Using a large sample of local galaxies (144,940) with -17.5< Mr <-22 and 0.025< z <0.107, selected from SDSS DR5, we compare AGN host galaxies with non-AGN galaxies at matched luminosity, velocity dispersion, color, color gradient, or concentration index, to investigate how AGN activity is related with galaxy properties. The AGN sample is composed of Type II AGNs identified with flux ratios of narrow-emission lines with S/N > 6. We find that the fraction of galaxies hosting an AGN (f_AGN) depends strongly on morphology together with color, and very weakly on luminosity or velocity dispersion of host galaxies. In particular, f_AGN of early-type galaxies is almost independent of luminosity nor velocity dispersion when color is fixed. The host galaxy color preferred by AGNs is u-r ~2.0 for early-type hosts and u-r=2.0-2.4 for late-type hosts. This trend suggests that AGNs are dominantly hosted by intermediate-mass late-type galaxies. We also investigate how the accretion power varies with galaxy properties. While the Eddington ratio ([OIII] line luminosity normalized by black hole mass) ranges over three orders of magnitude for both morphological types, late-type galaxies are the dominant hosts over all AGN power. Among late-type galaxies, bluer color galaxies host higher power AGNs. These results are consistent with a scenario that more massive and redder galaxies are harder to host AGNs since these galaxiesalready consumed gas at the center or do not have sufficient gas supply to feed the black hole. In contrast, intermediate-mass, intermediate-color, and more concentrated late-type galaxies are more likely to host AGNs, implying that perhaps some fraction of low-mass, blue, and less concentrated lat e-type galaxiesmay not host massive black holes or may host very low-power AGNs.
We study the issue of AGN-host connection in intermediate-z (1.2>z>0.4) galaxies with hybrid spectra (hybrid QSOs for short). The observed spectra redward of the Balmer limit are dominated by starlight, and the spectra at blue end by both an AGN continuum and a MgII broad emission line. Such unique property allows us to examine both AGN and its host galaxy in individual galaxy simultaneously. At first, 15 hybrid QSOs are selected from the Sloan Digital Sky Survey Data Release 6. The spectra are then analyzed in detail in three objects: SDSS J162446.49+461946.7, SDSS J102633.32+103443.8 and SDS…
We present a catalog of physical properties for galaxies hosting active galactic nuclei (AGN) detected by the Wide-field Infrared Survey Explorer (WISE). By fitting broadband spectral energy distributions of sources in the WISE AGN Catalog (Assef et al. 2018) with empirical galaxy and AGN templates, we derive photometric redshifts, AGN bolometric luminosities, measures of AGN obscuration, host galaxy stellar masses, and host galaxy star formation rates (SFRs) for 695,273 WISE AGN. The wide-area nature of this catalog significantly augments the known number of obscured AGN out to redshifts of z…
We combine ultraviolet to near-infrared photometry with HI 21cm line observations for a complete volume-limited sample of nearby galaxies in different environments (from isolated galaxies to Virgo cluster members), to study the migration of spirals from the blue to the red sequence. Although our analysis confirms that, in the transition region between the two sequences, a high fraction of spirals host active galactic nuclei (AGN), it clearly shows that late-types with quenched star formation are mainly HI deficient galaxies preferentially found in the Virgo cluster. This not only suggests that…
The processes that trigger Active Galactic Nuclei (AGN) remain poorly understood. While lower luminosity AGN may be triggered by minor disturbances to the host galaxy, stronger disturbances are likely required to trigger luminous AGN. Major wet mergers of galaxies are ideal environments for AGN triggering since they provide large gas supplies and galaxy scale torques. There is however little observational evidence for a strong connection between AGN and major mergers. We analyse the morphological properties of AGN host galaxies as a function of AGN and host galaxy luminosity and compare them t…
We analyze morphologies of the host galaxies of 35 X-ray selected active galactic nucleus (AGNs) at $z\sim2$ in the Cosmic Evolution Survey (COSMOS) field using Hubble Space Telescope/WFC3 imaging taken from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). We build a control sample of 350 galaxies in total, by selecting ten non-active galaxies drawn from the same field with the similar stellar mass and redshift for each AGN host. By performing two dimensional fitting with GALFIT on the surface brightness profile, we find that the distribution of S$è$rsic index (n) …
