Physics and evolution of obscured X-ray sources: a multiwavelength approach

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Google Scholar. Lotz, J. The effect of mass ratio on the morphology and time-scales of disc galaxy mergers. Luo, B.


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The chandra deep field-south survey: 2 ms source catalogs. The chandra deep field-south survey: 7 ms source catalogs. Lutz, D. Madau, P. Magorrian, J. The demography of massive dark objects in galaxy centers. Mullaney, J. Defining the intrinsic AGN infrared spectral energy distribution and measuring its contribution to the infrared output of composite galaxies. Ricci, C. Growing supermassive black holes in the late stages of galaxy mergers are heavily obscured.

Submission history

Rosario, D. Rovilos, E. Salpeter, E. The luminosity function and stellar evolution. Stanley, F. Treister, E. The evolution of obscuration in active galactic nuclei. Xue, Y. The chandra deep field-south survey: 4 ms source catalogs. Yaqoob, T. X-ray transmission in cold matter: nonrelativistic corrections for compton scattering. Keywords: galaxies: active, quasars: general, quasars: supermassive black holes, X-rays: galaxies, infrared: galaxies, galaxies: star formation. Space Sci. The use, distribution or reproduction in other forums is permitted, provided the original author s or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.

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    Production of X Rays

    Alexander 2 , Franz E. Bauer 3,4,5,6 , Emanuele Daddi 7 , Dale D. Kocevski 8 , Flora Stanley 9 and Daniel H. Our group built the first population synthesis model that connected X-rays to the rest of the spectral energy distribution, so that the data in every waveband constrained the model and thus the intrinsic properties of AGN Treister et al.

    However, that model was constrained only by the very small GOODS survey, so it probed only moderate-luminosity AGN, and its assumptions were overly simple. Most importantly, it includes luminous quasars, both obscured and unobscured. By tuning a fully developed population synthesis model to match these data, we will characterize the full AGN population across redshift and luminosity, in terms of accretion rate, obscuration, host galaxy, dust content and more.

    Moreover, this kind of multi-wavelength model constitutes a description of IR-through-X-ray light emitted over cosmic time due to black hole accretion. Assuming an accretion efficiency which depends on black hole spin , this translates to a description of the total mass accreted onto black holes. The model can also be disaggregated to explore the amount of radiation emitted or black hole mass accreted as a function of waveband, quasar luminosity, obscuring column density, instantaneous black hole mass, etc.

    Cosmological simulations will be improved by using data-validated descriptions of radiation deposited into galaxies. That is one of the broad scientific impacts of this proposal. Ingredients of the New Population Synthesis Model: The wealth of new data, especially in Stripe 82X, motivates a new population synthesis analysis, which will form the core of the graduate thesis of Yale graduate student Tonima Ananna.

    Following Treister et al. The second ingredient is the evolving hard X-ray luminosity function, for which the new Stripe 82X data are essential. Specifically, the recent luminosity function from Ueda et al. How this ratio evolves with redshift is a strong clue to how black hole accretion evolved, and whether mergers are relevant to galaxy-AGN co-evolution. Because of the greatly improved statistics and L-z coverage, Ms.

    We have information about the host galaxies types and masses from Stripe 82 value-added data, including Galaxy Zoo identifications. We are able to fully sample host galaxy types by combining different methods of AGN selection, particularly IR and optical, which are sensitive to different host properties. Roughly speaking, the quasar luminosity function QLF is a broken power law with a break that evolves with redshift; accretion at the break dominates overall black hole growth , so it is an important thing to determine.

    Stripe 82X surveys a large enough volume to constrain the number density of high redshift quasars. We will empirically determine the Stripe 82X selection function i. In this way we can determine the X-ray luminosity function, the bivariate optical luminosity function, and with multi-wavelength data the bolometric luminosity function for a relatively unbiased sample of X-ray-selected quasars. This will be the most accurate high-redshift QLF ever, given the hard X-ray selection and excellent statistics. Georgakakis et al. Figure 6.

    We reproduce here Figure 21 from Ueda et al. But their quasar sample is largely unobscured, whereas Stripe 82X is designed to find obscured quasars. Better-characterized AGN SEDs, particularly at high luminosity and redshift, will be an important product of this project, and are an essential input to the population synthesis model.

    In some cases, it is possible to separate the black hole-powered point source cleanly from the diffuse host galaxy light, improving the SED decomposition—a technique our group pioneered Simmons et al. A consistency check is the absorption implied by the X-ray spectrum, which is usually parameterized in terms of the equivalent hydrogen column density, N H , assuming solar abundances. Another consistency check is the ratio of Balmer lines, which gives an estimate of the reddening, A V.

