-11.5}M_\odot$) and to at least z~2.5, indicating that AGN in main-sequence galaxies are driven by the stochastic accretion of cold gas. We also consider quiescent galaxies and find significantly higher AGN fractions than predicted, given their low SFRs, indicating that AGN in quiescent galaxies are fuelled by additional mechanisms (e.g. stellar winds). Next, we bin galaxies according to their SFRs relative to the main sequence. We find that the AGN fraction is significantly elevated for galaxies that are still star-forming but with SFRs below the main sequence, indicating further triggering mechanisms enhance AGN activity within these sub-main-sequence galaxies. We also find that the incidence of high-accretion-rate AGN is enhanced in starburst galaxies and evolves more mildly with redshift than within the rest of the galaxy population, suggesting mergers play a role in driving AGN activity in such high-SFR galaxies., Comment: 19 pages, 15 figures. This is a pre-copyedited, author-produced version of an article accepted for publication in MNRAS following peer review

In the context of the upcoming SRG/eROSITA survey, we present an N-body simulation-based mock catalogue for X-ray-selected active galactic nucleus (AGN) samples. The model reproduces the observed hard X-ray AGN luminosity function (XLF) and the soft X-ray logN-logS from redshift 0 to 6. The XLF is reproduced to within +/- 5 per cent and the logN-logS to within +/- 20 per cent. We develop a joint X-ray - optical extinction and classification model. We adopt a set of empirical spectral energy distributions to predict observed magnitudes in the UV, optical, and NIR. With the latest eROSITA all sky survey sensitivity model, we create a high-fidelity full-sky mock catalogue of X-ray AGN. It predicts their distributions in right ascension, declination, redshift, and fluxes. Using empirical medium resolution optical spectral templates and an exposure time calculator, we find that 1.1 x 10(6) (4 x 10(5)) fibre-hours are needed to follow-up spectroscopically from the ground the detected X-ray AGN with an optical magnitude 21 < r < 22.8 (22.8 < r < 25) with a 4-m (8-m) class multiobject spectroscopic facility. We find that future clustering studies will measure the AGN bias to the per cent level at redshift z < 1.2 and should discriminate possible scenarios of galaxy-AGN co-evolution. We predict the accuracy to which the baryon acoustic oscillation standard ruler will be measured using X-ray AGN: better than 3 per cent for AGN between redshift 0.5 to 3 and better than 1 per cent using the Ly alpha forest of X-ray QSOs discovered between redshift 2 and 3. eROSITA will provide an outstanding set of targets for future galaxy evolution and cosmological studies.© 2019 The Author(s).Published by Oxford University Press on behalf of the Royal Astronomical Society, JB acknowledges support from the CONICYT-Chile grants Basal-CATA PFB-06/2007 & AFB-170002, FONDECYT Postdoctorados 3160439 and the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. This research was supported by the DFG cluster of excellence 'Origin and Structure of the Universe'. GY would like to thank MINECO/FEDER for financial support under project grant AYA2015-63810-P. MK acknowledges support from DLR grant 50OR1802. The CosmoSim data base is a service of the Leibniz-Institute for Astrophysics Potsdam (AIP). The MultiDark data base was developed in cooperation with the Spanish MultiDark Consolider Project CSD2009-00064.

VANDELS is a uniquely-deep spectroscopic survey of high-redshift galaxies with the VIMOS spectrograph on ESO's Very Large Telescope (VLT). The survey has obtained ultra-deep optical (0.48 < lambda < 1.0 micron) spectroscopy of ~2100 galaxies within the redshift interval 1.0 < z < 7.0, over a total area of ~0.2 sq. degrees centred on the CANDELS UDS and CDFS fields. Based on accurate photometric redshift pre-selection, 85% of the galaxies targeted by VANDELS were selected to be at z>=3. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the fundamental aim of the survey is to provide the high signal-to-noise ratio spectra necessary to measure key physical properties such as stellar population ages, masses, metallicities and outflow velocities from detailed absorption-line studies. Using integration times calculated to produce an approximately constant signal-to-noise ratio (20 < t_int < 80 hours), the VANDELS survey targeted: a) bright star-forming galaxies at 2.4 < z < 5.5, b) massive quiescent galaxies at 1.0 < z < 2.5, c) fainter star-forming galaxies at 3.0 < z < 7.0 and d) X-ray/Spitzer-selected active galactic nuclei and Herschel-detected galaxies. By targeting two extragalactic survey fields with superb multi-wavelength imaging data, VANDELS will produce a unique legacy data set for exploring the physics underpinning high-redshift galaxy evolution. In this paper we provide an overview of the VANDELS survey designed to support the science exploitation of the first ESO public data release, focusing on the scientific motivation, survey design and target selection., 19 pages, 9 figures, accepted for publication in MNRAS

This paper describes the observations and the first data release (DR1) of the ESO public spectroscopic survey "VANDELS, a deep VIMOS survey of the CANDELS CDFS and UDS fields". VANDELS' main targets are star-forming galaxies at 2.4, Comment: Submitted to A&A

An empirical forward-modeling framework is developed to interpret the multi-wavelength properties of Active Galactic Nuclei (AGN) and provide insights into the overlap and incompleteness of samples selected at different parts of the electromagnetic spectrum. The core of the model are observationally derived probabilites on the occupation of galaxies by X-ray selected AGN. These are used to seed mock galaxies drawn from stellar-mass functions with accretion events and then associate them with spectral energy distributions that describe both the stellar and AGN emission components. This approach is used to study the complementarity between X-ray and WISE mid-infrared AGN selection methods. We first show that the basic observational properties of the X-ray and WISE AGN (magnitude, redshift distributions) are adequately reproduced by the model. We then infer the level of contamination of the WISE selection and show that this is dominated by non-AGN at redshifts $z, full article at https://arxiv.org/abs/2009.00060