We investigate the effect of active galactic nucleus (AGN) variability on the observed connection between star formation and black hole accretion in extragalactic surveys. Recent studies have reported relatively weak correlations between observed AGN luminosities and the properties of AGN hosts, which has been interpreted to imply that there is no direct connection between AGN activity and star formation. However, AGNs may be expected to vary significantly on a wide range of timescales (from hours to Myr) that are far shorter than the typical timescale for star formation (>~100 Myr). This vari…
It is widely reported, based on clustering measurements of observed active galactic nuclei (AGN) samples, that AGN reside in similar mass host dark matter halos across the bulk of cosmic time, with log $M/M_\odot$~12.5-13.0 to z~2.5. We show that this is due in part to the AGN fraction in galaxies rising with increasing stellar mass, combined with AGN observational selection effects that exacerbate this trend. Here, we use AGN specific accretion rate distribution functions determined as a function of stellar mass and redshift for star-forming and quiescent galaxies separately, combined with th…
Multiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially important role when the host galaxies are star-forming. Selecting far-Infrared galaxies at 0.3<z<1, and using AGN tracers in the X-ray, optical spectra, mid-infrared, and radio regimes, we found a twice higher AGN fraction than previous studies, thanks to the combined AGN identification methods and in particular the recent Mass-Excitation (MEx) diagnostic diagra…
We analyse the relation between AGN host properties and large scale environment for a representative red and blue AGN host galaxy sample selected from the DR4 SDSS. A comparison is made with two carefully constructed control samples of non-active galaxies, covering the same redshift range and color baseline. The cross-correlation functions show that the density distribution of neighbours is almost identical for blue galaxies, either active, or non-active. Although active red galaxies inhabit environments less dense compared to non-active red galaxies, both reside in environments considerably d…
Using an advanced semi analytic model (SAM) for galaxy formation, we have investigated the statistical effects of assuming two different mechanisms for triggering AGN activity on the properties of AGN host galaxies. We have considered a first accretion mode where AGN activity is triggered by disk instabilities (DI) in isolated galaxies, and a second feeding mode where such an activity is triggered by galaxy mergers and fly-by events (interactions, IT). We obtained the following results:i) for hosts with $M_* \lesssim 10^{11} M_{\bigodot}$, both DI and IT modes are able to account for the obser…
We use machine learning techniques to investigate their performance in classifying active galactic nuclei (AGNs), including X-ray selected AGNs (XAGNs), infrared selected AGNs (IRAGNs), and radio selected AGNs (RAGNs). Using known physical parameters in the Cosmic Evolution Survey (COSMOS) field, we are able to well-established training samples in the region of Hyper Suprime-Cam (HSC) survey. We compare several Python packages (e.g., scikit-learn, Keras, and XGBoost), and use XGBoost to identify AGNs and show the performance (e.g., accuracy, precision, recall, F1 score, and AUROC). Our results…
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 o…
Studying the average properties of active galactic nuclei (AGN) host stellar populations is an important step in understanding the role of AGN in galaxy evolution and the processes which trigger and fuel AGN activity. Here we calculate model spectral energy distributions (SEDs) that include emission from the AGN, the host galaxy stellar population, and dust enshrouded star formation. Using the framework of cosmic X-ray background population synthesis modeling, the model AGN hosts are constrained using optical (B band) and near infrared (J band, 3.6 um, 5.7 um, 8.0 um, and 24 um) luminosity fun…
We present rest-frame far-infrared (FIR) and optical size measurements of AGN hosts and star-forming galaxies in the COSMOS field, enabled by high-resolution ALMA/1 mm (0.1 arcsec - 0.4 arcsec) and HST/F814W imaging (~ 0.1 arcsec). Our sample includes 27 galaxies at z<2.5, classified as infrared-selected AGN (3 sources), X-ray selected AGN (4 sources), and non-AGN star-forming galaxies (20 sources), for which high-resolution Band 6/7 ALMA images are available at 1 mm from our own observing program as well as archival observations. The sizes and SFR surface densities measured from both ALMA/1 m…
We use 3,213 Active Galactic Nuclei (AGNs) from the $\it{XMM}$-XXL northern field to investigate the relation of AGN type with host galaxy properties. Applying a Bayesian method, we derive the hardness ratios (HRs) and through these the hydrogen column density ($\rm N_H$) for each source. We consider as absorbed sources (type-2) those with $\rm N_H > 10^{21.5}\, \rm{cm^{-2}}$. We examine the star formation rate (SFR) as well the stellar mass (M$_*$) distributions for both absorbed and unabsorbed sources. Our work indicates that there is no significant link between the AGN type and these host g…
