BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog

NASA Astrophysics Data System (ADS)

Ricci, C.; Trakhtenbrot, B.; Koss, M. J.; Ueda, Y.; Del Vecchio, I.; Treister, E.; Schawinski, K.; Paltani, S.; Oh, K.; Lamperti, I.; Berney, S.; Gandhi, P.; Ichikawa, K.; Bauer, F. E.; Ho, L. C.; Asmus, D.; Beckmann, V.; Soldi, S.; Baloković, M.; Gehrels, N.; Markwardt, C. B.

2017-12-01

Hard X-ray (≥10 keV) observations of active galactic nuclei (AGNs) can shed light on some of the most obscured episodes of accretion onto supermassive black holes. The 70-month Swift/BAT all-sky survey, which probes the 14-195 keV energy range, has currently detected 838 AGNs. We report here on the broadband X-ray (0.3-150 keV) characteristics of these AGNs, obtained by combining XMM-Newton, Swift/XRT, ASCA, Chandra, and Suzaku observations in the soft X-ray band (≤slant 10 keV) with 70-month averaged Swift/BAT data. The nonblazar AGNs of our sample are almost equally divided into unobscured ({N}{{H}}< {10}22 {{cm}}-2) and obscured ({N}{{H}}≥slant {10}22 {{cm}}-2) AGNs, and their Swift/BAT continuum is systematically steeper than the 0.3-10 keV emission, which suggests that the presence of a high-energy cutoff is almost ubiquitous. We discuss the main X-ray spectral parameters obtained, such as the photon index, the reflection parameter, the energy of the cutoff, neutral and ionized absorbers, and the soft excess for both obscured and unobscured AGNs.

X-ray Obscured AGN in the GOODS-N

NASA Astrophysics Data System (ADS)

Georgantopoulos, I.; Akylas, A.; Rovilos, E.; Xilouris, E.

2010-07-01

We explore the X-ray properties of the Dust Obscured Galaxies (DOGs) i.e. sources with f24μ / fR > 1000. This population has been proposed to contain a significant fraction of Compton-thick sources at high redshift. In particular we study the X-ray spectra of the 14 DOGS detected in the CDFN 2Ms exposure. Their stacked spectrum is flat with Γ=1±0.1 very similar to the stacked spectrum of the undetected DOGs (Γ=0.8±0.2). However, most of our X-ray detected DOGs present only moderate absorption with column densities 1022 < NH < 1024 cm-2. Only three sources (20%) present very flat spectra and are probably associated with reflection dominated Compton-thick sources. Our finding is rather at odds with papers which claim that the vast majority of DOGs are associated with Compton-thick sources. In any case, such sources at high redshift (z > 2) present limited interest for the X-ray background: the population synthesis models predict a contribution, for the z > 2 Compton-thick AGN, to the X-ray background flux at 30 keV, of less than 1 percent.

Host Galaxy Properties Of The Swift Bat Hard X-ray Survey Of Agn

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.; Winter, L.

2010-03-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. In 2008, we observed 90 of these targets at Kitt Peak with the 2.1m in the SDSS ugriz bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, stellar mass, star formation, and AGN luminosity for a sample of 145 AGN Hard X-ray Selected AGN.

A Chandra-Swift View of Point Sources in Hickson Compact Groups: High AGN Fraction but a Dearth of Strong AGNs

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Gallagher, S. C.; Hornschemeier, A. E.; Fedotov, K.; Eracleous, M.; Brandt, W. N.; Desjardins, T. D.; Charlton, J. C.; Gronwall, C.

2014-01-01

We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (L(sub x)) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (gamma), hardness ratios, and L(sub X), in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L(sub X),0.5-8.0 keV > 10(exp 42) erg s-1, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known alpha OX-?L? (nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the 'non-AGN locus' in alpha OX-?L? (nearUV) space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR (is) less than -20 and L(sub X),0.5-8.0 keV (is) greater than 10(exp 41) erg s-1 is 0.08+0.35 -0.01, somewhat higher than the 5% fraction in galaxy clusters.

X-ray Properties of an Unbiased Hard X-ray Detected Sample of AGN

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Mushotzky, Richard F.; Tueller, Jack; Markwardt, Craig

2007-01-01

The SWIFT gamma ray observatory's Burst Alert Telescope (BAT) has detected a sample of active galactic nuclei (AGN) based solely on their hard X-ray flux (14-195keV). In this paper, we present for the first time XMM-Newton X-ray spectra for 22 BAT AGXs with no previously analyzed X-ray spectra. If our sources are a representative sample of the BAT AGN, as we claim, our results present for the first time global X-ray properties of an unbiased towards absorption (n(sub H) < 3 x 10(exp 25)/sq cm), local (< z >= 0.03), AGN sample. We find 9/22 low absorption (n(sub H) < 10(exp 23)/sq cm), simple power law model sources, where 4 of these sources have a statistically significant soft component. Among these sources, we find the presence of a warm absorber statistically significant for only one Seyfert 1 source, contrasting with the ASCA results of Reynolds (1997) and George et al. (1998), who find signatures of warm absorption in half or more of their Seyfert 1 samples at similar redshifts. Additionally, the remaining sources (13122) have more complex spectra, well-fit by an absorbed power law at E > 2.0 keV. Five of the complex sources (NGC 612, ESO 362-G018, MRK 417, ESO 506-G027, and NGC 6860) are classified as Compton-thick candidates. Further, we find four more sources (SWIFT J0641.3+3257, SWIFT J0911.2+4533, SWIFT J1200.8+0650, and NGC 4992) with properties consistent with the hidden/buried AGN reported by Ueda et al. (2007). Finally, we include a comparison of the XMM EPIC spectra with available SWIFT X-ray Telescope (XRT) observations. From these comparisons, we find 6/16 sources with varying column densities, 6/16 sources with varying power law indices, and 13/16 sources with varying fluxes, over periods of hours to months. Flux and power law index are correlated for objects where both parameters vary.

Unveiling the physics of AGN through X-ray variability

NASA Astrophysics Data System (ADS)

Hernández-García, L.; González-Martín, O.; Masegosa, J.; Márquez, I.

2017-03-01

Although variability is a general property characterizing active galactic nuclei (AGN), it is not well established whether the changes occur in the same way in every nuclei. The main purpose of this work is to study the X-ray variability pattern(s) in AGN selected at optical wavelengths in a large sample, including low ionization nuclear emission line regions (LINERs) and type 1.8, 1.9, and 2 Seyferts, using the public archives in Chandra and/or XMM-Newton. Spectra of the same source gathered at different epochs were simultaneously fitted to study long term variations; the variability patterns were studied allowing different parameters to vary during the spectral fit. Whenever possible, short term variations from the analysis of the light curves and long term UV flux variability were studied. Variations at X-rays in timescales of months/years are very common in all AGN families but short term variations are only found in type 1.8 and 1.9 Seyferts. The main driver of the long term X-ray variations seems to be related to changes in the nuclear power. Other variability patterns cannot be discarded in a few cases. We discuss the geometry and physics of AGN through the X-ray variability analysis.

Long-Term Variability of AGN at Hard X-Rays

NASA Technical Reports Server (NTRS)

Soldi, S.; Beckmann, V.; Baumgartner W. H.; Ponti, G.; Shrader, C. R.; Lubinski, P.; Krimm, H. A.; Mattana, F.; Tueller, J.

2013-01-01

Variability at all observed wavelengths is a distinctive property of active galactic nuclei (AGN). Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by absorption along the line of sight. Characterizing the intrinsic hard X-ray variability of a large AGN sample and comparing it to the results obtained at lower X-ray energies can significantly contribute to our understanding of the mechanisms underlying the high-energy radiation. Methods. Swift/BAT provides us with the unique opportunity to follow, on time scales of days to years and with a regular sampling, the 14-195 keV emission of the largest AGN sample available up to date for this kind of investigation. As a continuation of an early work on the first 9 months of BAT data, we study the amplitude of the variations, and their dependence on sub-class and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. About 80 of the AGN in the sample are found to exhibit significant variability on months to years time scales, radio loud sources being the most variable. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes of the absorption column density. In general, the variations in the 14-24 and 35-100 keV bands are well correlated, suggesting a common origin of the variability across the BAT energy band. However, radio quiet AGN display on average 10 larger variations at 14-24 keV than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on month time scale. In addition, sources with harder spectra are found to be more variable than softer ones. These properties are generally consistent with a variable power law continuum, in flux and shape, pivoting at energies 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at

EDDINGTON RATIO DISTRIBUTION OF X-RAY-SELECTED BROAD-LINE AGNs AT 1.0 < z < 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Hyewon; Hasinger, Günther; Steinhardt, Charles

2015-12-20

We investigate the Eddington ratio distribution of X-ray-selected broad-line active galactic nuclei (AGNs) in the redshift range 1.0 < z < 2.2, where the number density of AGNs peaks. Combining the optical and Subaru/Fiber Multi Object Spectrograph near-infrared spectroscopy, we estimate black hole masses for broad-line AGNs in the Chandra Deep Field South (CDF-S), Extended Chandra Deep Field South (E-CDF-S), and the XMM-Newton Lockman Hole (XMM-LH) surveys. AGNs with similar black hole masses show a broad range of AGN bolometric luminosities, which are calculated from X-ray luminosities, indicating that the accretion rate of black holes is widely distributed. We find a substantial fraction ofmore » massive black holes accreting significantly below the Eddington limit at z ≲ 2, in contrast to what is generally found for luminous AGNs at high redshift. Our analysis of observational selection biases indicates that the “AGN cosmic downsizing” phenomenon can be simply explained by the strong evolution of the comoving number density at the bright end of the AGN luminosity function, together with the corresponding selection effects. However, one might need to consider a correlation between the AGN luminosity and the accretion rate of black holes, in which luminous AGNs have higher Eddington ratios than low-luminosity AGNs, in order to understand the relatively small fraction of low-luminosity AGNs with high accretion rates in this epoch. Therefore, the observed downsizing trend could be interpreted as massive black holes with low accretion rates, which are relatively fainter than less-massive black holes with efficient accretion.« less

Twenty-two emission-line AGNs from the HEAO-1 X-ray survey

NASA Technical Reports Server (NTRS)

Remillard, R. A.; Bradt, H. V. D.; Brissenden, R. J. V.; Buckley, D. A. H.; Roberts, W.; Schwartz, D. A.; Stroozas, B. A.; Tuohy, I. R.

1993-01-01

We report 22 emission-line AGN as bright, hard X-ray sources. All of them appear to be new classifications with the exception of one peculiar IRAS source which is a known quasar and has no published spectrum. This sample exhibits a rich diversity in optical spectral properties and luminosities, ranging from a powerful broad-absorption-line quasar to a weak nucleus embedded in a nearby NGC galaxy. Two cases confer X-ray luminosities in excess of 10 exp 47 erg/s. However, there is a degree of uncertainty in the X-ray identification for the AGN fainter than V about 16.5. Optically, several AGN exhibit very strong Fe II emission. One Seyfert galaxy with substantial radio flux is an exception to the common association of strong Fe II emission and radio-quiet AGN. The previously recognized IRAS quasar shows extreme velocities in the profiles of the forbidden lines; the 0 III pair is broadened to the point that the lines are blended. Several of these AGN show evidence of intrinsic obscuration, illustrating the effectiveness of hard X-ray surveys in locating AGN through high column density.

Extragalactic Hard X-ray Surveys: From INTEGRAL to Simbol-X

NASA Astrophysics Data System (ADS)

Paltani, S.; Dwelly, T.; Walter, R.; McHardy, I. M.; Courvoisier, T. J.-L.

2009-05-01

We present some results of the deepest extragalactic survey performed by the INTEGRAL satellite. The fraction of very absorbed AGN is quite large. The sharp decrease in the absorption fraction with X-ray luminosity observed at lower-energy X-rays is not observed. The current lack of truly Compton-thick objects, with an upper limit of 14% to the size of this population, is just compatible with recent modeling of the cosmic X-ray background. We also study the prospects for a future hard X-ray serendipitous survey with Simbol-X. We show that Simbol-X will easily detect a large number of serendipitous AGN, allowing us to study the evolution of AGN up to redshifts about 2, opening the door to the cosmological study of hard X-ray selected AGN, which is barely possible with existing satellites like Swift and INTEGRAL.

X-Rays and Infrared Selected AGN

NASA Astrophysics Data System (ADS)

Kirhakos, S. D.; Steiner, J. E.

1990-11-01

RESUMEN. En la busqueda de nucleos activos galacticos (NAG) oscurecidos, seleccionamos una tnuestra de galaxias ernisoras de rayos S infrarrojos, Ia mayoria de las cuales son vistas de perf ii. La 6ptica de la regi6n nuclear de las galaxias seleccionadas revelan que el 76% de ellas muestran lineas de emisi5n La clasificaci6n de los es- pectros de acuerdo a los anchos y a la intensidad de cocientes de lineas muestran que existen 34 NAG, 34 objetos de tipo de transici6n y 34 galaxias de la regi6n con nucleos de tipo regi6n H II. Entre los NAG, 3 son del tipo Seyfert I y las otras son del tipo 2. Sugerimos que los objetos identificados como NAG de llneas angostas son objetos tipo Seyfert I oscurecidos ABSTRACT. Looking for obscured active galactic nuclei (AGN), we selected a sample of infrarediX-rays emitting galaxies, mos"t of which are seen as edge-on. Optical spectroscopy of the nuclear region of the selected galaxies revealed that 76 % of them show emission l 'nes. Classification of the spectra according to the widths and line intensity ratios shows that there are 34 AGN, 34 transition type objects and 43 nuclear HIl-like region galaxies. Among the AGN, three are Seyfert type 1 and the others are type 2 objects. We suggest that the objects identified as narrow line AGN are obscured Seyfert 1. o'L : GALAXIES-ACTIVE - X-RAY S-GENERAL

Why do we see Broad Lines in X-ray Absorbed, Red AGN?

NASA Astrophysics Data System (ADS)

Wilkes, B. J.; Ghosh, Himel; Cutri, R.; Hines, D.; Nelson, B.; Schmidt, G. D.; Smith, P. S.

2003-05-01

The Two Micron All-Sky Survey (2MASS) red AGN catalog has revealed a previously unknown population whose number density rivals that of optically-selected AGN as found in the many, relatively shallow surveys (e.g. PG, Hamburg). The Chandra X-ray spectra of these red, mostly broad-line AGN are hard. This, combined with their unusually high optical polarization, suggests substantial obscuration (log NH = 21-23 cm-2) toward the nuclear energy source, despite a clear view of the broad emission line region. We have expanded our Chandra-observed sub-sample to include 20 more 2MASS AGN yielding a set of 46 which includes all available optical classes. This sample is thus pre-selected for complex absorption and sufficient to study the relative X-ray and optical obscuration for each AGN class. Those observed to date continue the lack of a relation between the X-ray hardness ratio and optical class noted in our earlier sample. Combining this with X-ray spectral fits where we have sufficient counts and with our multi-wavelength data, we compare the spectral energy distributions with those of normal and other red AGN and investigate possible scenarios for the absorbing material. We gratefully ackowledge the financial support of NASA grant: GO1-2112A

The host galaxies of ultra hard X-ray selected AGN

NASA Astrophysics Data System (ADS)

Koss, Michael J.

One of the great mysteries surrounding active galactic nuclei (AGN) is their triggering mechanism. Since the discovery that almost all massive galaxies host nuclear supermassive black holes, it has become clear that a trigger mechanism is required to 'turn on' and continue to fuel the central black hole. While it is established that accretion processes are responsible for the energy emitted, the source of the accreting material is still controversial. Furthermore, the energy input from phases of black hole growth is thought to be a key regulator in the formation of galaxies and the establishment of various scaling relations. Theorists often invoke galaxy mergers as the violent mechanism to drive gas into the central regions and ignite luminous quasars, but among more common moderate luminosity AGN, there has been great controversy whether secular processes or mergers dominate AGN fueling. A survey in the ultra hard X-ray band (14--195 keV) is an important new way to answer the fundamental question of AGN fueling. This method is independent of selection effects such as dust extinction and obscuration that plague surveys at other wavelengths because of the ability of the primary continuum to easily pass through large columns of obscuring gas and dust (<10 24 cm-2). In this PhD, we have assembled the largest sample of ultra hard X-ray selected AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift BAT sample. We find that these AGN show much higher rates of both mergers and massive spirals suggesting both mergers and accretion of cold gas in late type systems are important in AGN fueling. We also find that the most common AGN survey technique, optical line diagnostics, is heavily biased against finding AGN in mergers or spirals. Finally, in agreement with the merger driven AGN link, we find that dual AGN systems may be more common than current observation suggest since some of them are only detected using high

The Global Implications of the Hard X-ray Excess in Type 1 AGN

NASA Astrophysics Data System (ADS)

Tatum, Malachi; Turner, T. J.; Miller, L.; Reeves, J. N.

2012-09-01

Suzaku observations of 1H 0419-577 and PDS 456 revealed a marked 'hard excess' of flux above 10 keV, likely due to the presence of a Compton-thick absorber covering a large fraction of the continuum source. The discovery is intriguing, given the clear view to the optical BLR in type 1 objects. These results motivated an exploratory study of the hard excess phenomenon in the local type 1 AGN population, using the Swift Burst Alert Telescope (BAT). We selected radio quiet type 1-1.9 AGN from the 58-month BAT catalog. The hardness of the X-ray spectrum, combined with measurements of the equivalent width of Fe Ka emission suggest that type 1 X-ray spectra are shaped by an ensemble of Compton-thick clouds, partially covering the continuum. I discuss our methodology, the observational findings & possible location of the Compton-thick gas.

X-ray View of Four High-Luminosity Swift-BAT AGN: Unveiling Obscuration and Reflection with Suzaku

NASA Technical Reports Server (NTRS)

Fiorettil, V.; Angelini, L.; Mushotzky, R. F.; Koss, M.; Malaguti, G.

2013-01-01

Aims. A complete census of obscured Active Galactic Nuclei (AGN) is necessary to reveal the history of the super massive black hole (SMBH) growth and galaxy evolution in the Universe given the complex feedback processes and the fact that much of this growth occurs in an obscured phase. In this context, hard X-ray surveys and dedicated follow-up observations represent a unique tool for selecting highly absorbed AGN and for characterizing the obscuring matter surrounding the SMBH. Here we focus on the absorption and reflection occurring in highly luminous, quasar-like AGN, to study the relation between the geometry of the absorbing matter and the AGN nature (e.g. X-ray, optical, and radio properties), and to help to determine the column density dependency on the AGN luminosity. Methods. The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10(exp -11) erg per square centimeter and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 less than LogLBAT less than 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis, adding an original spectral analysis when non was available from the literature. Results. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption (N(sub H) approximately 4 × 10(exp 23) per square centimeter) and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (less than 0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density

Fast Ionized X-Ray Absorbers in AGNs

NASA Technical Reports Server (NTRS)

Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

2016-01-01

We investigate the physics of the X-ray ionized absorbers often identified as warm absorbers (WAs) and ultra-fast outflows (UFOs) in Seyfert AGNs from spectroscopic studies in the context of magnetically-driven accretion-disk wind scenario. Launched and accelerated by the action of a global magnetic field anchored to an underlying accretion disk around a black hole, outflowing plasma is irradiated and ionized by an AGN radiation field characterized by its spectral energy density (SED). By numerically solving the Grad-Shafranov equation in the magnetohydrodynamic (MHD) framework, the physical property of the magnetized disk-wind is determined by a wind parameter set, which is then incorporated into radiative transfer calculations with xstar photoionization code under heating-cooling equilibrium state to compute the absorber's properties such as column density N(sub H), line-of-sight (LoS) velocity v, ionization parameter xi, among others. Assuming that the wind density scales as n varies as r(exp. -1), we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe K alpha absorption feature by focusing on a bright quasar PG 1211+143 as a case study and show the model's plausibility. In this note we demonstrate that the proposed MHD-driven disk-wind scenario is not only consistent with the observed X-ray data, but also help better constrain the underlying nature of the AGN environment in a close proximity to a central engine.

Fast ionized X-ray absorbers in AGNs

NASA Astrophysics Data System (ADS)

Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

2016-05-01

We investigate the physics of the X-ray ionized absorbers often identified as warm absorbers (WAs) and ultra-fast outflows (UFOs) in Seyfert AGNs from spectroscopic studies in the context of magnetically-driven accretion-disk wind scenario. Launched and accelerated by the action of a global magnetic field anchored to an underlying accretion disk around a black hole, outflowing plasma is irradiated and ionized by an AGN radiation field characterized by its spectral energy density (SED). By numerically solving the Grad-Shafranov equation in the magnetohydrodynamic (MHD) framework, the physical property of the magnetized disk-wind is determined by a wind parameter set, which is then incorporated into radiative transfer calculations with xstar photoionization code under heating-cooling equilibrium state to compute the absorber's properties such as column density N_H, line-of-sight (LoS) velocity v, ionization parameter ξ, among others. Assuming that the wind density scales as n ∝ r-1, we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe Kα absorption feature by focusing on a bright quasar PG 1211+143 as a case study and show the model's plausibility. In this note we demonstrate that the proposed MHD-driven disk-wind scenario is not only consistent with the observed X-ray data, but also help better constrain the underlying nature of the AGN environment in a close proximity to a central engine.

Deep ALMA photometry of distant X-ray AGN: improvements in star formation rate constraints, and AGN identification

NASA Astrophysics Data System (ADS)

Stanley, F.; Harrison, C. M.; Alexander, D. M.; Simpson, J.; Knudsen, K. K.; Mullaney, J. R.; Rosario, D. J.; Scholtz, J.

2018-05-01

We present the star formation rates (SFRs) of a sample of 109 galaxies with X-ray selected active galactic nuclei (AGN) with moderate to high X-ray luminosities (\\mathrel {L_2-8{keV}}= 10^{42} - 10^{45} \\mathrel {erg {} s^{-1}}), at redshifts 1 < z < 4.7, that were selected to be faint or undetected in the Herschel bands. We combine our deep ALMA continuum observations with deblended 8-500\\mathrel {μ m} photometry from Spitzer and Herschel, and use infrared (IR) SED fitting and AGN - star formation decomposition methods. The addition of the ALMA photometry results in an order of magnitude more X-ray AGN in our sample with a measured SFR (now 37 per cent). The remaining 63 per cent of the sources have SFR upper limits that are typically a factor of 2-10 times lower than the pre-ALMA constraints. With the improved constraints on the IR SEDs, we can now identify a mid-IR (MIR) AGN component in 50 per cent of our sample, compared to only ˜1 per cent previously. We further explore the F_{870\\mathrel {μ m}}/F_{24\\mathrel {μ m}}-redshift plane as a tool for the identification of MIR emitting AGN, for three different samples representing AGN dominated, star formation dominated, and composite sources. We demonstrate that the F_{870\\mathrel {μ m}}/F_{24\\mathrel {μ m}}-redshift plane can successfully split between AGN and star formation dominated sources, and can be used as an AGN identification method.

Pinpointing the base of the AGN jets through general relativistic X-ray reverberation studies

NASA Astrophysics Data System (ADS)

Emmanoulopoulos, D.

2015-03-01

Many theoretical models of Active Galactic Nuclei (AGN) predict that the X-ray corona, lying above the black hole, constitutes the base of the X-ray jet. Thus, by studying the exact geometry of the close black hole environment, we can pinpoint the launching site of the jet. Detection of negative X-ray reverberation time delays (i.e. soft band X-ray variations lagging behind the corresponding hard band X-ray variations) can yield significant information about the geometrical properties of the AGN, such as the location of the X-ray source, as well as the physical properties of the the black hole, such as its mass and spin. In the frame-work of the lamp-post geometry, I present the first systematic X-ray time-lag modelling results of an ensemble of 12 AGN, using a fully general relativistic (GR) ray tracing approach for the estimation of the systems' response functions. By combing these state-of-the art GR response models with statistically innovative fitting routines, I derive the geometrical layout of the close BH environment for each source, unveiling the position of the AGN jet-base.

X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities

NASA Astrophysics Data System (ADS)

Georgakakis, A.; Salvato, M.; Liu, Z.; Buchner, J.; Brandt, W. N.; Ananna, T. Tasnim; Schulze, A.; Shen, Yue; LaMassa, S.; Nandra, K.; Merloni, A.; McGreer, I. D.

2017-08-01

The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured active galactic nuclei (AGNs) at high accretion luminosities, LX(2-10 keV) ≳ 1044 erg s - 1, and out to redshift z ≈ 1.5. The sample covers an area of about 14 deg2 and provides constraints on the space density of powerful AGNs over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, NH ≈ 1024 cm - 2. The fraction of obscured Compton-thin (NH = 1022-1024 cm - 2) AGNs is estimated to be ≈0.35 for luminosities LX(2-10 keV) > 1044 erg s - 1, independent of redshift. For less luminous sources, the fraction of obscured Compton-thin AGNs increases from 0.45 ± 0.10 at z = 0.25 to 0.75 ± 0.05 at z = 1.25. Studies that select AGNs 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 AGNs (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGNs 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 AGNs is primarily a function of redshift. This fraction increases from about 20-30 per cent at z = 0.25 to about 50-70 per cent at z = 1.5.

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

NASA Astrophysics Data System (ADS)

Jacobsen, Idunn B.; Wu, Kinwah; On, Alvina Y. L.; Saxton, Curtis J.

2015-08-01

High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN) jets: their baryonic and leptonic contents, and particle production efficiency. Testing two standard neutrino production models for local source Cen A (Koers & Tinyakov and Becker & Biermann), we calculate the high-energy neutrino spectra of single AGN sources and derive the flux of high-energy neutrinos expected for the current epoch. Assuming that accretion determines both X-rays and particle creation, our parametric scaling relations predict neutrino yield in various AGN classes. We derive redshift-dependent number densities of each class, from Chandra and Swift/BAT X-ray luminosity functions (Silverman et al. and Ajello et al.). We integrate the neutrino spectrum expected from the cumulative history of AGN (correcting for cosmological and source effects, e.g. jet orientation and beaming). Both emission scenarios yield neutrino fluxes well above limits set by IceCube (by ˜4-106 × at 1 PeV, depending on the assumed jet models for neutrino production). This implies that: (i) Cen A might not be a typical neutrino source as commonly assumed; (ii) both neutrino production models overestimate the efficiency; (iii) neutrino luminosity scales with accretion power differently among AGN classes and hence does not follow X-ray luminosity universally; (iv) some AGN are neutrino-quiet (e.g. below a power threshold for neutrino production); (v) neutrino and X-ray emission have different duty cycles (e.g. jets alternate between baryonic and leptonic flows); or (vi) some combination of the above.

Do some AGN lack X-ray emission?

NASA Astrophysics Data System (ADS)

Simmonds, C.; Bauer, F. E.; Thuan, T. X.; Izotov, Y. I.; Stern, D.; Harrison, F. A.

2016-12-01

Context. Intermediate-mass black holes (IMBHs) are thought to be the seeds of early supermassive black holes (SMBHs). While ≳100 IMBH and small SMBH candidates have been identified in recent years, few have been robustly confirmed to date, leaving their number density in considerable doubt. Placing firmer constraints both on the methods used to identify and confirm IMBHs/SMBHs, as well as characterizing the range of host environments that IMBHs/SMBHs likely inhabit is therefore of considerable interest and importance. Additionally, finding significant numbers of IMBHs in metal-poor systems would be particularly intriguing, since such systems may represent local analogs of primordial galaxies, and therefore could provide clues of early accretion processes. Aims: Here we study in detail several candidate active galactic nuclei (AGN) found in metal-poor hosts. Methods: We utilize new X-ray and optical observations to characterize these metal-poor AGN candidates and compare them against known AGN luminosity relations and well-characterized IMBH/SMBH samples. Results: Despite having clear broad optical emission lines that are long-lived (≳10-13 yr), these candidate AGN appear to lack associated strong X-ray and hard UV emission, lying at least 1-2 dex off the known AGN correlations. If they are IMBHs/SMBHs, our constraints imply that they either are not actively accreting, their accretion disks are fully obscured along our line-of-sight, or their accretion disks are not producing characteristic high energy emission. Alternatively, if they are not AGN, then their luminous broad emission lines imply production by extreme stellar processes. The latter would have profound implications on the applicability of broad lines for mass estimates of massive black holes. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A64

STUDYING FAINT ULTRA-HARD X-RAY EMISSION FROM AGN IN GOALS LIRGS WITH SWIFT/BAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koss, Michael; Casey, Caitlin M.; Mushotzky, Richard

2013-03-10

We present the first analysis of the all-sky Swift Burst Alert Telescope (BAT) ultra-hard X-ray (14-195 keV) data for a targeted list of objects. We find that the BAT data can be studied at three-times-fainter limits than in previous blind detection catalogs based on prior knowledge of source positions and using smaller energy ranges for source detection. We determine the active galactic nucleus (AGN) fraction in 134 nearby (z < 0.05) luminous infrared galaxies (LIRGs) from the GOALS sample. We find that LIRGs have a higher detection frequency than galaxies matched in stellar mass and redshift at 14-195 keV andmore » 24-35 keV. In agreement with work at other wavelengths, the AGN detection fraction increases strongly at high IR luminosity with half of the high-luminosity LIRGs (50%, 6/12, log L{sub IR}/L{sub Sun} > 11.8) detected. The BAT AGN classification shows 97% (37/38) agreement with Chandra and XMM-Newton AGN classification using hardness ratios or detection of an iron K{alpha} line. This confirms our statistical analysis and supports the use of the Swift/BAT all-sky survey to study fainter populations of any category of sources in the ultra-hard X-ray band. BAT AGNs in LIRGs tend to show higher column densities with 40% {+-} 9% showing 14-195 keV/2-10 keV hardness flux ratios suggestive of high or Compton-thick column densities (log N{sub H} > 24 cm{sup -2}), compared to only 12% {+-} 5% of non-LIRG BAT AGNs. We also find that using specific energy ranges of the BAT detector can yield additional sources over total band detections with 24% (5/21) of detections in LIRGs at 24-35 keV not detected at 14-195 keV.« less

AGN Populations in Large-volume X-Ray Surveys: Photometric Redshifts and Population Types Found in the Stripe 82X Survey

NASA Astrophysics Data System (ADS)

Ananna, Tonima Tasnin; Salvato, Mara; LaMassa, Stephanie; Urry, C. Megan; Cappelluti, Nico; Cardamone, Carolin; Civano, Francesca; Farrah, Duncan; Gilfanov, Marat; Glikman, Eilat; Hamilton, Mark; Kirkpatrick, Allison; Lanzuisi, Giorgio; Marchesi, Stefano; Merloni, Andrea; Nandra, Kirpal; Natarajan, Priyamvada; Richards, Gordon T.; Timlin, John

2017-11-01

Multiwavelength surveys covering large sky volumes are necessary to obtain an accurate census of rare objects such as high-luminosity and/or high-redshift active galactic nuclei (AGNs). Stripe 82X is a 31.3 X-ray survey with Chandra and XMM-Newton observations overlapping the legacy Sloan Digital Sky Survey Stripe 82 field, which has a rich investment of multiwavelength coverage from the ultraviolet to the radio. The wide-area nature of this survey presents new challenges for photometric redshifts for AGNs compared to previous work on narrow-deep fields because it probes different populations of objects that need to be identified and represented in the library of templates. Here we present an updated X-ray plus multiwavelength matched catalog, including Spitzer counterparts, and estimated photometric redshifts for 5961 (96% of a total of 6181) X-ray sources that have a normalized median absolute deviation, σnmad=0.06, and an outlier fraction, η = 13.7%. The populations found in this survey and the template libraries used for photometric redshifts provide important guiding principles for upcoming large-area surveys such as eROSITA and 3XMM (in X-ray) and the Large Synoptic Survey Telescope (optical).

Precision cosmology from X-ray AGN clustering

NASA Astrophysics Data System (ADS)

Basilakos, Spyros; Plionis, Manolis

2009-11-01

We place tight constraints on the main cosmological parameters of spatially flat cosmological models by using the recent angular clustering results of XMM-Newton soft (0.5-2keV) X-ray sources, which have a redshift distribution with a median of z ~ 1. Performing a standard likelihood procedure, assuming a constant in comoving coordinates active galactic nuclei (AGN) clustering evolution, the AGN bias evolution model of Basilakos, Plionis & Ragone-Figueroa and the Wilkinson Microwave Anisotropy Probe5 value of σ8, we find stringent simultaneous constraints in the (Ωm, w) plane, with Ωm = 0.26 +/- 0.05, w = -0.93+0.11-0.19.

X-Ray Absorption, Nuclear Infrared Emission, and Dust Covering Factors of AGNs: Testing Unification Schemes

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.; Hernán-Caballero, A.; Barcons, X.; Asensio Ramos, A.; Watson, M. G.; Blain, A.; Caccianiga, A.; Ballo, L.; Braito, V.; Ramos Almeida, C.

2016-03-01

We present the distributions of the geometrical covering factors of the dusty tori (f2) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2-10 keV luminosities between 1042 and 1046 erg s-1, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1-20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f2 than type 1 AGNs. Nevertheless, ˜20% of type 1 AGNs have tori with large covering factors, while ˜23%-28% of type 2 AGNs have tori with small covering factors. Low f2 are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f2 increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f2 determine the optical appearance of an AGN and control the shape of the rest-frame ˜1-20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes.

Current and Future X-ray Studies of High-Redshift AGNs and the First Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Brandt, Niel

2016-01-01

X-ray observations of high-redshift AGNs at z = 4-7 have played a critical role in understanding the physical processes at work inthese objects as well as their basic demographics. Since 2000, Chandra and XMM-Newton have provided new X-ray detections for more than 120 such objects, and well-defined samples of z > 4 AGNs now allow reliable X-ray population studies. Once luminosity effectsare considered, the basic X-ray continuum properties of most high-redshift AGNs appear remarkably similar to those of local AGNs, although there are some notable apparent exceptions (e.g., highly radio-loud quasars). Furthermore, the X-ray absorption found in some objects has been used as a diagnostic of outflowing winds and circumnuclear material. Demographically, the X-ray data now support an exponential decline in the number density of luminous AGNs above z ~ 3, and quantitative space-density comparisons for optically selected and X-ray selected quasars indicate basic statistical agreement.The current X-ray discoveries point the way toward the future breakthroughs that will be possible with, e.g., Athena and the X-raySurveyor. These missions will execute powerful blank-field surveys to elucidate the demographics of the first growing supermassive black holes (SMBHs), including highly obscured systems, up to z ~ 10. They will also carry out complementary X-ray spectroscopic and variability investigations of high-redshift AGNs by targeting the most-luminous z = 7-10 quasars found in wide-field surveys by, e.g., Euclid, LSST, and WFIRST. X-ray spectroscopic and variability studies of the X-ray continuum and reflection signatures will help determine Eddington ratios and disk/corona properties; measuring these will clarify how the first quasars grew so quickly. Furthermore, absorption line/edge studies will reveal how outflows from the first SMBHs influenced the growth of the first galaxies. I will suggest some efficient observational strategies for Athena and the X-ray Surveyor.

Luminous Obscured AGN Unveiled in the Stripe 82 X-ray Survey

NASA Astrophysics Data System (ADS)

LaMassa, Stephanie; Glikman, Eilat; Brusa, Marcella; Rigby, Jane; Tasnim Ananna, Tonima; Stern, Daniel; Lira, Paulina; Urry, Meg; Salvato, Mara; Alexandroff, Rachael; Allevato, Viola; Cardamone, Carolin; Civano, Francesca Maria; Coppi, Paolo; Farrah, Duncan; Komossa, S.; Lanzuisi, Giorgio; Marchesi, Stefano; Richards, Gordon; Trakhtenbrot, Benny; Treister, Ezequiel

2018-01-01

Stripe 82X is a wide-area (30 deg2) X-ray survey overlapping the legacy Sloan Digital Sky Survey (SDSS) Stripe 82 field, designed to uncover rare, high luminosity active galactic nuclei (AGN). We report on the results of an on-going near-infrared (NIR) spectroscopic campaign to follow-up reddened AGN candidates with Palomar TripleSpec, Keck NIRSPEC, and Gemini GNIRS. We identified 8 AGN in our bright NIR sample (K < 16, Vega), selected to have red R-K colors (> 4, Vega); four of these sources had existing optical spectra in SDSS. We targeted four out of 34 obscured AGN candidates in our faint NIR sample (K > 17, Vega), all of which are undetected in the single-epoch SDSS imaging, making them the best candidates for the most obscured and/or the most distant reddend AGN in Stripe 82X. All twelve sources are Type 1 AGN, with the FWHM of at least one permitted emission line exceeding 1300 km/s. We find that our nearly complete bright NIR sample (12/13 obscured AGN candidates have spectroscopic redshifts) is more distant (z > 0.5) than a matched sample of blue Type 1 AGN from Stripe 82X; these AGN tend to be more luminous than their blue, unobscured counterparts. Results from our pilot program of faint NIR-selected obscured AGN candidates demonstrate that our selection recovers reddened quasars missed by SDSS.

X-RAY ABSORPTION, NUCLEAR INFRARED EMISSION, AND DUST COVERING FACTORS OF AGNs: TESTING UNIFICATION SCHEMES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.

2016-03-10

We present the distributions of the geometrical covering factors of the dusty tori (f{sub 2}) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2–10 keV luminosities between 10{sup 42} and 10{sup 46} erg s{sup −1}, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1–20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Opticallymore » classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f{sub 2} than type 1 AGNs. Nevertheless, ∼20% of type 1 AGNs have tori with large covering factors, while ∼23%–28% of type 2 AGNs have tori with small covering factors. Low f{sub 2} are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f{sub 2} increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f{sub 2} determine the optical appearance of an AGN and control the shape of the rest-frame ∼1–20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes.« less

X-ray Properties of the Central kpc of AGN and Starbursts: The Latest News from Chandra

NASA Technical Reports Server (NTRS)

Weaver, Kimberly A.; White, Nicholas E. (Technical Monitor)

2001-01-01

The X-ray properties of 15 nearby (v less than 3,000 km/s) galaxies that possess AGN (active galactic nuclei) and/or starbursts are discussed. Two-thirds have nuclear extended emission on scales from approx. 0.5 to approx. 1.5 kpc that is either clearly associated with a nuclear outflow or morphologically resembles an outflow. Galaxies that are AGN-dominated tend to have linear structures while starburst-dominated galaxies tend to have plume-like structures. Significant X-ray absorption is present in the starburst regions, indicating that a circumnuclear starburst is sufficient to block an AGN at optical wavelengths. Galaxies with starburst activity possess more X-ray point sources within their central kpc than non-starbursts. Many of these sources are more luminous than typical X-ray binaries. The Chandra results are discussed in terms of the starburst-AGN connection, a revised unified model for AGN, and possible evolutionary scenarios.

ALMA 26 arcmin2 Survey of GOODS-S at One-millimeter (ASAGAO): X-Ray AGN Properties of Millimeter-selected Galaxies

NASA Astrophysics Data System (ADS)

Ueda, Y.; Hatsukade, B.; Kohno, K.; Yamaguchi, Y.; Tamura, Y.; Umehata, H.; Akiyama, M.; Ao, Y.; Aretxaga, I.; Caputi, K.; Dunlop, J. S.; Espada, D.; Fujimoto, S.; Hayatsu, N. H.; Imanishi, M.; Inoue, A. K.; Ivison, R. J.; Kodama, T.; Lee, M. M.; Matsuoka, K.; Miyaji, T.; Morokuma-Matsui, K.; Nagao, T.; Nakanishi, K.; Nyland, K.; Ohta, K.; Ouchi, M.; Rujopakarn, W.; Saito, T.; Tadaki, K.; Tanaka, I.; Taniguchi, Y.; Wang, T.; Wang, W.-H.; Yoshimura, Y.; Yun, M. S.