The XMM-RM project was designed to provide X-ray coverage of the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) field. 41 XMM-Newton exposures, placed surrounding the Chandra AEGIS field, were taken, covering an area of 6.13 deg^2 and reaching a nominal exposure depth of ~15 ks. We present an X-ray catalog of 3553 sources detected in these data, using a PSF-fitting algorithm and a sample selection threshold that produces a ~5% fraction of spurious sources. In addition to the PSF-fitting likelihood, we calculate a second source reliability measure based on Poisson theory using source and background counts within an aperture. Using the Poissonian likelihood, we select a sub-sample with a high purity and find that it has similar number count profiles to previous X-ray surveys. The Bayesian method "NWAY" was employed to identify counterparts of the X-ray sources from the optical Legacy and the IR unWISE catalogs, using a 2-dimensional unWISE magnitude-color prior created from optical/IR counterparts of Chandra X-ray sources. A significant number of the optical/IR counterparts correspond to sources with low detection likelihoods, proving the value of retaining the low-likelihood detections in the catalog. 932 of the XMM-RM sources are covered by SDSS spectroscopic observations. 89% of them are classified as AGN, and 71% of these AGN are in the SDSS-RM quasar catalog. Among the SDSS-RM quasars, 80% are detectable at the depth of the XMM observations., Comment: ApJS accepted. 20 pages, 16 figures

In the context of the upcoming SRG/eROSITA survey, we present an N-body simulation-based mock catalogue for X-ray-selected active galactic nucleus (AGN) samples. The model reproduces the observed hard X-ray AGN luminosity function (XLF) and the soft X-ray logN-logS from redshift 0 to 6. The XLF is reproduced to within +/- 5 per cent and the logN-logS to within +/- 20 per cent. We develop a joint X-ray - optical extinction and classification model. We adopt a set of empirical spectral energy distributions to predict observed magnitudes in the UV, optical, and NIR. With the latest eROSITA all sky survey sensitivity model, we create a high-fidelity full-sky mock catalogue of X-ray AGN. It predicts their distributions in right ascension, declination, redshift, and fluxes. Using empirical medium resolution optical spectral templates and an exposure time calculator, we find that 1.1 x 10(6) (4 x 10(5)) fibre-hours are needed to follow-up spectroscopically from the ground the detected X-ray AGN with an optical magnitude 21

A semi-empirical model is presented that describes the distribution of Active Galactic Nuclei (AGN) on the cosmic web. It populates dark-matter halos in N-body simulations (MultiDark) with galaxy stellar masses using empirical relations based on abundance matching techniques, and then paints accretion events on these galaxies using state-of-the-art measurements of the AGN occupation of galaxies. The explicit assumption is that the large-scale distribution of AGN is independent of the physics of black-hole fueling. The model is shown to be consistent with current measurements of the two-point correlation function of AGN samples. It is then used to make inferences on the halo occupation of the AGN population. Mock AGN are found in halos with a broad distribution of masses with a mode of $\approx 10^{12}\,h^{-1} \, M_{\odot}$ and a tail extending to cluster-size halos. The clustering properties of the model AGN depend only weakly on accretion luminosity and redshift. The fraction of satellite AGN in the model increases steeply toward more massive halos, in contrast with some recent observational results. This discrepancy, if confirmed, could point to a dependence of the halo occupation of AGN on the physics of black-hole fueling., Comment: 22 pages, submitted to MNRAS, light-cones and correlation functions available at https://doi.org/10.5281/zenodo.2114283

The statistical distributions of active galactic nuclei (AGNs), i.e., accreting supermassive black holes (BHs), in mass, space, and time are controlled by a series of key properties, namely, the BH-galaxy scaling relations, Eddington ratio distributions, and fraction of active BH (duty cycle). Shedding light on these properties yields strong constraints on the AGN triggering mechanisms while providing a clear baseline to create useful mock catalogs for the planning of large galaxy surveys. Here we delineate a robust methodology to create mock AGN catalogs built on top of large N-body dark matter simulations via state-of-the-art semiempirical models. We show that by using as independent tests the AGN clustering at fixed X-ray luminosity, galaxy stellar mass, and BH mass, along with the fraction of AGNs in groups and clusters, it is possible to significantly narrow down the choice in the relation between BH mass and host galaxy stellar mass, the duty cycle, and the average Eddington ratio distribution, delivering well-suited constraints to guide cosmological models for the coevolution of BHs and galaxies. Avoiding such a step-by-step methodology inevitably leads to strong degeneracies in the final mock catalogs, severely limiting their usefulness in understanding AGN evolution and in survey planning and testing.

We present the X-UDS survey, a set of wide and deep Chandra observations of the Subaru-XMM Deep/UKIDSS Ultra Deep Survey (SXDS/UDS) field. The survey consists of 25 observations that cover a total area of 0.33 deg$^{2}$. The observations are combined to provide a nominal depth of ~600 ksec in the central 100 arcmin$^{2}$ region of the field that has been imaged with Hubble/WFC3 by the CANDELS survey and $\sim$200 ksec in the remainder of the field. In this paper, we outline the survey's scientific goals, describe our observing strategy, and detail our data reduction and point source detection algorithms. Our analysis has resulted in a total of 868 band-merged point sources detected with a false-positive Poisson probability of $, 15 pages, 11 figures, published in the Astrophysics Journal Supplement Series

The northern tile of the wide-area and shallow XMM-XXL X-ray survey field is used to estimate the average dark matter halo mass of relatively luminous X-ray selected AGN [$\rm log\, L_X (\rm 2-10\,keV)= 43.6^{+0.4}_{-0.4}\,erg/s$] in the redshift interval $z=0.5-1.2$. Spectroscopic follow-up observations of X-ray sources in the XMM-XXL field by the Sloan telescope are combined with the VIPERS spectroscopic galaxy survey to determine the cross-correlation signal between X-ray selected AGN (total of 318) and galaxies (about 20,\,000). We model the large scales (2-25\,Mpc) of the correlation function to infer a mean dark matter halo mass of $\log M / (M_{\odot} \, h^{-1}) = 12.50 ^{+0.22} _{-0.30}$ for the X-ray selected AGN sample. This measurement is about 0.5\,dex lower compared to estimates in the literature of the mean dark matter halo masses of moderate luminosity X-ray AGN [$L_X (\rm 2-10\,keV)\approx 10^{42} - 10^{43}\,erg/s$] at similar redshifts. Our analysis also links the mean clustering properties of moderate luminosity AGN with those of powerful UV/optically selected QSOs, which are typically found in halos with masses few times $10^{12}\,M_{\odot}$. There is therefore evidence for a negative luminosity dependence of the AGN clustering. This is consistent with suggestions that AGN have a broad dark matter halo mass distribution with a high mass tail that becomes sub-dominant at high accretion luminosities. We further show that our results are in qualitative agreement with semi-analytic models of galaxy and AGN evolution, which attribute the wide range of dark matter halo masses among the AGN population to different triggering mechanisms and/or black hole fueling modes., MNRAS accepted. 10 pages, 7 figures, 2 tables