We use a sample of active galaxies from the Cosmic Evolution Survey to show that host galaxy morphology is tied to the accretion rate and X-ray obscuration of its active galactic nucleus (AGN). Unobscured and rapidly accreting broad-line AGNs are more likely to be in spheroid-dominated hosts than weak or obscured AGNs, and obscured AGNs are more likely to have disturbed host galaxies. Much of the disagreement in previous work on the AGN-merger connection is likely due to each study probing AGNs with different obscuration and accretion properties. Only obscured AGNs seem to merger-driven, while…
Our understanding of the cosmic evolution of supermassive black holes (SMBHs) has been revolutionized by the advent of large multiwavelength extragalactic surveys, which have enabled detailed statistical studies of the host galaxies and large-scale structures of active galactic nuclei (AGN). We give an overview of some recent results on SMBH evolution, including the connection between AGN activity and star formation in galaxies, the role of galaxy mergers in fueling AGN activity, the nature of luminous obscured AGN, and the connection between AGN and their host dark matter halos. We conclude b…
We look into the abundance of Dual AGN in the largest hydrodynamical simulation from the EAGLE project. We define a Dual AGN as two active black holes (BHs) with a separation below 30 kpc. We find that only 1 per cent of AGN with $\LhX\geq 10^{42}\ergs$ are part of a Dual AGN system at $z=0.8-1$. During the evolution of a typical binary BH system, the rapid variability of the hard X-ray luminosity on Myr time-scales severely limits the detectability of Dual AGN. To quantify this effect, we calculate a probability of detection, $t_{\rm on}/t_{\rm 30}$, where $t_{\rm 30}$ is the time in which th…
Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, w…
Two effects have substantially increased the scatter in the AGN black hole mass - host galaxy bulge luminosity relationship derived from SDSS spectra. The first is that at a fixed black hole mass, the SDSS spectrum depends strongly on redshift because an SDSS fiber sees a larger fraction of the total light of more distant galaxies. The second is that at a given redshift, the fraction of host-galaxy light in the fiber increases with decreasing galaxy luminosity. We illustrate the latter effect using the Kormendy et al. (2009) light profiles of Virgo ellipticals. With allowance for the two effec…
Mergers of galaxies have been suspected to be a major trigger of AGN activity for many years. However, when compared to carefully matched control samples, AGN host galaxies often show no enhanced signs of interaction. A common explanation for this lack of observed association between AGN and mergers has often been that while mergers are of importance for triggering AGN, they only dominate at the very high luminosity end of the AGN population. In this study, we compare the morphologies of AGN hosts to a carefully matched control sample and particularly study the role of AGN luminosity. We find …
With the aim of assessing the effects of bars on active galactic nuclei (AGN), we present an analysis of host characteristics and nuclear activity of AGN galaxies with and without bars selected from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). By visual inspection of SDSS images we classified the hosts of face-on AGN spiral galaxies brighter than g < 16.5 into barred or unbarred. With the purpose of providing an appropriate quantification of the effects of bars, we also constructed a suitable control sample of unbarred AGN galaxies with similar redshift, magnitude, morphology, bulge…
We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift BAT sample. The BAT AGN host galaxies have intermediate optical colors (u-r and g-r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and …
We present uncontaminated rest-frame u - R colors of 78 X-ray-selected AGN hosts at 0.5 < z < 1.5 in the Chandra Deep Fields measured with HST/ACS/NICMOS and VLT/ISAAC imaging. We also present spatially-resolved NUV - R color gradients for a subsample of AGN hosts imaged by HST/WFC3. Integrated, uncorrected photometry is not reliable for comparing the mean properties of soft and hard AGN host galaxies at z ~ 1 due to color contamination from point-source AGN emission. We use a cloning simulation to develop a calibration between concentration and this color contamination and use this to correct…
Variability selection has been proposed as a powerful tool for identifying both low-luminosity AGN and those with unusual SEDs. However, a systematic study of sources selected in such a way has been lacking. In this paper, we present the multi-wavelength properties of the variability selected AGN in GOODS South. We demonstrate that variability selection indeed reliably identifies AGN, predominantly of low luminosity. We find contamination from stars as well as a very small sample of sources that show no sign of AGN activity, their number is consistent with the expected false positive rate. We …