2018-01-01

We investigate the X-ray active galactic nucleus (AGN) properties of millimeter galaxies in the Great Observatories Origins Deep Survey South (GOODS-S) field detected with the Atacama Large Millimeter/submillimeter Array (ALMA), by utilizing the Chandra 7-Ms data, the deepest X-ray survey to date. Our millimeter galaxy sample comes from the ASAGAO survey covering 26 arcmin2 (12 sources at a 1.2 mm flux-density limit of ≈ 0.6 mJy), supplemented by the deeper but narrower 1.3 mm survey of a part of the ASAGAO field by Dunlop et al. Ofthe 25 total millimeter galaxies, 14 have Chandra counterparts. The observed AGN fractions at z=1.5{--}3 are found to be {90}-19+8% and {57}-25+23% for the ultra-luminous and luminous infrared galaxies with log {L}{IR}/{L}ȯ = 12–12.8 and log {L}{IR}/{L}ȯ = 11.5–12, respectively. The majority (∼2/3) of the ALMA and/or Herschel detected X-ray AGNs at z = 1.5‑3 appear to be star-formation-dominant populations, having {L}{{X}}/ {L}{IR} ratios smaller than the “simultaneous evolution” value expected from the local black-hole-mass-to-stellar-mass ({M}{BH}–M *) relation. On the basis of the {L}{{X}} and stellar mass relation, we infer that a large fraction of star-forming galaxies at z=1.5{--}3 have black hole masses that are smaller than those expected from the local {M}{BH}–M * relation. This contrasts previous reports on luminous AGNs at the same redshifts detected in wider and shallower surveys, which are subject to selection biases against lower luminosity AGNs. Our results are consistent with an evolutionary scenario in which star formation occurs first, and an AGN-dominant phase follows later, in objects that finally evolve into galaxies with classical bulges.

X-ray Absorbers as Probes of AGN Unification

NASA Astrophysics Data System (ADS)

Kazannas, Demosthenes

We have developed, over the past few years, models of photoionized MHD winds off black hole accretion disks and showed that their properties are consistent with those of the AGN warm absorbers and those of the tori invoked in AGN unification schemes. Furthermore, we have shown that these models are sufficiently robust to reproduce the absorber properties (UV and X-ray) in AGN classes as diverse as Seyferts and BAL QSOs.With this proposal we request funding to model archival spectroscopic data of eighteen AGN with photoionized MHD winds. Successful implementation of this program will provide for the first time an association of the properties of warm absorbers with the parameters of a well-defined physical model, namely their density profiles, mass fluxes and inclination angles. Furthermore, determination of these parameters for our AGN sample will allow a statistical analysis of their properties and, as such, a better understanding of the properties of AGN structure. The value of our models lies in their simplicity: the winds are essentially analytic with only a small number of parameters. This simplicity makes possible the generation of a large grid of models which will be made available to the community through XSPEC/mtable for analysis of similar data by the observers.

A DEEP X-RAY VIEW OF THE BARE AGN ARK 120. I. REVEALING THE SOFT X-RAY LINE EMISSION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeves, J. N.; Braito, V.; Porquet, D.

2016-09-10

The Seyfert 1 galaxy Ark 120 is a prototype example of the so-called class of bare nucleus active galactic nuclei (AGNs), whereby there is no known evidence for the presence of ionized gas along the direct line of sight. Here deep (>400 ks exposure), high-resolution X-ray spectroscopy of Ark 120 is presented from XMM-Newton observations that were carried out in 2014 March, together with simultaneous Chandra /High Energy Transmission Grating exposures. The high-resolution spectra confirmed the lack of intrinsic absorbing gas associated with Ark 120, with the only X-ray absorption present originating from the interstellar medium (ISM) of our ownmore » Galaxy, with a possible slight enhancement of the oxygen abundance required with respect to the expected ISM values in the solar neighborhood. However, the presence of several soft X-ray emission lines are revealed for the first time in the XMM-Newton RGS spectrum, associated with the AGN and arising from the He- and H-like ions of N, O, Ne, and Mg. The He-like line profiles of N, O, and Ne appear velocity broadened, with typical FWHMs of ∼5000 km s{sup −1}, whereas the H-like profiles are unresolved. From the clean measurement of the He-like triplets, we deduce that the broad lines arise from a gas of density n {sub e} ∼ 10{sup 11} cm{sup −3}, while the photoionization calculations infer that the emitting gas covers at least 10% of 4 π steradian. Thus the broad soft X-ray profiles appear coincident with an X-ray component of the optical–UV broad-line region on sub-parsec scales, whereas the narrow profiles originate on larger parsec scales, perhaps coincident with the AGN narrow-line region. The observations show that Ark 120 is not intrinsically bare and substantial X-ray-emitting gas exists out of our direct line of sight toward this AGN.« less

BAT AGN Spectroscopic Survey. VIII. Type 1 AGN with Massive Absorbing Columns

NASA Astrophysics Data System (ADS)

Shimizu, T. Taro; Davies, Richard I.; Koss, Michael; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Schawinski, Kevin; Trakhtenbrot, Benny; Burtscher, Leonard; Genzel, Reinhard; Lin, Ming-yi; Lutz, Dieter; Rosario, David; Sturm, Eckhard; Tacconi, Linda

2018-04-01

We explore the relationship between X-ray absorption and optical obscuration within the BAT AGN Spectroscopic Survey (BASS), which has been collecting and analyzing the optical and X-ray spectra for 641 hard X-ray selected (E > 14 keV) active galactic nuclei (AGNs). We use the deviation from a linear broad Hα-to-X-ray relationship as an estimate of the maximum optical obscuration toward the broad line region (BLR) and compare the A V to the hydrogen column densities ({N}{{H}}) found through systematic modeling of their X-ray spectra. We find that the inferred columns implied by A V toward the BLR are often orders of magnitude less than the columns measured toward the X-ray emitting region, indicating a small-scale origin for the X-ray absorbing gas. After removing 30% of Sy 1.9s that potentially have been misclassified due to outflows, we find that 86% (164/190) of the Type 1 population (Sy 1–1.9) are X-ray unabsorbed as expected based on a single obscuring structure. However, 14% (26/190), of which 70% (18/26) are classified as Sy 1.9, are X-ray absorbed, suggesting that the BLR itself is providing extra obscuration toward the X-ray corona. The fraction of X-ray absorbed Type 1 AGNs remains relatively constant with AGN luminosity and Eddington ratio, indicating a stable BLR covering fraction.

The column density distribution of hard X-ray radio galaxies

NASA Astrophysics Data System (ADS)

Panessa, F.; Bassani, L.; Landi, R.; Bazzano, A.; Dallacasa, D.; La Franca, F.; Malizia, A.; Venturi, T.; Ubertini, P.

2016-09-01

In order to investigate the role of absorption in active galactic nuclei (AGN) with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/Imager on Board the Integral Satellite (IBIS) and Swift/The Burst Alert Telescope (BAT) AGN catalogues (˜7-10 per cent of the total AGN population). The 64 radio galaxies have a typical FR II radio morphology and are characterized by high 20-100 keV luminosities (from 1042 to 1046 erg s-1) and high Eddington ratios (log LBol/LEdd typically larger than ˜0.01). The observed fraction of absorbed AGN (NH > 1022 cm-2) is around 40 per cent among the total sample, and ˜75 per cent among type 2 AGN. The majority of obscured AGN are narrow-line objects, while unobscured AGN are broad-line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ˜2-3 per cent, in comparison with the 5-7 per cent found in radio-quiet hard X-ray selected AGN. We have estimated the absorption and Compton thick fractions in a hard X-ray sample containing both radio galaxies and non-radio galaxies and therefore affected by the same selection biases. No statistical significant difference was found in the absorption properties of radio galaxies and non-radio galaxies sample. In particular, the Compton thick objects are likely missing in both samples and the fraction of obscured radio galaxies appears to decrease with luminosity as observed in hard X-ray non-radio galaxies.

The active galactic nucleus population in X-ray-selected galaxy groups at 0.5 < Z < 1.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oh, Semyeong; Woo, Jong-Hak; Matsuoka, Kenta

2014-07-20

We use Chandra data to study the incidence and properties of active galactic nuclei (AGNs) in 16 intermediate redshift (0.5 < z < 1.1) X-ray-selected galaxy groups in the Chandra Deep Field-South. We measure an AGN fraction of f(L{sub X,H}>10{sup 42};M{sub R}<−20)=8.0{sub −2.3}{sup +3.0}% at z-bar ∼0.74, approximately a factor of two higher than the AGN fraction found for rich clusters at comparable redshift. This extends the trend found at low redshift for groups to have higher AGN fractions than clusters. Our estimate of the AGN fraction is also more than a factor of three higher than that of lowmore » redshift X-ray-selected groups. Using optical spectra from various surveys, we also constrain the properties of emission-line selected AGNs in these groups. In contrast to the large population of X-ray AGNs (N(L{sub X,{sub H}} > 10{sup 41} erg s{sup –1}) = 25), we find only four emission-line AGNs, three of which are also X-ray bright. Furthermore, most of the X-ray AGNs in our groups are optically dull (i.e., lack strong emission-lines), similar to those found in low redshift X-ray groups and clusters of galaxies. This contrasts with the AGN population found in low redshift optically selected groups which are dominated by emission-line AGNs. The differences between the optically and X-ray-selected AGNs populations in groups are consistent with a scenario where most AGNs in the densest environments are currently in a low accretion state.« less

Heavily Obscured AGN with SIMBOL-X

NASA Astrophysics Data System (ADS)

Della Ceca, R.; Caccianiga, A.; Severgnini, P.

2009-05-01

By comparing an optically selected sample of narrow lines AGN with an X-ray selected sample of AGN we have recently derived an estimate of the intrinsic (i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick AGNs. We will use this XLF to derive the number of Compton Thick AGN that will be found in the SIMBOL-X survey(s).

The fraction of AGNs in major merger galaxies and its luminosity dependence

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Treister, Ezequiel; Trakhtenbrot, Benny; Sanders, David B.

2018-05-01

We use a phenomenological model which connects the galaxy and active galactic nucleus (AGN) populations to investigate the process of AGNs triggering through major galaxy mergers at z ˜ 0. The model uses stellar mass functions as input and allows the prediction of AGN luminosity functions based on assumed Eddington ratio distribution functions (ERDFs). We show that the number of AGNs hosted by merger galaxies relative to the total number of AGNs increases as a function of AGN luminosity. This is due to more massive galaxies being more likely to undergo a merger and does not require the assumption that mergers lead to higher Eddington ratios than secular processes. Our qualitative analysis also shows that to match the observations, the probability of a merger galaxy hosting an AGN and accreting at a given Eddington value has to be increased by a factor ˜10 relative to the general AGN population. An additional significant increase of the fraction of high Eddington ratio AGNs among merger host galaxies leads to inconsistency with the observed X-ray luminosity function. Physically our results imply that, compared to the general galaxy population, the AGN fraction among merger galaxies is ˜10 times higher. On average, merger triggering does however not lead to significantly higher Eddington ratios.

The XMM-Newton Wide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Page, M. J.; Watson, M. G.; Corral, A.; Tedds, J. A.; Ebrero, J.; Krumpe, M.; Schwope, A.; Ceballos, M. T.

2010-02-01

Aims: We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2-10 keV (rest-frame) luminosities from 1042-1045 erg s-1 and are detected up to redshift 4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods: We fitted the observed 0.2-12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results: We constrained the mean spectral index of the broad band X-ray continuum to <Γ> = 1.96 ± 0.02 with intrinsic dispersion {σ< Γ >} = 0.27-0.02+0.01. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2-10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in ⪆3% of our objects, with rest-frame column densities a few ×1022 cm-2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is 36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT 100 eV and σkT 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled

The NuSTAR Extragalactic Survey: Average Broadband X-Ray Spectral Properties of the NuSTAR-detected AGNs

NASA Astrophysics Data System (ADS)

Del Moro, A.; Alexander, D. M.; Aird, J. A.; Bauer, F. E.; Civano, F.; Mullaney, J. R.; Ballantyne, D. R.; Brandt, W. N.; Comastri, A.; Gandhi, P.; Harrison, F. A.; Lansbury, G. B.; Lanz, L.; Luo, B.; Marchesi, S.; Puccetti, S.; Ricci, C.; Saez, C.; Stern, D.; Treister, E.; Zappacosta, L.

2017-11-01

We present a study of the average X-ray spectral properties of the sources detected by the NuSTAR extragalactic survey, comprising observations of the Extended Chandra Deep Field South (E-CDFS), Extended Groth Strip (EGS), and the Cosmic Evolution Survey (COSMOS). The sample includes 182 NuSTAR sources (64 detected at 8-24 keV), with 3-24 keV fluxes ranging between {f}3{--24{keV}}≈ {10}-14 and 6 × 10-13 erg cm-2 s-1 ({f}8{--24{keV}}≈ 3× {10}-14{--}3× {10}-13 erg cm-2 s-1) and redshifts in the range of z=0.04{--}3.21. We produce composite spectra from the Chandra + NuSTAR data (E≈ 2{--}40 {keV}, rest frame) for all the sources with redshift identifications (95%) and investigate the intrinsic, average spectra of the sources, divided into broad-line (BL) and narrow-line (NL) active galactic nuclei (AGNs), and also in different bins of X-ray column density and luminosity. The average power-law photon index for the whole sample is {{Γ }}={1.65}-0.03+0.03, flatter than the {{Γ }}≈ 1.8 typically found for AGNs. While the spectral slope of BL and X-ray unabsorbed AGNs is consistent with the typical values ({{Γ }}={1.79}-0.01+0.01), a significant flattening is seen in NL AGNs and heavily absorbed sources ({{Γ }}={1.60}-0.05+0.08 and {{Γ }}={1.38}-0.12+0.12, respectively), likely due to the effect of absorption and to the contribution from the Compton reflection component to the high-energy flux (E> 10 keV). We find that the typical reflection fraction in our spectra is R≈ 0.5 (for {{Γ }}=1.8), with a tentative indication of an increase of the reflection strength with X-ray column density. While there is no significant evidence for a dependence of the photon index on X-ray luminosity in our sample, we find that R decreases with luminosity, with relatively high levels of reflection (R≈ 1.2) for {L}10{--40{keV}}< {10}44 erg s-1 and R≈ 0.3 for {L}10{--40{keV}}> {10}44 erg s-1 AGNs, assuming a fixed spectral slope of {{Γ }}=1.8.

SPIDERS: selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys

NASA Astrophysics Data System (ADS)

Dwelly, T.; Salvato, M.; Merloni, A.; Brusa, M.; Buchner, J.; Anderson, S. F.; Boller, Th.; Brandt, W. N.; Budavári, T.; Clerc, N.; Coffey, D.; Del Moro, A.; Georgakakis, A.; Green, P. J.; Jin, C.; Menzel, M.-L.; Myers, A. D.; Nandra, K.; Nichol, R. C.; Ridl, J.; Schwope, A. D.; Simm, T.

2017-07-01

SPIDERS (SPectroscopic IDentification of eROSITA Sources) is a Sloan Digital Sky Survey IV (SDSS-IV) survey running in parallel to the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected active galactic nuclei (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 Wide-field Infrared Survey Explorer 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-localized 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 ˜12 000 ROSAT and ˜1500 XMM-Newton Slew survey sources that have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS programme, we expect to have collected homogeneous spectroscopic redshift information over a footprint of ˜7500 deg2 for >85 per cent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17 < r < 22.5, producing a large and highly complete sample of bright X-ray-selected AGN suitable for statistical studies of AGN evolution and clustering.

Unveiling the X-ray/UV properties of AGN winds using Broad and mini-Broad Absorption Line Quasars

NASA Astrophysics Data System (ADS)

Giustini, M.

2015-07-01

BAL/mini-BALs are observed in the UV spectra of ˜ 20-30% of optically selected AGN as broad absorption troughs blueshifted by several thousands km/s, indicative of powerful nuclear winds. They could be representative of the average AGN if their winds cover only 20-30% of the continuum source, and/or represent an evolutionary state analogous to the high-soft state of BHB, when the jet emission is quenched and strong X-ray absorbing equatorial disk winds are virtually ubiquitous. High-quality, possibly time-resolved X-ray/UV studies are crucial to assess the global amount and 'character' of absorption in BAL/mini-BAL QSOs and to constrain the physical mechanism responsible for the launch and acceleration of their winds, therefore placing them in the broader context of AGN geometry and evolution. I will review here the known X-ray properties of BAL/mini-BAL QSOs, and present new results from a comprehensive X-ray spectral analysis of all the Palomar-Green BAL/mini-BAL QSOs with available XMM-Newton observations, for a total of 51 pointings of 14 different sources. These will include the most recent results from a high-quality simultaneous XMM/HST observational campaign on the mini-BAL QSO PG 1126-041, that unveiled with stunning details the X-ray/UV connection in action in an AGN disk wind through correlated X-ray/UV absorption variability.

Testing warm Comptonization models for the origin of the soft X-ray excess in AGNs

NASA Astrophysics Data System (ADS)

Petrucci, P.-O.; Ursini, F.; De Rosa, A.; Bianchi, S.; Cappi, M.; Matt, G.; Dadina, M.; Malzac, J.

2018-03-01

The X-ray spectra of many active galactic nuclei (AGNs) show a soft X-ray excess below 1-2 keV on top of the extrapolated high-energy power law. The origin of this component is uncertain. It could be a signature of relativistically blurred, ionized reflection or the high-energy tail of thermal Comptonization in a warm (kT 1 keV), optically thick (τ ≃ 10-20) corona producing the optical/UV to soft X-ray emission. The purpose of the present paper is to test the warm corona model on a statistically significant sample of unabsorbed, radio-quiet AGNs with XMM-Newton archival data, providing simultaneous optical/UV and X-ray coverage. The sample has 22 objects and 100 observations. We use two thermal Comptonization components to fit the broadband spectra, one for the warm corona emission and one for the high-energy continuum. In the optical/UV, we also include the reddening, the small blue bump, and the Galactic extinction. In the X-rays, we include a warm absorber and a neutral reflection. The model gives a good fit (reduced χ2 < 1.5) to more than 90% of the sample. We find the temperature of the warm corona to be uniformly distributed in the 0.1-1 keV range, while the optical depth is in the range 10-40. These values are consistent with a warm corona covering a large fraction of a quasi-passive accretion disk, i.e., that mostly reprocesses the warm corona emission. The disk intrinsic emission represents no more than 20% of the disk total emission. According to this interpretation, most of the accretion power would be released in the upper layers of the accretion flow.

Extended X-ray emission in the IC 2497 - Hanny's Voorwerp system: energy injection in the gas around a fading AGN

NASA Astrophysics Data System (ADS)

Sartori, Lia F.; Schawinski, Kevin; Koss, Michael; Treister, Ezequiel; Maksym, W. Peter; Keel, William C.; Urry, C. Megan; Lintott, Chris J.; Wong, O. Ivy

2016-04-01

We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN. We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN (Lbol ˜ 1042-1044 erg s-1). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN ({{E}}_bub ˜ 10^{54}{-}10^{55} erg). A possible scenario is that this bubble is inflated by the fading AGN, which after changing accretion state is now in a kinetic mode. Other possibilities are that the bubble has been inflated by the past luminous quasar (Lbol ˜ 1046 erg s-1), or that the temperature gradient is an indication of a shock front from a superwind driven by the AGN. We discuss the possible scenarios and the implications for the AGN-host galaxy interaction, as well as an analogy between AGN and X-ray binaries lifecycles. We conclude that the AGN could inject mechanical energy into the host galaxy at the end of its lifecycle, and thus provide a source for mechanical feedback, in a similar way as observed for X-ray binaries.

Identifying Luminous AGN in Deep Surveys: Revised IRAC Selection Criteria

NASA Astrophysics Data System (ADS)

Donley, Jennifer; Koekemoer, A. M.; Brusa, M.; Capak, P.; Cardamone, C. N.; Civano, F.; Ilbert, O.; Impey, C. D.; Kartaltepe, J.; Miyaji, T.; Salvato, M.; Sanders, D. B.; Trump, J. R.; Zamorani, G.

2012-01-01

Spitzer IRAC selection is a powerful tool for identifying luminous AGN. The AGN selection wedges currently in use, however, are heavily contaminated by star-forming galaxies, especially at high redshift. Using the large samples of luminous AGN and high-redshift star-forming galaxies in COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys. The new IRAC criteria are designed to be both highly complete and reliable, and incorporate the best aspects of the current AGN selection wedges and of infrared power-law selection while excluding high redshift star-forming galaxies selected via the BzK, DRG, LBG, and SMG criteria. At QSO-luminosities of log L(2-10 keV)>44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 37% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 51% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates leads to a hard X-ray signal indicative of heavily obscured to mildly Compton-thick obscuration (log NH >= 23.7). While IRAC selection recovers a substantial fraction of luminous unobscured and obscured AGN, it is incomplete to low-luminosity and host-dominated AGN.

Searching for faint AGN in the CDFS: an X-ray (Chandra) vs optical variability (HST) comparison.

NASA Astrophysics Data System (ADS)

Georgantopoulos, I.; Pouliasis, E.; Bonanos, A.; Sokolovsky, K.; Yang, M.; Hatzidimitriou, D.; Bellas, I.; Gavras, P.; Spetsieri, Z.

2017-10-01

X-ray surveys are believed to be the most efficient way to detect AGN. Recently though, optical variability studies are claimed to probe even fainter AGN. We are presenting results from an HST study aimed to identify Active Galactic Nuclei (AGN) through optical variability selection in the CDFS.. This work is part of the 'Hubble Catalogue of Variables'project of ESA that aims to identify variable sources in the Hubble Source Catalogue.' In particular, we used Hubble Space Telescope (HST) z-band images taken over 5 epochs and performed aperture photometry to derive the lightcurves of the sources. Two statistical methods (standard deviation & interquartile range) resulting in a final sample of 175 variable AGN candidates, having removed the artifacts by visual inspection and known stars and supernovae. The fact that the majority of the sources are extended and variable indicates AGN activity. We compare the efficiency of the method by comparing with the 7Ms Chandra detections. Our work shows that the optical variability probes AGN at comparable redshifts but at deeper optical magnitudes. Our candidate AGN (non detected in X-rays) have luminosities of L_x<6×10^{40} erg/sec at z˜0.7 suggesting that these are associated with low luminosity Seyferts and LINERS.

The clustering amplitude of X-ray-selected AGN at z ˜ 0.8: evidence for a negative dependence on accretion luminosity

NASA Astrophysics Data System (ADS)

Mountrichas, G.; Georgakakis, A.; Menzel, M.-L.; Fanidakis, N.; Merloni, A.; Liu, Z.; Salvato, M.; Nandra, K.

2016-04-01

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 active galactic nucleus (AGN) [log {L}_X (2-10 keV)= 43.6^{+0.4}_{-0.4} erg s^{-1}] 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 VIMOS Public Extragalactic Redshift Survey 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_{{⊙}} 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 [LX(2-10 keV) ≈ 1042-1043 erg s- 1] at similar redshifts. Our analysis also links the mean clustering properties of moderate-luminosity AGN with those of powerful ultraviolet/optically selected QSOs, which are typically found in haloes with masses few times 1012 M⊙. 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 subdominant 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 fuelling modes.

Testing the Merger Paradigm: X-ray Observations of Radio-Selected Sub-Galactic-Scale Binary AGNs

NASA Astrophysics Data System (ADS)

Fu, Hai

2016-09-01

Interactions play an important role in galaxy evolution. Strong gas inflows are expected in the process of gas-rich mergers, which may fuel intense black hole accretion and star formation. Sub-galactic-scale binary/dual AGNs thus offer elegant laboratories to study the merger-driven co-evolution phase. However, previous samples of kpc-scale binaries are small and heterogeneous. We have identified a flux-limited sample of kpc-scale binary AGNs uniformly from a wide-area high-resolution radio survey conducted by the VLA. Here we propose Chandra X-ray characterization of a subset of four radio-confirmed binary AGNs at z 0.1. Our goal is to compare their X-ray properties with those of matched control samples to test the merger-driven co-evolution paradigm.

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael

2017-08-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve different telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics.

AGN Unification at z ~ 1: u - R Colors and Gradients in X-Ray AGN Hosts

NASA Astrophysics Data System (ADS)

Ammons, S. Mark; Rosario, David J. V.; Koo, David C.; Dutton, Aaron A.; Melbourne, Jason; Max, Claire E.; Mozena, Mark; Kocevski, Dale D.; McGrath, Elizabeth J.; Bouwens, Rychard J.; Magee, Daniel K.

2011-10-01

We present uncontaminated rest-frame u - R colors of 78 X-ray-selected active galactic nucleus (AGN) hosts at 0.5 < z < 1.5 in the Chandra Deep Fields measured with Hubble Space Telescope (HST)/Advanced Camera for Surveys/NICMOS and Very Large Telescope/ISAAC imaging. We also present spatially resolved NUV - R color gradients for a subsample of AGN hosts imaged by HST/Wide Field Camera 3 (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 host galaxy colors. The mean u - R color of the unobscured/soft hosts beyond ~6 kpc is statistically equivalent to that of the obscured/hard hosts (the soft sources are 0.09 ± 0.16 mag bluer). Furthermore, the rest-frame V - J colors of the obscured and unobscured hosts beyond ~6 kpc are statistically equivalent, suggesting that the two populations have similar distributions of dust extinction. For the WFC3/infrared sample, the mean NUV - R color gradients of unobscured and obscured sources differ by less than ~0.5 mag for r > 1.1 kpc. These three observations imply that AGN obscuration is uncorrelated with the star formation rate beyond ~1 kpc. These observations favor a unification scenario for intermediate-luminosity AGNs in which obscuration is determined geometrically. Scenarios in which the majority of intermediate-luminosity AGNs at z ~ 1 are undergoing rapid, galaxy-wide quenching due to AGN-driven feedback processes are disfavored.

The dependence of the soft X ray spectral slope with radio property, luminosity, and redshift, for a large sample of AGN from the Einstein IPC data base

NASA Technical Reports Server (NTRS)

Brunner, H.; Worrall, D. M.; Wilkes, Belinda J.; Elvis, Martin

1989-01-01

The dependence of the soft X-ray spectral slope on radio, optical and X-ray properties, and on redshift are reported for a large sample of Active Galactic Nuclei (AGN). The sample includes 317 optically and radio-selected AGN from a preliminary version of the Einstein Imaging Proportional Counter (IPC) quasar and AGN data base. The main results are: the difference in X-ray slope between radio-loud and radio-quiet AGN were confirmed for an independent and much larger sample of sources; a difference in X-ray slope between flat and steep radio spectrum AGN is observed only in high luminosity sub-sample; in flat radio spectrum AGNs there is an indication for a dependence of the X-ray spectral index on X-ray luminosity redshift and alpha sub 0x.

The Hard X-ray 20-40 keV AGN Luminosity Function

NASA Technical Reports Server (NTRS)

Beckmann, V.; Soldi, S.; Shrader, C. R.; Gehrels, N.; Produit, N.

2006-01-01

We have compiled a complete, significance limited extragalactic sample based on approximately 25,000 deg(sup 2) to a limiting flux of 3 x 10(exp -11) ergs per square centimeter per second. (approximately 7,000 deg(sup 2)) to a flux limit of 10(exp -11) ergs per square centimeter per second)) in the 20 - 40 keV band with INTEGRAL. We have constructed a detailed exposure map to compensate for effects of non-uniform exposure. The flux-number relation is best described by a power-law with a slope of alpha = 1.66 plus or minus 0.11. The integration of the cumulative flux per unit area leads to f(sub 20-40 keV) = 2.6 x 10(exp -10) ergs per square centimeter per second per sr(sup -1) which is about 1% of the known 20-40 keV X-ray background. We present the first luminosity function of AGN in the 20-40 keV energy range, based on 68 extragalactic objects detected by the imager IBIS/ISGRI on-board INTEGRAL. The luminosity function shows a smoothly connected two power-law form, with an index of gamma (sub 1) = 0.9 below, and gamma (sub 2) = 2.2 above the turn-over luminosity of L(sub *), = 4.6 x 10(sup 43) ergs per second. The emissivity of all INTEGRAL AGNs per unit volume is W(sub 20-40keV)(greater than 10(sup 41) ergs per second) = 2.8 x 10(sup 38) ergs per second h(sup 3)(sub 70) Mpc(sup -3). These results are consistent with those derived in the 2-20keV energy band and do not show a significant contribution by Compton-thick objects. Because the sample used in this study is truly local (z(raised bar) = 0.022)), only limited conclusions can be drawn for the evolution of AGNs in this energy band. But the objects explaining the peak in the cosmic X-ray background are likely to be either low luminosity AGN (L(sub x) less than 10(sup 41) ergs per second) or of other type, such as intermediate mass black holes, clusters, and star forming regions.

UNVEILING THE PHYSICS OF LOW-LUMINOSITY AGNs THROUGH X-RAY VARIABILITY: LINER VERSUS SEYFERT 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernández-García, L.; Masegosa, J.; Márquez, I.

X-ray variability is very common in active galactic nuclei (AGNs), but these variations may not occur similarly in different families of AGNs. We aim to disentangle the structure of low-ionization nuclear emission-line regions (LINERs) compared to Seyfert 2s by the study of their spectral properties and X-ray variations. We assembled the X-ray spectral parameters and variability patterns, which were obtained from simultaneous spectral fittings. Major differences are observed in the X-ray luminosities and the Eddington ratios, which are higher in Seyfert 2s. Short-term X-ray variations were not detected, while long-term changes are common in LINERs and Seyfert 2s. Compton-thick sourcesmore » generally do not show variations, most probably because the AGN is not accesible in the 0.5–10 keV energy band. The changes are mostly related to variations in the nuclear continuum, but other patterns of variability show that variations in the absorbers and at soft energies can be present in a few cases. We conclude that the X-ray variations may occur similarly in LINERs and Seyfert 2s, i.e., they are related to the nuclear continuum, although they might have different accretion mechanisms. Variations at UV frequencies are detected in LINER nuclei but not in Seyfert 2s. This is suggestive of at least some LINERs having an unobstructed view of the inner disk where the UV emission might take place, with UV variations being common in them. This result might be compatible with the disappeareance of the torus and/or the broad-line region in at least some LINERs.« less

An X-ray/SDSS sample. II. AGN-driven outflowing gas plasma properties

NASA Astrophysics Data System (ADS)

Perna, M.; Lanzuisi, G.; Brusa, M.; Cresci, G.; Mignoli, M.

2017-10-01

Aims: Galaxy-scale outflows are currently observed in many active galactic nuclei (AGNs); however, characterisation of them in terms of their (multi-) phase nature, amount of flowing material, and effects on their host galaxy is still unresolved. In particular, ionised gas mass outflow rate and related energetics are still affected by many sources of uncertainty. In this respect, outflowing gas plasma conditions, being largely unknown, play a crucial role. Methods: We have analysed stacked spectra and sub-samples of sources with high signal-to-noise temperature- and density-sensitive emission lines to derive the plasma properties of the outflowing ionised gas component. We did this by taking advantage of the spectroscopic analysis results we obtained while studying the X-ray/SDSS sample of 563 AGNs at z < 0.8 presented in our companion paper. For these sources, we also studied in detail various diagnostic diagrams to infer information about outflowing gas ionisation mechanisms. Results: We derive, for the first time, median values for electron temperature and density of outflowing gas from medium-size samples ( 30 targets) and stacked spectra of AGNs. Evidence of shock excitation are found for outflowing gas. Conclusions: We measure electron temperatures of the order of 1.7 × 104 K and densities of 1200 cm-3 for faint and moderately luminous AGNs (intrinsic X-ray luminosity 40.5 < log (LX) < 44 in the 2-10 keV band). We note that the electron density that is usually assumed (Ne = 100 cm-3) in ejected material might result in relevant overestimates of flow mass rates and energetics and, as a consequence, of the effects of AGN-driven outflows on the host galaxy.

The density and location of the X-ray absorbing gas in AGN

NASA Astrophysics Data System (ADS)

Netzer, H.

Chandra and XMM-Newton have opened the era of real X-ray spectroscopy. The launch of these spacecraft was followed with great expectations to solve some of the mysteries of AGN, including the determination of the accurate profile of the iron Kα line, the ionization and location of the warm absorbing gas (the "warm absorber", hereafter WA) and the AGN-starburst connection. So far, only a small subset of those big questions have been answered. In particular, new observations of several type-I AGN are providing the first clues about the nature of the various soft X-ray spectral components and the location of the WA. Perhaps the best example regarding the WA location and the various spectral components is the new Chandra observation of NGC 3516. This is a well known Seyfert 1 galaxy that happened to be in a very low state at the time of observations (October 2000). The analysis by Netzer et al (2002) gives the following new results: The X-ray continuum is extremely hard (Γ < 1) and is very different from a single power-law continuum. Its shape is entirely consistent with the fading of the source by a factor of ~8 between 1994 (ASCA observation) and 2000 assuming a 1022 cm-2 line-of sight WA which reacts to the flux of the central ionizing source. A correlation between the observed changes in the source spectral energy distribution (SED) and the hard (E>5 keV) energy luminosity of the source. This can be used to set an upper limit of about 6 × 1017 cm on the WA location. There is a significant contribution, at high energies, from a cold reflecting remote gas which is constant in time and is producing most of the narrow component of the Kα line. The combination of a highly variable central source and a constant far-away ``reflector'' is required to explain the time dependent SED of NGC 3516. The generalization of these results (assuming they are typical) to other type I AGN is very important. They suggest that in many sources much (or even most) of the apparent

Unveiling slim accretion disc in AGN through X-ray and Infrared observations

NASA Astrophysics Data System (ADS)

Castelló-Mor, Núria; Kaspi, Shai; Netzer, Hagai; Du, Pu; Hu, Chen; Ho, Luis C.; Bai, Jin-Ming; Bian, Wei-Hao; Yuan, Ye-Fei; Wang, Jian-Min

2017-05-01

In this work, which is a continuation of Castelló-Mor et al., we present new X-ray and infrared (IR) data for a sample of active galactic nuclei (AGN) covering a wide range in Eddington ratio over a small luminosity range. In particular, we rigorously explore the dependence of the optical-to-X-ray spectral index αOX and the IR-to-optical spectral index on the dimensionless accretion rate, \\dot{M} = \\dot{m}/η, where \\dot{m} = LAGN/LEdd and η is the mass-to-radiation conversion efficiency, in low- and high-accretion rate sources. We find that the spectral energy distribution (SED) of the faster accreting sources is surprisingly similar to those from the comparison sample of sources with lower accretion rate. In particular: (I) The optical-to-UV AGN SED of slow and fast accreting AGN can be fitted with thin accretion disc (AD) models. (II) The value of αOX is very similar in slow and fast accreting systems up to a dimensionless accretion rate \\dot{M}c ˜ 10. We only find a correlation between αOX and \\dot{M} for sources with \\dot{M} > \\dot{M}c. In such cases, the faster accreting sources appear to have systematically larger αOX values. (III) We also find that the torus in the faster accreting systems seems to be less efficient in reprocessing the primary AGN radiation having lower IR-to-optical spectral slopes. These findings, failing to recover the predicted differences between the SEDs of slim and thin ADs within the observed spectral window, suggest that additional physical processes or very special geometry act to reduce the extreme-UV radiation in fast accreting AGN. This may be related to photon trapping, strong winds and perhaps other yet unknown physical processes.

Relativistic Effects on Reflection X-ray Spectra of AGN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Khee-Gan; /University Coll. London; Fuerst, Steven V.

2007-01-05

We have calculated the reflection component of the X-ray spectra of active galactic nuclei (AGN) and shown that they can be significantly modified by the relativistic motion of the accretion flow and various gravitational effects of the central black hole. The absorption edges in the reflection spectra suffer severe energy shifts and smearing. The degree of distortion depends on the system parameters, and the dependence is stronger for some parameters such as the inner radius of the accretion disk and the disk viewing inclination angles. The relativistic effects are significant and are observable. Improper treatment of the reflection component ofmore » the X-ray continuum in spectral fittings will give rise to spurious line-like features, which will mimic the fluorescent emission lines and mask the relativistic signatures of the lines.« less

The shape of the cosmic X-ray background: nuclear starburst discs and the redshift evolution of AGN obscuration

NASA Astrophysics Data System (ADS)

Gohil, R.; Ballantyne, D. R.

2018-04-01

A significant number of active galactic nuclei (AGNs) are observed to be hidden behind dust and gas. The distribution of material around AGNs plays an important role in modelling the cosmic X-ray background (CXB), especially the fraction of type 2 AGNs (f2). One of the possible explanations for obscuration in Seyfert galaxies at intermediate redshifts is dusty starburst discs. We compute the two-dimensional (2D) hydrostatic structure of 768 nuclear starburst discs (NSDs) under various physical conditions and also the distribution of column density along the line of sight (NH) associated with these discs. Then the NH distribution is evolved with redshift by using the redshift-dependent distribution function of input parameters. Parameter f2 shows a strong positive evolution up to z = 2, but only a weak level of enhancement at higher z. The Compton-thin and Compton-thick AGN fractions associated with these starburst regions increase ∝ (1 + z)δ, where δ is estimated to be 1.12 and 1.45, respectively. The reflection parameter Rf associated with column density NH ≥ 1023.5 cm-2 extends from 0.13 at z = 0 to 0.58 at z = 4. A CXB model employing this evolving NH distribution indicates that more compact (Rout < 120 pc) NSDs provide a better fit to the CXB. In addition to `Seyfert-like' AGNs obscured by nuclear starbursts, we predict that 40-60 per cent of quasars must be Compton-thick to produce a peak of the CXB spectrum within the observational uncertainty. The predicted total number counts of AGNs in 8-24 keV bands are in fair agreement with observations from the Nuclear Spectroscopic Telescope Array (NuSTAR).

A Synthesis Of Cosmic X-ray And Infrared Background

NASA Astrophysics Data System (ADS)

Shi, Yong; Helou, G.; Armus, L.; Stierwalt, S.

2012-01-01

We present a synthesis model of cosmic IR and X-ray background, with the goal to derive a complete census of cosmic evolution of star formation (SF) and black-hole (BH) growth by complementing advantages of X-ray and IR surveys to each other. By assuming that individual galaxies are experiencing both SF and BH accretion, our model decomposes the total IR LF into SF and BH components while taking into account the luminosity-dependent SED and its dispersion of the SF component, and the extinction-dependent SED of the BH component. The best-fit parameters are derived by fitting to the number counts and redshift distributions at X-ray including both hard and soft bands, and mid-IR to submm bands including IRAS, Spitzer, Herschel, SCUBA, Aztec and MAMBO. Based on the fit result, our models provide a series of predictions on galaxy evolution and black-hole growth. For evolution of infrared galaxies, the model predicts that the total infrared luminosity function is best described through evolution in both luminosity and density. For evolution of AGN populations, the model predicts that the evolution of X-ray LF also shows luminosity and density dependent, that the type-1/type-2 AGN fraction is a function of both luminosity and redshift, and that the Compton-thick AGN number density evolves strongly with redshift, contributing about 20% to the total cosmic BH growth. For BH growth in IR galaxies, the model predicts that the majority of BH growth at z>1 occurs in infrared luminous galaxies and the AGN fraction as a function of IR survey is a strong function of the survey depth, ranging from >50% at bright end to below 10% at faint end. We also evaluates various AGN selection techniques at X-ray and IR wavelengths and offer predictions for future missions at X-ray and IR.