We report the results of a Sloan Digital Sky Survey-IV eBOSS program to target X-ray sources and mid-infrared-selected WISE AGN candidates in a 36.8 deg$^2$ region of Stripe 82. About half this survey (15.6 deg$^2$) covers the largest contiguous portion of the Stripe 82 X-ray survey. This program represents the largest spectroscopic survey of AGN candidates selected solely by their WISE colors. We combine this sample with X-ray and WISE AGN in the field identified via other sources of spectroscopy, producing a catalog of 4847 sources that is 82% complete to $r\sim22$. Based on X-ray luminosities or WISE colors, 4730 of these sources are AGN, with a median sample redshift of $z\sim1$. About 30% of the AGN are optically obscured (i.e., lack broad lines in their optical spectra). BPT analysis, however, indicates that 50% of the WISE AGN at $z 10^{44}$ erg s$^{-1}$), indicating that MIR selection misses a sizable fraction of the highest luminosity AGN, as well as lower luminosity sources where AGN heated dust is not dominating the MIR emission. Conversely, $\sim$58% of WISE AGN are undetected by X-rays, though we do not find that they are preferentially redder than the X-ray detected WISE AGN., resubmitted to AAS Journals after addressing referee's comments. 21 pages, 17 figures, 5 Tables. Tables 4 & 5 summarize the demographics of the sample. Figures 15 & 16 compare AGN populations from X-ray and MIR selection. The catalog (in fits format) can be downloaded at http://doi.org/10.5281/zenodo.2577357

The discoveries made over the past 20 years by Chandra and XMM-Newton surveys in conjunction with multiwavelength imaging and spectroscopic data available in the same fields have significantly changed the view of the supermassive black hole (SMBH) and galaxy connection. These discoveries have opened up several exciting questions that are beyond the capabilities of current X-ray telescopes and will need to be addressed by observatories in the next two decades. As new observatories peer into the early Universe, we will begin to understand the physics and demographics of SMBH infancy (at $z>6$) and investigate the influence of their accretion on the formation of the first galaxies ($��$ 2.1). We will also be able to understand the accretion and evolution over the cosmic history (at $z\sim$1-6) of the full population of black holes in galaxies, including low accretion rate, heavily obscured AGNs at luminosities beyond the reach of current X-ray surveys ($��$2.2 and $��$2.3), enabling us to resolve the connection between SMBH growth and their environment., 5 pages, 3 figures; Science white paper submitted to the Astro2020 Decadal Survey

VANDELS is a uniquely deep spectroscopic survey of high-redshift galaxies with the VIMOS spectrograph on ESO’s Very Large Telescope (VLT). The survey has obtained ultradeep optical (0.48 < λ < 1.0 μm) spectroscopy of ≃2100 galaxies within the redshift interval 1.0 ≤ z ≤ 7.0, over a total area of ≃0.2 deg2 centred on the CANDELS Ultra Deep Survey and Chandra Deep Field South fields. Based on accurate photometric redshift pre-selection, 85 per cent of the galaxies targeted by VANDELS were selected to be at z ≥ 3. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the fundamental aim of the survey is to provide the high-signal-to-noise ratio spectra necessary to measure key physical properties such as stellar population ages, masses, metallicities, and outflow velocities from detailed absorption-line studies. Using integration times calculated to produce an approximately constant signal-to-noise ratio (20 < tint< 80 h), the VANDELS survey targeted: (a) bright star-forming galaxies at 2.4 ≤ z ≤ 5.5, (b) massive quiescent galaxies at 1.0 ≤ z ≤ 2.5, (c) fainter star-forming galaxies at 3.0 ≤ z ≤ 7.0, and (d) X-ray/Spitzer-selected active galactic nuclei and Herschel-detected galaxies. By targeting two extragalactic survey fields with superb multiwavelength imaging data, VANDELS will produce a unique legacy data set for exploring the physics underpinning high-redshift galaxy evolution. In this paper, we provide an overview of the VANDELS survey designed to support the science exploitation of the first ESO public data release, focusing on the scientific motivation, survey design, and target selection.

© ESO 2018. This paper describes the observations and the first data release (DR1) of the ESO public spectroscopic survey "VANDELS, a deep VIMOS survey of the CANDELS CDFS and UDS fields". The main targets of VANDELS are star-forming galaxies at redshift 2.4 < z < 5.5, an epoch when the Universe had not yet reached 20% of its current age, and massive passive galaxies in the range 1 < z < 2.5. By adopting a strategy of ultra-long exposure times, ranging from a minimum of 20 h to a maximum of 80 h per source, VANDELS is specifically designed to be the deepest-ever spectroscopic survey of the high-redshift Universe. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the survey is obtaining ultra-deep optical spectroscopy covering the wavelength range 4800-10 000 Å with a sufficiently high signal-to-noise ratio to investigate the astrophysics of high-redshift galaxy evolution via detailed absorption line studies of well-defined samples of high-redshift galaxies. VANDELS-DR1 is the release of all medium-resolution spectroscopic data obtained during the first season of observations, on a 0.2 square degree area centered around the CANDELS-CDFS (Chandra deep-field south) and CANDELS-UDS (ultra-deep survey) areas. It includes data for all galaxies for which the total (or half of the total) scheduled integration time was completed. The DR1 contains 879 individual objects, approximately half in each of the two fields, that have a measured redshift, with the highest reliable redshifts reaching zspec ∼ 6. In DR1 we include fully wavelength-calibrated and flux-calibrated 1D spectra, the associated error spectrum and sky spectrum, and the associated wavelength-calibrated 2D spectra. We also provide a catalog with the essential galaxy parameters, including spectroscopic redshifts and redshift quality flags measured by the collaboration. We present the survey layout and observations, the data reduction and redshift measurement procedure, and the general properties of the VANDELS-DR1 sample. In particular, we discuss the spectroscopic redshift distribution and the accuracy of the photometricredshifts for each individual target category, and we provide some examples of data products for the various target typesand the different quality flags. All VANDELS-DR1 data are publicly available and can be retrieved from the ESO archive. Two further data releases are foreseen in the next two years, and a final data release is currently scheduled for June 2020, which will include an improved rereduction of the entire spectroscopic data set.