The goal of this work is to determine the nature of the relation between morphology and accretion mode in radio galaxies, including environmental parameters. The CoNFIG extended catalogue (improved by new Ks-band identifications and estimated redshifts from UKIDSS, and spectral index measurements from new GMRT observations) is used to select a sub-sample of 206 radio galaxies with z<0.3 over a wide range of radio luminosity, which are morphology-classified using the Fanaroff-Riley (FR) classification of extended radio sources. For each galaxy, spectroscopic data are retrieved to determine the …
We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the SDSS, Bootes and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared and radio wavelengths. Supermassive black holes undergoing radiatively-efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear …
[Abridged] We extend color-magnitude relations for moderate-luminosity X-ray AGN hosts and non-AGN galaxies through the galaxy formation epoch in the Chandra Deep Fields. We utilized analyses of color-magnitude diagrams (CMDs) to assess the role of moderate-luminosity AGNs in galaxy evolution. First, we confirm some previous results and extend them to higher redshifts, e.g., there is no apparent color bimodality for AGN hosts from z~0-2, but non-AGN galaxy color bimodality exists up to z~3; most AGNs reside in massive hosts and the AGN fraction rises strongly toward higher stellar mass up to z…
Clusters of galaxies have long been used as laboratories for the study of galaxy evolution, but despite intense, recent interest in feedback between AGNs and their hosts, the impact of environment on these relationships remains poorly constrained. We present results from a study of AGNs and their host galaxies found in low-redshift galaxy clusters. We fit model spectral energy distributions (SEDs) to the combined visible and mid-infrared (MIR) photometry of cluster members and use these model SEDs to determine stellar masses and star-formation rates (SFRs). We identify two populations of AGNs,…
Using new, highly accurate photometric redshifts from the MUSYC medium-band survey in the Extended Chandra Deep Field South (ECDF-S), we fit synthetic stellar population models to compare AGN host galaxies to inactive galaxies at 0.8 < z < 1.2. We find that AGN host galaxies are predominantly massive galaxies on the red sequence and in the green valley of the color-mass diagram. Because both passive and dusty galaxies can appear red in optical colors, we use rest-frame near-infrared colors to separate passively evolving stellar populations from galaxies that are reddened by dust. As with the o…
Environmental effects in stellar mass gravitational wave sources I: Expected fraction of signals with significant dephasing in the dynamical and AGN channels
We investigate the role of host galaxy classification and black hole mass in a heterogeneous sample of 276 mostly nearby (z<0.1) X-ray and IR selected AGN. Around 90% of Seyfert 1 AGN in bulge-dominated host galaxies (without disk contamination) span a very narrow range in the observed 12um to 2-10keV luminosity ratio (1<R_{IR/X}<7). This narrow dispersion incorporates all possible variations among AGN central engines, including accretion mechanism and efficiency, disk opening angle, orientation to sightline, covering fraction of absorbing material, patchiness of X-ray corona and measured vari…
Telescopes like Herschel and the Atacama Large Millimeter/submillimeter Array (ALMA) are creating new opportunities to study sources in the far infrared (FIR), a wavelength region dominated by cold dust emission. Probing cold dust in active galaxies allows for study of the star formation history of active galactic nuclei (AGN) hosts. The FIR is also an important spectral region for observing AGN which are heavily enshrouded by dust, such as Compton thick AGN. By using information from deep X-ray surveys and cosmic X-ray background synthesis models, we compute Cloudy photoionization simulations…
We compare the average star formation (SF) activity in X-ray selected AGN hosts with mass-matched control inactive galaxies,including star forming and quiescent sources, at 0.5<z<2.5. Recent observations carried out by PACS, the 60-210um Herschel photometric camera, in GOODS-S, GOODS-N and COSMOS allow us to unbiasedly estimate the far-IR luminosity, and hence the SF properties, of the two samples. Accurate AGN host stellar masses are measured by decomposing their total emission into the stellar and nuclear components. We find a higher average SF activity in AGN hosts with respect to non-AGNs.…