AGN UNIFICATION AT z {approx} 1: u - R COLORS AND GRADIENTS IN X-RAY AGN HOSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mark Ammons, S.; Rosario, David J. V.; Koo, David C., E-mail: ammons@as.arizona.edu, E-mail: rosario@ucolick.org, E-mail: koo@ucolick.org

2011-10-10

We present uncontaminated rest-frame u - R colors of 78 X-ray-selected active galactic nucleus (AGN) hosts at 0.5 < z < 1.5 in the Chandra Deep Fields measured with Hubble Space Telescope (HST)/Advanced Camera for Surveys/NICMOS and Very Large Telescope/ISAAC imaging. We also present spatially resolved NUV - R color gradients for a subsample of AGN hosts imaged by HST/Wide Field Camera 3 (WFC3). Integrated, uncorrected photometry is not reliable for comparing the mean properties of soft and hard AGN host galaxies at z {approx} 1 due to color contamination from point-source AGN emission. We use a cloning simulation tomore » develop a calibration between concentration and this color contamination and use this to correct host galaxy colors. The mean u - R color of the unobscured/soft hosts beyond {approx}6 kpc is statistically equivalent to that of the obscured/hard hosts (the soft sources are 0.09 {+-} 0.16 mag bluer). Furthermore, the rest-frame V - J colors of the obscured and unobscured hosts beyond {approx}6 kpc are statistically equivalent, suggesting that the two populations have similar distributions of dust extinction. For the WFC3/infrared sample, the mean NUV - R color gradients of unobscured and obscured sources differ by less than {approx}0.5 mag for r > 1.1 kpc. These three observations imply that AGN obscuration is uncorrelated with the star formation rate beyond {approx}1 kpc. These observations favor a unification scenario for intermediate-luminosity AGNs in which obscuration is determined geometrically. Scenarios in which the majority of intermediate-luminosity AGNs at z {approx} 1 are undergoing rapid, galaxy-wide quenching due to AGN-driven feedback processes are disfavored.« less

Estimative of conversion fractions of AGN magnetic luminosity to produce ultra high energy cosmic rays from the observation of Fermi-LAT gamma rays

NASA Astrophysics Data System (ADS)

Coimbra-Araújo, Carlos H.; Anjos, Rita C.

2017-01-01

A fraction of the magnetic luminosity (LB) produced by Kerr black holes in some active galactic nuclei (AGNs) can produce the necessary energy to accelerate ultra high energy cosmic rays (UHECRs) beyond the GZK limit, observed, e.g., by the Pierre Auger experiment. Nevertheless, the direct detection of those UHECRs has a lack of information about the direction of the source from where those cosmic rays are coming, since charged particles are deflected by the intergalactic magnetic field. This problem arises the needing of alternative methods to evaluate the luminosity of UHECRs (LCR) from a given source. Methods proposed in literature range from the observation of upper limits in gamma rays to the observation of upper limits in neutrinos produced by cascade effects during the propagation of UHECRs. In this aspect, the present work proposes a method to calculate limits of the main possible conversion fractions ηCR = LCR/LB for nine UHECR AGN Seyfert sources based on the respective observation of gamma ray upper limits from Fermi-LAT data.

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Balokovic, Mislav; Baronchelli, Linda; Gehrels, Neil; Stern, Daniel; Mushotzky, Richard; Veilleux, Sylvain; Ueda, Yoshihiro; Crenshaw, D. Michael; Harrison, Fiona; Fischer, Travis C.; Treister, Ezequiel; BASS Team; Swift BAT Team

2017-01-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve dierent telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics. Additionally, we discuss follow-on efforts to study the variation of [OIII] to Xray measurements, a new method to measure accretion rates from using line ratios, a sample of 100 AGN observed with NIR spectroscopy, and an effort to measure the accretion rates and obscuration with merger stage in a subsample of mergers.

Compton Reflection in AGN with Simbol-X

NASA Astrophysics Data System (ADS)

Beckmann, V.; Courvoisier, T. J.-L.; Gehrels, N.; Lubiński, P.; Malzac, J.; Petrucci, P. O.; Shrader, C. R.; Soldi, S.

2009-05-01

AGN exhibit complex hard X-ray spectra. Our current understanding is that the emission is dominated by inverse Compton processes which take place in the corona above the accretion disk, and that absorption and reflection in a distant absorber play a major role. These processes can be directly observed through the shape of the continuum, the Compton reflection hump around 30 keV, and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151, NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the simulations with recent observations on these sources by INTEGRAL, Swift and Suzaku. Constraining reflection models for AGN with Simbol-X will help us to get a clear view of the processes and geometry near to the central engine in AGN, and will give insight to which sources are responsible for the Cosmic X-ray background at energies >20 keV.

X-Ray Scattering Echoes and Ghost Halos from the Intergalactic Medium: Relation to the Nature of AGN Variability

NASA Astrophysics Data System (ADS)

Corrales, Lia

2015-05-01

X-ray bright quasars might be used to trace dust in the circumgalactic and intergalactic medium through the phenomenon of X-ray scattering, which is observed around Galactic objects whose light passes through a sufficient column of interstellar gas and dust. Of particular interest is the abundance of gray dust larger than 0.1 μ m, which is difficult to detect at other wavelengths. To calculate X-ray scattering from large grains, one must abandon the traditional Rayleigh-Gans approximation. The Mie solution for the X-ray scattering optical depth of the universe is ∼ 1%. This presents a great difficulty for distinguishing dust scattered photons from the point source image of Chandra, which is currently unsurpassed in imaging resolution. The variable nature of AGNs offers a solution to this problem, as scattered light takes a longer path and thus experiences a time delay with respect to non-scattered light. If an AGN dims significantly (≳ 3 dex) due to a major feedback event, the Chandra point source image will be suppressed relative to the scattering halo, and an X-ray echo or ghost halo may become visible. I estimate the total number of scattering echoes visible by Chandra over the entire sky: {{N}ech}∼ {{10}3}({{ν }fb}/y{{r}-1}), where {{ν }fb} is the characteristic frequency of feedback events capable of dimming an AGN quickly.

Deep Extragalactic X-Ray Surveys

NASA Astrophysics Data System (ADS)

Brandt, W. N.; Hasinger, G.

2005-09-01

Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-Ray Observatory and the X-Ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted, including (a) measurements of AGN evolution and the growth of supermassive black holes, (b) constraints on the demography and physics of high-redshift AGN, (c) the X-ray AGN content of infrared and submillimeter galaxies, and (d) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.

Measuring the Impact of AGN Outflows via Intensive UV and X-ray Monitoring Campaigns

NASA Astrophysics Data System (ADS)

Kriss, Gerard

2015-08-01

Observations of AGN outflows have progressed from the era of single-object surveys to intensive monitoring campaigns spanning weeks to months. The combination of multiple observations, improved temporal coverage, multi-wavelength monitoring in both the X-ray and UV bands, and the baseline of prior historical observations has enabled determinations of the locations, mass flux, and kinetic luminosities of the outflowing absorbing gas in several AGN, notably Mrk 509, NGC 5548, Mrk 335, and NGC 985. Another intensive campaign is planned for 2015-2016 on NGC 7469. In all cases, the mass flux and kinetic energy is dominated by the higher-ionization X-ray absorbing gas. But the higher-resolution UV observations give a kinematically resolved picture of the overall outflow. In most cases, the outflowing gas is located at parsec to kpc scales, with insufficient kinetic luminosity to have an evolutionary impact on the host galaxy. Typically, the kinetic luminosity is less than a percent of the Eddington luminosity. In some cases, transient, broad UV absorption troughs have appeared (e.g., Mrk 335 and NGC 5548), with variability timescales suggesting locations near the broad-line region of the AGN. Yet these higher-velocity outflows also have low-impact kinetic luminosities. In the best-studied case of NGC 5548, the strength of the broad UV absorption lines varies with the degree of soft X-ray obscuration first revealed by XMM-Newton spectra. The lower-ionization, narrow associated absorption lines in the UV spectrum of NGC 5548 that appeared concurrently with the soft X-ray obscuration vary in response to the changing UV flux on a daily basis. The intensive monitoring allows us to fit time-dependent photoionization models to the UV-absorbing gas, allowing precise determinations of the locations, mass flux, and kinetic luminosities of the absorbers.

X-ray inverse Compton emission from the radio halo of M87

NASA Technical Reports Server (NTRS)

Feigelson, E. D.

1984-01-01

A significant fraction of known galaxies contain an active galactic nucleus (AGN) at their cores, the site of violent activity and non-stellar radiation seen across the entire electromagnetic spectrum. This activity is thought to be due to the accretion of gas onto a massive black hole. A fraction of AGNs also eject collimated beams of energetic material, usually seen by virtue of its synchrotron emission in the radio band. Efforts to study these jets from AGNs in the X-ray band with the Einstein Observatory has led to several detections, most notably the jets in the nearby radio galaxies Centaurus A and Virgo A = M87. In their study of M87, Schreier, Gorenstein and Feigelson (1982) noted that, in addition to the synchrotron jet 10"-20" from the nucleus, X-rays appear to be generated in the diffuse radio halo 2'-5' from the nucleus. This finding may be particularly important as it may constitute the first known case of X-ray inverse Compton emission from AGN ejecta, allowing for the first time direct determination of the magnetic field strengths.

X-ray Evidence for Ultra-Fast Outflows in Local AGNs

NASA Astrophysics Data System (ADS)

Tombesi, F.; Cappi, M.; Sambruna, R. M.; Reeves, J. N.; Reynolds, C. S.; Braito, V.; Dadina, M.

2012-08-01

X-ray evidence for ultra-fast outflows (UFOs) has been recently reported in a number of local AGNs through the detection of blue-shifted Fe XXV/XXVI absorption lines. We present the results of a comprehensive spectral analysis of a large sample of 42 local Seyferts and 5 Broad-Line Radio Galaxies (BLRGs) observed with XMM-Newton and Suzaku. We detect UFOs in ga 40% of the sources. Their outflow velocities are in the range ˜ 0.03-0.3c, with a mean value of ˜ 0.14c. The ionization is high, in the range logℰ ˜3-6rm erg s-1 cm, and also the associated column densities are large, in the interval ˜ 1022-1024rm cm-2. Overall, these results point to the presence of highly ionized and massive outflowing material in the innermost regions of AGNs. Their variability and location on sub-pc scales favor a direct association with accretion disk winds/outflows. This also suggests that UFOs may potentially play a significant role in the AGN cosmological feedback besides jets, and their study can provide important clues on the connection between accretion disks, winds, and jets.

AEGIS: Demographics of X-ray and Optically Selected Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Yan, Renbin; Ho, Luis C.; Newman, Jeffrey A.; Coil, Alison L.; Willmer, Christopher N. A.; Laird, Elise S.; Georgakakis, Antonis; Aird, James; Barmby, Pauline; Bundy, Kevin; Cooper, Michael C.; Davis, Marc; Faber, S. M.; Fang, Taotao; Griffith, Roger L.; Koekemoer, Anton M.; Koo, David C.; Nandra, Kirpal; Park, Shinae Q.; Sarajedini, Vicki L.; Weiner, Benjamin J.; Willner, S. P.

2011-02-01

We develop a new diagnostic method to classify galaxies into active galactic nucleus (AGN) hosts, star-forming galaxies, and absorption-dominated galaxies by combining the [O III]/Hβ ratio with rest-frame U - B color. This can be used to robustly select AGNs in galaxy samples at intermediate redshifts (z < 1). We compare the result of this optical AGN selection with X-ray selection using a sample of 3150 galaxies with 0.3 < z < 0.8 and I AB < 22, selected from the DEEP2 Galaxy Redshift Survey and the All-wavelength Extended Groth Strip International Survey. Among the 146 X-ray sources in this sample, 58% are classified optically as emission-line AGNs, the rest as star-forming galaxies or absorption-dominated galaxies. The latter are also known as "X-ray bright, optically normal galaxies" (XBONGs). Analysis of the relationship between optical emission lines and X-ray properties shows that the completeness of optical AGN selection suffers from dependence on the star formation rate and the quality of observed spectra. It also shows that XBONGs do not appear to be a physically distinct population from other X-ray detected, emission-line AGNs. On the other hand, X-ray AGN selection also has strong bias. About 2/3 of all emission-line AGNs at L bol > 1044 erg s-1 in our sample are not detected in our 200 ks Chandra images, most likely due to moderate or heavy absorption by gas near the AGN. The 2-7 keV detection rate of Seyfert 2s at z ~ 0.6 suggests that their column density distribution and Compton-thick fraction are similar to that of local Seyferts. Multiple sample selection techniques are needed to obtain as complete a sample as possible.

AGN classification for X-ray sources in the 105 month Swift/BAT survey

NASA Astrophysics Data System (ADS)

Masetti, N.; Bassani, L.; Palazzi, E.; Malizia, A.; Stephen, J. B.; Ubertini, P.

2018-03-01

We here provide classifications for 8 hard X-ray sources listed as 'unknown AGN' in the 105 month Swift/BAT all-sky survey catalogue (Oh et al. 2018, ApJS, 235, 4). The corresponding optical spectra were extracted from the 6dF Galaxy Survey (Jones et al. 2009, MNRAS, 399, 683).

Mid- and Near-infrared spectral properties of a sample of Swift-BAT X-ray selected AGNs

NASA Astrophysics Data System (ADS)

Castro, Angel; Miyaji, Takamitsu; Malkan, Matthew A.; Ichikawa, Kohei; Ueda, Yoshihiro; Shirahata, M.; Nakagawa, Takao; Imanishi, Masatoshi; Oyabu, Shinki

2015-08-01

We present a comparative study of the mid- (MIR) to near-infrared (NIR) properties of a sample of X-ray selected AGNs from the Swift/Burst Alert Telescope (BAT) 70-month all-sky hard X-ray (14-195 keV) survey. For a sample of 78 AGNs, including both Seyfert 1 and Seyfert 2 sources with black hole masses derived from 2MASS K-band magnitudes and literature, we obtain spectroscopic data from the IRC (2.5 - 5 μm) and IRS (in the 5-14 μm band) instruments onboard the Akari and Spitzer satellites, respectively. We test possible correlations between the 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 μm polycyclic aromatic hydrocarbon (PAH) emission features, the continuum slope and CO optical depth, as well as CO2, H2O, and amorphous silicates. Using the 3.3, 6.2 and 11.3 μm PAH emission features as a proxy for the star-formation rate (SFR) we report the AGN type and Eddington-ratio dependences of circum-nuclear star formation.

The ΓX-L/LEdd relation in BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Ricci, Claudio; Koss, Michael; Schawinski, Kevin; Mushotzky, Richard; Ueda, Yoshihiro; Veilleux, Sylvain; Lamperti, Isabella; Oh, Kyuseok; Treister, Ezequiel; Stern, Daniel; Harrison, Fiona; Balokovic, Mislav

2018-01-01

We present a study of the relation between accretion rate (in terms of L/LEdd) and shape of the hard X-ray spectral energy distribution (namely the photon index Γx) for a large sample of over 200 hard X-ray-selected, low-redshift active galactic nuclei (AGNs), drawn from the Swift/BAT AGN Spectroscopic Survey (BASS). This includes 30 AGNs for which black hole mass (and therefore L/LEdd) is measured directly through masers, spatially resolved gas or stellar dynamics, or reverberation mapping. The high-quality and broad energy coverage of the data provided through BASS allow us to examine several alternative determinations of both Γx and L/LEdd. We find very weak correlation between Γx and L/LEdd for the BASS sample as a whole, with best-fitting relations that are considerably shallower than those reported in previous studies. Moreover, we find no corresponding correlations among the subsets of AGN with different MBH determination methodology, and in particular those AGN with direct or single-epoch MBH estimates. This latter finding is in contrast to several previous studies which focused on z > 0.5 broad-line AGN. We conclude that this tension can be partially accounted for if one adopts a simplified, power-law X-ray spectral model, combined with L/LEdd estimates that are based on the continuum emission and on single-epoch broad-line spectroscopy in the optical regime. Given these findings, we highlight the limitations of using Γx as a probe of supermassive black hole evolution in deep extragalactic X-ray surveys.

Electron-positron pairs, Compton reflection, and the X-ray spectra of active galactic nuclei

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Ghisellini, Gabriele; George, Ian M.; Fabian, A. C.; Svensson, Roland; Done, Chris

1990-01-01

It is shown here that reprocessing of radiation fron nonthermal pair cascades by cold material in the central parts of active galactic nuclei (AGN) gives rise to X-ray and gamma-ray spectra that satisfy current observational constraints. An average 1-30 keV X-ray spectral index alpha(x) of about 0.7 in the compact range 30-300 is obtained for a wide range of Lorentz factors of the injected electrons. The gamma-ray spectra are steep, with alpha(gamma) about two, and satisfy the observational constraints. Radiation from pair cascades exhibits steep power law decreases in soft X-rays similar to those observed in AGN. The overall picture is consistent with AGN having an accretion disk which intercepts and reprocesses a substantial fraction of the nonthermal continuum incident upon it from above and below.

Morphologies of mid-IR variability-selected AGN host galaxies

NASA Astrophysics Data System (ADS)

Polimera, Mugdha; Sarajedini, Vicki; Ashby, Matthew L. N.; Willner, S. P.; Fazio, Giovanni G.

2018-05-01

We use multi-epoch 3.6 and 4.5 μm data from the Spitzer Extended Deep Survey (SEDS) to probe the AGN population among galaxies to redshifts ˜3 via their mid-IR variability. About 1 per cent of all galaxies in our survey contain varying nuclei, 80 per cent of which are likely to be AGN. Twenty-three per cent of mid-IR variables are also X-ray sources. The mid-IR variables have a slightly greater fraction of weakly disturbed morphologies compared to a control sample of normal galaxies. The increased fraction of weakly distorted hosts becomes more significant when we remove the X-ray emitting AGN, while the frequency of strongly disturbed hosts remains similar to the control galaxy sample. These results suggest that mid-IR variability identifies a unique population of obscured, Compton-thick AGN revealing elevated levels of weak distortion among their host galaxies.

HOST GALAXY PROPERTIES OF THE SWIFT BAT ULTRA HARD X-RAY SELECTED ACTIVE GALACTIC NUCLEUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain

We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) active galactic nucleus (AGN) with host galaxy optical data to date, with 185 nearby (z < 0.05), moderate luminosity AGNs 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 AGNs 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 BATmore » AGNs are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGNs in massive galaxies (log M{sub *} >10.5) have a 5-10 times higher rate of spiral morphologies than in SDSS AGNs or inactive galaxies. We also see enhanced far-infrared emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGNs are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGNs have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] {lambda}5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGNs in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as a whole. In agreement with the unified model of AGNs, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGNs suggest that host galaxy morphology is related to the activation and fueling of local AGN.« less

CHANDRA X-RAY AND HUBBLE SPACE TELESCOPE IMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. II. HOST GALAXY MORPHOLOGY AND AGN ACTIVITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shangguan, Jinyi; Ho, Luis C.; Liu, Xin

Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W ( U -band) and F105W ( Y -band) images taken by the Wide Fieldmore » Camera 3 on board the Hubble Space Telescope . Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U − Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers.« less

Compton thick AGN: the hunt continues

NASA Astrophysics Data System (ADS)

Marchesi, Stefano

2017-09-01

The X-ray spectral analysis of Compton thick (CT-) active galactic nuclei (AGN) represents a fundamental step to understand the physics of the obscuring material surrounding the accreting supermassive black hole. However, at the present day CT-AGN remain extremely hard to detect. After a first, successful pilot program, we propose to target with a 10 ks Chandra observation 4 low redshift candidate CT-AGN from the Swift-BAT 100-month catalog. This analysis will refine our knowledge of the selection function of CT-AGN, therefore helping us in determine the true intrinsic fraction of CT-AGN and their contribution to the CXB.

The Frequency of Intrinsic X-Ray Weakness among Broad Absorption Line Quasars

NASA Astrophysics Data System (ADS)

Liu, Hezhen; Luo, B.; Brandt, W. N.; Gallagher, S. C.; Garmire, G. P.

2018-06-01

We present combined ≈14–37 ks Chandra observations of seven z = 1.6–2.7 broad absorption line (BAL) quasars selected from the Large Bright Quasar Survey (LBQS). These seven objects are high-ionization BAL (HiBAL) quasars, and they were undetected in the Chandra hard band (2–8 keV) in previous observations. The stacking analyses of previous Chandra observations suggested that these seven objects likely contain some candidates for intrinsically X-ray weak BAL quasars. With the new Chandra observations, six targets are detected. We calculate their effective power-law photon indices and hard-band flux weakness, and find that two objects, LBQS 1203+1530 and LBQS 1442–0011, show soft/steep spectral shapes ({{{Γ }}}eff}={2.2}-0.9+0.9 and {1.9}-0.8+0.9) and significant X-ray weakness in the hard band (by factors of ≈15 and 12). We conclude that the two HiBAL quasars are good candidates for intrinsically X-ray weak BAL quasars. The mid-infrared-to-ultraviolet spectral energy distributions of the two candidates are consistent with those of typical quasars. We constrain the fraction of intrinsically X-ray weak active galactic nuclei (AGNs) among HiBAL quasars to be ≈7%–10% (2/29–3/29), and we estimate it is ≈6%–23% (2/35–8/35) among the general BAL quasar population. Such a fraction is considerably larger than that among non-BAL quasars, and we suggest that intrinsically X-ray weak quasars are preferentially observed as BAL quasars. Intrinsically X-ray weak AGNs likely comprise a small minority of the luminous type 1 AGN population, and they should not affect significantly the completeness of these AGNs found in deep X-ray surveys.

BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics

NASA Astrophysics Data System (ADS)

Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Baloković, Mislav; Baronchelli, Linda; Crenshaw, D. Michael; Fischer, Travis; Gehrels, Neil; Harrison, Fiona; Hashimoto, Yasuhiro; Hogg, Drew; Ichikawa, Kohei; Masetti, Nicola; Mushotzky, Richard; Sartori, Lia; Stern, Daniel; Treister, Ezequiel; Ueda, Yoshihiro; Veilleux, Sylvain; Winter, Lisa

2017-11-01

We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey. We analyze optical spectra of the majority of the detected AGNs (77%, 642/836)based on their 14-195 keV emission in the 70-month Swift-BAT all-sky catalog. This includes redshift determination, absorption and emission-line measurements, and black hole mass and accretion rate estimates for the majority of obscured and unobscured AGNs (74%, 473/642), with 340 measured for the first time. With ˜90% of sources at z< 0.2, the survey represents a significant advance in the census of hard X-ray-selected AGNs in the local universe. In this first catalog paper, we describe the spectroscopic observations and data sets, and our initial spectral analysis. The FWHMs of the emission lines show broad agreement with the X-ray obscuration (˜94%), such that Sy 1-1.8 have {N}{{H}}< {10}21.9 cm-2, and Seyfert 2 have {N}{{H}}> {10}21.9 cm-2. Seyfert 1.9, however, show a range of column densities. Compared to narrow-line AGNs in the SDSS, the X-ray-selected AGNs have a larger fraction of dusty host galaxies ({{H}}α /{{H}}β > 5), suggesting that these types of AGN are missed in optical surveys. Using the [O III] λ5007/Hβ and [N II] λ6583/Hα emission-line diagnostic, about half of the sources are classified as Seyferts; ˜15% reside in dusty galaxies that lack an Hβ detection, but for which the upper limits on line emission imply either a Seyfert or LINER, ˜ 15 % are in galaxies with weak or no emission lines despite high-quality spectra, and a few percent each are LINERS, composite galaxies, H II regions, or in known beamed AGNs.

The XXL Survey. XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters

NASA Astrophysics Data System (ADS)

Koulouridis, E.; Poggianti, B.; Altieri, B.; Valtchanov, I.; Jaffé, Y.; Adami, C.; Elyiv, A.; Melnyk, O.; Fotopoulou, S.; Gastaldello, F.; Horellou, C.; Pierre, M.; Pacaud, F.; Plionis, M.; Sadibekova, T.; Surdej, J.

2016-06-01

Context. This article belongs to the first series of XXL publications. It presents multifibre spectroscopic observations of three 0.55 deg2 fields in the XXL Survey, which were selected on the basis of their high density of X-ray-detected clusters. The observations were obtained with the AutoFib2+WYFFOS (AF2) wide-field fibre spectrograph mounted on the 4.2 m William Herschel Telescope. Aims: The paper first describes the scientific rationale, the preparation, the data reduction, and the results of the observations, and then presents a study of active galactic nuclei (AGN) within three superclusters. Methods: To determine the redshift of galaxy clusters and AGN, we assign high priority to a) the brightest cluster galaxies (BCGs), b) the most probable cluster galaxy candidates, and c) the optical counterparts of X-ray point-like sources. We use the outcome of the observations to study the projected (2D) and the spatial (3D) overdensity of AGN in three superclusters. Results: We obtained redshifts for 455 galaxies in total, 56 of which are counterparts of X-ray point-like sources. We were able to determine the redshift of the merging supercluster XLSSC-e, which consists of six individual clusters at z ~ 0.43, and we confirmed the redshift of supercluster XLSSC-d at z ~ 0.3. More importantly, we discovered a new supercluster, XLSSC-f, that comprises three galaxy clusters also at z ~ 0.3. We find a significant 2D overdensity of X-ray point-like sources only around the supercluster XLSSC-f. This result is also supported by the spatial (3D) analysis of XLSSC-f, where we find four AGN with compatible spectroscopic redshifts and possibly one more with compatible photometric redshift. In addition, we find two AGN (3D analysis) at the redshift of XLSSC-e, but no AGN in XLSSC-d. Comparing these findings with the optical galaxy overdensity we conclude that the total number of AGN in the area of the three superclusters significantly exceeds the field expectations. All of the

X-ray obscured AGN in the GOODS-N

NASA Astrophysics Data System (ADS)

Georgantopoulos, I.; Akylas, A.; Rovilos, E.; Xilouris, M.

2010-07-01

We explore the X-ray properties of the Dust Obscured Galaxies (DOGs) i.e. sources with f24μ/fR>1000. This population has been proposed to contain a significan fraction of Compton-thick sources at high redshift. In particular we study the X-ray spectra of the 14 DOGS detected in the CDFN 2Ms exposure. Their stacked spectrum is fla with Γ = 1+/-0.1 very similar to the stacked spectrum of the undetected DOGs (Γ = 0.8+/-0.2). However, many of our X-ray detected DOGs present only moderate absorption with column densities 1022

BAT AGN Spectroscopic Survey (BASS) - VI. The ΓX-L/LEdd relation

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Ricci, Claudio; Koss, Michael J.; Schawinski, Kevin; Mushotzky, Richard; Ueda, Yoshihiro; Veilleux, Sylvain; Lamperti, Isabella; Oh, Kyuseok; Treister, Ezequiel; Stern, Daniel; Harrison, Fiona; Baloković, Mislav; Gehrels, Neil

2017-09-01

We study the relation between accretion rate (in terms of L/LEdd) and shape of the hard X-ray spectral energy distribution (namely the photon index Γx) for a large sample of 228 hard X-ray-selected, low-redshift active galactic nuclei (AGNs), drawn from the Swift/BAT AGN Spectroscopic Survey (BASS). This includes 30 AGNs for which black hole mass (and therefore L/LEdd) is measured directly through masers, spatially resolved gas or stellar dynamics, or reverberation mapping. The high-quality and broad energy coverage of the data provided through BASS allow us to examine several alternative determinations of both Γx and L/LEdd. For the BASS sample as a whole, we find a statistically significant, albeit very weak correlation between Γx and L/LEdd. The best-fitting relations we find, Γx ≃ 0.15 log L/LEdd + const., are considerably shallower than those reported in previous studies. Moreover, we find no corresponding correlations among the subsets of AGN with different MBH determination methodology. In particular, we find no robust evidence for a correlation when considering only those AGN with direct or single-epoch MBH estimates. This latter finding is in contrast to several previous studies which focused on z > 0.5 broad-line AGN. We discuss this tension and conclude that it can be partially accounted for if one adopts a simplified, power-law X-ray spectral model, combined with L/LEdd estimates that are based on the continuum emission and on single-epoch broad-line spectroscopy in the optical regime. We finally highlight the limitations on using Γx as a probe of supermassive black hole evolution in deep extragalactic X-ray surveys.

The 60-month all-sky BAT Survey of AGN and the Anisotropy of Nearby AGN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ajello, M.; /KIPAC, Menlo Park; Alexander, D.M.

2012-04-02

Surveys above 10 keV represent one of the the best resources to provide an unbiased census of the population of Active Galactic Nuclei (AGN). We present the results of 60 months of observation of the hard X-ray sky with Swift/BAT. In this timeframe, BAT detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGN, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of {approx}2 larger over similarly complete sets of AGN. Our sample contains (at least) 15 bona-fide Compton-thick AGN and 3 likely candidates. Compton-thickmore » AGN represent a {approx}5% of AGN samples detected above 15 keV. We use the BAT dataset to refine the determination of the LogN-LogS of AGN which is extremely important, now that NuSTAR prepares for launch, towards assessing the AGN contribution to the cosmic X-ray background. We show that the LogN-LogS of AGN selected above 10 keV is now established to a {approx}10% precision. We derive the luminosity function of Compton-thick AGN and measure a space density of 7.9{sub -2.9}{sup +4.1} x 10{sup -5} Mpc{sup -3} for objects with a de-absorbed luminosity larger than 2 x 10{sup 42} erg s{sup -1}. As the BAT AGN are all mostly local, they allow us to investigate the spatial distribution of AGN in the nearby Universe regardless of absorption. We find concentrations of AGN that coincide spatially with the largest congregations of matter in the local ({le} 85 Mpc) Universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions.« less

The Swift BAT Hard X-ray Survey - A New Window on the Local AGN Universe

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2009-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 keV sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6E24 atms/cm2) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

Studying AGN Activation in Galaxy Mergers

NASA Astrophysics Data System (ADS)

Negus, James; Blecha, Laura

2018-06-01

Simulations predict that galaxy mergers drive central gas inflows that result in a peak AGN fraction when the two galaxy bulges reach separations near 1 kpc. Moreover, observations have shown that the AGN fraction increases as the separation between two merging galaxies decreases from 100 kpc to 10 kpc; however, the trend has not yet been measured in the pivotal sub 10 kpc regime, where activity may drastically increase as the simulations suggest. We present a uniform sample of dual and offset AGN, which features AGN parameters (e.g., redshift, angular separation) and normalized cosmology-dependent parameters (e.g., physical separation, bolometric luminosity), using multi-wavelength observations (IR to X-ray) in this critical sub 10 kpc range. In addition, using galaxy merger simulations with GADGET-3, a smoothed particle hydrodynamics N-body code, we report how much time galaxy pairs spend at different separations during a merger. Using these results, we will discuss how galaxy bulge separation correlates to increases in the AGN fraction over varying timescales, and where AGN are primarily fueled during mergers with galaxy bulge separations < 10 kpc.

BLACK HOLE MASS AND EDDINGTON RATIO DISTRIBUTION FUNCTIONS OF X-RAY-SELECTED BROAD-LINE AGNs AT z {approx} 1.4 IN THE SUBARU XMM-NEWTON DEEP FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nobuta, K.; Akiyama, M.; Ueda, Y.

2012-12-20

In order to investigate the growth of supermassive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line active galactic nuclei (AGNs) at z {approx} 1.4 in the Subaru XMM-Newton Deep Survey (SXDS) field. A significant part of the accretion growth of SMBHs is thought to take place in this redshift range. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad Mg II line and 3000 A monochromatic luminosity. We supplement the Mg II FWHM values with the H{alpha} FWHM obtained from our NIRmore » spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMFs and ERDFs are calculated using the V{sub max} method. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMFs and ERDFs by applying the maximum likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local universe, then the corrected BHMF at z = 1.4 has a higher number density above 10{sup 8} M{sub Sun} but a lower number density below that mass range. The evolution may be indicative of a downsizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDFs from z = 1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rates close to the Eddington limit is higher at higher redshifts.« less

Are There Intrinsically X-Ray Quiet Quasars

NASA Technical Reports Server (NTRS)

Gallagher, S. C.; Brandt, W. N.; Laor, A.; Elvis, Martin; Mathur, S.; Wills, Beverly J.; Iyomoto, N.; White, Nicholas (Technical Monitor)

2000-01-01

Recent ROSAT studies have identified a significant population of Active Galactic Nuclei (AGN) that are notably faint in soft X-rays relative to their optical fluxes. Are these AGN intrinsically X-ray weak or are they just highly absorbed? Brandt, Laor & Wills have systematically examined the optical and UV spectral properties of a well-defined sample of these soft X-ray weak (SXW) AGN drawn from the Boroson & Green sample of all the Palomar Green AGN 00 with z < 0.5. We present ASCA observations of three of these SXW AGN: PG 1011-040, PG 1535+547 (Mrk 486), and PG 2112+059. In general, our ASCA observations support the intrinsic absorption scenario for explaining soft X-ray weakness; both PG 1535+547 and PG 2112+059 show significant column densities (NH is approximately 10(exp 22) - 10(exp 23)/sq cm) of absorbing gas. Interestingly, PG 1011-040 shows no spectral evidence for X-ray absorption. The weak X-ray emission may result from very strong absorption of a partially covered source, or this AGN may be intrinsically X-ray weak. PG 2112+059 is a Broad Absorption Line (BAL) QSO, and we find it to have the highest X-ray flux known of this class. It shows a typical power-law X-ray continuum above 3 keV; this is the first direct evidence that BAL QSOs indeed have normal X-ray continua underlying their intrinsic absorption. Finally, marked variability between the ROSAT and ASCA observations of PG 1535+547 and PG 2112+059 suggests that the soft X-ray weak designation may be transient, and multi-epoch 0.1-10.0 KeV X-ray observations are required to constrain variability of the absorber and continuum.

The BAT AGN Spectroscopic Survey (BASS) DR1-Spectral Measurements, Derived Quantities, and AGN Demographics

NASA Astrophysics Data System (ADS)

Koss, Michael; BASS Team

2018-01-01

We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey (BASS). We analyze optical spectra of the majority of AGN (77%, 641/836) detected based on their 14-195 keV emission in the 70-month Swift BAT all-sky catalog. This includes redshift determination, absorption and emission line measurements, and black hole mass and accretion rate estimates for the majority of obscured and un-obscured AGN (74%, 473/641) with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant census of hard-X-ray selected AGN in the local universe. In this first catalog paper, we describe the spectroscopic observations and datasets, and our initial spectral analysis. The FWHM of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have NH<10^21.9 cm^-2, and Seyfert 2, have NH>10^21.9 cm^-2. Seyfert 1.9 show a range of column densities. Compared to narrow line AGN in the SDSS, the X-ray selected AGN have a larger fraction of dusty host galaxies suggesting these types of AGN are missed in optical surveys. Using the most sensitive [OIII]/Hbeta and [NII]/Halpha emission line diagnostic, about half of the sources are classified as Seyferts, ~15% reside in dusty galaxies that lack an Hbeta detection, but for which the line upper limits imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high quality spectra, and a few percent each are LINERS, composite galaxies, HII regions, or in known beamed AGN.

Inferring Compton-thick AGN candidates at z > 2 with Chandra using the >8 keV rest-frame spectral curvature

NASA Astrophysics Data System (ADS)

Baronchelli, L.; Koss, M.; Schawinski, K.; Cardamone, C.; Civano, F.; Comastri, A.; Elvis, M.; Lanzuisi, G.; Marchesi, S.; Ricci, C.; Salvato, M.; Trakhtenbrot, B.; Treister, E.

2017-10-01

To fully understand cosmic black hole growth, we need to constrain the population of heavily obscured active galactic nuclei (AGNs) at the peak of cosmic black hole growth (z ˜1-3). Sources with obscuring column densities higher than 1024 atoms cm-2, called Compton-thick (CT) AGNs, can be identified by excess X-ray emission at ˜20-30 keV, called the 'Compton hump'. We apply the recently developed Spectral Curvature (SC) method to high-redshift AGNs (2 < z < 5) detected with Chandra. This method parametrizes the characteristic 'Compton hump' feature cosmologically redshifted into the X-ray band at observed energies <10 keV. We find good agreement in CT AGNs found using the SC method, and bright sources fit using their full spectrum with X-ray spectroscopy. In the Chandra Deep Field-South, we measure a CT fraction of 17^{+19}_{-11} per cent (3/17) for sources with observed luminosity >5 × 1043erg s-1. In the Cosmological Evolution Survey (COSMOS), we find an observed CT fraction of 15^{+4}_{-3} per cent (40/272) or 32 ± 11 per cent when corrected for the survey sensitivity. When comparing to low redshift AGNs with similar X-ray luminosities, our results imply that the CT AGN fraction is consistent with having no redshift evolution. Finally, we provide SC equations that can be used to find high-redshift CT AGNs (z > 1) for current (XMM-Newton) and future (eROSITA and ATHENA) X-ray missions.

Chandra X-Ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-scale Binary Active Galactic Nuclei. II. Host Galaxy Morphology and AGN Activity

NASA Astrophysics Data System (ADS)

Shangguan, Jinyi; Liu, Xin; Ho, Luis C.; Shen, Yue; Peng, Chien Y.; Greene, Jenny E.; Strauss, Michael A.

2016-05-01

Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W (U-band) and F105W (Y-band) images taken by the Wide Field Camera 3 on board the Hubble Space Telescope. Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U - Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers. Based, in part, on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program number GO 12363.

AXIS - Advanced X-ray Imaging Sarellite

NASA Astrophysics Data System (ADS)

Loewenstein, Michael; AXIS Team

2018-01-01

We present an overview of the Advanced X-ray Imaging Satellite (AXIS), a probe mission concept under study to the 2020 Decadal survey. AXIS follows in the footsteps of the spectacularly successful Chandra X-ray Observatory with similar or higher angular resolution and an order of magnitude more collecting area in the 0.3-10 keV band over a 15' field of view. These capabilities are designed to attain a wide range of science goals such as (i) measuring the event horizon scale structure in AGN accretion disks and the spin of supermassive black holes through monitoring of gravitationally microlensed quasars; (ii) understanding AGN and starburst feedback in galaxies and galaxy clusters through direct imaging of winds and interaction of jets and via spatially resolved imaging of galaxies at high-z; (iii) probing the fueling of AGN by resolving the SMBH sphere of influence in nearby galaxies; (iv) investigating hierarchical structure formation and the SMBH merger rate through measurement of the occurrence rate of dual AGN and occupation fraction of SMBHs; (v) advancing SNR physics and galaxy ecology through large detailed samples of SNR in nearby galaxies; (vi) measuring the Cosmic Web through its connection to cluster outskirts. With a nominal 2028 launch, AXIS benefits from natural synergies with LSST, ELTs, ALMA, WFIRST and ATHENA, and will be a valuable precursor to Lynx. AXIS utilizes breakthroughs in the construction of light-weight X-ray optics from mono-crystalline silicon blocks, and developments in the fabrication of large format, small pixel, high readout detectors.