    Extragalactic Surveys: A Chandra Science Workshop

    Even with deep observations, X-ray selection can miss heavily obscured AGN e. Spitzer IRAC colors provide evidence of a hot torus e. Within massive dusty galaxies, AGN and star formation may be linked through major mergers that provide the fuel for both e. Galaxies undergoing a merger are more likely to be Compton thick, so the predicted merger link between star-forming galaxies and AGN can be missed if only X-ray detected AGN are considered Kocevski et al.

    This makes identifying luminous quasars and buried AGN crucial to understanding what fueling mechanism drives black hole growth in massive star-forming host galaxies.

    The XXL survey. XXI. The environment and clustering of X-ray AGN in the XXL-South field

    At the same time, it appears that only the most luminous AGN are triggered by mergers; for most galaxies, high star-formation rates likely depend on gas fraction, which increases with look-back time e. Our data span the full luminosity and mass range, and using multiple, proven AGN selection techniques, we are in a unique position to explore the AGN-host galaxy connection for a range of host galaxy and black hole properties.

    Understanding the History of Black Hole Accretion: It is currently a matter of debate whether moderate luminosity AGN or quasars dominate the total mass accreted onto black holes. Theories invoking mergers suggest the accretion rate is highest during the most luminous and obscured phase, before excess gas and dust is expelled by the quasar e. The model from Ueda et al. But even this recent luminosity function from Ueda et al. The Stripe 82X data we will use for this regime are much more sensitive to obscured quasars.

    There may be three times as many quasars as detected by soft X-ray experiments, as suggested by fluctuations analysis Shafer and initial results from the Stripe 82X survey LaMassa et al. Fitting to the multi-wavelength Stripe 82X samples, in particular, will quantify the amount of black hole growth in rare, luminous quasars, and allow us to estimate for the first time the fraction of black hole growth that is obscured at high luminosity and high redshift. We will produce a data-validated description of when and where supermassive black holes grew, i.

    This is one of the broader impacts from our proposal. Using our IR-identified AGN and host galaxies we will measure, for the first time, the concurrent black hole accretion rate and star-formation rate density in individual galaxies across cosmic time. Comparing to quasar accretion rates described above , we can quantify which population of AGN dominate black hole growth. In some cases, these quasars will be brighter in the IR and thus accessible with Palomar or other 4-meter class telescopes that have excellent instrumentation.

    The black hole masses provide a direct check on the efficiency of converting mass to light and an independent constraint on the global accretion of mass onto black holes, which can be compared to the comprehensive population synthesis models discussed earlier. Comparing black hole mass functions and AGN SEDs in several redshift bins, we can constrain the evolving distribution of Eddington ratios , providing an important constraint on theories of accretion another broader impact of this proposal.

    In addition, the wealth of multi-wavelength data allows us to measure the mass function of the host galaxies in our samples to which we can add galaxy mass functions in the literature , and thus to determine whether black hole mass evolves proportionally with galaxy mass, or whether smaller galaxies hosted larger black holes in the past.

    This could shed light on when the M- s relation fell into place another broader impact. Measuring the Clustering of High-Redshift AGN: The study of AGN clustering and evolution is a powerful tool to understand, from a statistical point of view, what kind of environment is most likely to host AGN and how gas loses its angular momentum, is funneled to the central region of galaxy, and becomes available for accretion. The proposed work is unprecedented in using both data on large scales and relatively unbiased samples. So far, discrepant results are obtained based on AGN selection methods.

    From these we obtain true distribution of the radio loudness parameter which shows no sign of bi-modality and indicates that quasars were more radio loud at earlier epochs. An important goal that has driven the development of LOFAR since its inception is to explore the low frequency radio sky through several surveys. The main science driving the design of these surveys was to use the unique aspects of LOFAR to advance our understanding of the formation and evolution of galaxies, AGNs and galaxy clusters.

    In this presentation we will review the LOFAR facility, discuss the current state of the analysis techniques and present several new science results from the deepest low-frequency images ever produced. In the soft band 0. In addition, eROSITA is expected to yield a sample of around 3 million active galactic nuclei, which is bound to revolutionize our view of the evolution of supermassive black holes and their impact on the process of structure formation in the Universe.

    The survey will also provide new insights into a wide range of astrophysical phenomena, including isolated Neutron Stars and Black Holes, X-ray binaries, active stars and diffuse emission within the Galaxy, as well as more exotic ones such as gamma-ray bursts, tidal disruption of stars in galactic nuclei and binary black holes. In this talk I will present the main characteristics of the mission and focus on the scientific drivers for extragalactic all-sky surveys of AGN. Variability is a successful technique used to identify AGN in both ground and space-based galaxy surveys.