We describe the effect of AGN light on host galaxy optical and UV-optical colours, as determined from X-ray-selected AGN host galaxies at z~1, and compare the AGN host galaxy colours to those of a control sample matched to the AGN sample in both redshift and stellar mass. We identify as X-ray-selected AGNs 8.7 +4/-3 per cent of the red-sequence control galaxies, 9.8 +/-3 per cent of the blue-cloud control galaxies, and 14.7 +4/-3 per cent of the green-valley control galaxies. The nuclear colours of AGN hosts are generally bluer than their outer colours, while the control galaxies exhibit redde…
We estimate the fraction of AGNs hosted in starburst galaxies (f_bursty) as a function of the AGN luminosity predicted under the assumption that starburst events and AGN activity are triggered by galaxy interactions during their merging histories. The latter are described through Monte Carlo realizations, and are connected to star formation and BH accretion using a semi-analytic model of galaxy formation in a cosmological framework. The predicted fraction f_bursty increases steeply with AGN luminosity from <0.2 at L_X < 10^44 erg/s to >0.9 at L_X > 10^45 erg/s over a wide redshift interval fro…
Mergers are suspected to be reliable triggers of both starformation and AGN activity. However, the exact timing of this process remains poorly understood. Here, we present deep imaging and long slit spectroscopy data of a sample of four double-peaked [OIII] emitting AGN. These sources are often believed to host binary AGN, or at least be currently undergoing major mergers. The sample presented here either have previous IFU and high resolution imaging data that show double-nuclei in the IR as well as kinematicly and spatially distinct line emitting regions. Two sources have detections of double…
We present strong empirical evidence for a physical connection between the occurrence of a starburst (SB) and a luminous AGN phase. Drawing infrared (IR), X-ray, and optically selected samples from COSMOS, we find that the locus of type-2 AGN hosts in the optical colour-magnitude (U-V/V) and colour-colour (U-V/V-J) space significantly overlaps with that of IR-luminous (L_IR > 10^10 L_sun) galaxies. Based on our observations, we propose that, when simultaneously building their black hole and stellar masses, type-2 AGN hosts are located in the same part of colour-colour space as dusty star-formi…
We analyze a sample of 30,000 nearby obscured AGNs with optical spectra from SDSS and mid-IR photometry from WISE. Our aim is to investigate the AGN host galaxy properties with mid-IR luminosities as AGN activity indicator, and to compare with previous studies based on [OIII] emission lines. First we find that the [3.4] - [4.6] colour has weak dependence on host stellar age, but strong dependence on AGN activity. We then use a "pair-matching" technique to subtract the host 4.6 micron contribution. By combining Seyferts with a sample of SDSS quasars at z < 0.7, we show that the [OIII] and the i…
Low luminosity radio-loud active galactic nuclei (AGN) are generally found in massive red elliptical galaxies, where they are thought to be powered through gas accretion from their surrounding hot halos in a radiatively inefficient manner. These AGN are often referred to as "low-excitation" radio galaxies (LERGs). When radio-loud AGN are found in galaxies with a young stellar population and active star formation, they are usually high-power radiatively-efficient radio AGN ("high-excitation", HERG). Using a sample of low-redshift radio galaxies identified within the Sloan Digital Sky Survey (SD…
We present a novel Probabilistic Flux Variation Gradient (PFVG) approach to to separate the contributions of active galactic nuclei (AGN) and host galaxies in the context of photometric reverberation mapping (PRM) of AGN. We explored the ability of recovering the fractional contribution in a model-independent way using the entire set of light curves obtained through different filters and photometric apertures simultaneously. The method is based on the observed bluer when brighter phenomenon that is attributed to the superimposition of a two-component structure; the red host galaxy, which is co…
We perform a quantitative morphological comparison between the hosts of Active Galactic Nuclei (AGN) and quiescent galaxies at intermediate redshifts (z~0.7). The imaging data are taken from the large HST/ACS mosaics of the GEMS and STAGES surveys. Our main aim is to test whether nuclear activity at this cosmic epoch is triggered by major mergers. Using images of quiescent galaxies and stars, we create synthetic AGN images to investigate the impact of an optical nucleus on the morphological analysis of AGN hosts. Galaxy morphologies are parameterized using the asymmetry index A, concentration …
We assess the effects of simulated active galactic nuclei (AGNs) on the colour and morphology measurements of their host galaxies. To test the morphology measurements, we select a sample of galaxies not known to host AGNs and add a series of point sources scaled to represent specified fractions of the observed V band light detected from the resulting systems; we then compare morphology measurements of the simulated systems to measurements of the original galaxies. AGN contributions >20 per cent bias most of the morphology measurements tested, though the extent of the apparent bias depends on t…