The X-ray Absorber in the X-ray Transient NLS1 WPVS 007

NASA Astrophysics Data System (ADS)

Grupe, Dirk

This proposal is for a funding request for an approved XMM-Newton observations of the X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007. The request is for 4 month of salary for the PI for one year in order to do the data analysis, publish the results, and attend an international AGN meeting. XMM will observe WPVS 007 in June 2010 simultaneously with HST, Chandra, and Swift. The goal is to establish a tight connection between the UV broad absorption line troughs found in FUSE observations and the strong partial covering absorber feature found by Swift. WPVS 007 showed a dramatic transformation into a Broad Absorption line QSO like AGN between a 1996 HST observation and a 2003 FUSE observation. Several Swift monitoring observations have suggested that the absorber may have started to disappear. Therefore it is crucial for our HST COS UV spectroscopy to know what the status of the X-ray absorber is. The XMM observation will provide a well-exposed X-ray spectrum even if WPVS 007 will be in a low flux state. This spectrum will enable us to put constraints on the absorption column density and covering fraction of the partial covering absorber.

Can Radio Emission From Luminous Obscured AGN Blow Kpc-scale Ionized Outflows?

NASA Astrophysics Data System (ADS)

Goulding, Andy

2017-09-01

We propose joint VLA radio and Chandra X-ray to observe 4 AGN selected from the SDSS-BOSS and the Hyper Suprime-Cam surveys that present spectacular extended outflowing [O III] regions, reaching up to 50kpc in diameter. Our proposed observations allow us to study the mechanical and kinematical output of the AGN through radio and X-ray observations, measure the fraction of the AGN bolometric luminosity that is transferred to the outflow, and to determine the morphology and spectral index (by producing high-res continuum maps) of the radio emission that may be co-spatial with the extended ionized AGN outflow. In turn, our study will determine what role the AGN plays in producing extended outflows, and hence, provide an in-depth understanding of the physical drivers of AGN feedback.

Can AGN and galaxy clusters explain the surface brightness fluctuations of the cosmic X-ray background?

NASA Astrophysics Data System (ADS)

Kolodzig, Alexander; Gilfanov, Marat; Hütsi, Gert; Sunyaev, Rashid

2017-04-01

Fluctuations of the surface brightness of cosmic X-ray background (CXB) carry unique information about faint and low-luminosity source populations, which is inaccessible for conventional large-scale structure (LSS) studies based on resolved sources. We used XBOOTES (5ks deep Chandra X-ray Observatory ACIS-I maps of the ˜ 9 deg2 Bootes field of the NOAO Deep Wide-Field Survey) to conduct the most accurate measurement to date of the power spectrum of fluctuations of the unresolved CXB on the angular scales of 3 arcsec-17 arcmin. We find that at sub-arcmin angular scales, the power spectrum is consistent with the active galactic nucleus (AGN) shot noise, without much need for any significant contribution from their one-halo term. This is consistent with the theoretical expectation that low-luminosity AGN reside alone in their dark matter haloes. However, at larger angular scales, we detect a significant LSS signal above the AGN shot noise. Its power spectrum, obtained after subtracting the AGN shot noise, follows a power law with the slope of -0.8 ± 0.1 and its amplitude is much larger than what can be plausibly explained by the two-halo term of AGN. We demonstrate that the detected LSS signal is produced by unresolved clusters and groups of galaxies. For the flux limit of the XBOOTES survey, their flux-weighted mean redshift equals ˜ 0.3, and the mean temperature of their intracluster medium (ICM), ≈ 1.4 keV, corresponds to the mass of M500 ˜ 1013.5 M⊙. The power spectrum of CXB fluctuations carries information about the redshift distribution of these objects and the spatial structure of their ICM on the linear scales of up to ˜Mpc, I.e. of the order of the virial radius.

X-ray long-term variations in the low-luminosity AGN NGC 835 and its circumnuclear emission

NASA Astrophysics Data System (ADS)

González-Martín, O.; Hernández-García, L.; Masegosa, J.; Márquez, I.; Rodríguez-Espinosa, J. M.; Acosta-Pulido, J. A.; Alonso-Herrero, A.; Dultzin, D.; Esparza Arredondo, D.

2016-03-01

Context. Obscured active galactic nuclei (AGNs) are thought to be very common in the Universe. Observations and surveys have shown that the number of sources increases for near galaxies and at the low-luminosity regime (the so-called LLAGNs). Furthermore, many AGNs show changes in their obscuration properties at X-rays that may suggest a configuration of clouds very close to the accretion disk. However, these variations could also be due to changes in the intrinsic continuum of the source. It is therefore important to study nearby AGN to better understand the locus and distribution of clouds in the neighbourhood of the nucleus. Aims: We aim to study the nuclear obscuration of LLAGN NGC 835 and its extended emission using mid-infrared observations. Methods: We present sub-arcsecond-resolution mid-infrared 11.5 μm imaging of the LLAGN galaxy NGC 835 obtained with the instrument CanariCam in the Gran Telescopio CANARIAS (GTC), archival Spitzer/IRS spectroscopy, and archival Chandra data observed in 2000, 2008, and 2013. Results: The GTC/CanariCam 11.5 μm image reveals faint extended emission out to ~6 arcsec. We obtained a nuclear flux of F(11.5 μm) ~ 18 mJy, whereas the extended emission accounts for 90% of the total flux within the 6 arcsec. This means that the low angular resolution (~4 arcsec) IRS spectrum is dominated by this extended emission and not by the AGN. This is clearly seen in the Spitzer/IRS spectrum, which resembles that of star-forming galaxies. Although the extended soft X-ray emission shows some resemblance with that of the mid-infrared, the knots seen at X-rays are mostly located in the inner side of this mid-infrared emission. The nuclear X-ray spectrum of the source has undergone a spectral change between 2000/2008 and 2013. We argue that this variation is most probably due to changes in the hydrogen column density from ~8 × 1023 cm-2 to ~3 × 1023 cm-2. NGC 835 therefore is one of the few LLAGN, together with NGC 1052, in which changes in

Enhancement of AGN Activity in Distant Galaxy Clusters

NASA Astrophysics Data System (ADS)

Krishnan, Charutha; Hatch, Nina; Almaini, Omar

2017-07-01

I present our recent study of the prevalence of X-ray AGN in the high-redshift protocluster Cl 0218.3-0510 at z=1.62, and review the implications for our understanding of galaxy evolution. There has long been a consensus that X-ray AGN avoid clusters in the local universe, particularly their cores. The high-redshift universe appears to not follow these trends, as there is a reversal in the local anti-correlation between galaxy density and AGN activity. In this z=1.62 protocluster, we find a large overdensity of AGN by a factor of 23, and an enhancement in the AGN fraction among massive galaxies relative to the field by a factor of 2. I will discuss the comparison of the properties of AGN in the protocluster to the field, and explain how our results point towards similar triggering mechanisms in the two environments. I will also describe how our study of the morphologies of these galaxies provide tentative evidence towards galaxy mergers and interactions being responsible for triggering AGN, and explain the reversal of the local anti-correlation between galaxy density and AGN activity.

The effect of AGN feedback on the X-ray morphologies of clusters: Simulations vs. observations

NASA Astrophysics Data System (ADS)

Chon, Gayoung; Puchwein, Ewald; Böhringer, Hans

2016-07-01

Clusters of galaxies probe the large-scale distribution of matter and are a useful tool to test the cosmological models by constraining cosmic structure growth and the expansion of the Universe. It is the scaling relations between mass observables and the true mass of a cluster through which we obtain the cosmological constraints by comparing to theoretical cluster mass functions. These scaling relations are, however, heavily influenced by cluster morphology. The presence of the slight tension in recent cosmological constraints on Ωm and σ8 based on the CMB and clusters has boosted the interests in looking for possible sources for the discrepancy. Therefore we study here the effect of active galactic nucleus (AGN) feedback as one of the major mechanisms modifying the cluster morphology influencing scaling relations. It is known that AGN feedback injects energies up to 1062 erg into the intracluster medium, controls the heating and cooling of a cluster, and re-distributes cold gas from the centre to outer radii. We have also learned that cluster simulations with AGN feedback can reproduce observed cluster properties, for example, the X-ray luminosity, temperature, and cooling rate at the centre better than without the AGN feedback. In this paper using cosmological hydrodynamical simulations we investigate how the AGN feedback changes the X-ray morphology of the simulated systems, and compare this to the observed Representative XMM-Newton Cluster Structure Survey (REXCESS) clusters. We apply two substructure measures, centre shifts (w) and power ratios (e.g. P3/P0), to characterise the cluster morphology, and find that our simulated clusters are more substructured than the observed clusters based on the values of w and P3/P0. We also show that the degree of this discrepancy is affected by the inclusion of AGN feedback. While the clusters simulated with the AGN feedback are in much better agreement with the REXCESS LX-T relation, they are also more substructured

The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV

NASA Astrophysics Data System (ADS)

Lansbury, G. B.; Alexander, D. M.; Aird, J.; Gandhi, P.; Stern, D.; Koss, M.; Lamperti, I.; Ajello, M.; Annuar, A.; Assef, R. J.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Brandt, W. N.; Brightman, M.; Chen, C.-T. J.; Civano, F.; Comastri, A.; Del Moro, A.; Fuentes, C.; Harrison, F. A.; Marchesi, S.; Masini, A.; Mullaney, J. R.; Ricci, C.; Saez, C.; Tomsick, J. A.; Treister, E.; Walton, D. J.; Zappacosta, L.

2017-09-01

We identify sources with extremely hard X-ray spectra (I.e., with photon indices of {{Γ }}≲ 0.6) in the 13 deg2 NuSTAR serendipitous survey, to search for the most highly obscured active galactic nuclei (AGNs) detected at > 10 {keV}. Eight extreme NuSTAR sources are identified, and we use the NuSTAR data in combination with lower-energy X-ray observations (from Chandra, Swift XRT, and XMM-Newton) to characterize the broadband (0.5-24 keV) X-ray spectra. We find that all of the extreme sources are highly obscured AGNs, including three robust Compton-thick (CT; {N}{{H}}> 1.5× {10}24 cm-2) AGNs at low redshift (z< 0.1) and a likely CT AGN at higher redshift (z = 0.16). Most of the extreme sources would not have been identified as highly obscured based on the low-energy (< 10 keV) X-ray coverage alone. The multiwavelength properties (e.g., optical spectra and X-ray-mid-IR luminosity ratios) provide further support for the eight sources being significantly obscured. Correcting for absorption, the intrinsic rest-frame 10-40 keV luminosities of the extreme sources cover a broad range, from ≈ 5× {10}42 to 1045 erg s-1. The estimated number counts of CT AGNs in the NuSTAR serendipitous survey are in broad agreement with model expectations based on previous X-ray surveys, except for the lowest redshifts (z< 0.07), where we measure a high CT fraction of {f}{CT}{obs}={30}-12+16 % . For the small sample of CT AGNs, we find a high fraction of galaxy major mergers (50% ± 33%) compared to control samples of “normal” AGNs.

Probing large-scale structure with large samples of X-ray selected AGN. I. Baryonic acoustic oscillations

NASA Astrophysics Data System (ADS)

Hütsi, Gert; Gilfanov, Marat; Kolodzig, Alexander; Sunyaev, Rashid

2014-12-01

We investigate the potential of large X-ray-selected AGN samples for detecting baryonic acoustic oscillations (BAO). Though AGN selection in X-ray band is very clean and efficient, it does not provide redshift information, and thus needs to be complemented with an optical follow-up. The main focus of this study is (i) to find the requirements needed for the quality of the optical follow-up and (ii) to formulate the optimal strategy of the X-ray survey, in order to detect the BAO. We demonstrate that redshift accuracy of σ0 = 10-2 at z = 1 and the catastrophic failure rate of ffail ≲ 30% are sufficient for a reliable detection of BAO in future X-ray surveys. Spectroscopic quality redshifts (σ0 = 10-3 and ffail ~ 0) will boost the confidence level of the BAO detection by a factor of ~2. For meaningful detection of BAO, X-ray surveys of moderate depth of Flim ~ few 10-15 erg s-1/cm2 covering sky area from a few hundred to ~ten thousand square degrees are required. The optimal strategy for the BAO detection does not necessarily require full sky coverage. For example, in a 1000 day-long survey by an eROSITA type telescope, an optimal strategy would be to survey a sky area of ~9000 deg2, yielding a ~16σ BAO detection. A similar detection will be achieved by ATHENA+ or WFXT class telescopes in a survey with a duration of 100 days, covering a similar sky area. XMM-Newton can achieve a marginal BAO detection in a 100-day survey covering ~400 deg2. These surveys would demand a moderate-to-high cost in terms the optical follow-ups, requiring determination of redshifts of ~105 (XMM-Newton) to ~3 × 106 objects (eROSITA, ATHENA+, and WFXT) in these sky areas.

Compton-thick AGN at high and low redshift

NASA Astrophysics Data System (ADS)

Akylas, A.; Georgantopoulos, I.; Corral, A.; Ranalli, P.; Lanzuisi, G.

2017-10-01

The most obscured sources detected in X-ray surveys, the Compton-thick AGN present great interest both because they represent the hidden side of accretion but also because they may signal the AGN birth. We analyse the NUSTAR observations from the serendipitous observations in order to study the Compton-thick AGN at the deepest possible ultra-hard band (>10 keV). We compare our results with our SWIFT/BAT findings in the local Universe, as well as with our results in the CDFS and COSMOS fields. We discuss the comparison with X-ray background synthesis models finding that a low fraction of Compton-thick sources (about 15 per cent of the obscured population) is compatible with both the 2-10keV band results and those at harder energies.

Constraining MHD Disk-Winds with X-ray Absorbers

NASA Astrophysics Data System (ADS)

Fukumura, Keigo; Tombesi, F.; Shrader, C. R.; Kazanas, D.; Contopoulos, J.; Behar, E.

2014-01-01

From the state-of-the-art spectroscopic observations of active galactic nuclei (AGNs) the robust features of absorption lines (e.g. most notably by H/He-like ions), called warm absorbers (WAs), have been often detected in soft X-rays (< 2 keV). While the identified WAs are often mildly blueshifted to yield line-of-sight velocities up to ~100-3,000 km/sec in typical X-ray-bright Seyfert 1 AGNs, a fraction of Seyfert galaxies such as PG 1211+143 exhibits even faster absorbers (v/ 0.1-0.2) called ultra-fast outflows (UFOs) whose physical condition is much more extreme compared with the WAs. Motivated by these recent X-ray data we show that the magnetically- driven accretion-disk wind model is a plausible scenario to explain the characteristic property of these X-ray absorbers. As a preliminary case study we demonstrate that the wind model parameters (e.g. viewing angle and wind density) can be constrained by data from PG 1211+143 at a statistically significant level with chi-squared spectral analysis. Our wind models can thus be implemented into the standard analysis package, XSPEC, as a table spectrum model for general analysis of X-ray absorbers.

X-raying the most luminous quasars at cosmic noon

NASA Astrophysics Data System (ADS)

Piconcelli, E.; Martocchia, S.; Zappacosta, L.

2017-10-01

The WISE/SDSS hyper-luminous (log L_Bol > 47) quasar (WISSH) survey is performing a multi-band systematic exploration of the most luminous AGN shining at the golden epoch of AGN activity (i.e. z ˜ 2-4). This gives the opportunity of overcoming the luminosity bias in the exploration of the accretion phenomenon and the impact of AGN radiative output on the host. In this talk, I present the results of our study of the X-ray spectra of 40 WISSH quasars. I report on the correlations between the X-ray and Optical, UV and MIR properties, and the behavior of the X-ray bolometric correction at the brightest end of the luminosity function. I discuss the relative X-ray weakness of these very powerful quasars compared to less luminous AGN. This X-ray weakness can be a key ingredient for accelerating powerful ionized outflows (ubiquitously revealed in the UV/optical spectra of WISSH quasars) and, furthermore, radiation-driven winds can be effective in destroying the X-ray corona and quenching the X-ray emission. The potential offered by Athena in studying this extreme class of AGN is also discussed.

X-Ray Emission from Active Galactic Nuclei with Intermediate-Mass Black Holes

NASA Astrophysics Data System (ADS)

Dewangan, G. C.; Mathur, S.; Griffiths, R. E.; Rao, A. R.

2008-12-01

We present a systematic X-ray study of eight active galactic nuclei (AGNs) with intermediate-mass black holes (MBH ~ 8-95 × 104 M⊙) based on 12 XMM-Newton observations. The sample includes the two prototype AGNs in this class—NGC 4395 and POX 52 and six other AGNs discovered with the Sloan Digitized Sky Survey. These AGNs show some of the strongest X-ray variability, with the normalized excess variances being the largest and the power density break timescales being the shortest observed among radio-quiet AGNs. The excess-variance-luminosity correlation appears to depend on both the BH mass and the Eddington luminosity ratio. The break timescale-black hole mass relations for AGN with IMBHs are consistent with that observed for massive AGNs. We find that the FWHM of the Hβ/Hα line is uncorrelated with the BH mass, but shows strong anticorrelation with the Eddington luminosity ratio. Four AGNs show clear evidence for soft X-ray excess emission (kTin ~ 150-200 eV). X-ray spectra of three other AGNs are consistent with the presence of the soft excess emission. NGC 4395 with lowest L/LEdd lacks the soft excess emission. Evidently small black mass is not the primary driver of strong soft X-ray excess emission from AGNs. The X-ray spectral properties and optical-to-X-ray spectral energy distributions of these AGNs are similar to those of Seyfert 1 galaxies. The observed X-ray/UV properties of AGNs with IMBHs are consistent with these AGNs being low-mass extensions of more massive AGNs, those with high Eddington luminosity ratio looking more like narrow-line Seyfert 1 s and those with low L/LEdd looking more like broad-line Seyfert 1 galaxies.

X-ray evidence for ultra-fast outflows in AGNs

NASA Astrophysics Data System (ADS)

Tombesi, Francesco; Sambruna, Rita; Braito, Valentina; Reeves, James; Reynolds, Christopher; Cappi, Massimo

2012-07-01

X-ray evidence for massive, highly ionized, ultra-fast outflows (UFOs) has been recently reported in a number of AGNs through the detection of blue-shifted Fe XXV/XXVI absorption lines. We present the results of a comprehensive spectral analysis of a large sample of 42 local Seyferts and 5 radio galaxies observed with XMM-Newton and Suzaku. We assessed the global detection significance of the absorption lines and performed a detailed photo-ionization modeling. We find that UFOs are common phenomena, being present in >40% of the sources. Their outflow velocity distribution is in the range ˜0.03--0.3c, with mean value of ˜0.14c. The ionization parameter is very high, in the range logξ˜3--6 erg~s^{-1}~cm, and the associated column densities are also large, in the range ˜10^{22}--10^{24} cm^{-2}. Their location is constrained at ˜0.0003--0.03pc (˜10^2--10^4 r_s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are in the interval ˜0.01--1M_{⊙}~yr^{-1} and the associated mechanical power is high, in the range ˜10^{43}--10^{45} erg/s. Therefore, UFOs are capable to provide a significant contribution to the AGN cosmological feedback and their study can provide important clues on the connection between accretion disks, winds and jets.

Large-scale clustering measurements with photometric redshifts: comparing the dark matter haloes of X-ray AGN, star-forming and passive galaxies at z ≈ 1

NASA Astrophysics Data System (ADS)

Georgakakis, A.; Mountrichas, G.; Salvato, M.; Rosario, D.; Pérez-González, P. G.; Lutz, D.; Nandra, K.; Coil, A.; Cooper, M. C.; Newman, J. A.; Berta, S.; Magnelli, B.; Popesso, P.; Pozzi, F.

2014-10-01

We combine multi-wavelength data in the AEGIS-XD and C-COSMOS surveys to measure the typical dark matter halo mass of X-ray selected active galactic nuclei (AGN) [LX(2-10 keV) > 1042 erg s- 1] in comparison with far-infrared selected star-forming galaxies detected in the Herschel/PEP survey (PACS Evolutionary Probe; LIR > 1011 L⊙) and quiescent systems at z ≈ 1. We develop a novel method to measure the clustering of extragalactic populations that uses photometric redshift probability distribution functions in addition to any spectroscopy. This is advantageous in that all sources in the sample are used in the clustering analysis, not just the subset with secure spectroscopy. The method works best for large samples. The loss of accuracy because of the lack of spectroscopy is balanced by increasing the number of sources used to measure the clustering. We find that X-ray AGN, far-infrared selected star-forming galaxies and passive systems in the redshift interval 0.6 < z < 1.4 are found in haloes of similar mass, log MDMH/(M⊙ h-1) ≈ 13.0. We argue that this is because the galaxies in all three samples (AGN, star-forming, passive) have similar stellar mass distributions, approximated by the J-band luminosity. Therefore, all galaxies that can potentially host X-ray AGN, because they have stellar masses in the appropriate range, live in dark matter haloes of log MDMH/(M⊙ h-1) ≈ 13.0 independent of their star formation rates. This suggests that the stellar mass of X-ray AGN hosts is driving the observed clustering properties of this population. We also speculate that trends between AGN properties (e.g. luminosity, level of obscuration) and large-scale environment may be related to differences in the stellar mass of the host galaxies.

Destruction of PAHs by X-Rays in circumnuclear regions of AGNs

NASA Astrophysics Data System (ADS)

Monfredini, T.; Wolff, W.; Boechat-Roberty, H. M.; Sales, D. A.; Pastoriza, M. G.

2017-07-01

Emission bands associated with PAH molecules are observed in the direction of some classes of AGNs like Seyfert 2, LINERs and obscured quasars (e.g. Kaneda et al., 2008, Sansigre et al., 2008 and Sales et al. 2013). The molecular stability in these environments suggest the presence of very dense gas (˜ 1023-24 cm-2) to shield the cloud of PAHs against X-ray radiation (Voit, 1992, Tielens, 2011, Sales et al., 2013). We examined the photochemistry of simple PAHs: naphtalene (C10H8), anthracene (C14H10), methyl-anthracene (C15H12) and pyrene (C16H10) at the photon energies of 275 eV, 310 eV, 1900 eV and 2500 eV in order to apply the findings at the AGN scenario. The absolute single and double photoionization and photodissociation cross sections were determined for each molecule at each energy. Their ionization and destruction induced by X-rays were examined in the conditions of the circumnuclear region of NGC 1808, a Seyfert 2 galaxy, where PAH emission was detected at 26 pc from the central object (Sales et al., 2013). It was verified the higher photostability of PAHs without functional groups attached. At higher photon energies, the results suggest a higher production yield of double charged PAHs in comparision with the single charged ones (e.g., 2 × higher for double ionized naphtalene at 2500 eV). The production of double charged molecules increase with the size of the molecules. We also discuss a minimum formation rate of PAH to balance the photodestruction rate and maintain a minimum density for their detection (e.g. 4,0× 10-7 M⊙ year-1 for a column density NH of 1023 cm-2 at 26 pc).

X-ray fluctuation timescale and Black Hole mass relation in AGN

NASA Astrophysics Data System (ADS)

Wandel, Amri; Malkan, Mathew

We analyze the fluctuations in the X-ray flux of 20 AGN (mainly Seyfert 1 galaxies) monitored by RXTE and XMM-Newton with a sampling frequency ranging from hours to years, using structure function (SF) analysis. We derive SFs over four orders of magnitude in the time domain (0.03-300 days). Most objects show a characteristic time scale, where the SF flattens or changes slope. For 10 objects with published power-spectral density (PSD) the break time scales in the SF and PSD are similar and show a good correlation. We also find a significant correlation between the SF timescale and the mass of the central black hole, determined for most objects by reverberation mapping.

Chandra-SDSS Normal and Star-Forming Galaxies. I. X-Ray Source Properties of Galaxies Detected by the Chandra X-Ray Observatory in SDSS DR2

NASA Astrophysics Data System (ADS)

Hornschemeier, A. E.; Heckman, T. M.; Ptak, A. F.; Tremonti, C. A.; Colbert, E. J. M.

2005-01-01

We have cross-correlated X-ray catalogs derived from archival Chandra X-Ray Observatory ACIS observations with a Sloan Digital Sky Survey Data Release 2 (DR2) galaxy catalog to form a sample of 42 serendipitously X-ray-detected galaxies over the redshift interval 0.03X-ray-studied samples of normal galaxies and those in the deepest X-ray surveys. Our chief purpose is to compare optical spectroscopic diagnostics of activity (both star formation and accretion) with X-ray properties of galaxies. Our work supports a normalization value of the X-ray-star formation rate correlation consistent with the lower values published in the literature. The difference is in the allocation of X-ray emission to high-mass X-ray binaries relative to other components, such as hot gas, low-mass X-ray binaries, and/or active galactic nuclei (AGNs). We are able to quantify a few pitfalls in the use of lower resolution, lower signal-to-noise ratio optical spectroscopy to identify X-ray sources (as has necessarily been employed for many X-ray surveys). Notably, we find a few AGNs that likely would have been misidentified as non-AGN sources in higher redshift studies. However, we do not find any X-ray-hard, highly X-ray-luminous galaxies lacking optical spectroscopic diagnostics of AGN activity. Such sources are members of the ``X-ray-bright, optically normal galaxy'' (XBONG) class of AGNs.

Low-Luminosity AGN As Analogues of Galactic Black Holes in the Low/Hard State: Evidence from X-Ray Timing of NGC 4258

NASA Technical Reports Server (NTRS)

Markowitz, A.; Uttley, P.

2005-01-01

We present a broadband power spectral density function (PSD) measured from extensive RXTE monitoring data of the low-luminosity AGN NGC 4258, which has an accurate, maser-determined black hole mass of (3.9 plus or minus 0.1) x 10(exp 7) solar mass. We constrain the PSD break time scale to be greater than 4.5 d at greater than 90% confidence, which appears to rule out the possibility that NGC 4258 is an analogue of black hole X-ray binaries (BHXRBs) in the high/soft state. In this sense, the PSD of NGC 4258 is different to that of some more-luminous Seyferts, which appear similar to the PSDs of high/soft state X-ray binaries. This result supports previous analogies between LLAGN and X-ray binaries in the low/hard state based on spectral energy distributions, indicating that the AGN/BHXRB analogy is valid across a broad range of accretion rates.

X-Ray Bolometric Corrections for Compton-thick Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Brightman, M.; Baloković, M.; Ballantyne, D. R.; Bauer, F. E.; Boorman, P.; Buchner, J.; Brandt, W. N.; Comastri, A.; Del Moro, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Koss, M.; Lanz, L.; Masini, A.; Ricci, C.; Stern, D.; Vasudevan, R.; Walton, D. J.

2017-07-01

We present X-ray bolometric correction factors, {κ }{Bol} (≡{L}{Bol}/{L}{{X}}), for Compton-thick (CT) active galactic nuclei (AGNs) with the aim of testing AGN torus models, probing orientation effects, and estimating the bolometric output of the most obscured AGNs. We adopt bolometric luminosities, {L}{Bol}, from literature infrared (IR) torus modeling and compile published intrinsic 2-10 keV X-ray luminosities, {L}{{X}}, from X-ray torus modeling of NuSTAR data. Our sample consists of 10 local CT AGNs, where both of these estimates are available. We test for systematic differences in {κ }{Bol} values produced when using two widely used IR torus models and two widely used X-ray torus models, finding consistency within the uncertainties. We find that the mean {κ }{Bol} of our sample in the range of {L}{Bol}≈ {10}42{--}{10}45 {erg} {{{s}}}-1 is log10 {κ }{Bol} = 1.44 ± 0.12 with an intrinsic scatter of ˜0.2 dex, and that our derived {κ }{Bol} values are consistent with previously established relationships between {κ }{Bol} and {L}{Bol} and {κ }{Bol} and Eddington ratio ({λ }{Edd}). We investigate if {κ }{Bol} is dependent on {N}{{H}} by comparing our results on CT AGNs to published results on less-obscured AGNs, finding no significant dependence. Since many of our sample are megamaser AGNs, known to be viewed edge-on, and furthermore under the assumptions of AGN unification whereby unobscured AGNs are viewed face-on, our result implies that the X-ray emitting corona is not strongly anisotropic. Finally, we present {κ }{Bol} values for CT AGNs identified in X-ray surveys as a function of their observed {L}{{X}}, where an estimate of their intrinsic {L}{{X}} is not available, and redshift, useful for estimating the bolometric output of the most obscured AGNs across cosmic time.

XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Barcons, X.; Carrera, F. J.; Ceballos, M. T.; Hasinger, G.; Lehmann, I.; Fabian, A. C.; Streblyanska, A.

2005-12-01

This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise (>500 source counts) for all objects down to 0.2-12 keV fluxes of 5×10-15 erg cm-2 s-1 (flux limit of 6×10-16 erg cm-2 s-1 in the 0.5-2 and 2-10 keV bands). At the time of the analysis, we had optical spectroscopic identifications for 60% of the sources, 46 being optical type-1 AGN and 28 optical type-2 AGN. Using a single power law model our sources' average spectral slope hardens at faint 0.5-2 keV fluxes but not at faint 2-10 keV fluxes. We have been able to explain this effect in terms of an increase in X-ray absorption at faint fluxes. We did not find in our data any evidence for the existence of a population of faint intrinsically harder sources. The average spectral slope of our sources is 1.9, with an intrinsic dispersion of 0.28. We detected X-ray absorption (F-test significance ≥95%) in 37% of the sources, 10% in type-1 AGN (rest-frame {NH ˜ 1.6 × 1021{-}1.2 × 1022 cm-2}) and 77% (rest-frame {NH ˜ 1.5 ×1021{-}4× 1023 cm-2}) in type-2 AGN. Using X-ray fluxes corrected for absorption, the fraction of absorbed objects and the absorbing column density distribution did not vary with X-ray flux. Our type-1 and type-2 AGN do not appear to have different continuum shapes, but the distribution of intrinsic (rest-frame) absorbing column densities is different among both classes. A significant fraction of our type-2 AGN (5 out of 28) were found to display no substantial absorption ({NH<1021 cm-2}). We discuss possible interpretations to this in terms of Compton-thick AGN and intrinsic Broad Line Region properties. An emission line compatible with Fe Kα was detected in 8 sources (1 type-1 AGN, 5 type-2 AGN and 2 unidentified) with rest frame equivalent widths

Active Galactic Nuclei and X-ray Ovservations

NASA Astrophysics Data System (ADS)

Vasylenko, A. A.; Zhdanov, V. I.; Fedorova, E. V.

2016-11-01

Active galactic nuclei (AGN) are the brightest objects in the Universe and their brightness is mainly caused by accretion of m atter onto supermassive black holes (SMBH). This is the common reason of the AGN activity. However, every AGN has differences and fine features, which are the subject of an intensive investigation. The occurrence of such highly-relativistic objects as SMBH residing at the AGN core makes them an excellent laboratory for testing the fundamental physical theories. The X-rays and gamma-rays generated in a corona of an accretion disc around SMBH yield valuable information for these tests, the radiation in the range of 1-100 keV being at present the most informative source. However, there are a number of obstacles for such a study due to different physical processes that complicate the interpretation of observations in different bands of the electromagnetic radiation. In this paper, we review the current concepts concerning the structure of AGNs with a focus on the central part of these objects th at require relativistic theories for their understanding. The basic notions of the unified AGN schemes are considered; some modifications are reviewed. The paper contains the following sections. I. Introduction; II. Observational manifestations and classification of galaxies with active nuclei (II.A. Optical observations; II.B. Radio observations; II.C. X-ray data; II.D Infrared data; II.E. AGN anatomy with multywave data); III. AGN "central machine"; III.A. Black holes; III.B. Accretion disc types; III.C. Corona; III.D. AGN unified scheme); IV. Simulation X-ray AGN spectra (IV.A. The power-law contimuum and the exponential cut-off; IV.B. The absorption of X-rays; IV.C. Reflection; IV.D. Fe K a line; IV.E. Spin paradigm); V. AGN as a laboratory to test the fundamental interactions (V.A. Strong gravitational fields; V.B. Dynamic dark energy near compact astrophysical objects

The Disk-Jet Connection in Radio-Loud AGN: The X-Ray Perspective

NASA Technical Reports Server (NTRS)

Sambruna, Rita

2008-01-01

Unification schemes assume that radio-loud active galactic nuclei (AGN) contain an accretion disk and a relativistic jet perpendicular to the disk, and an obscuring molecular torus. The jet dominance decreases with larger viewing angles from blazars to Broad-Line and Narrow-Line Radio Galaxies. A fundamental question is how accretion and ejecta are related. The X-rays provide a convenient window to study these issues, as they originate in the innermost nuclear regions and penetrate large obscuring columns. I review the data, using observations by Chandra but also from other currently operating high-energy experiments. Synergy with the upcoming GLAST mission will also be highlighted.

NUCLEAR X-RAY PROPERTIES OF THE PECULIAR RADIO-LOUD HIDDEN AGN 4C+29.30

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolewska, M. A.; Siemiginowska, Aneta; Migliori, G.

2012-10-20

We present results from a study of nuclear emission from a nearby radio galaxy, 4C+29.30, over a broad 0.5-200 keV X-ray band. This study used new XMM-Newton ({approx}17 ks) and Chandra ({approx}300 ks) data, and archival Swift/BAT data from the 58 month catalog. The hard (>2 keV) X-ray spectrum of 4C+29.30 can be decomposed into an intrinsic hard power law ({Gamma} {approx} 1.56) modified by a cold absorber with an intrinsic column density N {sub H,z} {approx} 5 Multiplication-Sign 10{sup 23} cm{sup -2}, and its reflection (|{Omega}/2{pi}| {approx} 0.3) from a neutral matter including a narrow iron K{alpha} emission linemore » at a rest-frame energy {approx}6.4 keV. The reflected component is less absorbed than the intrinsic one with an upper limit on the absorbing column of N {sup refl} {sub H,z} < 2.5 Multiplication-Sign 10{sup 22} cm{sup -2}. The X-ray spectrum varied between the XMM-Newton and Chandra observations. We show that a scenario invoking variations of the normalization of the power law is favored over a model with variable intrinsic column density. X-rays in the 0.5-2 keV band are dominated by diffuse emission modeled with a thermal bremsstrahlung component with temperature {approx}0.7 keV, and contain only a marginal contribution from the scattered power-law component. We hypothesize that 4C+29.30 belongs to a class of 'hidden' active galactic nuclei containing a geometrically thick torus. However, unlike the majority of hidden AGNs, 4C+29.30 is radio-loud. Correlations between the scattering fraction and Eddington luminosity ratio, and between black hole mass and stellar velocity dispersion, imply that 4C+29.30 hosts a black hole with {approx}10{sup 8} M {sub Sun} mass.« less

High-redshift Galaxies and Black Holes Detectable with the JWST: A Population Synthesis Model from Infrared to X-Rays

NASA Astrophysics Data System (ADS)

Volonteri, Marta; Reines, Amy E.; Atek, Hakim; Stark, Daniel P.; Trebitsch, Maxime

2017-11-01

The first billion years of the Universe has been a pivotal time: stars, black holes (BHs), and galaxies formed and assembled, sowing the seeds of galaxies as we know them today. Detecting, identifying, and understanding the first galaxies and BHs is one of the current observational and theoretical challenges in galaxy formation. In this paper we present a population synthesis model aimed at galaxies, BHs, and active galactic nuclei (AGNs) at high redshift. The model builds a population based on empirical relations. The spectral energy distribution of galaxies is determined by age and metallicity, and that of AGNs by BH mass and accretion rate. We validate the model against observations, and predict properties of galaxies and AGN in other wavelength and/or luminosity ranges, estimating the contamination of stellar populations (normal stars and high-mass X-ray binaries) for AGN searches from the infrared to X-rays, and vice versa for galaxy searches. For high-redshift galaxies with stellar ages < 1 {Gyr}, we find that disentangling stellar and AGN emission is challenging at restframe UV/optical wavelengths, while high-mass X-ray binaries become more important sources of confusion in X-rays. We propose a color-color selection in the James Webb Space Telescope bands to separate AGN versus star-dominated galaxies in photometric observations. We also estimate the AGN contribution, with respect to massive, hot, and metal-poor stars, at driving high-ionization lines, such as C IV and He II. Finally, we test the influence of the minimum BH mass and occupation fraction of BHs in low-mass galaxies on the restframe UV/near-IR and X-ray AGN luminosity function.

X-ray observations of dust obscured galaxies in the Chandra deep field south

NASA Astrophysics Data System (ADS)

Corral, A.; Georgantopoulos, I.; Comastri, A.; Ranalli, P.; Akylas, A.; Salvato, M.; Lanzuisi, G.; Vignali, C.; Koutoulidis, L.

2016-08-01

candidates, the non-detection of the line could be because of the low number of counts in their X-ray spectra, but their location in the L2-10 keV/L12 μm plot supports their CT classification. Although a higher number of CT sources could be hidden among the X-ray undetected DOGs, our results indicate that DOGs could be as well composed of only a fraction of CT AGN plus a number of moderate to highly absorbed AGN, as previously suggested. From our study of the X-ray undetected DOGs in the CDF-S, we estimate a percentage between 13 and 44% of CT AGN among the whole population of DOGs.

The NuSTAR Serendipitous Survey: The 40-month Catalog and the Properties of the Distant High-energy X-Ray Source Population

NASA Astrophysics Data System (ADS)

Lansbury, G. B.; Stern, D.; Aird, J.; Alexander, D. M.; Fuentes, C.; Harrison, F. A.; Treister, E.; Bauer, F. E.; Tomsick, J. A.; Baloković, M.; Del Moro, A.; Gandhi, P.; Ajello, M.; Annuar, A.; Ballantyne, D. R.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Chen, C.-T. J.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Forster, K.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R. C.; Jiang, B.; Jun, H. D.; Koss, M.; Marchesi, S.; Melo, A. D.; Mullaney, J. R.; Noirot, G.; Schulze, S.; Walton, D. J.; Zappacosta, L.; Zhang, W. W.

2017-02-01

We present the first full catalog and science results for the Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ≈20 Ms of effective exposure time over 331 fields, with an areal coverage of 13 deg2, and 497 sources detected in total over the 3-24 keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic follow-up. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily composed of active galactic nuclei (AGNs), detected over a large range in redshift from z = 0.002 to 3.4 (median of < z> =0.56), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from {log}({f}3-24{keV}/{erg} {{{s}}}-1 {{cm}}-2)≈ -14 to -11, and in rest-frame 10-40 keV luminosity, from {log}({L}10-40{keV}/{erg} {{{s}}}-1)≈ 39 to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower-energy (<10 keV) X-ray counterparts from XMM-Newton, Chandra, and Swift XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from ≈15% at the highest luminosities ({L}{{X}}> {10}44 erg s-1) to ≈80% at the lowest luminosities ({L}{{X}}< {10}43 erg s-1). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (I.e., the type 2 fraction) is {F}{Type2}={53}-15+14 % , for a well-defined subset of the 8-24 keV selected sample. This is higher, albeit at a low significance level, than the type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10 keV X-ray missions.