VANDELS is a uniquely-deep spectroscopic survey of high-redshift galaxies with the VIMOS spectrograph on ESO’s Very Large Telescope (VLT). The survey has obtained ultra-deep optical (0.48 < λ < 1.0 μm) spectroscopy of ≃2100 galaxies within the redshift interval 1.0 ≤ z ≤ 7.0, over a total area of ≃ 0.2 deg2 centred on the CANDELS UDS and CDFS fields. Based on accurate photometric redshift pre-selection, 85% of the galaxies targeted by VANDELS were selected to be at z ≥ 3. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the fundamental aim of the survey is to provide the high signal-to-noise ratio spectra necessary to measure key physical properties such as stellar population ages, masses, metallicities and outflow velocities from detailed absorption-line studies. Using integration times calculated to produce an approximately constant signal-to-noise ratio (20 < tint < 80 hours), the VANDELS survey targeted: a) bright star-forming galaxies at 2.4 ≤ z ≤ 5.5, b) massive quiescent galaxies at 1.0 ≤ z ≤ 2.5, c) fainter star-forming galaxies at 3.0 ≤ z ≤ 7.0 and d) X-ray/Spitzer-selected active galactic nuclei and Herschel-detected galaxies. By targeting two extragalactic survey fields with superb multi-wavelength imaging data, VANDELS will produce a unique legacy data set for exploring the physics underpinning high-redshift galaxy evolution. In this paper we provide an overview of the VANDELS survey designed to support the science exploitation of the first ESO public data release, focusing on the scientific motivation, survey design and target selection. Postprint

We use deep Chandra X-ray imaging to measure the distribution of specific black hole accretion rates ($L_X$ relative to the stellar mass of the galaxy) and thus trace AGN activity within star-forming and quiescent galaxies, as a function of stellar mass (from $10^{8.5}-10^{11.5} M_\odot$) and redshift (to $z \sim 4$). We adopt near-infrared selected samples of galaxies from the CANDELS and UltraVISTA surveys, extract X-ray data for every galaxy, and use a flexible Bayesian method to combine these data and to measure the probability distribution function of specific black hole accretion rates, $\lambda_{sBHAR}$. We identify a broad distribution of $\lambda_{sBHAR}$ in both star-forming and quiescent galaxies---likely reflecting the stochastic nature of AGN fuelling---with a roughly power-law shape that rises toward lower $\lambda_{sBHAR}$, a steep cutoff at $\lambda_{sBHAR} \gtrsim 0.1-1$ (in Eddington equivalent units), and a turnover or flattening at $\lambda_{sBHAR} \lesssim 10^{-3}-10^{-2}$. We find that the probability of a star-forming galaxy hosting a moderate $\lambda_{sBHAR}$ AGN depends on stellar mass and evolves with redshift, shifting toward higher $\lambda_{sBHAR}$ at higher redshifts. This evolution is truncated at a point corresponding to the Eddington limit, indicating black holes may self-regulate their growth at high redshifts when copious gas is available. The probability of a quiescent galaxy hosting an AGN is generally lower than that of a star-forming galaxy, shows signs of suppression at the highest stellar masses, and evolves strongly with redshift. The AGN duty cycle in high-redshift ($z\gtrsim2$) quiescent galaxies thus reaches $\sim$20 per cent, comparable to the duty cycle in star-forming galaxies of equivalent stellar mass and redshift., Comment: 20 pages + 3 appendices (27 pages total) with 15 figures. The sketch shown in Figure 9 summarizes our findings. Data tables available at http://doi.org/10.5281/zenodo.1009605 . Updated FAST SED fitting code available at https://github.com/jamesaird/FAST . This is a pre-copyedited, author-produced version of an article accepted for publication in MNRAS following peer review

We combine deep X-ray survey data from the Chandra observatory and the wide-area/shallow XMM-XXL field to estimate the AGN X-ray luminosity function in the redshift range z=3-5. The sample consists of nearly 340 sources with either photometric (212) or spectroscopic (128) redshift in the above range. The combination of deep and shallow survey fields provides a luminosity baseline of three orders of magnitude, Lx(2-10keV)~1e43-1e46erg/s at z>3. We follow a Bayesian approach to determine the binned AGN space density and explore their evolution in a model-independent way. Our methodology accounts for Poisson errors in the determination of X-ray fluxes and uncertainties in photometric redshift estimates. We demonstrate that the latter is essential for unbiased measurement of space densities. We find that the AGN X-ray luminosity function evolves strongly between the redshift intervals z=3-4 and z=4-5. There is also suggestive evidence that the amplitude of this evolution is luminosity dependent. The space density of AGN with Lx1e45erg/s. The faint-end slope of UV/optical luminosity functions however, is steeper than for X-ray selected AGN. This implies that the type-I AGN fraction increases with decreasing luminosity at z>3, opposite to trends established at lower redshift. We also assess the significance of AGN in keeping the hydrogen ionised at high redshift. Our X-ray luminosity function yields ionising photon rate densities that are insufficient to keep the Universe ionised at redshift z>4. A source of uncertainty in this calculation is the escape fraction of UV photons for X-ray selected AGN., MNRAS accepted

SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV survey running in parallel to the eBOSS cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected AGN and galaxy cluster members detected in wide area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS: X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colour-magnitude information from the WISE survey, to select the most probable optical counterpart to each X-ray detection. We empirically demonstrate the high fidelity of our counterpart selection method using a reference sample of bright well-localised X-ray sources collated from XMM-Newton, Chandra and Swift-XRT serendipitous catalogues, and also by examining blank-sky locations. We describe the down-selection steps which resulted in the final set of SPIDERS-AGN targets put forward for spectroscopy within the eBOSS/TDSS/SPIDERS survey, and present catalogues of these targets. We also present catalogues of ~12000 ROSAT and ~1500 XMM-Newton Slew survey sources which have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS program, we expect to have collected homogeneous spectroscopic redshift information over a footprint of ~7500 deg$^2$ for >85 percent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17, Comment: MNRAS, accepted

Full list of authors: Pâris, Isabelle; Petitjean, Patrick; Ross, Nicholas P.; Myers, Adam D.; Aubourg, Éric; Streblyanska, Alina; Bailey, Stephen; Armengaud, Éric; Palanque-Delabrouille, Nathalie; Yèche, Christophe; Hamann, Fred; Strauss, Michael A.; Albareti, Franco D.; Bovy, Jo; Bizyaev, Dmitry; Niel Brandt, W.; Brusa, Marcella; Buchner, Johannes; Comparat, Johan; Croft, Rupert A. C. Dwelly, Tom; Fan, Xiaohui; Font-Ribera, Andreu; Ge, Jian; Georgakakis, Antonis; Hall, Patrick B.; Jiang, Linhua; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; McMahon, Richard G.; Menzel, Marie-Luise; Merloni, Andrea; Nandra, Kirpal; Noterdaeme, Pasquier; Oravetz, Daniel; Pan, Kaike; Pieri, Matthew M.; Prada, Francisco; Salvato, Mara; Schlegel, David J.; Schneider, Donald P.; Simmons, Audrey; Viel, Matteo; Weinberg, David H.; Zhu, Liu., We present the Data Release 12 Quasar catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities M [z = 2] 2.15 (184 101, of which 167 742 are new discoveries) is about an order of magnitude greater than the number of z > 2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (C iv, C iii], Mg ii). The catalog identifies 29 580 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag together with some information on the optical morphology and the selection criteria. When available, the catalog also provides information on the optical variability of quasars using SDSS and Palomar Transient Factory multi-epoch photometry. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3600-10 500 Å at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 4841 quasars that have been identified serendipitously outside of the superset defined to derive the main quasar catalog. © 2017 ESO., I.P. was supported by PRIN INAF 2012 "The X-Shooter sample of 100 quasar spectra at z-3.5:Digging into cosmology and galaxy evolution with quasar absorption lines". This work has been carried out thanks to the support of the A*MIDEX project (ANR-11-IDEX-0001-02) funded by the "Investissements d'Avenir" French Government program, managed by the French National Research Agency (ANR). The French Participation Group to SDSS-III was supported by the Agence Nationale de la Recherche under contracts ANR-08-BLAN-0222 and ANR-12-BS05-0015. A.D.M was partially supported by NASA ADAP award NNX12AE38G and by NSF awards 1211112 and 1515404. W.N.B. was supported by NSF grant AST-1516784. I.P. thanks S. Twain, D. Hoff, D. Dintei and Brian A. J. Richardson for their inspiring contribution to this work. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. AllWISE makes use of data from WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231.

In this paper we describe and publicly release a catalogue consisting of 8445 point-like X-ray sources detected in the XMM-XXL north survey. For the 2512 AGN which have reliable spectroscopy, we present the X-ray spectral fitting which has been computed with a Bayesian approach. We have also applied an X-ray spectral stacking method to different sub-samples. We confirm the well-known Iwasawa-Taniguchi effect in our luminosity-redshift sub-samples, and argue that such an effect is due to a decrease in the covering factor of a distant obscuring torus with increasing X-ray luminosity. By comparing the distribution of the reflection fraction, the ratio of the normalization of the reflected component to the direct radiation, we find that the low-luminosity, low-redshift sub-sample had systematically higher reflection fraction values than the high-redshift, high-luminosity one. On the other hand, no significant difference is found between samples having similar luminosity but different redshift, suggesting that the structure of the torus does not evolve strongly with redshift. Contrary to previous works, we do not find evidence for an increasing photon index at high Eddington ratio. This may be an indication that the structure of the accretion disc changes as the Eddington ratio approaches unity. Comparing our X-ray spectral analysis results with the optical spectral classification, we find that $\sim20$ per cent of optical type-1 AGN show an X-ray absorbing column density higher than $10^{21.5}\,\rm{cm^{-2}}$, and about 50 per cent of type-2 AGN have an X-ray absorbing column density less than $10^{21.5}\,\rm{cm^{-2}}$. We suggest that the excess X-ray absorption shown in the high-luminosity optical type-1 AGN can be due to small-scale dust-free gas within (or close to) the broad line region, while in the low-luminosity ones it can be due to a clumpy torus with a large covering factor., published in MNRAS. The full X-ray point-like source catalogue and Table 2,3 can be retrieved from http://www.mpe.mpg.de/XraySurveys/XMM-XXL/

We present the Data Release 14 Quasar catalog (DR14Q) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). This catalog includes all SDSS-IV/eBOSS objects that were spectroscopically targeted as quasar candidates and that are confirmed as quasars via a new automated procedure combined with a partial visual inspection of spectra, have luminosities $M_{\rm i} \left[ z=2 \right] < -20.5$ (in a $\Lambda$CDM cosmology with $H_0 = 70 \ {\rm km \ s^{-1} \ Mpc ^{-1}}$, $\Omega_{\rm M} = 0.3$, and $\Omega_{\rm \Lambda} = 0.7$), and either display at least one emission line with a full width at half maximum (FWHM) larger than $500 \ {\rm km \ s^{-1}}$ or, if not, have interesting/complex absorption features. The catalog also includes previously spectroscopically-confirmed quasars from SDSS-I, II and III. The catalog contains 526,356 quasars 144,046 are new discoveries since the beginning of SDSS-IV) detected over 9,376 deg$^2$ (2,044 deg$^2$ having new spectroscopic data available) with robust identification and redshift measured by a combination of principal component eigenspectra. The catalog is estimated to have about 0.5% contamination. The catalog identifies 21,877 broad absorption line quasars and lists their characteristics. For each object, the catalog presents SDSS five-band CCD-based photometry with typical accuracy of 0.03 mag. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys., Comment: Accepted for publication in A&A. The catalog is available at https://data.sdss.org/sas/dr14/eboss/qso/DR14Q/DR14Q_v4_4.fits