    Mid-IR variability surveys using Spitzer observations have identified a significant numbers of AGN and are particularly sensitive to obscured sources. Many variability detected AGN are not strong X-ray sources or lack the characteristic mid-IR colors of AGN and would thus be unidentified using other selection techniques. I will discuss the nature of the variable sources and their host galaxies from both optical and mid-IR surveys.

    A significant variability is often observed, with time scales from a few minutes to months and years. The spectral energy distribution SED of these blazars typically shows two bumps from the radio to the TeV range, which can usually be described by leptonic or hadronic processes. While elementary bricks of the VHE emission scenarios seem now reasonably well identified, a global picture of these sources, describing the geometry and dynamics of the VHE zone, is not yet available.

    Multiwavelength monitoring and global alert network will be important to better constrain the picture, especially with the perspective of CTA, a major project of the next generation in ground-based gamma-ray astronomy. Various observational techniques have been used to survey galaxies and AGN, from X-rays to radio frequencies, both photometric and spectroscopic. I will review these techniques aimed at the study of galaxy evolution and of the role of AGNs and star formation as the two main energy production mechanisms. I will then present as a new observational approach the far-IR spectroscopic surveys that could be done with planned astronomical facilities of the next future.

    I will discuss several aspects of the mid-IR obscured AGN population, ranging from detailed studies of extreme sources, the so-called WISE ultraluminous 'hot dust-obscured galaxy' or 'hot DOG' sample, as well as more general studies comparing obscured and unobscured AGN identified in wide-area surveys. It is well known that some percentage of Active Galaxies with strong emission lines show double or multiple nuclei sometimes associated with jets. The sizes of these features are a few hundred parsecs and even kiloparsecs. The physical nature of these structures is not well understood.

    One prominent hypothesis is that they are the manifestation of colliding and merging galaxies. Another hypothesis is just some violent activity taking place in the nuclei of galaxies causing major disruptions, though at present no explanation exists for the origin of such activity. We discuss spectroscopic observations of such galaxies made with the Palomar 5m telescope, the Byurakan 2. We conclude that the major explanation of the nature of the double or multiple nuclei is not yet clear.

    Further study is needed. In order to fully understand galaxy formation we need to know when in the cosmic history are supermassive black holes SMBHs growing more intensively, in what type of galaxies this growth is happening and what fraction of these sources are invisible at most wavelengths due to obscuration.

    However, this is not the complete history, as a large fraction of black hole growth does not emit significantly in X-rays either due to obscuration, intrinsic low luminosities or large distances. We obtain stacked rest-frame X-ray spectra for samples of galaxies binned in terms of their IR luminosity, stellar mass and other galaxy properties. We find that the AGN fraction and their typical luminosities, and thus black hole accretion rates, increase with IR luminosity.

    The XXL survey. XXI. The environment and clustering of X-ray AGN in the XXL-South field

    We utilize a maximum likelihood method to reproduce the count-rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, the contribution from Compton-thick AGNs, and AGN broad band X-ray spectra including reflection components from tori based on the luminosity and redshift dependent unified scheme.

    These results establish the standard population synthesis model of the X-Ray Background XRB , which well reproduces the source counts in both soft and hard bands, the observed fractions of Compton-thick AGNs, and the spectrum of the hard XRB. Finally, the growth history of supermassive black holes is discussed on the basis of the AGN bolometric luminosity function constructed from the new XLF. There has been considerable theoretical support in recent years for the idea of quenching star formation in massive galaxies via AGN-driven winds, but relatively little direct observational evidence for it, until now.

    Recent models of joint evolution of super-massive black holes SMBHs and their host galaxies predict the presence of a key phase where accretion, traced by obscured Active Galactic Nuclei AGN emission, is likely coupled with powerful star formation.

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    At the end of this phase, feedback processes likely play a major role in self-regulating the SMBH growth and in quenching the star-formation activity. AGN in this important evolutionary phase have been revealed in the last decade via surveys at different wavelengths. On the one hand, moderate-to-deep X-ray surveys have allowed a systematic search for heavily obscured AGN, whose main X-ray signature is the presence of a strong iron emission line over a flat X-ray continuum.

    On the other hand, infrared surveys have been invaluable in offering complementary methods to select obscured AGN either via spectroscopy or photometry also in cases where the nuclear X-ray emission below 10 keV is totally obscured. Invited talks.



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