Identifying Distant AGNs

NASA Astrophysics Data System (ADS)

Trouille, Laura; Barger, Amy; Tremonti, Christy

2014-07-01

The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([OIII]/Hβ versus [NII]/Hα, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation (BPT-SF) from those dominated by AGN activity (BPT-AGN). Yet the BPT diagram is limited to z<0.5, the redshift at which [NII]λ6584 leaves the optical spectral window. Using the Sloan Digital Sky Survey (SDSS), we construct a new diagnostic, or TBT diagram, that is based on rest-frame g-z color, [NeIII]λ3869, and [OII]λλ3726+3729 and can be used for galaxies out to z<1.4. The TBT diagram identifies 98.7% of the SDSS BPT-AGN as TBT-AGN and 97% of the SDSS BPT-SF as TBT-SF. Furthermore, it identifies 97% of the OPTX Chandra X-ray selected AGNs as TBT-AGN. This is in contrast to the BPT diagram, which misidentifies 20% of X-ray selected AGNs as BPT-SF.

The NuSTAR  Extragalactic Surveys: X-Ray Spectroscopic Analysis of the Bright Hard-band Selected Sample

NASA Astrophysics Data System (ADS)

Zappacosta, L.; Comastri, A.; Civano, F.; Puccetti, S.; Fiore, F.; Aird, J.; Del Moro, A.; Lansbury, G. B.; Lanzuisi, G.; Goulding, A.; Mullaney, J. R.; Stern, D.; Ajello, M.; Alexander, D. M.; Ballantyne, D. R.; Bauer, F. E.; Brandt, W. N.; Chen, C.-T. J.; Farrah, D.; Harrison, F. A.; Gandhi, P.; Lanz, L.; Masini, A.; Marchesi, S.; Ricci, C.; Treister, E.

2018-02-01

We discuss the spectral analysis of a sample of 63 active galactic nuclei (AGN) detected above a limiting flux of S(8{--}24 {keV})=7× {10}-14 {erg} {{{s}}}-1 {{cm}}-2 in the multi-tiered NuSTAR extragalactic survey program. The sources span a redshift range z=0{--}2.1 (median < z> =0.58). The spectral analysis is performed over the broad 0.5–24 keV energy range, combining NuSTAR with Chandra and/or XMM-Newton data and employing empirical and physically motivated models. This constitutes the largest sample of AGN selected at > 10 {keV} to be homogeneously spectrally analyzed at these flux levels. We study the distribution of spectral parameters such as photon index, column density ({N}{{H}}), reflection parameter ({\\boldsymbol{R}}), and 10–40 keV luminosity ({L}{{X}}). Heavily obscured ({log}[{N}{{H}}/{{cm}}-2]≥slant 23) and Compton-thick (CT; {log}[{N}{{H}}/{{cm}}-2]≥slant 24) AGN constitute ∼25% (15–17 sources) and ∼2–3% (1–2 sources) of the sample, respectively. The observed {N}{{H}} distribution agrees fairly well with predictions of cosmic X-ray background population-synthesis models (CXBPSM). We estimate the intrinsic fraction of AGN as a function of {N}{{H}}, accounting for the bias against obscured AGN in a flux-selected sample. The fraction of CT AGN relative to {log}[{N}{{H}}/{{cm}}-2]=20{--}24 AGN is poorly constrained, formally in the range 2–56% (90% upper limit of 66%). We derived a fraction (f abs) of obscured AGN ({log}[{N}{{H}}/{{cm}}-2]=22{--}24) as a function of {L}{{X}} in agreement with CXBPSM and previous z< 1 X-ray determinations. Furthermore, f abs at z=0.1{--}0.5 and {log}({L}{{x}}/{erg} {{{s}}}-1)≈ 43.6{--}44.3 agrees with observational measurements/trends obtained over larger redshift intervals. We report a significant anti-correlation of R with {L}{{X}} (confirmed by our companion paper on stacked spectra) with considerable scatter around the median R values.

An XMM-Newton spectral survey of 12 μm selected galaxies - II. Implications for AGN selection and unification

NASA Astrophysics Data System (ADS)

Brightman, Murray; Nandra, Kirpal

2011-07-01

We present a multi-waveband analysis of a 126-galaxy sub-sample of the 12 μm galaxy sample (12MGS), for which we have carried out a detailed X-ray spectral analysis in a previous paper. We determine the activity class of the galaxies by way of optical-line ratio diagnostics and characterize the optical classes by their X-ray, 12 μm and [O III] luminosities and X-ray spectral properties. Our most interesting results from this investigation are as follows. (i) Seyfert (Sy) 1s and Sy2s show a significantly different X-ray luminosity distributions from each other. (ii) Sy2 galaxies with a detection of a hidden broad-line region show a significantly higher X-ray luminosity than those without a detection, supporting the findings of Tran. (iii) Sy1s also present a significantly different 12 μm luminosity distribution from both intermediate Sy types and Sy2s. (iv) The Sy2 fraction decreases towards high X-ray luminosities. (v) X-ray indications of active galactic nuclei (AGN) power agree well with the optical classifications. (vi) There is X-ray evidence for the presence of an AGN in 17 per cent of H II/AGN composite galaxies and 40 per cent of LINERs. (vii) We advocate the use of a 2-10 keV X-ray luminosity of 1041 erg s-1 in the X-ray selection of AGN, rather than 1042 erg s-1, which we find gives a contamination rate of only 3 per cent from star-forming galaxies. (viii) From an analysis of the X-ray power-law index, Γ, we find that Sy1s and Sy2 have the same intrinsic distributions, implying that the central engines are the same, in support of AGN unification schemes. (ix) In 24 per cent of cases the absorption measured in the X-ray spectra does not correspond directly to that implied in the optical band from the visibility of the broad-line regions (BLRs), which is in conflict with AGN unification schemes. (x) We confirm the previous work showing that the obscured fraction in AGN declines at high X-ray luminosity, but also find a decrease at low luminosity having

Infrared-faint radio sources: a cosmological view. AGN number counts, the cosmic X-ray background and SMBH formation

NASA Astrophysics Data System (ADS)

Zinn, P.-C.; Middelberg, E.; Ibar, E.

2011-07-01

Context. Infrared-faint radio sources (IFRS) are extragalactic emitters clearly detected at radio wavelengths but barely detected or undetected at optical and infrared wavelengths, with 5σ sensitivities as low as 1 μJy. Aims: Spectral energy distribution (hereafter SED) modelling and analyses of their radio properties indicate that IFRS are consistent with a population of (potentially extremely obscured) high-redshift AGN at 3 ≤ z ≤ 6. We demonstrate some astrophysical implications of this population and compare them to predictions from models of galaxy evolution and structure formation. Methods: We compiled a list of IFRS from four deep extragalactic surveys and extrapolated the IFRS number density to a survey-independent value of (30.8 ± 15.0) deg-2. We computed the IFRS contribution to the total number of AGN in the Universe to account for the cosmic X-ray background. By estimating the black hole mass contained in IFRS, we present conclusions for the SMBH mass density in the early universe and compare it to relevant simulations of structure formation after the Big Bang. Results: The number density of AGN derived from the IFRS density was found to be ~310 deg-2, which is equivalent to a SMBH mass density of the order of 103 M⊙ Mpc-3 in the redshift range 3 ≤ z ≤ 6. This produces an X-ray flux of 9 × 10-16 W m-2 deg-2 in the 0.5-2.0 keV band and 3 × 10-15 W m-2 deg-2 in the 2.0-10 keV band, in agreement with the missing unresolved components of the Cosmic X-ray Background. To address SMBH formation after the Big Bang we invoke a scenario involving both halo gas accretion and major mergers.

Ionized absorbers, ionized emitters, and the X-ray spectrum of active galactic nuclei

NASA Technical Reports Server (NTRS)

Netzer, Hagai

1993-01-01

Broad absorption features are common in the X-ray spectrum of low-luminosity AGNs. The features have been modeled by leaky neutral absorbers or by highly ionized gas that completely occult the continuum source. Such models are incomplete since they do not take into account all the physical processes in the gas. In particular, no previous model included the X-ray emission by the ionized absorbing gas and the reflection of the continuum source radiation. The present work discusses the emission, absorption, and reflection properties of photoionized gases with emphasis on conditions thought to prevail in AGNs. It shows that such gas is likely to produce intense X-ray line and continuum radiation and to reflect a sizable fraction of the nonstellar continuum at all energies. If such gas is indeed responsible for the observed X-ray absorption, then absorption edges are much weaker than commonly assumed, and some residual X-ray continuum is likely to be observed even if the line of sight is completely blocked. Moreover, X-ray emission features may show up in sources not showing X-ray absorption. This has immense consequences for medium-resolution X-ray missions, such as BBXRT and Astro-D, and for the planned high-resolution experiments on board XMM and AXAF.

A deep X-ray view of the bare AGN Ark 120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes

NASA Astrophysics Data System (ADS)

Porquet, D.; Reeves, J. N.; Matt, G.; Marinucci, A.; Nardini, E.; Braito, V.; Lobban, A.; Ballantyne, D. R.; Boggs, S. E.; Christensen, F. E.; Dauser, T.; Farrah, D.; Garcia, J.; Hailey, C. J.; Harrison, F.; Stern, D.; Tortosa, A.; Ursini, F.; Zhang, W. W.

2018-01-01

Context. The physical characteristics of the material closest to supermassive black holes (SMBHs) are primarily studied through X-ray observations. However, the origins of the main X-ray components such as the soft X-ray excess, the Fe Kα line complex, and the hard X-ray excess are still hotly debated. This is particularly problematic for active galactic nuclei (AGN) showing a significant intrinsic absorption, either warm or neutral, which can severely distort the observed continuum. Therefore, AGN with no (or very weak) intrinsic absorption along the line of sight, so-called "bare AGN", are the best targets to directly probe matter very close to the SMBH. Aims: We perform an X-ray spectral analysis of the brightest and cleanest bare AGN known so far, Ark 120, in order to determine the process(es) at work in the vicinity of the SMBH. Methods: We present spectral analyses of data from an extensive campaign observing Ark 120 in X-rays with XMM-Newton (4 × 120 ks, 2014 March 18-24), and NuSTAR (65.5 ks, 2014 March 22). Results: During this very deep X-ray campaign, the source was caught in a high-flux state similar to the earlier 2003 XMM-Newton observation, and about twice as bright as the lower-flux observation in 2013. The spectral analysis confirms the "softer when brighter" behavior of Ark 120. The four XMM-Newton/pn spectra are characterized by the presence of a prominent soft X-ray excess and a significant Fe Kα complex. The continuum is very similar above about 3 keV, while significant variability is present for the soft X-ray excess. We find that relativistic reflection from a constant-density, flat accretion disk cannot simultaneously produce the soft excess, broad Fe Kα complex, and hard X-ray excess. Instead, Comptonization reproduces the broadband (0.3-79 keV) continuum well, together with a contribution from a mildly relativistic disk reflection spectrum. Conclusions: During this 2014 observational campaign, the soft X-ray spectrum of Ark 120 below 0

An Axisymmetric Hydrodynamical Model for the Torus Wind in AGN. 2; X-ray Excited Funnel Flow

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.; Proga, D.

2008-01-01

We have calculated a series of models of outflows from the obscuring torus in active galactic nuclei (AGN). Our modeling assumes that the inner face of a rotationally supported torus is illuminated and heated by the intense X-rays from the inner accretion disk and black hole. As a result of such heating a strong biconical outflow is observed in our simulations. We calculate 3-dimensional hydrodynamical models, assuming axial symmetry, and including the effects of X-ray heating, ionization, and radiation pressure. We discuss the behavior of a large family of these models, their velocity fields, mass fluxes and temperature, as functions of the torus properties and X-ray flux. Synthetic warm absorber spectra are calculated, assuming pure absorption, for sample models at various inclination angles and observing times. We show that these models have mass fluxes and flow speeds which are comparable to those which have been inferred from observations of Seyfert 1 warm absorbers, and that they can produce rich absorption line spectra.

Spectral properties of x-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero Colmenero, Encarnacion

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha ~ 1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for NH. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law spectral slope of the average NELG is S = 0.45 +/- 0.09, whilst that of the AGN is S = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (< 2 x 10-15erg cm-2 s -1), thus suggesting that NELGs are important contributors to the residual soft (< 2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (S ~ 0.4, 1-10 keV) is harder than that of AGN (S ~ 1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha ~ 0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to

Cloudy Skies over AGN: Observations with Simbol-X

NASA Astrophysics Data System (ADS)

Salvati, M.; Risaliti, G.

2009-05-01

Recent time-resolved spectroscopic X-ray studies of bright obscured AGN show that column density variability on time scales of hours/days may be common, at least for sources with NH>1023 cm-2. This opens new oppurtunities in the analysis of the structure of the circumnuclear medium and of the X-ray source: resolving the variations due to single clouds covering/uncovering the X-ray source provides tight constraints on the source size, the clouds' size and distance, and their average number, density and column density. We show how Simbol-X will provide a breakthrough in this field, thanks to its broad band coverage, allowing (a) to precisely disentangle the continuum and NH variations, and (2) to extend the NH variability analysis to column densities >1023 cm-2.

Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN

NASA Technical Reports Server (NTRS)

Mushotzy, Richard F.; Winter, Lisa M.; McIntosh, Daniel H.; Tueller, Jack

2008-01-01

We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of 10(exp 3) in luminosity (L(sub IR) approx.equals L(sub BAT)(sup 1.25) and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.

Spectral properties of X-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero-Colmenero, E.

1998-03-01

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha~1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for N_H. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law slope of the average NELG is alpha = 0.45 +/- 0.09, whilst that of the AGN is alpha = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (<= 2e-15 ergs cm-2 s-1), thus suggesting that NELGs are important contributors to the residual soft (<2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (alpha~0.4, 1-10 keV) is harder than that of AGN (alpha~1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha~0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to

The AGN Luminosity Fraction in Galaxy Mergers

NASA Astrophysics Data System (ADS)

Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

2017-01-01

Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

A decade of Rossi X-ray Timing Explorer Seyfert observations: An RXTE Seyfert spectral database

NASA Astrophysics Data System (ADS)

Mattson, Barbara Jo

2008-10-01

With over forty years of X-ray observations, we should have a grasp on the X- ray nature of active galactic nuclei (AGN). The unification model of Antonucci and Miller (1985) offered a context for understanding observations by defining a "typical" AGN geometry, with observed spectral differences explained by line- of-sight effects. However, the emerging picture is that the central AGN is more complex than unification alone can describe. We explore the unified model with a systematic X-ray spectral study of bright Seyfert galaxies observed by the Rossi X-Ray Timing Explorer (RXTE) over its first 10 years. We develop a spectral-fit database of 821 time-resolved spectra from 39 Seyfert galaxies fitted to a model describing the effects of an X-ray power-law spectrum reprocessed and absorbed by material in the central AGN region. We observe a relationship between radio and X-ray properties for Seyfert 1s, with the spectral parameters differing between radio-loud and radio-quiet Seyfert 1s. We also find a complex relationship between the Fe K equivalent width ( EW ) and the power-law photon index (Gamma) for the Seyfert 1s, with a correlation for the radio-loud sources and an anti-correlation for the radio- quiet sources. These results can be explained if X-rays from the relativistic jet in radio-loud sources contribute significantly to the observed spectrum. We observe scatter in the EW-Gamma relationship for the Seyfert 2s, suggesting complex environments that unification alone cannot explain. We see a strong correlation between Gamma and the reflection fraction ( R ) in the Seyfert 1 and 2 samples, but modeling degeneracies are present, so this relationship cannot be trusted as instructive of the AGN physics. For the Seyfert 1 sample, we find an anticorrelation between EW and the 2 to 10 keV luminosity ( L x ), also known as the X-ray Baldwin effect. This may suggest that higher luminosity sources contain less material or may be due to a time-lag effect. We do not

AGN Feedback And Evolution of Radio Sources: Discovery of An X-Ray Cluster Associated With Z=1 Quasar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siemiginowska, Aneta; /Harvard-Smithsonian Ctr. Astrophys.; Cheung, C.C.

2006-01-11

We report the first significant detection of an X-ray cluster associated with a powerful (L{sub bol} {approx} 10{sup 47} erg sec{sup -1}) radio-loud quasar at high redshift (z=1.06). Diffuse X-ray emission is detected out to {approx} 120 kpc from the CSS quasar 3C 186. A strong Fe-line emission at the z{sub rest} = 1.06 confirms its thermal nature. We find that the CSS radio source is highly overpressured with respect to the thermal cluster medium by 2-3 orders of magnitude. This provides direct observational evidence that the radio source is not thermally confined as posited in the ''frustrated'' scenario formore » CSS sources. Instead, the radio source may be young and at an early stage of its evolution. This source provides the first detection of the AGN in outburst in the center of a cooling flow cluster. Powerful radio sources are thought to be triggered by the cooling flows. The evidence for the AGN activity and intermittent outbursts comes from the X-ray morphology of low redshift clusters, which usually do not harbour quasars. 3C186 is a young active radio source which can supply the energy into the cluster and potentially prevent its cooling. We discuss energetics related to the quasar activity and the cluster cooling flow, and possible feedback between the evolving radio source and the cluster.« less

Merging and Clustering of the Swift BAT AGN Sample

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa

2010-06-01

We discuss the merger rate, close galaxy environment, and clustering on scales up to an Mpc of the Swift BAT hard X-ray sample of nearby (z<0.05), moderate-luminosity active galactic nuclei (AGNs). We find a higher incidence of galaxies with signs of disruption compared to a matched control sample (18% versus 1%) and of close pairs within 30 kpc (24% versus 1%). We also find a larger fraction with companions compared to normal galaxies and optical emission line selected AGNs at scales up to 250 kpc. We hypothesize that these merging AGNs may not be identified using optical emission line diagnostics because of optical extinction and dilution by star formation. In support of this hypothesis, in merging systems we find a higher hard X-ray to [O III] flux ratio, as well as emission line diagnostics characteristic of composite or star-forming galaxies, and a larger IRAS 60 μm to stellar mass ratio.

Deepest View of AGN X-Ray Variability with the 7 Ms Chandra Deep Field-South Survey

NASA Astrophysics Data System (ADS)

Zheng, X. C.; Xue, Y. Q.; Brandt, W. N.; Li, J. Y.; Paolillo, M.; Yang, G.; Zhu, S. F.; Luo, B.; Sun, M. Y.; Hughes, T. M.; Bauer, F. E.; Vito, F.; Wang, J. X.; Liu, T.; Vignali, C.; Shu, X. W.

2017-11-01

We systematically analyze the X-ray variability of active galactic nuclei (AGNs) in the 7 Ms Chandra Deep Field-South survey. On the longest timescale (≈17 years), we find only a weak (if any) dependence of X-ray variability amplitudes on energy bands or obscuration. We use four different power spectral density (PSD) models to fit the anticorrelation between normalized excess variance ({σ }{nxv}2) and luminosity, and obtain a best-fit power-law index β ={1.16}-0.05+0.05 for the low-frequency part of the AGN PSD. We also divide the whole light curves into four epochs in order to inspect the dependence of {σ }{nxv}2 on these timescales, finding an overall increasing trend. The analysis of these shorter light curves also infers a β of ˜1.3 that is consistent with the above-derived β, which is larger than the frequently assumed value of β =1. We then investigate the evolution of {σ }{nxv}2. No definitive conclusion is reached because of limited source statistics, but if present, the observed trend goes in the direction of decreasing AGN variability at fixed luminosity toward high redshifts. We also search for transient events and find six notable candidate events with our considered criteria. Two of them may be a new type of fast transient events, one of which is reported here for the first time. We therefore estimate a rate of fast outbursts < \\dot{N}> ={1.0}-0.7+1.1× {10}-3 {{galaxy}}-1 {{yr}}-1 and a tidal disruption event (TDE) rate < {\\dot{N}}{TDE}> ={8.6}-4.9+8.5× {10}-5 {{galaxy}}-1 {{yr}}-1 assuming the other four long outbursts to be TDEs.

The SWIFT AGN and Cluster Survey. I. Number Counts of AGNs and Galaxy Clusters

NASA Astrophysics Data System (ADS)

Dai, Xinyu; Griffin, Rhiannon D.; Kochanek, Christopher S.; Nugent, Jenna M.; Bregman, Joel N.

2015-05-01

The Swift active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg2 of Swift X-ray Telescope serendipitous fields with variable depths surrounding γ-ray bursts to provide a medium depth (4× {{10}-15} erg cm-2 s-1) and area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. Here, we present a catalog of 22,563 point sources and 442 extended sources and examine the number counts of the AGN and galaxy cluster populations. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. We use Wide-field Infrared Survey Explorer mid-infrared (MIR) colors to classify the sources. For AGNs we can roughly separate the point sources into MIR-red and MIR-blue AGNs, finding roughly equal numbers of each type in the soft X-ray band (0.5-2 keV), but fewer MIR-blue sources in the hard X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from cosmic variance, are also consistent with previous surveys but span a much larger continuous flux range. Deep optical or IR follow-up observations of this cluster sample will significantly increase the number of higher-redshift (z\\gt 0.5) X-ray-selected clusters.

The Chandra COSMOS-Legacy Survey: Source X-Ray Spectral Properties

NASA Astrophysics Data System (ADS)

Marchesi, S.; Lanzuisi, G.; Civano, F.; Iwasawa, K.; Suh, H.; Comastri, A.; Zamorani, G.; Allevato, V.; Griffiths, R.; Miyaji, T.; Ranalli, P.; Salvato, M.; Schawinski, K.; Silverman, J.; Treister, E.; Urry, C. M.; Vignali, C.

2016-10-01

We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. A total of 38% of the sources are optically classified type 1 active galactic nuclei (AGNs), 60% are type 2 AGNs, and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index Γ and of the intrinsic absorption {N}{{H},{{z}}} based on the sources’ optical classification: type 1 AGNs have a slightly steeper mean photon index Γ than type 2 AGNs, which, on the other hand, have average {N}{{H},{{z}}} ˜ 3 times higher than type 1 AGNs. We find that ˜15% of type 1 AGNs have {N}{{H},{{z}}}\\gt {10}22 cm-2, I.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have {L}2{--10{keV}} \\gt 1044 erg s-1. The existence of these objects suggests that optical and X-ray obscuration can be caused by different phenomena, the X-ray obscuration being, for example, caused by dust-free material surrounding the inner part of the nuclei. Approximately 18% of type 2 AGNs have {N}{{H},{{z}}}\\lt {10}22 cm-2, and most of these sources have low X-ray luminosities (L {}2{--10{keV}} \\lt 1043 erg s-1). We expect a part of these sources to be low-accretion, unobscured AGNs lacking broad emission lines. Finally, we also find a direct proportional trend between {N}{{H},{{z}}} and host-galaxy mass and star formation rate, although part of this trend is due to a redshift selection effect.

Narrow vs. Broad line Seyfert 1 galaxies: X-ray, optical and mid-infrared AGN characteristics

NASA Astrophysics Data System (ADS)

Lakićević, Maša; Popović, Luka Č.; Kovačević-Dojčinović, Jelena

2018-05-01

We investigated narrow line Seyfert 1 galaxies (NLS1s) at optical, mid-infrared (MIR) and X-ray wavelengths, comparing them to the broad line active galactic nuclei (BLAGNs). We found that black hole mass, coronal line luminosities, X-ray hardness ratio and X-ray, optical and MIR luminosities are higher for the BLAGNs than for NLS1s, while policyclic aromatic hydrocarbon (PAH) contribution and the accretion rates are higher for the NLS1s. Furthermore, we found some trends among spectral parameters that NLS1s have and BLAGNs do not have. The evolution of FWHM(Hβ) with the luminosities of MIR and coronal lines, continuum luminosities, PAH contribution, Hβ broad line luminosity, FWHM[O III] and EW(HβNLR), are important trends found for NLS1s. That may contribute to the insight that NLS1s are developing AGNs, growing their black holes, while their luminosities and FWHM(Hβ) consequently grow, and that BLAGNs are mature, larger objects of slower and/or different evolution. Black hole mass is related to PAH contribution only for NLS1s, which may suggest that PAHs are more efficiently destroyed in NLS1s.

UNDERSTANDING X-RAY STARS:. The Discovery of Binary X-ray Sources

NASA Astrophysics Data System (ADS)

Schreier, E. J.; Tananbaum, H.

2000-09-01

The discovery of binary X-ray sources with UHURU introduced many new concepts to astronomy. It provided the canonical model which explained X-ray emission from a large class of galactic X-ray sources: it confirmed the existence of collapsed objects as the source of intense X-ray emission; showed that such collapsed objects existed in binary systems, with mass accretion as the energy source for the X-ray emission; and provided compelling evidence for the existence of black holes. This model also provided the basis for explaining the power source of AGNs and QSOs. The process of discovery and interpretation also established X-ray astronomy as an essential sub-discipline of astronomy, beginning its incorporation into the mainstream of astronomy.

X-RAY PROPERTIES OF THE NORTHERN GALACTIC CAP SOURCES IN THE 58 MONTH SWIFT/BAT CATALOG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevan, Ranjan V.; Mushotzky, Richard F.; Shimizu, Thomas T.

2013-02-15

We present a detailed X-ray spectral analysis of the non-beamed, hard X-ray selected active galactic nuclei (AGNs) in the northern Galactic cap of the 58 month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGNs with b > 50 Degree-Sign . This sky area has excellent potential for further dedicated study due to a wide range of multi-wavelength data that are already available, and we propose it as a low-redshift analog to the 'deep field' observations of AGNs at higher redshifts (e.g., CDFN/S, COSMOS, Lockman Hole). We present distributions of luminosity, absorbing column density, and other key quantities formore » the catalog. We use a consistent approach to fit new and archival X-ray data gathered from XMM-Newton, Swift/XRT, ASCA, and Swift/BAT. We probe to deeper redshifts than the 9 month BAT catalog ((z) = 0.043 compared to (z) = 0.03 for the 9 month catalog), and uncover a broader absorbing column density distribution. The fraction of obscured (log N {sub H} {>=} 22) objects in the sample is {approx}60%, and 43%-56% of the sample exhibits 'complex' 0.4-10 keV spectra. We present the properties of iron lines, soft excesses, and ionized absorbers for the subset of objects with sufficient signal-to-noise ratio. We reinforce previous determinations of the X-ray Baldwin (Iwasawa-Taniguchi) effect for iron K{alpha} lines. We also identify two distinct populations of sources; one in which a soft excess is well-detected and another where the soft excess is undetected, suggesting that the process responsible for producing the soft excess is not at work in all AGNs. The fraction of Compton-thick sources (log N {sub H} > 24.15) in our sample is {approx}9%. We find that 'hidden/buried AGNs' (which may have a geometrically thick torus or emaciated scattering regions) constitute {approx}14% of our sample, including seven objects previously not identified as hidden. Compton reflection is found to be important in a large fraction of our sample using joint

X-Ray Properties of Lyman Break Galaxies in the Hubble Deep Field North Region

NASA Technical Reports Server (NTRS)

Nandra, K.; Mushotzky, R. F.; Arnaud, K.; Steidel, C. C.; Adelberger, K. L.; Gardner, J. P.; Teplitz, H. I.; Windhorst, R. A.; White, Nicholas E. (Technical Monitor)

2002-01-01

We describe the X-ray properties of a large sample of z approximately 3 Lyman Break Galaxies (LBGs) in the region of the Hubble Deep Field North, derived from the 1 Ms public Chandra observation. Of our sample of 148 LBGs, four are detected individually. This immediately gives a measure of the bright AGN (active galactic nuclei) fraction in these galaxies of approximately 3 per cent, which is in agreement with that derived from the UV (ultraviolet) spectra. The X-ray color of the detected sources indicates that they are probably moderately obscured. Stacking of the remainder shows a significant detection (6 sigma) with an average luminosity of 3.5 x 10(exp 41) erg/s per galaxy in the rest frame 2-10 keV band. We have also studied a comparison sample of 95 z approximately 1 "Balmer Break" galaxies. Eight of these are detected directly, with at least two clear AGN based on their high X-ray luminosity and very hard X-ray spectra respectively. The remainder are of relatively low luminosity (< 10(exp 42) erg/s, and the X-rays could arise from either AGN or rapid star-formation. The X-ray colors and evidence from other wavebands favor the latter interpretation. Excluding the clear AGN, we deduce a mean X-ray luminosity of 6.6 x 10(exp 40) erg/s, a factor approximately 5 lower than the LBGs. The average ratio of the UV and X-ray luminosities of these star forming galaxies L(sub UV)/L (sub X), however, is approximately the same at z = 1 as it is at z = 3. This scaling implies that the X-ray emission follows the current star formation rate, as measured by the UV luminosity. We use our results to constrain the star formation rate at z approximately 3 from an X-ray perspective. Assuming the locally established correlation between X-ray and far-IR (infrared) luminosity, the average inferred star formation rate in each Lyman break galaxy is found to be approximately 60 solar mass/yr, in excellent agreement with the extinction-corrected UV estimates. This provides an external

X-ray spectra and time variability of active galactic nuclei

NASA Technical Reports Server (NTRS)

Mushotzky, R. F.

1984-01-01

The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha = .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales.

Black hole growth and starburst activity at z = 0.6-4 in the Chandra Deep Field South. Host galaxies properties of obscured AGN

NASA Astrophysics Data System (ADS)

Brusa, M.; Fiore, F.; Santini, P.; Grazian, A.; Comastri, A.; Zamorani, G.; Hasinger, G.; Merloni, A.; Civano, F.; Fontana, A.; Mainieri, V.

2009-12-01

Aims: 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 1 Ms observation and their host galaxies. Methods: 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 masses and star formation rates. In particular, we: 1) refined the X-ray/infrared/optical association of 179 sources in the MUSIC area detected in the Chandra observation; 2) studied the host galaxies observed and rest frame colors and properties. Results: We found that X-ray selected (LX ⪆ 1042 erg s-1) AGN show Spitzer colors consistent with both AGN and starburst dominated infrared continuum; the latter would not have been selected as AGN from infrared diagnostics. The host galaxies of X-ray selected obscured AGN are all massive (Mast > 1010 M_⊙) and, in 50% of the cases, are also actively forming stars (1/SSFR < tHubble) in dusty environments. The median L/LEdd value of the active nucleus is between 2% and 10% depending on the assumed MBH/Mast ratio. Finally, we found that the X-ray selected AGN fraction increases with the stellar mass up to a value of 30% at z > 1 and Mast > 3 × 1011 M_⊙, a fraction significantly higher than in the local Universe for AGN of similar luminosities. Tables [see full textsee full textsee full text] and [see full textsee full textsee full text] are only available in electronic form at http://www.aanda.org

X-ray detections of submillimetre galaxies: active galactic nuclei versus starburst contribution

NASA Astrophysics Data System (ADS)

Johnson, S. P.; Wilson, G. W.; Wang, Q. D.; Williams, C. C.; Scott, K. S.; Yun, M. S.; Pope, A.; Lowenthal, J.; Aretxaga, I.; Hughes, D.; Kim, M. J.; Kim, S.; Tamura, Y.; Kohno, K.; Ezawa, H.; Kawabe, R.; Oshima, T.

2013-05-01

We present a large-scale study of the X-ray properties and near-IR-to-radio spectral energy distributions (SEDs) of submillimetre galaxies (SMGs) detected at 1.1 mm with the AzTEC instrument across a ˜1.2 square degree area of the sky. Combining deep 2-4 Ms Chandra data with Spitzer IRAC/MIPS and Very Large Array data within the Great Observatories Origins Deep Survey North (GOODS-N), GOODS-S and COSMOS fields, we find evidence for active galactic nucleus (AGN) activity in ˜14 per cent of 271 AzTEC SMGs, ˜28 per cent considering only the two GOODS fields. Through X-ray spectral modelling and multiwavelength SED fitting using Monte Carlo Markov chain techniques to Siebenmorgen et al. (AGN) and Efstathiou, Rowan-Robinson & Siebenmorgen (starburst) templates, we find that while star formation dominates the IR emission, with star formation rates (SFRs) ˜100-1000 M⊙ yr-1, the X-ray emission for most sources is almost exclusively from obscured AGNs, with column densities in excess of 1023 cm-2. Only for ˜6 per cent of our sources do we find an X-ray-derived SFR consistent with NIR-to-radio SED derived SFRs. Inclusion of the X-ray luminosities as a prior to the NIR-to-radio SED effectively sets the AGN luminosity and SFR, preventing significant contribution from the AGN template. Our SED modelling further shows that the AGN and starburst templates typically lack the required 1.1 mm emission necessary to match observations, arguing for an extended, cool dust component. The cross-correlation function between the full samples of X-ray sources and SMGs in these fields does not indicate a strong correlation between the two populations at large scales, suggesting that SMGs and AGNs do not necessarily trace the same underlying large-scale structure. Combined with the remaining X-ray-dim SMGs, this suggests that sub-mm-bright sources may evolve along multiple tracks, with X-ray-detected SMGs representing transitionary objects between periods of high star formation and AGN

Evidence for a mass-dependent AGN Eddington ratio distribution via the flat relationship between SFR and AGN luminosity

NASA Astrophysics Data System (ADS)

Bernhard, E.; Mullaney, J. R.; Aird, J.; Hickox, R. C.; Jones, M. L.; Stanley, F.; Grimmett, L. P.; Daddi, E.

2018-05-01

The lack of a strong correlation between AGN X-ray luminosity (LX; a proxy for AGN power) and the star formation rate (SFR) of their host galaxies has recently been attributed to stochastic AGN variability. Studies using population synthesis models have incorporated this by assuming a broad, universal (i.e. does not depend on the host galaxy properties) probability distribution for AGN specific X-ray luminosities (i.e. the ratio of LX to host stellar mass; a common proxy for Eddington ratio). However, recent studies have demonstrated that this universal Eddington ratio distribution fails to reproduce the observed X-ray luminosity functions beyond z ˜ 1.2. Furthermore, empirical studies have recently shown that the Eddington ratio distribution may instead depend upon host galaxy properties, such as SFR and/or stellar mass. To investigate this further, we develop a population synthesis model in which the Eddington ratio distribution is different for star-forming and quiescent host galaxies. We show that, although this model is able to reproduce the observed X-ray luminosity functions out to z ˜ 2, it fails to simultaneously reproduce the observed flat relationship between SFR and X-ray luminosity. We can solve this, however, by incorporating a mass dependency in the AGN Eddington ratio distribution for star-forming host galaxies. Overall, our models indicate that a relative suppression of low Eddington ratios (λEdd ≲ 0.1) in lower mass galaxies (M* ≲ 1010 - 11 M⊙) is required to reproduce both the observed X-ray luminosity functions and the observed flat SFR/X-ray relationship.

The NuSTAR Extragalactic Surveys: The Number Counts Of Active Galactic Nuclei And The Resolved Fraction Of The Cosmic X-ray Background

NASA Technical Reports Server (NTRS)

Harrison, F. A.; Aird, J.; Civano, F.; Lansbury, G.; Mullaney, J. R.; Ballentyne, D. R.; Alexander, D. M.; Stern, D.; Ajello, M.; Barret, D.;

Reversing cooling flows with AGN jets: shock waves, rarefaction waves and trailing outflows

NASA Astrophysics Data System (ADS)

Guo, Fulai; Duan, Xiaodong; Yuan, Ye-Fei

2018-01-01

The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains highly debated. Using an idealized simulation of a cool-core cluster, we study the development of central cooling catastrophe and how a subsequent powerful AGN jet event averts cooling flows, with a focus on complex gasdynamical processes involved. We find that the jet drives a bow shock, which reverses cooling inflows and overheats inner cool-core regions. The shocked gas moves outward in a rarefaction wave, which rarefies the dense core and adiabatically transports a significant fraction of heated energy to outer regions. As the rarefaction wave propagates away, inflows resume in the cluster core, but a trailing outflow is uplifted by the AGN bubble, preventing gas accumulation and catastrophic cooling in central regions. Inflows and trailing outflows constitute meridional circulations in the cluster core. At later times, trailing outflows fall back to the cluster centre, triggering central cooling catastrophe and potentially a new generation of AGN feedback. We thus envisage a picture of cool cluster cores going through cycles of cooling-induced contraction and AGN-induced expansion. This picture naturally predicts an anti-correlation between the gas fraction (or X-ray luminosity) of cool cores and the central gas entropy, which may be tested by X-ray observations.

The cosmic X-ray background-IRAS galaxy correlation and the local X-ray volume emissivity

NASA Technical Reports Server (NTRS)

Miyaji, Takamitsu; Lahav, Ofer; Jahoda, Keith; Boldt, Elihu

1994-01-01

We have cross-correlated the galaxies from the IRAS 2 Jy redshift survey sample and the 0.7 Jy projected sample with the all-sky cosmic X-ray background (CXB) map obtained from the High Energy Astronomy Observatory (HEAO) 1 A-2 experiment. We have detected a significant correlation signal between surface density of IRAS galaxies and the X-ray background intensity, with W(sub xg) = (mean value of ((delta I)(delta N)))/(mean value of I)(mean value of N)) of several times 10(exp -3). While this correlation signal has a significant implication for the contribution of the local universe to the hard (E greater than 2 keV) X-ray background, its interpretation is model-dependent. We have developed a formulation to model the cross-correlation between CXB surface brightness and galaxy counts. This includes the effects of source clustering and the X-ray-far-infrared luminosity correlation. Using an X-ray flux-limited sample of active galactic nuclei (AGNs), which has IRAS 60 micrometer measurements, we have estimated the contribution of the AGN component to the observed CXB-IRAS galaxy count correlations in order to see whether there is an excess component, i.e., contribution from low X-ray luminosity sources. We have applied both the analytical approach and Monte Carlo simulations for the estimations. Our estimate of the local X-ray volume emissivity in the 2-10 keV band is rho(sub x) approximately = (4.3 +/- 1.2) x 10(exp 38) h(sub 50) ergs/s/cu Mpc, consistent with the value expected from the luminosity function of AGNs alone. This sets a limit to the local volume emissivity from lower luminosity sources (e.g., star-forming galaxies, low-ionization nuclear emission-line regions (LINERs)) to rho(sub x) less than or approximately = 2 x 10(exp 38) h(sub 50) ergs/s/cu Mpc.

Canadian Led X-ray Polarimeter Mission CXP

NASA Technical Reports Server (NTRS)

Kaspi, V.; Hanna, D.; Weisskopf, M.; Ramsey, B.; Ragan, K.; Vachon, B.; Elsner, R.; Heyl, J.; Pavlov, G.; Cumming, A.;

Obscured AGN at z ~ 1 from the zCOSMOS-Bright Survey. I. Selection and optical properties of a [Ne v]-selected sample

NASA Astrophysics Data System (ADS)

Mignoli, M.; Vignali, C.; Gilli, R.; Comastri, A.; Zamorani, G.; Bolzonella, M.; Bongiorno, A.; Lamareille, F.; Nair, P.; Pozzetti, L.; Lilly, S. J.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Le Fèvre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Pellò, R.; Peng, Y.; Perez Montero, E.; Presotto, V.; Silverman, J. D.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Bordoloi, R.; Cappi, A.; Cimatti, A.; Koekemoer, A. M.; McCracken, H. J.; Moresco, M.; Welikala, N.