We study the clustering dependence of X-ray AGN and normal galaxies on the stellar mass (M$_\star$), star-formation rate (SFR) and specific star-formation rate (sSFR) of the (host) galaxy. Towards this end, we use 407 X-ray AGN from the XMM-XXL survey ($\sim$ 25 deg$^2$ in the North) and $\sim45,000$ galaxies in the VIPERS field (W1: $\sim$16 deg$^2$). We match the AGN and galaxy samples to have the same M$_\star$, SFR and redshift distributions. Based on our results, the two populations live in DMHs with similar mass ($\log M / (M_{\odot} \, h^{-1})\approx 12.8$) and have similar dependence on the galaxy properties. Specifically, our measurements show a positive dependence of the AGN and galaxy clustering on M$_\star$ and a negative dependence on SFR and sSFR. We also find that the X-ray clustering is independent of the location of the host galaxy above or below the star-forming main sequence., Comment: MNRAS accepted, 15 pages, 13 figures, 9 Tables

We examine the fraction of massive (M* > 1010 M) compact star-forming galaxies (cSFGs) that host an active galactic nucleus (AGN) at z ~ 2. These cSFGs are likely the direct progenitors of the compact quiescent galaxies observed at this epoch, which are the first population of passive galaxies to appear in large numbers in the early Universe. We identify cSFGs that host an AGN using a combination of Hubble WFC3 imaging and Chandra X-ray observations in four fields: the Chandra Deep Fields, the Extended Groth Strip, and the UKIDSS Ultra Deep Survey field. We find that - 39.2+ % 3.6 3.9 (65/166) of cSFGs at 1.4 < z < 3.0 host an X-ray detected AGN. This fraction is 3.2 times higher than the incidence of AGN in extended star-forming galaxies with similar masses at these redshifts. This difference is significant at the 6.2s level. Our results are consistent with models in which cSFGs are formed through a dissipative contraction that triggers a compact starburst and concurrent growth of the central black hole. We also discuss our findings in the context of cosmological galaxy evolution simulations that require feedback energy to rapidly quench cSFGs. We show that the AGN fraction peaks precisely where energy injection is needed to reproduce the decline in the number density of cSFGs with redshift. Our results suggest that the first abundant population of massive quenched galaxies emerged directly following a phase of elevated supermassive black hole growth and further hints at a possible connection between AGN and the rapid quenching of star formation in these galaxies.

The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured AGN at high accretion luminosities, $L_X (\rm 2-10 \, keV) > 10^{44} \, erg \,s ^{-1}$, and out to redshift $z\approx1.5$. The sample covers an area of about $\rm14\,deg^2$ and provides constraints on the space density of powerful AGN over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, $\rm N_H\approx10^{24}\,cm^{-2}$. The fraction of obscured Compton-thin ($\rm N_H=10^{22}-10^{24}\,cm^{-2}$) AGN is estimated to be $\approx0.35$ for luminosities $L_X(\rm 2-10\,keV)>10^{44}\,erg\,s^{-1}$ independent of redshift. For less luminous sources the fraction of obscured Compton-thin AGN increases from $0.45\pm0.10$ at $z=0.25$ to $0.75\pm0.05$ at $z=1.25$. Studies that select AGN in the infrared via template fits to the observed Spectral Energy Distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGN (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGN as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGN is primarily a function of redshift. This fraction increases from about 20-30% at z=0.25 to about 50-70% at $z=1.5$., MNRAS accepted

We use deep Chandra imaging to measure the distribution of X-ray luminosities (L_X) for samples of star-forming galaxies as a function of stellar mass and redshift, using a Bayesian method to push below the nominal X-ray detection limits. Our luminosity distributions all show narrow peaks at L_X < 10^{42} erg/s that we associate with star formation, as opposed to AGN that are traced by a broad tail to higher L_X. Tracking the luminosity of these peaks as a function of stellar mass reveals an "X-ray main sequence" with a constant slope ~0.63 +/- 0.03 over 8.5 < log M*/Msun < 11.5 and 0.1 < z < 4, with a normalization that increases with redshift as (1+z)^{3.79+/-0.12}. We also compare the peak X-ray luminosities with UV-to-IR tracers of star formation rates (SFRs) to calibrate the scaling between L_X and SFR. We find that L_X \propto SFR^{0.83} x (1+z)^{1.3}, where the redshift evolution and non-linearity likely reflect changes in high-mass X-ray binary populations of star-forming galaxies. Using galaxies with a broader range of SFR, we also constrain a stellar-mass-dependent contribution to L_X, likely related to low-mass X-ray binaries. Using this calibration, we convert our X-ray main sequence to SFRs and measure a star-forming main sequence with a constant slope ~0.76+/-0.06 and a normalization that evolves with redshift as (1+z)^{2.95+/-0.33}. Based on the X-ray emission, there is no evidence for a break in the main sequence at high stellar masses, although we cannot rule out a turnover given the uncertainties in the scaling of L_X to SFR., 18 pages + 4 appendices (27 pages total) with 13 figures. The main results are shown by Figures 3 and 4. This is a pre-copyedited, author-produced version of an article accepted for publication in MNRAS following peer review