We use multi-band spatially resolved photometry from the Cosmic Assembly Near-IR Deep Legacy Survey (CANDELS) in the 4 MSec Chandra Deep Field-South (CDF-S) to explore the nuclear and extended colors, color gradients and stellar populations of X-ray selected AGN host galaxies out to z=3. Based on a study of their central light, we develop X-ray based criteria to exclude objects with strong AGN contamination. We use stellar masses from the FIREWORKS database to understand and account for stellar mass selection effects, and carefully study, for the first time, the resolved host galaxy properties…
We have employed emission-line diagnostics derived from DEIMOS and NIRSPEC spectroscopy to determine the origin of the [OII] emission line observed in six AGN hosts at z~0.9. These galaxies are a subsample of AGN hosts detected in the Cl1604 supercluster that exhibit strong Balmer absorption lines in their spectra and appear to be in a post-starburst or post-quenched phase, if not for their [OII] emission. Examining the flux ratio of the [NII] to Halpha lines, we find that in five of the six hosts the dominant source of ionizing flux is AGN continuum emission. Furthermore, we find that four of…
Sensitive Herschel far-infrared observations can break degeneracies that were inherent to previous studies of star formation in high-z AGN hosts. Combining PACS 100 and 160um observations of the GOODS-N field with 2Msec Chandra data, we detect ~20% of X-ray AGN individually at >3sig. The host far-infrared luminosity of AGN with L2-10~10^43erg/s increases with redshift by an order of magnitude from z=0 to z~1. In contrast, there is little dependence of far-infrared luminosity on AGN luminosity, for L2-10<~10^44erg/s AGN at z>~1. We do not find a dependence of far-infrared luminosity on X-ray ob…
We use stellar population synthesis modeling to analyze the host galaxy properties of a sample of 33 UV-selected, narrow-lined active galactic nuclei (AGNs) at z ~ 2 - 3. In order to quantify the contribution of AGN emission to host galaxy broadband spectral energy distributions (SEDs), we use the subsample of 11 AGNs with photometric coverage spanning from rest-frame UV through near-IR wavelengths. Modeling the SEDs of these objects with a linear combination of stellar population and AGN templates, we infer the effect of the AGN on derived stellar population parameters. We also estimate the t…
SHARDS is an ongoing ESO/GTC large program that is obtaining ultra-deep photometry of the GOODS-North field in 24 medium-band filters (reaching m=26.5 AB in all bands) in the 500-950 nm range with GTC/OSIRIS. It is designed to study the properties of high-z massive galaxies, but it can also provide very valuable information about the population of AGN at intermediate redshifts (z~0.5-2). Here we present preliminary results on a study of the stellar populations and star formation activity in the host galaxies of X-ray selected optically faint AGN at 0.6<z<1.1. We demonstrate that the SHARDS pho…
There exist strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies. It is however still unclear what the exact role of nuclear activity, in the form of accretion onto these supermassive black holes, in this co-evolution is. We use a rich multi-wavelength dataset available for the North Ecliptic Pole field, most notably surveyed by the AKARI satellite infrared telescope to study the host galaxy properties of AGN. In particular we are interested in investigating star-formation in the host galaxies of radio-AGN and the putative radio feedback mecha…
The connection between AGN and their host galaxies has been widely studied over recent years, showing it to be of great importance for providing answers to some fundamental questions related with AGN fueling mechanisms, their formation and evolution. Using X-ray and one of the deepest broad-band optical data sets, we studied morphology and colours in relationship with X-ray properties for sources at redshifts z < 2.0, using a sample of 262 AGN in the Subaru/XMM-Newton Deep Survey (SXDS). Morphological classification was obtained using the galSVM code, one of the new methods useful especially w…
The normalized radial distribution of young stellar populations (and cold gas) in nearby galactic disks is compared between AGN host galaxies and starforming galaxies (both with Hubble types between S0/a and Scd) by using type II supernovae (SNe) as tracers. A subset of 140 SNe\,II with available supernova position measurements are selected from the SAI-SDSS image catalog by requiring available SDSS spectroscopy data of their host galaxies. Our sample is finally composed of 46 AGNs and 94 starforming galaxies. Both directly measured number distributions and inferred surface density distributio…