2013-08-01

Aims: The application of multi-wavelength selection techniques is essential for obtaining a complete and unbiased census of active galactic nuclei (AGN). We present here a method for selecting z ~ 1 obscured AGN from optical spectroscopic surveys. Methods: A sample of 94 narrow-line AGN with 0.65 < z < 1.20 was selected from the 20k-Bright zCOSMOS galaxy sample by detection of the high-ionization [Ne v] λ3426 line. The presence of this emission line in a galaxy spectrum is indicative of nuclear activity, although the selection is biased toward low absorbing column densities on narrow-line region or galactic scales. A similar sample of unobscured (type 1 AGN) was collected applying the same analysis to zCOSMOS broad-line objects. This paper presents and compares the optical spectral properties of the two AGN samples. Taking advantage of the large amount of data available in the COSMOS field, the properties of the [Ne v]-selected type 2 AGN were investigated, focusing on their host galaxies, X-ray emission, and optical line-flux ratios. Finally, a previously developed diagnostic, based on the X-ray-to-[Ne v] luminosity ratio, was exploited to search for the more heavily obscured AGN. Results: We found that [Ne v]-selected narrow-line AGN have Seyfert 2-like optical spectra, although their emission line ratios are diluted by a star-forming component. The ACS morphologies and stellar component in the optical spectra indicate a preference for our type 2 AGN to be hosted in early-type spirals with stellar masses greater than 109.5 - 10 M⊙, on average higher than those of the galaxy parent sample. The fraction of galaxies hosting [Ne v]-selected obscured AGN increases with the stellar mass, reaching a maximum of about 3% at ≈2 × 1011 M⊙. A comparison with other selection techniques at z ~ 1, namely the line-ratio diagnostics and X-ray detections, shows that the detection of the [Ne v] λ3426 line is an effective method for selecting AGN in the optical band, in

Mini Survey of SDSS [OIII] AGN with Swift: Testing the Hypothesis that L(sub [OIII]) Traces AGN Luminosity

NASA Technical Reports Server (NTRS)

2007-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work strongly suggests every massive galaxy has a central black hole. However most of these objects either are not radiating or have been very difficult to detect We are now in the era of large surveys, and the luminosity function (LF] of AGN has been estimated in various ways. In the X-ray band. Chandra and XMM surveys have revealed that the LF of hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(sub x) (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects. If as been suggested, hard X ray and optical emission line can both can be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

X-Ray Characteristics of Megamaser Galaxies

NASA Astrophysics Data System (ADS)

Leiter, K.; Kadler, M.; Wilms, J.; Braatz, J.; Grossberger, C.; Krauss, F.; Kreikenbohm, A.; Langejahn, M.; Litzinger, E.; Markowitz, A.

2017-10-01

Water megamaser galaxies are a rare subclass of Active Galactic Nuclei (AGN). They play a key role in modern cosmology, providing a significant improvement for measuring geometrical distances with high precision. Megamaser studies presently measure H_{0} to about 5%. The goal of modern programs is to reach 3%, which strongly constrains the equation of state of dark energy. An increasing number of independent measurements of suitable water masers is providing the statistics necessary to decrease the uncertainties. X-ray studies of maser galaxies yield important constraints on target-selection criteria for future surveys, increasing their detection rate. We studied the X-ray properties of a homogeneous sample of Type 2 AGN with water maser activity observed by XMM-Newton to investigate the properties of megamaser-hosting galaxies compared to a control sample of non-maser galaxies. Comparing the luminosity distributions confirm previous results that water maser galaxies appear more luminous than non-maser sources. The maser phenomenon goes along with more complex X-ray spectra, higher column densities and higher equivalent widths of the Fe Kα line. Both a sufficiently luminous X-ray source and a high absorbing column density in the line of sight are necessary prerequisites to favour the appearance of the water megamaser phenomenon in AGN.

Clustering of moderate luminosity X-ray-selected type 1 and type 2 AGNs at z ∼ 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allevato, V.; Finoguenov, A.; Civano, F.

2014-11-20

We investigate, for the first time at z ∼ 3, the clustering properties of 189 Type 1 and 157 Type 2 X-ray active galactic nuclei (AGNs) of moderate luminosity ((L {sub bol}) = 10{sup 45.3} erg s{sup –1}), with photometric or spectroscopic redshifts in the range 2.2 < z < 6.8. These samples are based on Chandra and XMM-Newton data in COSMOS. We find that Type 1 and Type 2 COSMOS AGNs at z ∼ 3 inhabit DMHs with typical mass of log M{sub h} = 12.84{sub −0.11}{sup +0.10} and 11.73{sub −0.45}{sup +0.39} h {sup –1} M {sub ☉}, respectively.more » This result requires a drop in the halo masses of Type 1 and 2 COSMOS AGNs at z ∼ 3 compared to z ≲ 2 XMM-COSMOS AGNs with similar luminosities. Additionally, we infer that unobscured COSMOS AGNs at z ∼ 3 reside in 10 times more massive halos compared to obscured COSMOS AGNs, at the 2.6σ level. This result extends to z ∼ 3 the results found in COSMOS at z ≲ 2, and rules out the picture in which obscuration is purely an orientation effect. A model which assumes that the AGNs activity is triggered by major mergers is quite successful in predicting both the low halo mass of COSMOS AGNs and the typical mass of luminous SDSS quasars at z ∼ 3, with the latter inhabiting more massive halos respect to moderate luminosity AGNs. Alternatively we can argue, at least for Type 1 COSMOS AGNs, that they are possibly representative of an early phase of fast (i.e., Eddington limited) BH growth induced by cosmic cold flows or disk instabilities. Given the moderate luminosity, these new fast growing BHs have masses of ∼10{sup 7-8} M {sub ☉} at z ∼ 3 which might evolve into ∼10{sup 8.5-9} M {sub ☉} mass BHs at z = 0. Following our clustering measurements, we argue that this fast BH growth at z ∼ 3 in AGNs with moderate luminosity occurs in DMHs with typical mass of ∼ 6× 10{sup 12} h {sup –1} M {sub ☉}.« less

FRESH ACTIVITY IN OLD SYSTEMS: RADIO AGNs IN FOSSIL GROUPS OF GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L., E-mail: hess@ast.uct.ac.za, E-mail: ewilcots@astro.wisc.edu, E-mail: vhartwick@wisc.edu

2012-08-15

We present the first systematic 1.4 GHz Very Large Array radio continuum survey of fossil galaxy group candidates. These are virialized systems believed to have assembled over a gigayear in the past through the merging of galaxy group members into a single, isolated, massive elliptical galaxy and featuring an extended hot X-ray halo. We use new photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 7 to determine that three of the candidates are clearly not fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud (L{sub 1.4GHz} > 10{sup 23} W Hz{sup -1}) active galactic nucleusmore » (AGN) at the center of their dominant elliptical galaxy. We find a weak correlation between the radio luminosity of the AGN and the X-ray luminosity of the halo suggesting that the AGN contributes to energy deposition into the intragroup medium. We only find a correlation between the radio and optical luminosity of the central elliptical galaxy when we include X-ray-selected, elliptically dominated non-fossil groups, indicating a weak relationship between AGN strength and the mass assembly history of the groups. The dominant elliptical galaxy of fossil groups is on average roughly an order of magnitude more luminous than normal group elliptical galaxies in optical, X-ray, and radio luminosities and our findings are consistent with previous results that the radio-loud fraction in elliptical galaxies is linked to the stellar mass of a population. The current level of activity in fossil groups suggests that AGN fueling continues long after the last major merger. We discuss several possibilities for fueling the AGN at the present epoch.« less

A Unified View of X-ray Absorbers in AGNs and XRBs with MHD Winds

NASA Astrophysics Data System (ADS)

Fukumura, Keigo; Kazanas, Demosthenes; Shrader, Chris R.; Tombesi, Francesco; Behar, Ehud; Contopoulos, John

2016-01-01

The presence of UV and X-ray absorbers (aka. warm absorbers or WAs) has been long known for decades from extensive spectroscopic studies across diverse AGN populations such as nearby Seyfert galaxies and distant quasars. Furthermore, another class of seemingly distinct type of absorbers, ultra-fast outflows or UFOs, is becoming increasingly known today. Nonetheless, a physical identification of such absorbers, such as geometrical property and physical conditions, is very elusive to date despite the recent state-of-the-art observations. We develop a coherent scenario in which the detected absorbers are driven primarily (if not exclusively) by the action of global magnetic fields originating from a black hole accretion disk. In the context of MHD disk-wind of density profile of n~1/r, it is found that the properties of the observed WAs/UFOs are successfully described assuming a characteristic SED. As a case study, we analyze PG1211+143 and GRO J1655-40 to demonstrate that our wind model can systematically unify apparently diverse absorbers in both AGNs and XRBs in terms of explaining their global behavior as well as individual spectral lines.

X-ray Emission Line Spectroscopy of Nearby Galaxies

NASA Astrophysics Data System (ADS)

Wang, Daniel

What are the origins of the diffuse soft X-ray emission from non-AGN galaxies? Preliminary analysis of XMM-Newton RGS spectra shows that a substantial fraction of the emission cannot arise from optically-thin thermal plasma, as commonly assumed, and may originate in charge exchange at the interface with neutral gas. We request the support for a comprehensive observing, data analysis, and modeling program to spectroscopically determine the origins of the emission. First, we will use our scheduled XMM-Newton AO-10 368 ks observations of the nearest compact elliptical galaxy M32 to obtain the first spectroscopic calibration of the cumulative soft X-ray emission from the old stellar population and will develop a spectral model for the charge exchange, as well as analysis tools to measure the spatial and kinematic properties of the X-ray line- emitting plasma. Second, we will characterize the truly diffuse emission from the hot plasma and/or its interplay with the neutral gas in a sample of galactic spheroids and active star forming/starburst regions in nearby galaxies observed by XMM-Newton. In particular, we will map out the spatial distributions of key emission lines and measure (or tightly constrain) the kinematics of hot plasma outflows for a few X-ray-emitting regions with high-quality RGS data. For galaxies with insufficient counting statistics in individual emission lines, we will conduct a spectral stacking analysis to constrain the average properties of the X-ray-emitting plasma. We will use the results of these X-ray spectroscopic analyses, together with complementary X-ray CCD imaging/spectral data and observations in other wavelength bands, to test the models of the emission. In addition to the charge exchange, alternative scenarios such as resonance scattering and relic AGN photo-ionization will also be examined for suitable regions. These studies are important to the understanding of the relationship between the diffuse soft X-ray emission and various

Cosmological evolution of supermassive black holes in galactic centers unveiled by hard X-ray observations.

PubMed

Ueda, Yoshihiro

2015-01-01

We review the current understanding of the cosmological evolution of supermassive black holes in galactic centers elucidated by X-ray surveys of active galactic nuclei (AGNs). Hard X-ray observations at energies above 2 keV are the most efficient and complete tools to find "obscured" AGNs, which are dominant populations among all AGNs. Combinations of surveys with various flux limits and survey area have enabled us to determine the space number density and obscuration properties of AGNs as a function of luminosity and redshift. The results have essentially solved the origin of the X-ray background in the energy band below ∼10 keV. The downsizing (or anti-hierarchical) evolution that more luminous AGNs have the space-density peak at higher redshifts has been discovered, challenging theories of galaxy and black hole formation. Finally, we summarize unresolved issues on AGN evolution and prospects for future X-ray missions.

Broad Band Properties of the BAT Selected AGN

NASA Technical Reports Server (NTRS)

Mushotzky, Richard; Winter, Lisa; Tueller, jack

2008-01-01

We will present the x-ray spectral properties of approximately 150 Burst Alert Telescope (BAT) selected active galactic nuclei (AGN) focusing on the issues of spectral complexity, x-ray absorption and its distribution and that contribution of sources to the x-ray background. If time permits we will also present the nature of the host galaxies of the AGN and their relationship to merger candidates.

Cosmological evolution of supermassive black holes in galactic centers unveiled by hard X-ray observations

PubMed Central

UEDA, Yoshihiro

2015-01-01

We review the current understanding of the cosmological evolution of supermassive black holes in galactic centers elucidated by X-ray surveys of active galactic nuclei (AGNs). Hard X-ray observations at energies above 2 keV are the most efficient and complete tools to find “obscured” AGNs, which are dominant populations among all AGNs. Combinations of surveys with various flux limits and survey area have enabled us to determine the space number density and obscuration properties of AGNs as a function of luminosity and redshift. The results have essentially solved the origin of the X-ray background in the energy band below ∼10 keV. The downsizing (or anti-hierarchical) evolution that more luminous AGNs have the space-density peak at higher redshifts has been discovered, challenging theories of galaxy and black hole formation. Finally, we summarize unresolved issues on AGN evolution and prospects for future X-ray missions. PMID:25971656

Gamma-ray monitoring of AGN and galactic black hole candidates by the Gamma-Ray Observatory

NASA Technical Reports Server (NTRS)

Wheaton, Wm. A.; Ling, James C.; Skelton, R. T.; Harmon, Alan; Fishman, Gerald J.; Meegan, Charles A.; Paciesas, William S.; Rubin, Brad; Wilson, Robert B.; Gruber, Duane E.

1992-01-01

The Burst and Transient Spectroscopy Experiment (BATSE) on the Compton Gamma-Ray Observatory has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both AGN and Galactic black hole candidates such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Progress in background modeling indicates that the data accept region, or fit window tau, around the occultation step can be substantially increased over that conservatively assumed in earlier estimates of BATSE's Earth occultation sensitivity. We show samples of large-tau fits to background and source edges. As a result we expect to be able to perform long-term monitoring of Cygnus X-1 and many of the brighter AGN for the duration of the CGRO mission.

AGN Obscuration from Winds: From Dusty Infrared-Driven to Warm and X-Ray Photoionized

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.

2012-01-01

We present calculations of AGN winds at approximate parsec scales, along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L=0.05 - 0.6L(sub Edd) the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72? -75? regardless of the luminosity. At L 0.1 the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations (theta) greater than or approximately 70? and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR supported flow. At luminosities less than or equal to 0.1L(sub Edd) episodes of outflow are followed by extended periods when the wind switches to slow accretion.

N uSTAR Hard X-Ray Data and Gemini 3D Spectra Reveal Powerful AGN and Outflow Histories in Two Low-redshift Lyα Blobs

NASA Astrophysics Data System (ADS)

Kawamuro, Taiki; Schirmer, Mischa; Turner, James E. H.; Davies, Rebecca L.; Ichikawa, Kohei

2017-10-01

We have shown that Lyα blobs (LABs) may still exist even at z˜ 0.3, about seven billion years later than most other LABs known (Shirmer et al.). Their luminous Lyα and [O III] emitters at z˜ 0.3 offer new insights into the ionization mechanism. This paper focuses on the two X-ray brightest LABs at z˜ 0.3, SDSS J0113+0106 (J0113) and SDSS J1155-0147 (J1155), comparable in size and luminosity to “B1,” one of the best-studied LABs at z≳ 2. Our NuSTAR hard X-ray (3-30 keV) observations reveal powerful active galactic nuclei (AGN) with {L}2{--10{keV}}=(0.5{--}3)× {10}44 erg s-1. J0113 also faded by a factor of ˜5 between 2014 and 2016, emphasizing that variable AGN may cause apparent ionization deficits in LABs. Joint spectral analyses including Chandra data constrain column densities of {N}{{H}}={5.1}-3.3+3.1× {10}23 cm-2 (J0113) and {N}{{H}}={6.0}-1.1+1.4× {10}22 cm-2 (J1155). J0113 is likely buried in a torus with a narrow ionization cone, but ionizing radiation is also leaking in other directions, as revealed by our Gemini/GMOS 3D spectroscopy. The latter shows a bipolar outflow over 10 kpc, with a peculiar velocity profile that is best explained by AGN flickering. X-ray analysis of J1155 reveals a weakly absorbed AGN that may ionize over a wide solid angle, consistent with our 3D spectra. Extinction-corrected [O III] log-luminosities are high, ˜43.6. The velocity dispersions are low, ˜100-150 km s-1, even at the AGN positions. We argue that this is a combination of high extinction hiding the turbulent gas and previous outflows that have cleared the escape paths for their successors.

Chandra Survey of Nearby Galaxies: Testing the Accretion Model for Low-luminosity AGNs

NASA Astrophysics Data System (ADS)

She, Rui; Ho, Luis C.; Feng, Hua; Cui, Can

2018-06-01

From a Chandra sample of active galactic nuclei (AGNs) in nearby galaxies, we find that for low-luminosity AGNs, either the intrinsic absorption column density, or the fraction of absorbed AGNs, positively scales with the Eddington ratio for L bol/L Edd ≲ 10‑2. Such a behavior, along with the softness of the X-ray spectrum at low luminosities, is in good agreement with the picture that they are powered by hot accretion flows surrounding supermassive black holes. Numerical simulations find that outflows are inevitable with hot accretion flows, and the outflow rate is correlated with the innermost accretion rate in the low-luminosity regime. This agrees well with our results, suggesting that the X-ray absorption originates from, or is associated with, the outflow material. Gas and dust on larger scales may also produce the observed correlation. Future correlation analyses may help differentiate the two scenarios.

Compton thick AGN in Chandra sureys

NASA Astrophysics Data System (ADS)

Brightman, Murray; Nandra, Kirpal

2014-07-01

We present the results from the X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured, Compton thick (CT, N H > 104 cm-2) sources. Our sample is comprised of 3088 X-ray selected sources, which has a high rate of redshift completeness (97%). The aim is to produce the largest and cleanest uniform sample of these sources from the data as possible. We identify these sources through X-ray spectral fitting, utilising torus spectral models designed for heavily obscured AGN which self consistently include the spectral signatures of heavy absorption, being Compton scattering, photoelectric absorption and iron Kα fluorescence. We identify a total of 163 CT AGN covering an intrinsic 2-10 keV X-ray luminosity range of 102 -3 × 105 erg s-1 and from z = 0.1-7.

Hard X-Ray Emission and the Ionizing Source in LINERs

NASA Technical Reports Server (NTRS)

Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.

2000-01-01

We report X-ray fluxes in the 2-10 keV band from LINERs (low-ionization nuclear emission-line regions) and low-luminosity Seyfert galaxies obtained with the ASCA satellite. Observed X-ray luminosities are in the range between 4 x 10(exp 39) and 5 x 10(exp 41) ergs/s, which are significantly smaller than that of the "classical" low-luminosity Seyfert 1 galaxy NGC 4051. We found that X-ray luminosities in 2-10 keV of LINERs with broad H.alpha emission in their optical spectra (LINER 1s) are proportional to their Ha luminosities. This correlation strongly supports the hypothesis that the dominant ionizing source in LINER 1s is photoionization by hard photons from low-luminosity AGNs. On the other hand, the X-ray luminosities of most LINERs without broad H.alpha emission (LINER 2s) in our sample are lower than LINER 1s at a given H.alpha luminosity. The observed X-ray luminosities in these objects are insufficient to power their H.alpha luminosities, suggesting that their primary ionizing source is other than an AGN, or that an AGN, if present, is obscured even at energies above 2 keV.

Utilizing X-ray gas velocity measurements as a new probe of AGN feedback in giant elliptical galaxies

NASA Astrophysics Data System (ADS)

Ogorzalek, Anna; Zhuravleva, Irina; Allen, Steven W.; Pinto, Ciro; Werner, Norbert; Mantz, Adam; Canning, Rebecca; Fabian, Andrew C.; Kaastra, Jelle S.; de Plaa, Jelle

2017-08-01

Velocity structure of hot atmospheres of massive early-type galaxies remains a key open question in our understanding of galaxy formation and mechanical AGN feedback. Using a combination of resonant scattering and direct line broadening techniques applied to deep XMM-Newton Reflection Grating Spectrometer observations has allowed us to for the first time measure turbulent velocities in the cores of 13 nearby giant early-type galaxies, opening up the possibility of population studies of hot gas motions in such objects. Our method has also been successfully applied to the Hitomi Perseus observation, serving as an independent velocity probe of the cluster ICM. In this talk I will introduce our measurements and discuss their implications on the physics of kinetic AGN feedback. I will also outline future directions, emphasizing the role of resonant scattering in studying gas dynamics of cooler (~1 keV) systems, such as giant galaxies, as well as its importance for the correct interpretation of high resolution X-ray spectra from XARM and Athena.

The space density of Compton-thick AGN at z ≈ 0.8 in the zCOSMOS-Bright Survey

NASA Astrophysics Data System (ADS)

Vignali, C.; Mignoli, M.; Gilli, R.; Comastri, A.; Iwasawa, K.; Zamorani, G.; Mainieri, V.; Bongiorno, A.

2014-11-01

Context. The obscured accretion phase in black hole growth is a crucial ingredient in many models linking the active galactic nuclei (AGN) activity with the evolution of their host galaxy. At present, a complete census of obscured AGN is still missing, although several attempts in this direction have been carried out recently, mostly in the hard X-rays and at mid-infrared wavelengths. Aims: The purpose of this work is to assess whether the [Ne v] emission line at 3426 Å can reliably pick up obscured AGN up to z ≈ 1 by assuming that it is a reliable proxy of the intrinsic AGN luminosity and using moderately deep X-ray data to characterize the amount of obscuration. Methods: A sample of 69 narrow-line (Type 2) AGN at z ≈ 0.65-1.20 were selected from the 20k-zCOSMOS Bright galaxy sample on the basis of the presence of the [Ne v]3426 Å emission. The X-ray properties of these galaxies were then derived using the Chandra-COSMOS coverage of the field; the X-ray-to-[Ne v] flux ratio, coupled with X-ray spectral and stacking analyses, was then used to infer whether Compton-thin or Compton-thick absorption is present in these sources. Then the [Ne v] luminosity function was computed to estimate the space density of Compton-thick AGN at z ≈ 0.8. Results: Twenty-three sources were detected by Chandra, and their properties are consistent with moderate obscuration (on average, ≈a few × 1022 cm-2). The X-ray properties of the remaining 46 X-ray undetected Type 2 AGN (among which we expect to find the most heavily obscured objects) were derived using X-ray stacking analysis. Current data, supported by Monte Carlo simulations, indicate that a fraction as high as ≈40% of the present sample is likely to be Compton thick. The space density of Compton-thick AGN with logL2-10 keV> 43.5 at z = 0.83 is ΦThick = (9.1 ± 2.1) × 10-6 Mpc-3, in good agreement with both X-ray background model expectations and the previously measured space density for objects in a similar

Spatially offset AGN candidates in the CLASS survey

NASA Astrophysics Data System (ADS)

Skipper, Chris J.; Browne, Ian W. A.

2018-04-01

Prompted by a recent claim by Barrows et al. that X-ray active galactic nuclei (AGNs) are often found significantly offset from the centres of their host galaxies, we have looked for examples of compact radio sources that are offset from the optical centroids of nearby (z < 0.2) galaxies. We have selected a sample of 345 galaxies from the Sloan Digital Sky Survey (SDSS) galaxy catalogue, which have nearby compact radio sources listed in the Cosmic-Lens All Sky Survey (CLASS) catalogue. We find only three matches (˜0.87 per cent of the sample) with offsets greater than 600 milliarcsec (mas), which is considerably fewer than we would have expected from the Barrows et al. X-ray survey. We fit our histogram of offsets with a Rayleigh distribution with σ = 60.5 mas, but find that there is an excess of objects with separations greater than ˜150 mas. Assuming that this excess represents AGNs with real offsets, we place an upper limit of ˜17 per cent on the fraction of offset AGNs in our radio-selected sample. We select 38 objects with offsets greater than 150 mas, and find they have some diverse properties: Some are well known, such as Mrk 273 and Arp 220, some have dust lanes, which may have affected the optical astrometry, and a few are strong new candidates for offset AGNs.

Mini-Survey on SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

Angelini, Lorella

2008-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. There is a common wisdom that every massive galaxy has a massive black hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low $L_X$ (at all $z$). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of {it optically-selected samples} shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [O{\\sc iii}] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a min-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([O{\\sc iii}]) to check the relation with the $L_X$ observed with Swift.

Introductory Overview of Intermediate-luminosity X-ray Objects

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.

2001-05-01

Intermediate-luminosity X-ray Objects (IXOs) are defined as compact objects having X-ray luminosities between those of X-ray binaries and low-luminosity AGNs (i.e., 1039.0 erg s-1 < ~ LX [IXOs] < ~ 1041.0 erg s-1). It is not currently known if these objects are intermediate-mass (M ~ 102-104 Msun) black holes accreting near the Eddington limit, near-solar-mass black holes in a super-Eddington state, or are, in some cases, just supermassive black holes accreting at very low rates. However, the first idea has been popularized by recent press coverage. IXOs are quite common (present in about half of spiral galaxies) and are typically found displaced from the optical nucleus, reducing the likelihood that they are low-luminosity AGN. Nearly all of our knowledge of these objects comes from X-ray observations, as observations of optical, NIR and radio counterparts are not widely known. In this session, we will address (1) the phenomenology of the objects, (2) possible geometry and accretion mechanisms for these objects (i.e., are they more similar to black hole X-ray binaries or AGNs), (3) the central black hole masses, and (4) the formation mechanism for these black holes, if they are of intermediate mass. In this talk, I will focus primarily on giving background information of these fascinating objects.

X-Ray properties of Post-Merger Spheroidal Galaxies: The Missing Link in Understanding the Merger-AGN connection

NASA Astrophysics Data System (ADS)

Nair, Preethi

2017-09-01

We propose to characterize the AGN properties of post-merger spheroidal galaxies, a well-defined, significant post starburst phase in merging galaxies. These galaxies probe the "coalesced" late stage of mergers lying between ULIRGs and quenched elliptical galaxies. They are characterized by shells and tidal tails with lifetimes (0.5 - 1 Gyr) similar to those of low luminosity AGN. The AGN detection fraction for 12 serendipitous Chandra sources is 83%. These `shell' galaxies may represent a key time step in major mergers which has previously been unexplored. We propose to image a well selected sample of 12 shells drawn from SDSS to investigate this missing chapter in mergers.

Uncovering Heavily Obscured AGN with WISE and NuSTAR

NASA Astrophysics Data System (ADS)

Hickox, Ryan C.; Carroll, Christopher M.; Yan, Wei; DiPompeo, Michael A.; Hainline, Kevin N.; NuSTAR Obscured AGN Team

2018-01-01

Supermassive black holes gain their mass through accretion as active galactic nuclei (AGN), but it is now clear that a large fraction of this growth is "hidden" behind large columns of gas and dust. Of particular interest are Compton-thick (CT) AGN, with columns NH > 1024 cm-2, that have been difficult to identify using optical or soft X-ray surveys. We will present two studies of heavily obscured AGN that aim to uncover more of the full population of "hidden" growing black holes: (1) Analysis of the spectral energy distributions of millions of galaxies with photometry from WISE (mid-IR), UKIDSS (near-IR), and SDSS (optical), that uncovers large populations of weak or heavily buried AGN, and (2) NuSTAR observations of a sample of candidate highly obscured AGN, selected from WISE and SDSS photometry,and confirmed using SALT and Keck spectroscopy. The NuSTAR data reveal the existence of powerful CT quasars with extremely large columns NH > 1025 cm-2, which may represent a significant fraction of previously hidden black hole growth. This work is supported by NASA grant numbers NNX16AN48G and NNX15AP24G, and the NSF through grant numbers 1515364 and 1554584.

The Advanced X-ray Imaging Satellite (AXIS)

NASA Astrophysics Data System (ADS)

Reynolds, Christopher S.; Mushotzky, Richard

2017-08-01

The Advanced X-ray Imaging Satellite (AXIS) will follow in the footsteps of the spectacularly successful Chandra X-ray Observatory with similar or higher angular resolution and an order of magnitude more collecting area in the 0.3-10keV band. These capabilities will enable major advances in many of the most active areas of astrophysics, including (i) mapping event horizon scale structure in AGN accretion disks and the determination of supermassive black hole (SMBH) spins through monitoring of gravitationally-microlensed quasars; (ii) dramatically deepening our understanding of AGN feedback in galaxies and galaxy clusters out to high-z through the direct imaging of AGN winds and the interaction of jets with the hot interstellar/intracluster medium; (iii) understanding the fueling of AGN by probing hot flows inside of the SMBH sphere of influence; (iv) obtaining geometric distance measurements using dust scattering halos. With a nominal 2028 launch, AXIS will be enormously synergistic with LSST, ALMA, WFIRST and ATHENA, and will be a valuable precursor to Lynx. AXIS is enabled by breakthroughs in the construction of light-weight X-ray optics from mono-crystalline silicon blocks, building on recent developments in the semiconductor industry. Here, we describe the straw-man concept for AXIS, some of the high profile science that this observatory will address, and how you can become involved.

Intraday X-Ray Variability of QSOs/AGN Using the Chandra Archives

NASA Astrophysics Data System (ADS)

Tartamella, C.; Busche, J.

2005-05-01

X-ray variability is a common characteristic of Active Galactic Nuclei (AGN), and it can be used to probe the nuclear region at short time scales. Quantitative analysis of this variability has been difficult due to low signal-to-noise ratios and short time baselines, but serendipitous Chandra data acquired within the last six years have opened the door to such analysis. Cross-correlation of the Chandra archives with QSO/AGN catalogs on NASA's HEASARC website (e.g. Veron, Sloan) yields a sample of 50+ objects that satisfy the following criteria: absolute magnitude M≤ -22.5, proper time baselines greater than 2 hours, and count rates leading to 10% error bars for 8+ flux points on the light curve. The sample includes a range of red-shifts, magnitudes, and type (e.g. radio loud, radio quiet), and hence may yield empirical clues about luminosity or evolutionary trends. As a beginning of such analysis, we present 11 light curves for 9 objects for which the exposure time was greater than 10 hours. The variability was analyzed using three different statistical methods. The Kolmogorov-Smirnov (KS) test proved to be impractical because of the unavoidably small number of data points and the simplistic nature of the test. A χ2 test indicated in most cases that there were significant departures from constant brightness (as expected). Autocorrelation plots were also generated for each light curve. With more work and a larger sample size, these plots can be used to identify any trends in the lightcurve such as whether the variability is stochastic or periodic in nature. This test was useful even with the small number of datapoints available. In future work, more sophisticated analyses based on Fourier series, power density spectra, or wavelets are likely to yield more meaningful and useful results.

The joint fit of the BHMF and ERDF for the BAT AGN Sample

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Koss, Michael; Ricci, Claudio; Trakhtenbrot, Benny; Oh, Kyuseok; Schawinski, Kevin; Lamperti, Isabella

2018-01-01

A natural product of an AGN survey is the AGN luminosity function. This statistical measure describes the distribution of directly measurable AGN luminosities. Intrinsically, the shape of the luminosity function depends on the distribution of black hole masses and Eddington ratios. To constrain these fundamental AGN properties, the luminosity function thus has to be disentangled into the black hole mass and Eddington ratio distribution function. The BASS survey is unique as it allows such a joint fit for a large number of local AGN, is unbiased in terms of obscuration in the X-rays and provides black hole masses for type-1 and type-2 AGN. The black hole mass function at z ~ 0 represents an essential baseline for simulations and black hole growth models. The normalization of the Eddington ratio distribution function directly constrains the AGN fraction. Together, the BASS AGN luminosity, black hole mass and Eddington ratio distribution functions thus provide a complete picture of the local black hole population.

Average Heating Rate of Hot Atmospheres in Distant Galaxy Clusters by Radio AGN: Evidence for Continuous AGN Heating

NASA Astrophysics Data System (ADS)

Ma, Cheng-Jiun; McNamara, B.; Nulsen, P.; Schaffer, R.

2011-09-01

X-ray observations of nearby clusters and galaxies have shown that energetic feedback from AGN is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 -- 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in 400SD, but cannot rule out the presence of weak cooling flows. The average jet power of central radio AGN is approximately 2 10^{44} erg/s. The jet power corresponds to an average heating of approximately 0.2 keV/particle for gas within R_500. Assuming the current AGN heating rate remained constant out to redshifts of about 2, these figures would rise by a factor of two. Our results show that the integrated energy injected from radio AGN outbursts in clusters is statistically significant compared to the excess entropy in hot atmospheres that is required for the breaking of self-similarity in cluster scaling relations. It is not clear that central AGN in 400SD clusters are maintained by a self-regulated feedback loop at the base of a cooling flow. However, they may play a significant role in preventing the development of strong cooling flows at early epochs.

An unbiased view of X-ray obscuration amongst active galactic nuclei with NuLANDS

NASA Astrophysics Data System (ADS)

Boorman, Peter Gregory; Gandhi, Poshak; Stern, Daniel; Harrison, Fiona; NuSTAR Obscured AGN Team

2018-01-01

Nearly all active galactic nuclei (AGN) are obscured in X-rays behind column densities of NH ≥ 1022 cm-2. Hard X-ray studies have proven very effective to quanitfy the levels of obscuration amongst AGN, up to and just above the Compton-thick limit (NH ˜ 1.5 × 1024 cm-2). However, Compton-thick sources with NH values beyond this limit are typically missed in hard X-ray all-sky surveys such as Swift/BAT, requiring many studies to apply considerable bias corrections to account for the loss. Incorrectly quanitfying the heavily obscured AGN population can have a dramatic effect on synthesis models designed to fit the Cosmic X-ray Background spectrum, due to their significant contribution to the peak flux of the background at ~30 keV. This is what motivated the NuSTAR Local AGN NH Distribution Survey (NuLANDS) - a NuSTAR 1 Ms legacy survey of an obscuration-independent, infrared selected sample of AGN, undetected by BAT and unobserved by NuSTAR before - a considerable number of which are predicted to be heavily obscured. NuSTAR is the first true X-ray focusing instrument capable of spectral analysis > 10 keV, and as such can and will place robust constraints on the NH values of these elusive AGN. In this poster, I will present the first results from NuLANDS, including multiple newly identified Compton-thick AGN, previously undetected in the Swift/BAT 70-month catalog. I will further highlight the exciting prospects for the complete NuLANDS sample, with the ultimate goal of constructing a representative NH distribution of AGN in the local Universe, requiring minimal bias corrections.

AGN Science with STROBE-X

NASA Astrophysics Data System (ADS)

Ballantyne, David; Balokovic, Mislav; Garcia, Javier; Koss, Michael; STROBE-X

2018-01-01

The probe concept STROBE-X, with its combination of large collecting area, wide-field monitor, broad bandpass, and rapid timing capability, is a powerful tool for studying many aspects of AGN astrophysics. This unique combination of features opens up the possibility for studying AGNs in ways current and other future missions are unable to accomplish. Here, we show a few of the novel new investigations made possible by STROBE-X: probing the structure of the BLR and torus with reverberation of the narrow Fe Kα line and line-of-sight column density, tracking changes in coronal parameters, investigating the origin of the soft excess, Fe Kα emission line surveys, and efficient Compton-thick characterization. Additional ideas and suggestions are always welcome and can be communicated to any member of the STROBE-X team.

The Wide Field X-ray Telescope Mission

NASA Astrophysics Data System (ADS)

Murray, Stephen S.; WFXT Team

2010-01-01

To explore the high-redshift Universe to the era of galaxy formation requires an X-ray survey that is both sensitive and extensive, which complements deep wide-field surveys at other wavelengths. The Wide-Field X-ray Telescope (WFXT) is designed to be two orders of magnitude more effective than previous and planned X-ray missions for surveys. WFXT consists of three co-aligned wide-field X-ray telescopes with a 1 sq. deg. field of view and <10 arc sec (goal of 5 arc sec) angular resolution over the full field. With nearly ten times Chandra's collecting area and more than ten times Chandra's field of view, WFXT will perform sensitive deep surveys that will discover and characterize extremely large populations of high redshift AGN and galaxy clusters. In five years, WFXT will perform three extragalactic surveys: 1) 20,000 sq. deg. of extragalactic sky at 100-1000 times the sensitivity, and twenty times better angular resolution than the ROSAT All Sky Survey; 2) 3000 sq.deg. to deep Chandra sensitivity; and 3) 100 sq.deg. to the deepest Chandra sensitivity. WFXT will generate a legacy dataset of >500,000 galaxy clusters to redshifts about 2, measuring redshift, gas abundance and temperature for a significant fraction of them, and a sample of more than 10 million AGN to redshifts > 6, many with X-ray spectra sufficient to distinguish obscured from unobscured quasars. These surveys will address fundamental questions of how supermassive black holes grow and influence the evolution of the host galaxy and how clusters form and evolve, as well as providing large samples of massive clusters that can be used in cosmological studies. WFXT surveys will map systems spanning many square degrees including Galactic star forming regions, the Magellanic Clouds and the Virgo Cluster. WFXT data will become public through annual Data Releases that will constitute a vast scientific legacy.

The NuSTAR Extragalactic Surveys: The Number Counts of Active Galactic Nuclei and The Resolved Fraction of The Cosmic X-Ray Background

DOE PAGES

Harrison, F. A.; Aird, J.; Civano, F.; ...

2016-11-07

Here, we present the 3–8 keV and 8–24 keV number counts of active galactic nuclei (AGNs) identified in the Nuclear Spectroscopic Telescope Array (NuSTAR) extragalactic surveys. NuSTAR has now resolved 33%–39% of the X-ray background in the 8–24 keV band, directly identifying AGNs with obscuring columns up tomore » $$\\sim {10}^{25}\\,{\\mathrm{cm}}^{-2}$$. In the softer 3–8 keV band the number counts are in general agreement with those measured by XMM-Newton and Chandra over the flux range $$5\\times {10}^{-15}\\,\\lesssim $$ S(3–8 keV)/$$\\mathrm{erg}\\,{{\\rm{s}}}^{-1}\\,{\\mathrm{cm}}^{-2}\\,\\lesssim \\,{10}^{-12}$$ probed by NuSTAR. In the hard 8–24 keV band NuSTAR probes fluxes over the range $$2\\times {10}^{-14}\\,\\lesssim $$ S(8–24 keV)/$$\\mathrm{erg}\\,{{\\rm{s}}}^{-1}\\,{\\mathrm{cm}}^{-2}\\,\\lesssim \\,{10}^{-12}$$, a factor ~100 fainter than previous measurements. The 8–24 keV number counts match predictions from AGN population synthesis models, directly confirming the existence of a population of obscured and/or hard X-ray sources inferred from the shape of the integrated cosmic X-ray background. The measured NuSTAR counts lie significantly above simple extrapolation with a Euclidian slope to low flux of the Swift/BAT 15–55 keV number counts measured at higher fluxes (S(15–55 keV) gsim 10-11 $$\\mathrm{erg}\\,{{\\rm{s}}}^{-1}\\,{\\mathrm{cm}}^{-2}$$), reflecting the evolution of the AGN population between the Swift/BAT local ($$z\\lt 0.1$$) sample and NuSTAR's $$z\\sim 1$$ sample. CXB synthesis models, which account for AGN evolution, lie above the Swift/BAT measurements, suggesting that they do not fully capture the evolution of obscured AGNs at low redshifts.« less

Galaxies in the X-Ray Band

NASA Technical Reports Server (NTRS)

Hornschemeier, Ann

2008-01-01

This talk will provide a brief review of progress an X-ray emission from normal (non-AGN) galaxy populations, including important constraints on the evolution of accreting binary populations over important cosmological timescales. We will also look to the future, anticipating constraints from near-term imaging hard X-ray missions such as NuSTAR, Simbol-X and NeXT and then the longer-term prospects for studying galaxies with the Generation-X mission,

Galaxies in the X-ray Band

NASA Technical Reports Server (NTRS)

Hornschemeier, Ann

2008-01-01

This talk will provide a brief review of progress on X-ray emission from normal (non-AGN) galaxy populations, including important constraints on the evolution of accreting binary populations over important cosmological timescales. We will also look to the future, anticipating constraints from near-term imaging hard X-ray missions such as NuSTAR, Simbol-X and NeXT and then the longer-term prospects for studying galaxies with the Generation-X mission.