Chandra data in the COSMOS, AEGIS-XD and 4Ms CDFS are combined with optical/near-IR photometry to determine the rest-frame U-V vs V-J colours of X-ray AGN hosts at mean redshifts 0.40 and 0.85. This combination of colours (UVJ) provides an efficient means of separating quiescent from star-forming, including dust reddened, galaxies. Morphological information emphasises differences between AGN split by their UVJ colours. AGN in quiescent galaxies are dominated by spheroids, while star-forming hosts are split between bulges and disks. The UVJ diagram of AGN hosts is then used to set limits on the accretion density associated with evolved and star-forming systems. Most of the black hole growth since z~1 is associated with star-forming hosts. Nevertheless, ~15-20% of the X-ray luminosity density since z~1, is taking place in the quiescent region of the UVJ diagram. For the z~0.40 subsample, there is tentative evidence (2sigma significance), that AGN split by their UVJ colours differ in Eddington ratio. AGN in star-forming hosts dominate at high Eddington ratios, while AGN in quiescent hosts become increasingly important as a fraction of the total population toward low Eddington ratios. At higher redshift, z~0.8, such differences are significant at the 2sigma level only at Eddington ratios >1e-3. These findings are consistent with scenarios in which diverse accretion modes are responsible for the build-up of SMBHs at the centres of galaxies. We compare our results with the GALFORM semi-analytic model, which postulates two black hole fuelling modes, the first linked to star-formation and the second occuring in passive galaxies. GALFORM predicts a larger fraction of black hole growth in quiescent galaxies at z, MNRAS accepted

This paper presents a survey of X-ray selected active galactic nuclei (AGN) with optical spectroscopic follow-up in a $\sim 18\, \rm{deg^2}$ area of the equatorial XMM-XXL north field. A sample of 8445 point-like X-ray sources detected by XMM-Newton above a limiting flux of $F_{\rm 0.5-10\, keV} > 10^{-15} \rm\,erg\, cm^{-2}\, s^{-1}$ was matched to optical (SDSS) and infrared (WISE) counterparts. We followed up 3042 sources brighter than $r=22.5$ mag with the SDSS BOSS spectrograph. The spectra yielded a reliable redshift measurement for 2578 AGN in the redshift range $z=0.02-5.0$, with $0.5-2\rm\, keV$ luminosities ranging from $10^{39}-10^{46}\rm\,erg\,s^{-1}$. This is currently the largest published spectroscopic sample of X-ray selected AGN in a contiguous area. The BOSS spectra of AGN candidates show a bimodal distribution of optical line widths allowing a separation between broad- and narrow-emission line AGN. The former dominate our sample (70 per cent) due to the relatively bright X-ray flux limit and the optical BOSS magnitude limit. We classify the narrow emission line objects (22 per cent of full sample) using standard BPT diagnostics: the majority have line ratios indicating the dominant source of ionization is the AGN. A small number (8 per cent of full sample) exhibit the typical narrow line ratios of star-forming galaxies, or only have absorption lines in their spectra. We term the latter two classes "elusive'' AGN. We also compare X-ray, optical and infrared color AGN selections in this field. X-ray observations reveal, the largest number of AGN. The overlap between the selections, which is a strong function of the imaging depth in a given band, is also remarkably small. We show using spectral stacking that a large fraction of the X-ray AGN would not be selectable via optical or IR colours due to host galaxy contamination., 26 pages, 21 figures. Accepted for publication in MNRAS. We publicly release the catalogue of X-ray selected AGN on the following webpage: http://www.mpe.mpg.de/XraySurveys/XMM-XXL/

The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5-2 keV) and hard X-rays (2-10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5-10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2-10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three. Our sample does not show evidence of a rapid decline of the AGN luminosity function up to redshift four.

We use a combination of the XMM-Newton serendipitous X-ray survey with the optical SDSS, and the infrared WISE all-sky survey in order to check the efficiency of the low X-ray to infrared luminosity selection method in finding heavily obscured AGN. We select sources in the 2-8 keV X-ray band which have a redshift determination in the SDSS catalogue. We match this sample with the WISE catalogue, and fit the SEDs of the 2844 sources which have three, or more, photometric data-points in the infrared. We then select the heavily obscured AGN candidates by comparing their 12 micron AGN luminosity to the observed 2-10 keV X-ray luminosity and their expected intrinsic relation. With this approach we find 20 candidates, and we examine their X-ray and optical spectra. Of the 20 initial candidates, we find nine (64%; out of the 14, for which X-ray spectra could be fit) based on the X-ray spectra, and seven (78%; out of the nine detected spectroscopically in the SDSS) based on the [OIII] line fluxes. Combining all criteria, we determine the final number of heavily obscured AGN to be 12-19, and the number of Compton-thick AGN to be 2-5, showing that the method is reliable in finding obscured AGN, but not Compton-thick. However those numbers are smaller than what would be expected from X-ray background population synthesis models, which demonstrates how the optical-infrared selection and the scatter of the L_x-L_MIR relation introduced by observational constraints limit the efficiency of the method. Finally, we test popular obscured AGN selection methods based on mid-infrared colours, and find that the probability of an AGN to be selected by its mid-infrared colours increases with the X-ray luminosity. However, a selection scheme based on a relatively low X-ray luminosity and mid-infrared colours characteristic of QSOs would not select ~25% of the heavily obscured AGN of our sample. (abridged), Comment: Accepted for publication in MNRAS