We present Keck/LRIS-B spectra for a sample of ten AEGIS X-ray AGN host galaxies and thirteen post-starburst galaxies from SDSS and DEEP2 at 0.2<z<0.8 in order to investigate the presence, properties, and influence of outflowing galactic winds at intermediate redshifts. We focus on galaxies that either host a low-luminosity AGN or have recently had their star formation quenched to test whether these galaxies have winds of sufficient velocity to potentially clear gas from the galaxy. We find, using absorption features of Fe II, Mg II, and Mg I, that six of the ten (60%) X-ray AGN host galaxies …
We study the AGN-host co-evolution issue here by focusing on the correlation between the hard X-ray emission from central AGNs and the stellar populations of the host galaxies. By focusing on the galaxies with strong H$α$ line emission (EW(H$α)>5$Å), both X-ray and optical spectral analysis are performed on 67 (partially) obscured AGNs that are selected from the \it XMM-Newton\rm\ 2XMMi/SDSS-DR7 catalog originally cross-matched by Pineau et al. The sample allows us to study central AGN activity and host galaxy directly and simultaneously in individual objects. Combining the spectral analysis i…
We describe X-ray observations with Chandra and XMM-Newton of 18 galaxy groups (M_group ~ 1-6x10^13 Msolar, z~0.05) from the Zurich Environmental Study (ZENS). We aim to establish the frequency and properties, unaffected by host galaxy dilution and obscuration, of AGNs in central and satellite galaxy members, also as a function of halo-centric distance. X-ray point-source detections are reported for 22 of 177 observed galaxies, down to a limit of f_(0.5-8 keV) ~ 5x10^-15 erg cm^-2 s^-1, corresponding to a limiting luminosity of L_(0.5-8 keV)~3x10^40 erg s^-1. With the majority of the X-ray sou…
We study the host galaxy properties of radio sources in the AKARI-North Ecliptic Pole (NEP) field, using an ensemble of multi-wavelength datasets. We identify both radio-loud and radio-quiet AGN and study their host galaxy properties by means of SED fitting. We investigate the relative importance of nuclear and star-formation activity in radio-AGN and assess the role of radio-AGN as efficient quenchers of star-formation in their host galaxies.
Using HST/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), we examine the role that major galaxy mergers play in triggering active galactic nuclei (AGN) activity at z~2. Our sample consists of 72 moderate-luminosity (Lx ~ 1E42-1E44 erg/s) AGN at 1.5<z<2.5 that are selected using the 4 Msec Chandra observations in the Chandra Deep Field South, the deepest X-ray observations to date. Employing visual classifications, we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control …
The co-evolution of host galaxies and the active black holes which reside in their centre is one of the most important topics in modern observational cosmology. Here we present a study of the properties of obscured Active Galactic Nuclei (AGN) detected in the CDFS 1Ms observation and their host galaxies. We limited the analysis to the MUSIC area, for which deep K-band observations obtained with ISAAC@VLT are available, ensuring accurate identifications of the counterparts of the X-ray sources as well as reliable determination of photometric redshifts and galaxy parameters, such as stellar mass…
We are looking for radio `relics' and `halos' in an X-ray selected sample of clusters of galaxies. These radio features are not a product of the Active Galactic Nuclei (AGN)-mechanism, but more likely are associated with past cluster merger events. AGN hosts of cooling flow clusters contain particle bubbles that show non-thermal radio emission. These bubbles could explain the presence of radio relics and halos if they can restrict cosmic rays efficiently. Intracluster magnetic fields and cluster environments can reveal the acceleration mechanisms of cosmic rays. Using radio/X-ray data and anal…
We present evidence that the incidence of active galactic nuclei (AGNs) and the distribution of their accretion rates do not depend on the stellar masses of their host galaxies, contrary to previous studies. We use hard (2-10 keV) X-ray data from three extragalactic fields (XMM-LSS, COSMOS and ELAIS-S1) with redshifts from the Prism Multi-object Survey to identify 242 AGNs with L_{2-10 keV}=10^{42-44} erg /s within a parent sample of ~25,000 galaxies at 0.2<z<1.0 over ~3.4 deg^2 and to i~23. We find that although the fraction of galaxies hosting an AGN at fixed X-ray luminosity rises strongly …
We use morphological information of X-ray selected AGN hosts to set limits on the fraction of the accretion density of the Universe at z~1 that is not likely to be associated with major mergers. Deep X-ray observations are combined with high resolution optical data from the Hubble Space Telescope in the AEGIS, GOODS North and GOODS South fields to explore the morphological breakdown of X-ray sources in the redshift interval 0.5<z<1.3. The sample is split into disks, early-type bulge dominated galaxies, peculiar systems and point-sources in which the nuclear source outshines the host galaxy. Th…