Towards A Complete Census of the Compton-thick AGN population and the NH Distribution of AGN in the Local Universe.

NASA Astrophysics Data System (ADS)

Annuar, A.

2015-09-01

We present updated results from an ongoing project to establish the most unbiased census of the Compton- thick active galactic nucleus (CTAGN) population and the intrinsic column density (NH) distribution of the overall AGN population in the local universe, using a sample of mid-infrared (mid-IR) selected AGN within 15 Mpc. We find that 20% of the AGN in the sample are bona-fide CTAGN based upon hard X-ray studies (E > 10 keV). More candidates are then selected using multiwavelength techniques, i.e. mid-IR:X-ray and optical [OIII]5007:X-ray flux ratios. Based on these analyses along with evidence from previous literature, we initially find a further 25% of potential candidates. We then observed two of these candidates, NGC 5643 and NGC 3486, using NuSTAR and is able to confirm the former as a CTAGN and rule out the latter as an obscured AGN. This constrains the total CTAGN population in the sample to 25-40%, though it could potentially be as high as 65% accounting for those that still lack data. Finally, we use these results to estimate the intrinsic NH distribution of the local AGN population. Two more of our CTAGN candidates are scheduled to be observed by NuSTAR, bringing the completeness of hard X-ray energy data of the sample to 65%. This work provides a well-defined local benchmark for AGN unification studies.

Searching for hidden AGN in nearby star-forming galaxies with Chandra

NASA Astrophysics Data System (ADS)

Tzanavaris, P.; Georgantopoulos, I.

2007-06-01

of an AGN is likely in massive, disturbed starbursts. The contribution of X-ray emission from these AGN is small: For the central source, the bolometric luminosity is a fraction of a few ×10-5 of the Eddington luminosity. The X-ray flux of the central source is between 10 and 20% of the total galactic flux in the 0.2-10 keV band.

Are Compton-thick AGNs the Missing Link between Mergers and Black Hole Growth?

NASA Astrophysics Data System (ADS)

Kocevski, Dale D.; Brightman, Murray; Nandra, Kirpal; Koekemoer, Anton M.; Salvato, Mara; Aird, James; Bell, Eric F.; Hsu, Li-Ting; Kartaltepe, Jeyhan S.; Koo, David C.; Lotz, Jennifer M.; McIntosh, Daniel H.; Mozena, Mark; Rosario, David; Trump, Jonathan R.

2015-12-01

We examine the host morphologies of heavily obscured active galactic nuclei (AGNs) at z∼ 1 to test whether obscured super-massive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGNs with {N}{{H}}\\gt {10}23.5 {{cm}}-2 and z\\lt 1.5. Using visual classifications, we compare the morphologies of these AGNs to control samples of moderately obscured (1022 cm{}-2\\lt {N}{{H}}\\lt {10}23.5 {{cm}}-2) and unobscured ({N}{{H}}\\lt {10}22 {{cm}}-2) AGN. These control AGNs have similar redshifts and intrinsic X-ray luminosities to our heavily obscured AGN. We find that heavily obscured AGNs are twice as likely to be hosted by late-type galaxies relative to unobscured AGNs ({65.3}-4.6+4.1% versus {34.5}-2.7+2.9%) and three times as likely to exhibit merger or interaction signatures ({21.5}-3.3+4.2% versus {7.8}-1.3+1.9%). The increased merger fraction is significant at the 3.8σ level. If we exclude all point sources and consider only extended hosts, we find that the correlation between the merger fraction and obscuration is still evident, although at a reduced statistical significance (2.5σ ). The fact that we observe a different disk/spheroid fraction versus obscuration indicates that the viewing angle cannot be the only thing differentiating our three AGN samples, as a simple unification model would suggest. The increased fraction of disturbed morphologies with obscuration supports an evolutionary scenario, in which Compton-thick AGNs are a distinct phase of obscured super-massive black hole (SMBH) growth following a merger/interaction event. Our findings also suggest that some of the merger-triggered SMBH growth predicted by recent AGN fueling models may be hidden among the heavily obscured, Compton-thick population.

Spectral-luminosity evolution of active galactic nuclei (AGN)

NASA Technical Reports Server (NTRS)

Leiter, Darryl; Boldt, Elihu

1992-01-01

The origin of the cosmic X-ray and gamma-ray backgrounds is explained via the mechanism of AGN spectral-luminosity evolution. The spectral evolution of precursor active galaxies into AGN, and Newton-Raphson input and output parameters are discussed.

The Nature of the Torus in the Heavily Obscured AGN Markarian 3: an X-Ray Study

NASA Technical Reports Server (NTRS)

Guainazzi, M.; Risaliti, G.; Awaki, H.; Arevalo, P.; Bauer, F. E.; Bianchi, S.; Boggs, S.E; Brandt, W. N.; Brightman, M.; Christensen, F. E.;

Towards A Complete Census of the Compton-thick AGN Population in our Cosmic Backyard

NASA Astrophysics Data System (ADS)

Annuar, Ady

2016-09-01

We propose for Chandra and NuSTAR observations of two local AGNs to characterise their obscuring properties. We are using Chandra and NuSTAR to form the first complete measurement of the column density (N_H) distribution of AGN at D<15 Mpc. Even at this distance the distribution was only 50% complete. We have recently improved this, and found a Compton-thick (CT) AGN fraction of >35%. We also found that Chandra resolution is key in resolving the AGN from off-nuclear X-ray sources. When combined with NuSTAR, this allow us to accurately characterise the broadband spectrum of the AGN, and identify it as CT. These new observations will provide Chandra data for all D<15Mpc AGNs and boost up the N_H distribution up to 85% complete. This will be fully completed with future NuSTAR observations.

Cross-Correlation of the X-Ray Background with Nearby Galaxies: Erratum

NASA Astrophysics Data System (ADS)

Jahoda, Keith; Lahav, Ofer; Mushotzky, Richard F.; Boldt, Elihu

1992-11-01

In the Letter "Cross-Correlation of the X-Ray Background with Nearby Galaxies" by Keith Jahoda, Ofer Lahav, Richard F. Mushotzky, & Elihu Boldt (ApJ, 378, L37, [1991]) there is an error in the evaluation of equation(5): the numerical constant is too small by a factor of 4.5 (the solid angle of the HEAO 1 A2 beam). The revised X-ray emissivity values (over the volume sampled by the UGC and ESO galaxies) are as follows. For UGC (using the median of Table 1) ρ_x_ = (10.5 +/- 6.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^, where the error reflects the scatter in Table 1 and the uncertainty in R_*_, the effective depth of the catalogs (the Hubble constant is in units of H_0_ = 50 h_50_ km s^-1^ Mpc^-1^). Similarly for ESO ρ_x = (14.5 +/- 8.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^. For the combined data (UGC and ESO)our revised value is the mean of the two samples,ρ_x_ = (12.5 +/- 7.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^. This correction has important consequences for the discussion section of the paper. First, the fraction of the X-ray background which can be produced by nonevolving X-ray sources distributed out to high redshift (assuming a look-back factor of f=0.5) can be as large as 50% +/- 30% and 70% +/- 40% for UGC and ESO, respectively. Second, this measurement of ρ_x_ exceeds the upper limit calculated by E. Boldt (IAU Colloq. 123,451 [1990]) based on an approximation of the total extragalactic X-ray dipole, unless b{OMEGA}^-0.6^<~ 1.3, less than about half the value derived for bright X-ray AGNs by T. Miyaji & E. Boldt (ApJ, 353, L3 [1990]) and T. Miyaji, K. Jahoda, & E. Boldt (AIP Conf. Proc. 222,431 [1991]). However, an improved determination of the extragalactic X-ray dipole, now obtained by performing a direct vector sum of the all-sky X-ray data (excluding only points near known Galactic point sources and their antipodes and points with |b| < 20^deg^), and subtracting the high-latitude contribution predicted by the Galactic model of D. Iwan et al. (ApJ, 260

A complete hard X-ray selected sample of local, luminous AGNs

NASA Astrophysics Data System (ADS)

Burtscher, Leonard; Davies, Ric; Lin, Ming-yi; Orban de Xivry, Gilles; Rosario, David

2016-08-01

Choosing a very well defined sample is essential for studying the AGN phenomenon. Only the most luminous AGNs can be expected to require a coherent feeding mechanism to sustain their activity and since host galaxy properties and AGN activity are essentially uncorrelated, nuclear scales must be resolved in order to shed light on the feeding mechanisms of AGNs. For these reasons we are compiling a sample of the most powerful, local AGNs. In this talk we present our on-going programme to observe a complete volume limited sample of nearby active galaxies selected by their 14-195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow.

Obscured AGNs in Bulgeless Hosts discovered by WISE: The Case Study of SDSS J1224+5555

NASA Astrophysics Data System (ADS)

Satyapal, S.; Secrest, N. J.; Rothberg, B.; O'Connor, J. A.; Ellison, S. L.; Hickox, R. C.; Constantin, A.; Gliozzi, M.; Rosenberg, J. L.

2016-08-01

There is mounting evidence that supermassive black holes (SMBHs) form and grow in bulgeless galaxies. However, a robust determination of the fraction of active galactic nuclei (AGNs) in bulgeless galaxies, an important constraint to models of SMBH seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for AGNs in low-mass galaxies. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3σ level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of {L}2-10{keV}=(1.1+/- 0.4)× {10}40 erg s-1. Ground-based near-infrared spectroscopy with the Large Binocular Telescope and multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of {N}{{H}}\\gt {10}24 cm-2. The hard X-ray luminosity of the putative AGN corrected for absorption is {L}2-10{keV}˜ 3× {10}42 erg s-1, which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of {L}{bol}.˜ 6× {10}43-3 × 1044 {erg} {{{s}}}-1 and a lower mass limit for the black hole of {M}{BH}≃ 2× {10}6 {M}⊙ , based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of ˜ 2.0× {10}10 {M}⊙ and an above solar metallicity (12 + {logO}/{{H}} = 9.11), typical of our WISE-selected bulgeless galaxy sample. While collectively these

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-01-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Paggi, Alessandro; Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-04-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Contribution of parsec-scale material onto the polarized X-ray spectrum of type-1 Seyfert galaxies

NASA Astrophysics Data System (ADS)

Marin, F.; Dovčiak, M.; Kammoun, E. S.

2018-04-01

Type-1 radio-quiet active galactic nuclei (AGN) are seen from the polar direction and offer a direct view of their central X-ray engine. If most of X-ray photons have traveled from the primary source to the observer with minimum light-matter interaction, a fraction of radiation is emitted at different directions and is reprocessed by the parsec-scale equatorial circumnuclear region or the polar outflows. It is still unclear how much the polarization expected from type-1 AGN is affected by radiation that have scattered on the distant AGN components. In this paper, we examine the contribution of remote material onto the polarized X-ray spectrum of type-1 Seyfert galaxies using radiative transfer Monte Carlo codes. We find that the observed X-ray polarization strongly depends on the initial polarization emerging from the disk-corona system. For unpolarized and parallelly polarized photons (parallel to the disk), the contribution is negligible below 3 keV and tends to increase the polarization degree by up to one percentage points at higher energies, smoothing out the energy-dependent variations of the polarization angle. For perpendicularly polarized corona photons, the addition of the circumnuclear scattered (parallel) component adds to the polarization above 10keV, decreases polarization below 10 keV and shifts the expected 90° rotation of the polarization angle to lower energies. In conclusion, we found that simulations of Seyfert-1s that do not account for reprocessing on the parsec-scale equatorial and polar material are under- or over-estimating the X-ray polarization by 0.1 - 1 percentage points.

X-ray Counterparts of Infrared Faint Radio Sources

NASA Astrophysics Data System (ADS)

Schartel, Norbert

2011-10-01

Infrared Faint Radio Sources (IFRS) are radio sources with extremely faint or even absent infrared emission in deep Spitzer Surveys. Models of their spectral energy distributions, the ratios of radio to infrared flux densities and their steep radio spectra strongly suggest that IFRS are AGN at high redshifts (2AGN numbers at these redshifts will account for the unresolved part of the X-ray background. The identification of X-ray counterparts of IFRS is considered to be the smoking gun for this hypothesis. We propose to observe 8 IFRS using 30ks pointed observations. X-ray detections of IFRS with different ratios of radio-to-infrared fluxes, will constrain the class-specific SED.

Free-Free Radiation Cannot Make the UV/Soft-X-Ray Excess in AGN

NASA Astrophysics Data System (ADS)

Kriss, G. A.

1994-05-01

Thermal gas always has associated atomic spectral features either in absorption or in emission. In optically thin gas the emission spectrum is dominated by line radiation and recombination continua. An example of radiation from optically thin material in accreting systems is the emission-line-dominated spectrum of a cataclysmic variable in its low state. Barvainis (1993, ApJ, 412, 513) and others have proposed that the UV/soft-X-ray excess prominent in the spectra of many AGN is due to free-free emission from gas at temperatures of 10(5) - 10(6) K. Simple arguments using only atomic data show that the recombination radiation from emission lines would produce UV, optical, and soft X-ray spectral features orders of magnitude stronger than observed. Collisional excitation produces even more line radiation under most physical conditions. As a particular example I take the Astro-1 observations of the Seyfert 1 galaxy Mrk 335 by HUT and BBXRT. Depending on the ionization state of the gas (which may be photoionized by the central source), the emission measure of the free-free radiation necessary to produce the UV continuum (3 times 10(68) cm(-3) at 8.2 times 10(5) K for H_o = 75 km s(-1) Mpc(-1) ) implies line emission from O VI, O VII, or O VIII more than a factor of 10 stronger than any features observed by HUT or BBXRT.

THE XMM-NEWTON WIDE FIELD SURVEY IN THE COSMOS FIELD: REDSHIFT EVOLUTION OF AGN BIAS AND SUBDOMINANT ROLE OF MERGERS IN TRIGGERING MODERATE-LUMINOSITY AGNs AT REDSHIFTS UP TO 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allevato, V.; Hasinger, G.; Salvato, M.

2011-08-01

We present a study of the redshift evolution of the projected correlation function of 593 X-ray selected active galactic nuclei (AGNs) with I{sub AB} < 23 and spectroscopic redshifts z < 4, extracted from the 0.5-2 keV X-ray mosaic of the 2.13 deg{sup 2} XMM- Cosmic Evolution Survey (COSMOS). We introduce a method to estimate the average bias of the AGN sample and the mass of AGN hosting halos, solving the sample variance using the halo model and taking into account the growth of the structure over time. We find evidence of a redshift evolution of the bias factor formore » the total population of XMM-COSMOS AGNs from b-bar (z-bar =0.92)=2.30{+-}0.11 to b-bar (z-bar =1.94)=4.37{+-}0.27 with an average mass of the hosting dark matter (DM) halos log M{sub 0}(h{sup -1} M{sub sun}) {approx} 13.12 {+-} 0.12 that remains constant at all z < 2. Splitting our sample into broad optical line AGNs (BL), AGNs without broad optical lines (NL), and X-ray unobscured and obscured AGNs, we observe an increase of the bias with redshift in the range z-bar = 0.7-2.25 and z-bar = 0.6-1.5 which corresponds to a constant halo mass of log M{sub 0}(h{sup -1} M{sub sun}) {approx} 13.28 {+-} 0.07 and log M{sub 0}(h{sup -1} M{sub sun}) {approx} 13.00 {+-} 0.06 for BL/X-ray unobscured AGNs and NL/X-ray obscured AGNs, respectively. The theoretical models, which assume a quasar phase triggered by major mergers, cannot reproduce the high bias factors and DM halo masses found for X-ray selected BL AGNs with L{sub BOL} {approx} 2 x 10{sup 45} erg s{sup -1}. Our work extends up to z {approx} 2.2 the z {approx}< 1 statement that, for moderate-luminosity X-ray selected BL AGNs, the contribution from major mergers is outnumbered by other processes, possibly secular ones such as tidal disruptions or disk instabilities.« less

AXIS - A High Angular Resoltuion X-ray Probe Concept Study

NASA Astrophysics Data System (ADS)

Mushotzky, Richard; AXIS Study Team

2018-01-01

AXIS is a probe-class concept under study to the 2020 Decadal survey. AXIS will extend and enhance the science of high angular resolution x-ray imaging and spectroscopy in the next decade with ~0.3" angular resolution over a 7' radius field of view and an order of magnitude more collecting area than Chandra in the 0.3-12 keV band with a cost consistent with a probe.These capabilities enable major advances in a wide range of science such as: (1) measuring the event horizon scale structure in AGN accretion disks and the spins of supermassive black holes through observations of gravitationally-microlensed quasars; (ii) determining AGN and starburst feedback in galaxies and galaxy clusters through direct imaging of winds and interaction of jets and via spatially resolved imaging of galaxies at high-z; (iii) fueling of AGN by probing the Bondi radius of over 20 nearby galaxies; (iv) hierarchical structure formation and the SMBH merger rate through measurement of the occurrence rate of dual AGN and occupation fraction of SMBHs; (v) advancing SNR physics and galaxy ecology through large detailed samples of SNR in nearby galaxies; (vi) measuring the Cosmic Web through its connection to cluster outskirts. With a nominal 2028 launch, AXIS benefits from natural synergies with the ELTs, LSST, ALMA, WFIRST and ATHENA. AXIS utilizes breakthroughs in the construction of lightweight X-ray optics from mono-crystalline silicon blocks, and developments in the fabrication of large format, small pixel, high readout rate detectors allowing a robust and cost effective design. The AXIS team welcomes input and feedback from the community in preparation for the 2020 Decadal review.

Mini-Survey Of SDSS of [OIII] AGN With Swift

NASA Technical Reports Server (NTRS)

Angelini, L.; George, I. M.; Hill, J.; Padgett, C. A.; Mushotzky, R. F.

2008-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work (e.g. Ferrarese and Merritt 2000) strongly suggests every massive galaxy has a central black hole. However, most of these objects either are not radiating or have been very difficult to detect. We are now in the era of large surveys, and the luminosity function (LF) of AGN has been estimated in various ways. In the X-ray band, Chandra and XMM surveys (e.g., Barger et al. 2005; Hasinger, et al. 2005) have revealed that the LF of Hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(x) (at al z). This is seen for all types of AGN, but is stronger for the broad-line objects (e.g., Steffen et al. 2004). In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects (Hao et al. 2005). If, as been suggested, hard X-ray and optical emission line can both be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

NuSTAR constraints on coronal cutoffs in Swift-BAT selected Seyfert 1 AGN

NASA Astrophysics Data System (ADS)

Kamraj, Nikita; Harrison, Fiona; Balokovic, Mislav; Brightman, Murray; Stern, Daniel

2017-08-01

The continuum X-ray emission from Active Galactic Nuclei (AGN) is believed to originate in a hot, compact corona above the accretion disk. Compton upscattering of UV photons from the inner accretion disk by coronal electrons produces a power law X-ray continuum with a cutoff at energies determined by the electron temperature. The NuSTAR observatory, with its high sensitivity in hard X-rays, has enabled detailed broadband modeling of the X-ray spectra of AGN, thereby allowing tight constraints to be placed on the high-energy cutoff of the X-ray continuum. Recent detections of low cutoff energies in Seyfert 1 AGN in the NuSTAR band have motivated us to pursue a systematic search for low cutoff candidates in Swift-BAT detected Seyfert 1 AGN that have been observed with NuSTAR. We use our constraints on the cutoff energy to map out the location of these sources on the compactness - temperature diagram for AGN coronae, and discuss the implications of low cutoff energies for the cooling and thermalization mechanisms in the corona.

The X-ray view of radio-loud active galactic nuclei: The central engine and its environment

NASA Astrophysics Data System (ADS)

Donato, Davide

The non-thermal emission from many Active Galactic Nuclei (AGN) is obscured by optically thick circumnuclear matter, particularly at optical and ultraviolet wavelengths. In radio-loud (RL) sources, the AGN activity is coupled with the presence of a bipolar jet that emit radio through g-ray light which is relativistically beamed along the jet axes. The combination of absorption and beaming produces highly anisotropic radiation. The understanding of the origin and magnitude of this radiation allows astronomers to unify different classes of AGN; that is, to identify each single, underlying AGN type that gives rise to different classes through different orientations with respect to the jet axis. This is the fundamental notion behind what are called "unification models" of AGN. Although this general idea is well accepted, many aspects remain matter of debate. In fact, the explanation of the wide and complex variety of AGN phenomena must be searched in a combination of apparent differences (like orientation) and real differences in a number of physical parameters (like gas/dust content and distribution, luminosity, etc.). The goal of this thesis is to address some of the RL unification open questions using X-ray data. The improved sensitivity and angular resolution of a new generation of satellites, combined with the fact that X-rays provide useful information on a variety of AGN phenomena, will allow me to: (1) Study the broadband X-ray continua of BL Lacertae objects (BL Lacs) and Flat Spectrum Radio Quasars (FSRQs); (2) Probe the emission from the very inner region of an AGN; (3) Determine the presence and characteristic of extended X-ray emission from the AGN environment. The results obtained from theses studies will provide me insights into (1) the X-ray average spectral properties of BL Lacs and FSRQs and the physical processes responsible of the emission; (2) the presence of the obscuring torus and the amount of absorption, (3) the nature of X-ray emission, and (4

Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291

NASA Technical Reports Server (NTRS)

Luo, B.; Fabbiano, G.; Fragos, T.; Kim, D. W.; Belczynski, K.; Brassington, N. J.; Pellegrini, S.; Tzanavaris, P.; Wang, J.; Zezas, A.

2012-01-01

We present Chandra studies of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available Chandra observations totaling an effective exposure of 179 ks. We report photometric properties of these sources in a point-source catalog. There are approx. 40% of the bulge sources and approx. 25% of the ring sources showing > 3(sigma) long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (approx. 75%) and ring (approx. 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity AGN with moderate obscuration; spectral variability is observed between individual observations. We construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. We reach 90% completeness limits of approx.1.5 x 10(exp 37) and approx. 2.2 x 10(exp 37) erg/s for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. We perform detailed population synthesis modeling of the XRB populations in NGC 1291 , which suggests that the observed combined XLF is dominated by aD old LMXB population. We compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative over-density of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

NASA Astrophysics Data System (ADS)

Farrah, Duncan; Baloković, Mislav; Stern, Daniel; Harris, Kathryn; Kunimoto, Michelle; Walton, Dominic J.; Alexander, David M.; Arévalo, Patricia; Ballantyne, David R.; Bauer, Franz E.; Boggs, Steven; Brandt, William N.; Brightman, Murray; Christensen, Finn; Clements, David L.; Craig, William; Fabian, Andrew; Hailey, Charles; Harrison, Fiona; Koss, Michael; Lansbury, George B.; Luo, Bin; Paine, Jennie; Petty, Sara; Pitchford, Kate; Ricci, Claudio; Zhang, William

2016-11-01

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel, X-ray data from NuSTAR, Swift, Suzaku, and Chandra, and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1-1000 μm luminosity of 5.5 × 1046 erg s-1 and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 1046 erg s-1 and a viewing angle and half-opening angle both of approximately 36° from pole-on. The starburst has a star formation rate of (110 ± 34) M ⊙ yr-1 and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Γ ≃ 1.8 and a line-of-sight column density of N H ≃ 5 × 1023 cm-2. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N H and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L bol ˜ (0.5-2.5) × 1047 erg s-1. The X-ray and infrared data are further consistent with coaligned AGN obscurers in which the line of sight “skims” the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.

A Comparison of the X-Ray Emission from Tidal Disruption Events with those of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Auchettl, Katie; Ramirez-Ruiz, Enrico; Guillochon, James

2018-01-01

One of the main challenges of current tidal disruption events (TDEs) studies is that emission arising from active galactic nucleus (AGN) activity may potentially mimic the expected X-ray emission of a TDE. Here we compare the X-ray properties of TDEs and AGNs to determine a set of characteristics that would allow us to discriminate between flares arising from these two objects. We find that at peak, TDEs are brighter than AGNs found at similar redshifts. However, compared to pre-flare upper limits, highly variable AGNs can produce flares of a similar order of magnitude as those seen from X-ray TDEs. Nevertheless, TDEs decay significantly more monotonically, and their emission exhibits little variation in spectral hardness as a function of time. We also find that X-ray TDEs are less absorbed, and their emission is much softer than the emission detected from AGNs found at similar redshifts. We derive the X-ray luminosity function (LF) for X-ray TDEs using the events from Auchettl et al. Interestingly, our X-ray LF closely matches the theoretically derived LF by Milosavljević et al., which assumes a higher TDE rate currently estimated from observations. Using our results and the results of Stone & Metzger, we estimate a TDE rate of (0.7–4.7) × 10‑4 year‑1 per galaxy, higher than current observational estimates. We find that TDEs can contribute significantly to the LF of AGNs for z ≲ 0.4, while there is no evidence that TDEs influence the growth of 106–7 M ⊙ BHs. However, BHs < 106 M ⊙ can grow from TDEs arising from super-Eddington accretion without contributing significantly to the observed AGN LF at z = 0.

Mini-Survey of SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

Angelina, Lorella; George, Ian

2007-01-01

There is a common wisdom that every massive galaxy has a massive block hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low Lx (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of (optically-selected samples) shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [OIII] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a mini-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([OIII]) to check the relation with the Lx observed with Swift.

Contribution of parsec-scale material on to the polarized X-ray spectrum of type 1 Seyfert galaxies

NASA Astrophysics Data System (ADS)

Marin, F.; Dovčiak, M.; Kammoun, E. S.

2018-07-01

Type 1 radio-quiet active galactic nuclei (AGN) are seen from the polar direction and offer a direct view of their central X-ray engine. If most of X-ray photons have travelled from the primary source to the observer with minimum light-matter interaction, a fraction of radiation is emitted at different directions and is reprocessed by the parsec-scale equatorial circumnuclear region or the polar outflows. It is still unclear how much the polarization expected from type 1 AGN is affected by radiation that have scattered on the distant AGN components. In this paper, we examine the contribution of remote material on to the polarized X-ray spectrum of type 1 Seyfert galaxies (Seyfert-1s) using radiative transfer Monte Carlo codes. We find that the observed X-ray polarization strongly depends on the initial polarization emerging from the disc-corona system. For unpolarized and parallelly polarized photons (parallel to the disc), the contribution is negligible below 3 keV and tends to increase the polarization degree by up to one percentage points at higher energies, smoothing out the energy-dependent variations of the polarization angle. For perpendicularly polarized corona photons, the addition of the circumnuclear scattered (parallel) component adds to the polarization above 10 keV, decreases polarization below 10 keV and shifts the expected 90° rotation of the polarization angle to lower energies. In conclusion, we found that simulations of Seyfert-1s that do not account for reprocessing on the parsec-scale equatorial and polar material are under- or overestimating the X-ray polarization by 0.1-1 percentage points.

The Complete Local-Volume Groups Sample (CLoGS): Early results from X-ray and radio observations

NASA Astrophysics Data System (ADS)

Vrtilek, Jan M.; O'Sullivan, Ewan; David, Laurence P.; Giacintucci, Simona; Kolokythas, Konstantinos

2017-08-01

Although the group environment is the dominant locus of galaxy evolution (in contrast to rich clusters, which contain only a few percent of galaxies), there has been a lack of reliable, representative group samples in the local Universe. In particular, X-ray selected samples are strongly biased in favor of the X-ray bright, centrally-concentrated cool-core systems. In response, we have designed the Complete Local-Volume Groups Sample (CLoGS), an optically-selected statistically-complete sample of 53 groups within 80 Mpc which is intended to overcome the limitations of X-ray selected samples and serve as a representative survey of groups in the local Universe. We have supplemented X-ray data from Chandra and XMM (70% complete to date, using both archival and new observations, with a 26-group high richness subsample 100% complete) with GMRT radio continuum observations (at 235 and 610 MHz, complete for the entire sample). CLoGS includes groups with a wide variety of properties in terms of galaxy population, hot gas content, and AGN power. We here describe early results from the survey, including the range of AGN activity observed in the dominant galaxies, the relative fraction of cool-core and non-cool-core groups in our sample, and the degree of disturbance observed in the IGM.

Luminosity function and cosmological evolution of X-ray selected quasars

NASA Technical Reports Server (NTRS)

Maccacaro, T.; Gioia, I. M.

1983-01-01

The preliminary analysis of a complete sample of 55 X-ray sources is presented as part of the Medium Sensitivity Survey of the Einstein Observatory. A pure luminosity evolutionary law is derived in order to determine the uniform distribution of the sources and the rates of evolution for Active Galactic Nuclei (AGNs) observed by X-ray and optical techniques are compared. A nonparametric representation of the luminosity function is fitted to the observational data. On the basis of the reduced data, it is determined that: (1) AGNs evolve cosmologically; (2) less evolution is required to explain the X-ray data than the optical data; (3) the high-luminosity portion of the X-ray luminosity can be described by a power-law with a slope of gamma = 3.6; and (4) the X-ray luminosity function flattens at low luminosities. Some of the implications of the results for conventional theoretical models of the evolution of quasars and Seyfert galaxies are discussed.

The physics of black hole x ray novae

NASA Technical Reports Server (NTRS)

Wheeler, J. C.; Kim, S.-W.; Moscoso, M. D.; Mineshige, S.

1994-01-01

X-ray transients that are established or plausible black hole candidates have been discovered at a rate of about one per year in the galaxy for the last five years. There are now well over a dozen black hole candidates, most being in the category of X-ray novae with low-mass companions. There may be hundreds of such transient systems in the galaxy yet to be discovered. Classic black hole candidates like Cygnus X-1 with massive companions are in the minority, and their census in the galaxy and magellanic clouds is likely to be complete. The black hole X-ray novae (BHXN) do not represent only the most common environment in which to discover black holes. Their time dependence gives a major new probe with which to study the physics of accretion into black holes. The BHXN show both a soft X-ray flux from an optically thick disk and a hard power law tail that is reminiscent of AGN spectra. The result may be new insight into the classical systems like Cyg X-1 and LMC X-1 that show similar power law tails, but also to accretion into supermassive black holes and AGN.

THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lusso, E.; Hennawi, J. F.; Richards, G. T.

2013-11-10

The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 bandmore » COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.« less

The XXL Survey. VI. The 1000 brightest X-ray point sources

NASA Astrophysics Data System (ADS)

Fotopoulou, S.; Pacaud, F.; Paltani, S.; Ranalli, P.; Ramos-Ceja, M. E.; Faccioli, L.; Plionis, M.; Adami, C.; Bongiorno, A.; Brusa, M.; Chiappetti, L.; Desai, S.; Elyiv, A.; Lidman, C.; Melnyk, O.; Pierre, M.; Piconcelli, E.; Vignali, C.; Alis, S.; Ardila, F.; Arnouts, S.; Baldry, I.; Bremer, M.; Eckert, D.; Guennou, L.; Horellou, C.; Iovino, A.; Koulouridis, E.; Liske, J.; Maurogordato, S.; Menanteau, F.; Mohr, J. J.; Owers, M.; Poggianti, B.; Pompei, E.; Sadibekova, T.; Stanford, A.; Tuffs, R.; Willis, J.

2016-06-01

Context. X-ray extragalactic surveys are ideal laboratories for the study of the evolution and clustering of active galactic nuclei (AGN). Usually, a combination of deep and wide surveys is necessary to create a complete picture of the population. Deep X-ray surveys provide the faint population at high redshift, while wide surveys provide the rare bright sources. Nevertheless, very wide area surveys often lack the ancillary information available for modern deep surveys. The XXL survey spans two fields of a combined 50 deg2 observed for more than 6Ms with XMM-Newton, occupying the parameter space that lies between deep surveys and very wide area surveys; at the same time it benefits from a wealth of ancillary data. Aims: This paper marks the first release of the XXL point source catalogue including four optical photometry bands and redshift estimates. Our sample is selected in the 2 - 10 keV energy band with the goal of providing a sizable sample useful for AGN studies. The limiting flux is F2 - 10 keV = 4.8 × 10-14 erg s-1 cm-2. Methods: We use both public and proprietary data sets to identify the counterparts of the X-ray point-like sources by means of a likelihood ratio test. We improve upon the photometric redshift determination for AGN by applying a Random Forest classification trained to identify for each object the optimal photometric redshift category (passive, star forming, starburst, AGN, quasi-stellar objects (QSO)). Additionally, we assign a probability to each source that indicates whether it might be a star or an outlier. We apply Bayesian analysis to model the X-ray spectra assuming a power-law model with the presence of an absorbing medium. Results: We find that the average unabsorbed photon index is ⟨Γ⟩ = 1.85 ± 0.40 while the average hydrogen column density is log ⟨NH⟩ = 21.07 ± 1.2 cm-2. We find no trend of Γ or NH with redshift and a fraction of 26% absorbed sources (log NH> 22) consistent with the literature on bright sources (log

Challenges in Finding AGNs in the Low Luminosity Regime

NASA Astrophysics Data System (ADS)

Satyapal, Shobita; Abel, Nick; Secrest, Nathan; Singh, Amrit; Ellison, Sara

2016-08-01

Low luminosity AGNs are an important component of the AGN population. They are often found in the lowest mass galaxies or galaxies that lack classical bulges, a demographic that places important constraints to models of supermassive black hole seed formation and merger-free models of AGN fueling. The detection of AGNs in this low luminosity regime is challenging both because star formation in the host galaxy can dominate the optical spectrum and gas and dust can obscure the central engine at both optical and X-ray wavelengths. Thus while mid-infrared color selection and X-ray observations at energies <10 keV are often powerful tools in uncovering optically unidentified AGNs at higher luminosities, this is not the case in the low luminosity regime. In this talk, I will review the effectiveness of uncovering AGNs in the low luminosity regime using multiwavength investigations, with a focus on infrared spectroscopic signatures.

AGN Variability in the GOODS Fields

NASA Astrophysics Data System (ADS)

Sarajedini, Vicki

2007-07-01

Variability is a proven method to identify intrinsically faint active nuclei in galaxies found in deep HST surveys. We propose to extend our short-term variability study of the GOODS fields to include the more recent epochs obtained via supernovae searchers, increasing the overall time baseline from 6 months to 2.5 years. Based on typical AGN lightcurves, we expect to detect 70% more AGN by including these more recent epochs. Variable-detected AGN samples complement current X-ray and mid-IR surveys for AGN by providing unambigous evidence of nuclear activity. Additionallty, a significant number of variable nuclei are not associated with X-ray or mid-IR sources and would thus go undetected. With the increased time baseline, we will be able to construct the structure function {variability amplitude vs. time} for low-luminosity AGN to z 1. The inclusion of the longer time interval will allow for better descrimination among the various models describing the nature of AGN variability. The variability survey will be compared against spectroscopically selected AGN from the Team Keck Redshift Survey of the GOODS-N and the upcoming Flamingos-II NIR survey of the GOODS-S. The high-resolution ACS images will be used to separate the AGN from the host galaxy light and study the morphology, size and environment of the host galaxy. These studies will address questions concerning the nature of low-luminosity AGN evolution and variability at z 1.

Characterisation of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M.; Heida, M.

2018-05-01

We present Chandra and optical observations of a candidate dual AGN discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalog (2XMMi) and SDSS-DR7 galaxies with a separation no larger than ten times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionisation. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission line ratios dominated by stellar photoionisation with a "composite" signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity vs [OIII] luminosity both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution we infer that both galaxies host rotationally supported bulges (Sersic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalising.

Characterization of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M. A. P.; Heida, M.

2018-07-01

We present Chandra and optical observations of a candidate dual active galactic nucleus (AGN) discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalogue (2XMMi) and SDSS-DR7 galaxies with a separation no larger than 10 times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionization. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission-line ratios dominated by stellar photoionization with a `composite' signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity versus [OIII] luminosity, both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum, we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution, we infer that both galaxies host rotationally supported bulges (Sérsic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalizing.

An X-Ray/SDSS Sample: Observational Characterization of The Outflowing Gas

NASA Astrophysics Data System (ADS)

Perna, Michele; Brusa, M.; Lanzuisi, G.; Mignoli, M.

2016-10-01

Powerful ionised AGN-driven outflows, commonly detected both locally and at high redshift, are invoked to contribute to the co-evolution of SMBH and galaxies through feedback phenomena. Our recent works (Brusa+2015; 2016; Perna+2015a,b) have shown that the XMM-COSMOS targets with evidence of outflows collected so far ( 10 sources) appear to be associated with low X-ray kbol corrections (Lbol /LX ˜ 18), in spite of their spread in obscuration, in the locations on the SFR-Mstar diagram, in their radio emission. A higher statistical significance is required to validate a connection between outflow phenomena and a X-ray loudness. Moreover, in order to validate their binding nature to the galaxy fate, it is crucial to correctly determine the outflow energetics. This requires time consuming integral field spectroscopic (IFS) observations, which are, at present, mostly limited to high luminosity objectsThe study of SDSS data offers a complementary strategy to IFS efforts. I will present physical and demographic characterization of the AGN-galaxy system during the feedback phase obtained studying a sample of 500 X-ray/SDSS AGNs, at z<0.8. Outflow velocity inferred from [OIII]5007 emission line profile has been related to optical (e.g., [OIII] and bolometric luminosities, Eddington ratio, stellar velocity dispersion) and X-ray properties (intrinsic X-ray luminosity, obscuration and X-ray kbol correction), to determine what drives ionised winds. Several diagnostic line ratios have been used to infer the physical properties of the ionised outflowing gas. The knowledge of these properties can reduce the actual uncertainties in the outflow energetics by a factor of ten, pointing to improve our understanding of the AGN outflow phenomenon and its impact on galaxy evolution.

Tracing the Far-Infrared Roles of AGN in Dusty Star-Forming Galaxies

NASA Astrophysics Data System (ADS)

Brown, Arianna; Nayyeri, Hooshang; Cooray, Asantha R.; Mitchell-Wynne, Ketron

2017-01-01

Active galactic nuclei (AGNs) are suggested to play an important role in quenching their host galaxy’s star formation rate (SFR) by heating up and/or consuming the cool gas necessary to create stars. This mechanism is theorized as a critical step in AGN evolutionary models. The efforts to study this effect suffer in part from low-number statistics at high x-ray luminosities (LXR > 1044 ergs/s) for AGNs at z≈1-3, and a lack of separately estimated SFRs for AGN in dusty, star-forming galaxies (DSFGs). In this work, we extend our analysis to build a more complete picture using the variety of available multi-wavelength data in the XBoötes region. The Chandra XBoötes Survey is a 5-ks X-ray survey of the 9.3 square degree Boötes Field of the NOAO Deep Wide-Field Survey, a survey imaged from the optical to the near-IR. We estimate AGN spectral energy distributions and SFRs for ~400 x-ray sources using available data in all four Spitzer IRAC bands, the Spitzer MIPS 24µm band, all five Herschel SPIRE and PACS bands, along with NEWFIRM optical bands. Preliminary results show an exponential correlation between x-ray luminosity and star formation. As a comparison, we will use a stacking technique for the ~500 x-ray sources that were not detected at submillimeter wavelengths, where sources are binned by x-ray luminosity. We will compare these two samples and expect to see a difference in slope. Using these techniques, we hope to place tighter constraints on the mean SFRs of high-luminosity AGNs inside DSFGs, and determine if x-ray luminosities are independent of average SFRs for our sample in the Boötes field.