Heavily obscured, Compton Thick (CT, NH>10^24 cm^-2) AGN may represent an important phase in AGN/galaxy co-evolution and are expected to provide a significant contribution to the cosmic X-ray background (CXB). Through direct X-ray spectra analysis, we selected 39 heavily obscured AGN (NH>3x10^23 cm^-2) in the 2 deg^2 XMM-COSMOS survey. After selecting CT AGN based on the fit of a simple absorbed two power law model to the XMM data, the presence of CT AGN was confirmed in 80% of the sources using deeper Chandra data and more complex models. The final sample of CT AGN comprises 10 sources spanning a large range of redshift and luminosity. We collected the multi-wavelength information available for all these sources, in order to study the distribution of SMBH and host properties, such as BH mass (M_BH), Eddington ratio (\lambda_Edd), stellar mass (M*), specific star formation rate (sSFR) in comparison with a sample of unobscured AGN. We find that highly obscured sources tend to have significantly smaller M_BH and higher \lambda_edd with respect to unobscured ones, while a weaker evolution in M* is observed. The sSFR of highly obscured sources is consistent with the one observed in the main sequence of star forming galaxies, at all redshift. We also present optical spectra, spectral energy distribution (SED) and morphology for the sample of 10 CT AGN: all the available optical spectra are dominated by the stellar component of the host galaxy, and a highly obscured torus component is needed in the SED of the CT sources. Exploiting the high resolution Hubble-ACS images available, we conclude that these highly obscured sources have a significantly larger merger fraction with respect to other X-ray selected samples of AGN. Finally we discuss implications in the context of AGN/galaxy co-evolutionary models, and compare our results with the predictions of CXB synthesis models., Comment: Revised version after referee comments. Accepted for publication in Astronomy & Astrophysics on 25 November 2014. 23 pages, 2 tables, 16 figures

We examine the fraction of massive ($M_{*}>10^{10} M_{\odot}$), compact star-forming galaxies (cSFGs) that host an active galactic nucleus (AGN) at $z\sim2$. These cSFGs are likely the direct progenitors of the compact quiescent galaxies observed at this epoch, which are the first population of passive galaxies to appear in large numbers in the early Universe. We identify cSFGs that host an AGN using a combination of Hubble WFC3 imaging and Chandra X-ray observations in four fields: the Chandra Deep Fields, the Extended Groth Strip, and the UKIDSS Ultra Deep Survey field. We find that $39.2^{+3.9}_{-3.6}$\% (65/166) of cSFGs at $1.4, Comment: Published in the Astrophysical Journal

We present photometric redshifts for 1031 X-ray sources in the X-ATLAS field using the machine-learning technique TPZ. X-ATLAS covers 7.1 deg observed with XMM-Newton within the Science Demonstration Phase of the H-ATLAS field, making it one of the largest contiguous areas of the sky with both XMM-Newton and Herschel coverage. All of the sources have available SDSS photometry, while 810 additionally have mid-IR and/or near-IR photometry. A spectroscopic sample of 5157 sources primarily in the XMM/XXL field, but also from several X-ray surveys and the SDSS DR13 redshift catalogue, was used to train the algorithm. Our analysis reveals that the algorithm performs best when the sources are split, based on their optical morphology, into point-like and extended sources. Optical photometry alone is not enough to estimate accurate photometric redshifts, but the results greatly improve when at least mid-IR photometry is added in the training process. In particular, our measurements show that the estimated photometric redshifts for the X-ray sources of the training sample have a normalized absolute median deviation, nmad - 0.06, and a percentage of outliers, - = 10-14%, depending upon whether the sources are extended or point like. Our final catalogue contains photometric redshifts for 933 out of the 1031 X-ray sources with a median redshift of 0.9., The research leading to these results has received funding from the European Union’s Horizon 2020 Programme under the AHEAD project (grant agreement No. 654215). G.M. acknowledges financial support from the AHEAD project, which is funded by the European Union as Research and Innovation Action under Grant No: 654215. F.J.C. and A.C.R. acknowledge financial support through grant AYA2015-64346-C2-1-P (MINECO/FEDER). A.C.R. also acknowledges financial support by the European Space Agency (ESA) under the PRODEX program.

This paper estimates the specific accretion-rate distribution of AGN using a sample of 4821 X-ray sources from both deep and shallow surveys. The specific accretion-rate distribution is defined as the probability of a galaxy with a given stellar mass and redshift hosting an active nucleus with a certain specific accretion rate. We find that the probability of a galaxy hosting an AGN increases with decreasing specific accretion rate. There is evidence that this trend reverses at low specific accretion rates, $\lambda, Comment: MNRAS submitted

Data from the AEGIS, COSMOS and ECDFS surveys are combined to infer the bias and dark matter halo mass of moderate luminosity [LX(2-10 keV) = 42.9 erg s-1] X-ray AGN at z~1 via their cross-correlation function with galaxies. In contrast to standard cross-correlation function estimators, we present a method that requires spectroscopy only for the AGN and uses photometric redshift probability distribution functions for galaxies to determine the projected real-space AGN/galaxy cross-correlation function. The estimated dark matter halo mass of X-ray AGN in the combined AEGIS, COSMOS and ECDFS fields is ~13h-1M_solar, in agreement with previous studies at similar redshift and luminosity ranges. Removing from the sample the 5 per cent of the AGN associated with X-ray selected groups results in a reduction by about 0.5 dex in the inferred AGN dark matter halo mass. The distribution of AGN in dark matter halo mass is therefore skewed and the bulk of the population lives in moderate mass haloes. This result favour cold gas accretion as the main channel of supermassive black hole growth for most X-ray AGN., 16 pages, 17 figures, 5 tables MNRAS accepted

X-ray selection provides a powerful method of identifying AGN across a variety of host galaxies and with a wide range of accretion rates. However, careful consideration of the underlying selection biases are vital to reveal the true underlying distribution of accretion rates and determine how the incidence of AGN is related to the properties of the galaxies that host them. I will present new measurements of the distribution of specific accretion rates (scaled relative to the total host galaxy mass, roughly tracing the Eddington ratio) within both star-forming and quiescent galaxy populations. We combine near-infrared selected samples of galaxies from the CANDELS/3D-HST and UltraVISTA surveys with deep Chandra X-ray data and use an advanced Bayesian technique to constrain the underlying distribution of specific accretion rates as a function of stellar mass and redshift. Our results reveal a broad distribution of accretion rates (reflecting long-term variability in the level of AGN fuelling) in both galaxy types. The probability of a star-forming galaxy hosting an AGN (above a fixed specific accretion rate) has a strong stellar mass dependence – revealing an intrinsically higher incidence of AGN in massive star-forming galaxies – and undergoes a stellar-mass-dependent evolution with redshift. The probability of a quiescent galaxy hosting an AGN is generally lower but does not depend on stellar mass and evolves differently with redshift. These results provide vital insights into the relationship between the growth of black hole and the physical properties of their host galaxies.