New Spectral Model for Constraining Torus Covering Factors from Broadband X-Ray Spectra of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Baloković, M.; Brightman, M.; Harrison, F. A.; Comastri, A.; Ricci, C.; Buchner, J.; Gandhi, P.; Farrah, D.; Stern, D.

2018-02-01

The basic unified model of active galactic nuclei (AGNs) invokes an anisotropic obscuring structure, usually referred to as a torus, to explain AGN obscuration as an angle-dependent effect. We present a new grid of X-ray spectral templates based on radiative transfer calculations in neutral gas in an approximately toroidal geometry, appropriate for CCD-resolution X-ray spectra (FWHM ≥ 130 eV). Fitting the templates to broadband X-ray spectra of AGNs provides constraints on two important geometrical parameters of the gas distribution around the supermassive black hole: the average column density and the covering factor. Compared to the currently available spectral templates, our model is more flexible, and capable of providing constraints on the main torus parameters in a wider range of AGNs. We demonstrate the application of this model using hard X-ray spectra from NuSTAR (3–79 keV) for four AGNs covering a variety of classifications: 3C 390.3, NGC 2110, IC 5063, and NGC 7582. This small set of examples was chosen to illustrate the range of possible torus configurations, from disk-like to sphere-like geometries with column densities below, as well as above, the Compton-thick threshold. This diversity of torus properties challenges the simple assumption of a standard geometrically and optically thick toroidal structure commonly invoked in the basic form of the unified model of AGNs. Finding broad consistency between our constraints and those from infrared modeling, we discuss how the approach from the X-ray band complements similar measurements of AGN structures at other wavelengths.

Predicting the X-ray polarization of type 2 Seyfert galaxies

NASA Astrophysics Data System (ADS)

Marin, F.; Dovčiak, M.; Muleri, F.; Kislat, F. F.; Krawczynski, H. S.

2018-01-01

Infrared, optical and ultraviolet spectropolarimetric observations have proven to be ideal tools for the study of the hidden nuclei of type 2 active galactic nuclei (AGN) and for constraining the composition and morphology of the sub-parsec scale emission components. In this paper, we extend the analysis to the polarization of the X-rays from type 2 AGN. Combining two radiative transfer codes, we performed the first simulations of photons originating in the gravity-dominated vicinity of the black hole and scattering in structures all the way out to the parsec-scale torus and polar winds. We demonstrate that, when strong gravity effects are accounted for, the X-ray polarimetric signal of Seyfert-2s carries as much information about the central AGN components as spectropolarimetric observations of Seyfert-1s. The spectropolarimetric measurements can constrain the spin of the central supermassive black hole even in edge-on AGN, the hydrogen column density along the observer's line-of-sight and the composition of the polar outflows. However, the polarization state of the continuum source is washed out by multiple scattering, and should not be measurable unless the initial polarization is exceptionally strong. Finally, we estimate that modern X-ray polarimeters, either based on the photoelectric effect or on Compton scattering, will require long observational times on the order of a couple of megaseconds to be able to properly measure the polarization of type 2 AGN.

On the mean radiative efficiency of accreting massive black holes in AGNs and QSOs

NASA Astrophysics Data System (ADS)

Zhang, XiaoXia; Lu, YouJun

2017-10-01

Radiative efficiency is an important physical parameter that describes the fraction of accretion material converted to radiative energy for accretion onto massive black holes (MBHs). With the simplest Sołtan argument, the radiative efficiency of MBHs can be estimated by matching the mass density of MBHs in the local universe to the accreted mass density by MBHs during AGN/QSO phases. In this paper, we estimate the local MBH mass density through a combination of various determinations of the correlations between the masses of MBHs and the properties of MBH host galaxies, with the distribution functions of those galaxy properties. We also estimate the total energy density radiated by AGNs and QSOs by using various AGN/QSO X-ray luminosity functions in the literature. We then obtain several hundred estimates of the mean radiative efficiency of AGNs/QSOs. Under the assumption that those estimates are independent of each other and free of systematic effects, we apply the median statistics as described by Gott et al. and find the mean radiative efficiency of AGNs/QSOs is ɛ = 0.105 -0.008 +0.006 , which is consistent with the canonical value 0.1. Considering that about 20% Compton-thick objects may be missed from current available X-ray surveys, the true mean radiative efficiency may be actually 0.12.

A deep X-ray view of the bare AGN Ark 120. III. X-ray timing analysis and multiwavelength variability

NASA Astrophysics Data System (ADS)

Lobban, A. P.; Porquet, D.; Reeves, J. N.; Markowitz, A.; Nardini, E.; Grosso, N.

2018-03-01

We present the spectral/timing properties of the bare Seyfert galaxy Ark 120 through a deep ˜420 ks XMM-Newton campaign plus recent NuSTAR observations and a ˜6-month Swift monitoring campaign. We investigate the spectral decomposition through fractional rms, covariance and difference spectra, finding the mid- to long-time-scale (˜day-year) variability to be dominated by a relatively smooth, steep component, peaking in the soft X-ray band. Additionally, we find evidence for variable Fe K emission redward of the Fe Kα core on long time-scales, consistent with previous findings. We detect a clearly defined power spectrum which we model with a power law with a slope of α ˜ 1.9. By extending the power spectrum to lower frequencies through the inclusion of Swift and Rossi X-ray Timing Explorer data, we find tentative evidence of a high-frequency break, consistent with existing scaling relations. We also explore frequency-dependent Fourier time lags, detecting a negative (`soft') lag for the first time in this source with the 0.3-1 keV band lagging behind the 1-4 keV band with a time delay, τ, of ˜900 s. Finally, we analyse the variability in the optical and ultraviolet (UV) bands using the Optical/UV Monitor onboard XMM-Newton and the Ultra-Violet/Optical Telescope onboard Swift and search for time-dependent correlations between the optical/UV/X-ray bands. We find tentative evidence for the U-band emission lagging behind the X-rays with a time delay of τ = 2.4 ± 1.8 d, which we discuss in the context of disc reprocessing.

Inflow Generated X-ray Corona Around Supermassive Black Holes and Unified Model for X-ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-01-01

Three-dimensional hydrodynamic simulations, covering the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass 108 M⊙, with detailed radiative cooling processes, are performed. Generically found is the existence of a significant amount of shock heated, high temperature (≥108 K) coronal gas in the inner (≤104 rsch) region. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures are in reasonable agreement with the overall ensemble spectrum of AGNs and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shape, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

SPECTRAL SURVEY OF X-RAY BRIGHT ACTIVE GALACTIC NUCLEI FROM THE ROSSI X-RAY TIMING EXPLORER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard, E-mail: erivers@ucsd.edu

2011-03-15

Using long-term monitoring data from the Rossi X-ray Timing Explorer (RXTE), we have selected 23 active galactic nuclei (AGNs) with sufficient brightness and overall observation time to derive broadband X-ray spectra from 3 to {approx}>100 keV. Our sample includes mainly radio-quiet Seyferts, as well as seven radio-loud sources. Given the longevity of the RXTE mission, the greater part of our data is spread out over more than a decade, providing truly long-term average spectra and eliminating inconsistencies arising from variability. We present long-term average values of absorption, Fe line parameters, Compton reflection strengths, and photon indices, as well as fluxesmore » and luminosities for the hard and very hard energy bands, 2-10 keV and 20-100 keV, respectively. We find tentative evidence for high-energy rollovers in three of our objects. We improve upon previous surveys of the very hard X-ray energy band in terms of accuracy and sensitivity, particularly with respect to confirming and quantifying the Compton reflection component. This survey is meant to provide a baseline for future analysis with respect to the long-term averages for these sources and to cement the legacy of RXTE, and especially its High Energy X-ray Timing Experiment, as a contributor to AGN spectral science.« less

Disentangling Dominance: Obscured AGN Activity versus Star Formation in BPT-Composites

NASA Astrophysics Data System (ADS)

Trouille, Laura

2011-11-01

Approximately 20% of SDSS emission-line galaxies (ELG) lie in the BPT-comp regime, between the Kauffmann et al. (2003) empirically determined SF-dominated regime and the Kewley et al. (2001) theoretically predicted AGN-dominated regime. BPT-AGN, on the other hand, make up only 11% of the ELG population. Whether to include the significant number of BPT-comp in samples of AGN or samples of star-forming galaxies is an open question and has important implications for galaxy evolution studies, metallicity studies, etc. Using a large pectroscopic sample of GOODS-N and LH galaxies with deep Chandra imaging, we perform an X-ray stacking analysis of BPT-comp. We find the stacked signal to be X-ray hard. This X-ray hardness can be indicative of obscured AGN activity or the presence of HMXBs associated with ongoing star formation. In order to distinguish between these scenarios, we perform an IR stacking analysis using Spitzer 24 micron data. The stacked BPT-comp lies well above the expected value for L_x/L_IR for pure star-forming galaxies; similarly for the X-ray detected BPT-comp. We also find that the BPT-comp lie in the AGN-dominated regime of our new TBT diagnostic, which uses [NeIII]/[OII] versus rest-frame g-z colour to identify AGN and star forming galaxies out to z=1.4. [NeIII], which has a higher ionisation potential than other commonly used forbidden emission lines, appears to foster a more reliable selection of AGN-dominated galaxies. These findings suggest that both the X-ray and optical signal in BPT-comp are dominated by obscured or low accretion rate AGN activity rather than star formation. This is in contrast to claims by previous optical emission-line studies that the signal in BPT-comp is dominated by star-formation activity. Therefore, we recommend that groups carefully consider the impact of excluding or including BPT-comp on the interpretation of their results. For example, for studies involving determining the bolometric contribution from AGN activity

THE GEOMETRY OF THE INFRARED AND X-RAY OBSCURER IN A DUSTY HYPERLUMINOUS QUASAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farrah, Duncan; Harris, Kathryn; Baloković, Mislav

2016-11-01

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel , X-ray data from NuSTAR , Swift , Suzaku , and Chandra , and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1–1000 μ m luminosity of 5.5 × 10{sup 46} erg s{sup −1} and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 10{sup 46} erg s{sup −1} and a viewing angle and half-openingmore » angle both of approximately 36° from pole-on. The starburst has a star formation rate of (110 ± 34) M {sub ⊙} yr{sup −1} and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Γ ≃ 1.8 and a line-of-sight column density of N {sub H} ≃ 5 × 10{sup 23} cm{sup −2}. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N {sub H} and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L {sub bol} ∼ (0.5–2.5) × 10{sup 47} erg s{sup −1}. The X-ray and infrared data are further consistent with coaligned AGN obscurers in which the line of sight “skims” the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.« less

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

NASA Technical Reports Server (NTRS)

Farrah, Duncan; Balokovic, Mislav; Stern, Daniel; Harris, Kathryn; Kunimoto, Michelle; Walton, Dominc J.; Alexander, David M.; Arevalo, Patricia; Ballantyne, David R.; Bauer, Franz E.;

VLA observations of a complete sample of extragalactic X-ray sources. II

NASA Technical Reports Server (NTRS)

Schild, R.; Zamorani, G.; Gioia, I. M.; Feigelson, E. D.; Maccacaro, T.

1983-01-01

A complete sample of 35 X-ray selected sources found with the Einstein Observatory has been observed with the Very Large Array at 6 cm to investigate the relationship between radio and X-ray emission in extragalactic objects. Detections include three active galactic nuclei (AGNs), two clusters or groups of galaxies, two individual galaxies, and two BL Lac objects. The frequency of radio emission in X-ray selected AGNs is compared with that of optically selected quasars using the integral radio-optical luminosity function. The result suggests that the probability for X-ray selected quasars to be radio sources is higher than for those optically selected. No obvious correlation is found in the sample between the richness of X-ray luminosity of the cluster and the presence of a galaxy with radio luminosity at 5 GHz larger than 10 to the 30th ergs/s/Hz.

Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

NASA Astrophysics Data System (ADS)

Assef, R. J.; Walton, D. J.; Brightman, M.; Stern, D.; Alexander, D.; Bauer, F.; Blain, A. W.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Finkelstein, S. L.; Hickox, R. C.; Tsai, C.-W.; Wu, J. W.

2016-03-01

Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (I) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (II) a second unobscured AGN in the system; or (III) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13-050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M⊙ yr-1. Deep polarimetry observations could confirm the reflection hypothesis.

HOT DUST OBSCURED GALAXIES WITH EXCESS BLUE LIGHT: DUAL AGN OR SINGLE AGN UNDER EXTREME CONDITIONS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Assef, R. J.; Diaz-Santos, T.; Walton, D. J.

Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGsmore » that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13–050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M{sub ⊙} yr{sup −1}. Deep polarimetry observations could confirm the reflection hypothesis.« less

The WISSH quasars project. III. X-ray properties of hyper-luminous quasars

NASA Astrophysics Data System (ADS)

Martocchia, S.; Piconcelli, E.; Zappacosta, L.; Duras, F.; Vietri, G.; Vignali, C.; Bianchi, S.; Bischetti, M.; Bongiorno, A.; Brusa, M.; Lanzuisi, G.; Marconi, A.; Mathur, S.; Miniutti, G.; Nicastro, F.; Bruni, G.; Fiore, F.

2017-12-01

We performed a survey of the X-ray properties of 41 objects from the WISE/SDSS selected hyper-luminous (WISSH) quasars sample, which includes 86 broad-line quasars with bolometric luminosity LBol ≳ 2 × 1047 erg s-1 shining at z 2-4. We used both proprietary and archival Chandra and XMM-Newton observations. Twenty-one quasars have sufficient quality data to perform a spectroscopic analysis, while for the remaining sources, X-ray properties are derived through hardness-ratio analysis (apart for six sources that result to be undetected). The bulk ( 70%) of the detected WISSH quasars exhibit NH <5 × 1022 cm-2, in agreement with their optical Type 1 AGN classification. All but three quasars show unabsorbed 2-10 keV luminosities L2-10≥ 1045 erg s-1. Thanks to their extreme radiative output across the mid-IR-to-X-ray range, WISSH quasars therefore offer the opportunity to significantly extend and validate the existing relations involving L2-10. Specifically, we studied the X-ray luminosity as a function of (i) X-ray-to-optical (X/O) flux ratio; (ii) mid-IR luminosity (LMIR); (iii) LBol, and (iv) αOX versus 2500 Å luminosity. We find that the WISSH quasars show (i) unreported very low X/O ( <0.1) compared to typical AGN values; (ii) L2-10/LMIR ratios that are significantly smaller than those derived for AGN with lower luminosity; (iii) a large X-ray bolometric correction, kBol,X ≈ 100-1000; and (iv) steep -2≳αOX≳-1.7. These results lead to a scenario in which the X-ray emission of hyper-luminous quasars is relatively weaker compared to lower luminosity AGN. Models predict that such an X-ray weakness can be relevant for the acceleration of powerful high-ionization, emission-line-driven winds, which are commonly detected in the UV spectra of WISSH quasars and can, in turn, perturb the X-ray corona and weaken its emission. Accordingly, hyper-luminous quasars represent the ideal laboratory to study the link between the AGN energy output and wind acceleration

No evidence for a significant AGN contribution to cosmic hydrogen reionization

NASA Astrophysics Data System (ADS)

Parsa, Shaghayegh; Dunlop, James S.; McLure, Ross J.

2018-03-01

We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei (AGN) at redshifts z > 4, which has reignited the debate as to whether young galaxies or AGN reionized the Universe. These sources lie within the Great Observatories Origins Deep Survey-South (GOODS-S)/Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) field, and we examine both the robustness of the claimed X-ray detections (within the Chandra 4Ms imaging) and perform an independent analysis of the photometric redshifts of the optical/infrared counterparts. We confirm the reality of only 15 of the 22 reported X-ray detections, and moreover find that only 12 of the 22 optical/infrared counterpart galaxies actually lie robustly at z > 4. Combining these results we find convincing evidence for only seven X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We recalculate the evolving far-ultraviolet (1500 Å) luminosity density produced by AGN at high redshift, and find that it declines rapidly from z ≃ 4 to z ≃ 6, in agreement with several other recent studies of the evolving AGN luminosity function. The associated rapid decline in inferred hydrogen ionizing emissivity contributed by AGN falls an order-of-magnitude short of the level required to maintain hydrogen ionization at z ≃ 6. We conclude that all available evidence continues to favour a scenario in which young galaxies reionized the Universe, with AGN making, at most, a very minor contribution to cosmic hydrogen reionization.

A Multi-Wavelength Study of the X-Ray Sources in the NGC 5018

NASA Technical Reports Server (NTRS)

Ghosh, Kajal K.; Swartz, Douglas A.; Tennant, Allyn F.; Wu, Kinwah; Saripalli, Lakshmi

2004-01-01

The E3 giant elliptical galaxy NGC-5018 was observed with the cxo X-ray Observatory's Advanced CCD Imaging Spectrometer for 30-h on 14 April 2001. Results of analysis of these X-ray data as well as of complementary optical, infrared, and radio data are reported. Seven X-ray point sources, including the nucleus, were detected. If they are intrinsic to NGC-5018, then all six non-nuclear sources have luminosities exceeding 10(exp 39)-ergl in the 0.5-8.0-keV energy band; placing them in the class of Ultra- luminous X-ray sources. Comparison of X-ray source positions to archival Hubble Space Telescope/Wide Field Planetary Camera 2 (hst/WFPC2) images reveal four of the six non-nuclear sources are spatially--coincident with bright, M$(sub V)LA -8.6 mag, objects. These four objects have optical magnitudes and (V-I) colors consistent with globular clusters in NGC-5018. However, one of these objects was observed to vary by siml mag in both V and I between observations taken 28 July 1997 and 04 Feb 1999 indicating this source is a background active galactic nucleus (AGN). The nature of the other three optically-bright objects cannot be determined from the available optical data but all have X-ray-to-optical flux ratios consistent with background AGNs. Strong, unpolarized, radio emission has been detected from another of the optically-bright counterparts. It displays an inverted radio spectrum and is the most absorbed of the seven sources in the X-ray band. It, too, is most readily explained as a background AGN, though alternative explanations cannot be ruled out. Extended X-ray emission is detected within a siml5 arcsec radius of the galaxy center at a luminosity of sim lO(exp 40)-ergl in the X-ray band. Its thermal X-ray spectrum (kT sim0.4-keV) and its spatial coincidence with strong H(alpha) emission are consistent with a hot gas origin. The nucleus itself is a weak X-ray source, LA-5 times 10(exp 39)-ergl, but displays a radio spectrum typical of AGN.

Mildly obscured active galaxies and the cosmic X-ray background

NASA Astrophysics Data System (ADS)

Esposito, V.; Walter, R.

2016-05-01

Context. The diffuse cosmic X-ray background (CXB) is the sum of the emission of discrete sources, mostly massive black-holes accreting matter in active galactic nuclei (AGN). The CXB spectrum differs from the integration of the spectra of individual sources, calling for a large population, undetected so far, of strongly obscured Compton-thick AGN. Such objects are predicted by unified models, which attribute most of the AGN diversity to their inclination on the line of sight, and play an important role for the understanding of the growth of black holes in the early Universe. Aims: The percentage of strongly obscured Compton-thick AGN at low redshift can be derived from the observed CXB spectrum, if we assume AGN spectral templates and luminosity functions. Methods: We show that high signal-to-noise stacked hard X-ray spectra, derived from more than a billion seconds of effective exposure time with the Swift/BAT instrument, imply that mildly obscured Compton-thin AGN feature a strong reflection and contribute massively to the CXB. Results: A population of Compton-thick AGN larger than that which is effectively detected is not required to reproduce the CXB spectrum, since no more than 6% of the CXB flux can be attributed to them. The stronger reflection observed in mildly obscured AGN suggests that the covering factor of the gas and dust surrounding their central engines is a key factor in shaping their appearance. These mildly obscured AGN are easier to study at high redshift than Compton-thick sources are.

Active galactic nucleus X-ray variability in the XMM-COSMOS survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lanzuisi, G.; Ponti, G.; Salvato, M.

2014-02-01

We used the observations carried out by XMM in the COSMOS field over 3.5 yr to study the long term variability of a large sample of active galactic nuclei (AGNs) (638 sources) in a wide range of redshifts (0.1 < z < 3.5) and X-ray luminosities (10{sup 41} < L {sub 0.5-10} <10{sup 45.5}). Both a simple statistical method to assess the significance of variability and the Normalized Excess Variance (σ{sub rms}{sup 2}) parameter were used to obtain a quantitative measurement of the variability. Variability is found to be prevalent in most AGNs, whenever we have good statistics to measuremore » it, and no significant differences between type 1 and type 2 AGNs were found. A flat (slope –0.23 ± 0.03) anti-correlation between σ{sub rms}{sup 2} and X-ray luminosity is found when all significantly variable sources are considered together. When divided into three redshift bins, the anti-correlation becomes stronger and evolving with z, with higher redshift AGNs being more variable. We prove, however, that this effect is due to the pre-selection of variable sources: when considering all of the sources with an available σ{sub rms}{sup 2} measurement, the evolution in redshift disappears. For the first time, we were also able to study long term X-ray variability as a function of M {sub BH} and Eddington ratio for a large sample of AGNs spanning a wide range of redshifts. An anti-correlation between σ{sub rms}{sup 2} and M {sub BH} is found, with the same slope of anti-correlation between σ{sub rms}{sup 2} and X-ray luminosity, suggesting that the latter may be a by-product of the former. No clear correlation is found between σ{sub rms}{sup 2} and the Eddington ratio in our sample. Finally, no correlation is found between the X-ray σ{sub rms}{sup 2} and optical variability.« less

Variable X-Ray Absorption in the Mini-BAL QSO PG 1126-041

NASA Technical Reports Server (NTRS)

Giustini, M.; Cappi, M.; Chartas, G.; Dadina, M.; Eracleous, M.; Ponti, G.; Proga, D.; Tombesi, F.; Vignali, C.; Palumbo, G. G. C.

2011-01-01

Context. X-ray studies of AGN with powerful nuclear winds are important to constrain the physics of the inner accretion/ejection flow around SMBH, and to understand the impact of such winds on the AGN environment. Aims. Our main scientific goal is to constrain the properties of a variable outflowing absorber that is thought to be launched near the SMBH of the mini-BAL QSO PG 1126-041 using a multi-epoch observational campaign performed with XMM-Newton. Methods. We performed temporally resolved X-ray spectroscopy and simultaneous UV and X-ray photometry on the most complete set of observations and on the deepest X-ray exposure of a mini-BAL QSO to date. Results. We found complex X-ray spectral variability on time scales of both months and hours, best reproduced by means of variable massive ionized absorbers along the line of sight. As a consequence, the observed optical-to-X-ray spectral index is found to be variable with time. In the highest signal-to-noise observation we detected highly ionized X-ray absorbing material outflowing much faster (u(sub X) approx. 16 500 km/s) than the UV absorbing one (u(sub uv) approx. 5,000 km/s). This highly ionized absorber is found to be variable on very short (a few kiloseconds) time scales. Conclusions. Our findings are qualitatively consistent with line driven accretion disk winds scenarios. Our observations have opened the time-resolved X-ray spectral analysis field for mini-BAL QSOs; only with future deep studies will we be able to map the dynamics of the inner flow and understand the physics of AGN winds and their impact on the environment.

A POWERFUL AGN OUTBURST IN RBS 797

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavagnolo, K. W.; McNamara, B. R.; Wise, M. W.

2011-05-10

Utilizing {approx}50 ks of Chandra X-Ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper X-ray image has revealed additional structure associated with the active galactic nucleus (AGN). The surface brightness decrements of the two cavities are unusually large and are consistent with elongated cavities lying close to our line of sight. We estimate a total AGN outburst energy and mean jet power of {approx}(3-6) x 10{sup 60} erg and {approx}(3-6) x 10{supmore » 45} erg s{sup -1}, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is {approx}1 M{sub sun} yr{sup -1}. We show that accretion of cold gas onto the AGN at this level is plausible, but that Bondi accretion of the hot atmosphere is probably not. The brightest cluster galaxy (BCG) harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of {approx}2 x 10{sup 44} erg s{sup -1}. The nuclear emission is probably associated with a rapidly accreting, radiatively inefficient accretion flow. We present tentative evidence that star formation in the BCG is being triggered by the radio jets and suggest that the cavities may be driving weak shocks (M {approx} 1.5) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.« less

Starburst or AGN Dominance in Submillimetre-Luminous Candidate AGN?

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Pope, Alexandra; Menéndez-Delmestre, Karín; Alexander, David M.; Dunlop, James

2010-06-01

It is widely believed that ultraluminous infrared (IR) galaxies and active galactic nuclei (AGN) activity are triggered by galaxy interactions and merging, with the peak of activity occurring at z~2, where submillimetre galaxies are thousands of times more numerous than local ULIRGs. In this evolutionary picture, submillimetre galaxies (SMGs) would host an AGN, which would eventually grow a black hole (BH) strong enough to blow off all of the gas and dust leaving an optically luminous QSO. To probe this evolutionary sequence we have focussed on the `missing link' sources, which demonstrate both strong starburst (SB) and AGN signatures, in order to determine if the SB is the main power source even in SMGs when we have evidence that an AGN is present from their IRAC colours. The best way to determine if a dominant AGN is present is to look for their signatures in the mid-infrared with the Spitzer IRS, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We present the results of our audit of the energy balance between star-formation and AGN within this special sub-population of SMGs-where the BH has grown appreciably to begin heating the dust emission.

Suzaku  Observations of Heavily Obscured (Compton-thick) Active Galactic Nuclei Selected by the Swift/BAT Hard X-Ray Survey

NASA Astrophysics Data System (ADS)

Tanimoto, Atsushi; Ueda, Yoshihiro; Kawamuro, Taiki; Ricci, Claudio; Awaki, Hisamitsu; Terashima, Yuichi

2018-02-01

We present a uniform broadband X-ray (0.5–100.0 keV) spectral analysis of 12 Swift/Burst Alert Telescope selected Compton-thick ({log}{N}{{H}}/{{cm}}-2≥slant 24) active galactic nuclei (CTAGNs) observed with Suzaku. The Suzaku data of three objects are published here for the first time. We fit the Suzaku and Swift spectra with models utilizing an analytic reflection code and those utilizing the Monte-Carlo-based model from an AGN torus by Ikeda et al. The main results are as follows: (1) The estimated intrinsic luminosity of a CTAGN strongly depends on the model; applying Compton scattering to the transmitted component in an analytic model may largely overestimate the intrinsic luminosity at large column densities. (2) Unabsorbed reflection components are commonly observed, suggesting that the tori are clumpy. (3) Most of CTAGNs show small scattering fractions (<0.5%), implying a buried AGN nature. (4) Comparison with the results obtained for Compton-thin AGNs suggests that the properties of these CTAGNs can be understood as a smooth extension from Compton-thin AGNs with heavier obscuration; we find no evidence that the bulk of the population of hard-X-ray-selected CTAGNs are different from less obscured objects.

The nature of fifty Palermo Swift-BAT hard X-ray objects through optical spectroscopy

NASA Astrophysics Data System (ADS)

Rojas, A. F.; Masetti, N.; Minniti, D.; Jiménez-Bailón, E.; Chavushyan, V.; Hau, G.; McBride, V. A.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, G.; Gavignaud, I.; Landi, R.; Malizia, A.; Morelli, L.; Palazzi, E.; Patiño-álvarez, V.; Stephen, J. B.; Ubertini, P.

2017-07-01

We present the nature of 50 unidentified hard X-ray emitting objects detected with Swift-BAT and listed as of unidentified nature in the 54-month Palermo BAT catalogue. We found 45 extragalactic sources: 26 type 1 AGN, 15 type 2 AGN, one type 1 QSO, one starburst galaxy, one X-ray bright optically normal galaxy, and one LINER. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary, and one is an active star.

The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars

NASA Astrophysics Data System (ADS)

Chen, Chien-Ting J.; Hickox, Ryan C.; Goulding, Andrew D.; Stern, Daniel; Assef, Roberto; Kochanek, Christopher S.; Brown, Michael J. I.; Harrison, Chris M.; Hainline, Kevin N.; Alberts, Stacey; Alexander, David M.; Brodwin, Mark; Del Moro, Agnese; Forman, William R.; Gorjian, Varoujan; Jones, Christine; Murray, Stephen S.; Pope, Alexandra; Rovilos, Emmanouel

2017-03-01

Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity ({L}MIR}) and the rest-frame 2–10 keV luminosity (L X) for luminous quasars. To understand the origin of the difference in the observed {L}{{X}}{--}{L}MIR} relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Boötes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed {L}{{X}}{--}{L}MIR} relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different {L}{{X}}{--}{L}MIR} relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 μ {{m}}, or {L}6μ {{m}}) of our sample of type 1 AGNs follow a bilinear relation in the log–log plane: {log}{L}{{X}}=(0.84+/- 0.03)× {log}{L}6μ {{m}}/{10}45 erg s‑1 + (44.60 ± 0.01) for {L}6μ {{m}}< {10}44.79 erg s‑1, and {log}{L}{{X}}=(0.40+/- 0.03)× {log}{L}6μ {{m}}/{10}45 erg s‑1 + (44.51 ± 0.01) for {L}6μ {{m}} ≥slant {10}44.79 erg s‑1. This suggests that the luminous type 1 quasars have a shallower {L}{{X}}{--}{L}6μ {{m}} correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent {L}{{X}}{--}{L}MIR} relation and implies that assuming a linear {L}{{X}}{--}{L}6μ {{m}} relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars.

Goddard X-ray astronomy contributions to the IAU/COSPAR (1982)

NASA Technical Reports Server (NTRS)

Holt, S. S.; Petre, R.; Shafer, R. A.; Urry, C. M.; Mushotzky, R. F.

1982-01-01

The relation of X-ray flux to both the continuum flux in the optical and radio bands, and to the line emission properties of these objects were studied. The Einstein Observatory, because of increased sensitivity and improved angular resolution, increased substantially the number of known X-ray emitting active galactic nuclei. The Einstein imaging instruments detected morphology in AGN X-ray emission, in particular from jetlike structures in Cen-A, M87, and 3C273. The improved energy resolution and sensitivity of the spectrometers onboard the Observatory provide information on the geometry and ionization structure of the region responsible for the broad optical emission lines in a few AGN's. This information, combined with theoretical modeling and IUE and optical observations, allows the construction of a moderately detailed picture of the broad line region in these objects.

Highly variable AGN from the XMM-Newton slew survey

NASA Astrophysics Data System (ADS)

Strotjohann, N. L.; Saxton, R. D.; Starling, R. L. C.; Esquej, P.; Read, A. M.; Evans, P. A.; Miniutti, G.

2016-07-01

Aims: We investigate the properties of a variability-selected complete sample of active galactic nuclei (AGN) in order to identify the mechanisms which cause large amplitude X-ray variability on timescales of years. Methods: A complete sample of 24 sources was constructed, from AGN which changed their soft X-ray luminosity by more than one order of magnitude over 5-20 years between ROSAT observations and the XMM-Newton slew survey. Follow-up observations were obtained with the Swift satellite. We analysed the spectra of these AGN at the Swift and XMM observation epochs, where six sources had continued to display extreme variability. Multiwavelength data are used to calculate black hole masses and the relative X-ray brightness αOX. Results: After removal of two probable spurious sources, we find that the sample has global properties which differ little from a non-varying control sample drawn from the wider XMM-slew/ROSAT/Veron sample of all secure AGN detections. A wide range of AGN types are represented in the varying sample. The black hole mass distributions for the varying and non-varying sample are not significantly different. This suggests that long timescale variability is not strongly affected by black hole mass. There is marginal evidence that the variable sources have a lower redshift (2σ) and X-ray luminosity (1.7σ). Apart from two radio-loud sources, the sample sources have normal optical-X-ray ratios (αOX) when at their peak but are X-ray weak during their lowest flux measurements. Conclusions: Drawing on our results and other studies, we are able to identify a variety of variability mechanisms at play: tidal disruption events, jet activity, changes in absorption, thermal emission from the inner accretion disc, and variable accretion disc reflection. Little evidence for strong absorption is seen in the majority of the sample and single-component absorption can be excluded as the mechanism for most sources.

Merger-driven fueling of active galactic nuclei: Six dual and of AGNs discovered with Chandra and Hubble Space Telescope observations

DOE PAGES

Comerford, Julia M.; Pooley, David; Barrows, R. Scott; ...

2015-06-19

Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically selected dual AGN candidates atmore » $$z\\lt 0.34$$, where we use the X-rays to identify AGNs. We also present Hubble Space Telescope/Wide Field Camera 3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation $${\\rm \\Delta }x=2.2$$ kpc, where the two stellar bulges have coincident [O iii] λ5007 and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations $${\\rm \\Delta }x\\lt 10$$ kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, and these AGNs are 10 times more luminous, on average, than the single AGNs in our sample. This hints that major mergers may preferentially trigger higher luminosity AGNs. Further, we find that confirmed dual AGNs have hard X-ray luminosities that are half of those of single AGNs at fixed [O III] λ5007 luminosity, on average. Lastly, this could be explained by high densities of gas funneled to galaxy centers during mergers, and emphasizes the need for deeper X-ray observations of dual AGN candidates.« less

Constraints on Massive Axion-Like Particles from X-ray Observations of NGC1275

NASA Astrophysics Data System (ADS)

Chen, Linhan; Conlon, Joseph P.

2018-06-01

If axion-like particles (ALPs) exist, photons can convert to ALPs on passage through regions containing magnetic fields. The magnetised intracluster medium of large galaxy clusters provides a region that is highly efficient at ALP-photon conversion. X-ray observations of Active Galactic Nuclei (AGNs) located within galaxy clusters can be used to search for and constrain ALPs, as photon-ALP conversion would lead to energy-dependent quasi-sinusoidal modulations in the X-ray spectrum of an AGN. We use Chandra observations of the central AGN of the Perseus Cluster, NGC1275, to place bounds on massive ALPs up to ma ˜ 10-11eV, extending previous work that used this dataset to constrain massless ALPs.

THE CHANDRA COSMOS SURVEY. III. OPTICAL AND INFRARED IDENTIFICATION OF X-RAY POINT SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Civano, F.; Elvis, M.; Aldcroft, T.

2012-08-01

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg{sup 2} of the COSMOS field down to limiting depths of 1.9 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1} in the soft (0.5-2 keV) band, 7.3 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1} in the hard (2-10 keV) band, and 5.7 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1} in the full (0.5-10 keV) band. In this paper we report the i, K, and 3.6 {mu}m identifications of the 1761 X-ray point sources. We use the likelihood ratio technique tomore » derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only two sources are truly empty fields. The full catalog, including spectroscopic and photometric redshifts and classification described here in detail, is available online. Making use of the large number of X-ray sources, we update the 'classic locus' of active galactic nuclei (AGNs) defined 20 years ago in soft X-ray surveys and define a new locus containing 90% of the AGNs in the survey with full-band luminosity >10{sup 42} erg s{sup -1}. We present the linear fit between the total i-band magnitude and the X-ray flux in the soft and hard bands, drawn over two orders of magnitude in X-ray flux, obtained using the combined C-COSMOS and XMM-COSMOS samples. We focus on the X-ray to optical flux ratio (X/O) and we test its known correlation with redshift and luminosity, and a recently introduced anti-correlation with the concentration index (C). We find a strong anti-correlation (though the dispersion is of the order of 0.5 dex) between X/O computed in the hard band and C and that 90% of the obscured AGNs in the sample with

Soft X-ray Emission from Large-Scale Galactic Outflows in Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.; Baum, S.; O'Dea, C.; Veilleux, S.

1998-01-01

Kiloparsec-scale soft X-ray nebulae extend along the galaxy minor axes in several Seyfert galaxies, including NGC 2992, NGC 4388 and NGC 5506. In these three galaxies, the extended X-ray emission observed in ROSAT HRI images has 0.2-2.4 keV X-ray luminosities of 0.4-3.5 x 10(40) erg s(-1) . The X-ray nebulae are roughly co-spatial with the large-scale radio emission, suggesting that both are produced by large-scale galactic outflows. Assuming pressure balance between the radio and X-ray plasmas, the X-ray filling factor is >~ 10(4) times as large as the radio plasma filling factor, suggesting that large-scale outflows in Seyfert galaxies are predominantly winds of thermal X-ray emitting gas. We favor an interpretation in which large-scale outflows originate as AGN-driven jets that entrain and heat gas on kpc scales as they make their way out of the galaxy. AGN- and starburst-driven winds are also possible explanations if the winds are oriented along the rotation axis of the galaxy disk. Since large-scale outflows are present in at least 50 percent of Seyfert galaxies, the soft X-ray emission from the outflowing gas may, in many cases, explain the ``soft excess" X-ray feature observed below 2 keV in X-ray spectra of many Seyfert 2 galaxies.

New Constraints for X-ray Reprocessing Around Supermassive Black Holes: Near and Far with State-of-the-Art Multi-Mission Modeling

NASA Astrophysics Data System (ADS)

Tzanavaris, Panayiotis

Fluorescent Fe K emission from neutral matter in AGN spectracan arise in the accretion disk around the centralsupermassive black hole [SMBH] ("broad" line) and/or in distant matter ("narrow"line). If it is broad, it provides a unique windowto the strong gravity SMBH regime, including information on SMBH spin;if it is narrow, it probesthe distant reprocessor, likely a clumpy torus. We will use broadband X-ray data from four NASA X-ray missionsfor 45 nearby AGNs, and 1. Assess whether any known "broad" relativistic lines can be modeledas "narrow"instead, by means of self-consistent modeling of fluorescence,direct, and scattered continua; 2. Measure absorbing column densities both in and out of the line of sight; 3. Bootstrap measures of intrinsic bolometric AGN luminosity, with X-ray and optical data. This work will provide updated results on a) black hole spin, with implications on AGN jet power and accretion history; b) the census of highly-obscured (Compton thick) vs. Compton thin AGNs, with implications on models of the Cosmic X-ray Background; c) calibrations of Fe K line, X-ray intrinsic continuum, [OIII] and [OIV] luminosities as measures of intrinsc bolometric AGN luminosity, with implications on AGN feedback and galaxy evolution. Key in our approach is a physically based, self-consistent modeling of the narrow line, with finite column density in and out of the line of sight, and the latest relativistic modeling of the broad line.

Variable soft X-ray excesses in active galactic nuclei from nonthermal electron-positron pair cascades

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Coppi, Paolo S.

1991-01-01

In the present study of the formation of steep soft X-ray excesses that are superposed on flatter, hard X-ray power-law spectra in nonthermal electron-positron pair cascade sources, the soft excess in pair-cascade AGN models appears as a steep power law superposed on the tail of the UV bump and the flat nonthermal (hard X-ray) power law. The model-parameter space in which an excess in soft X-rays is visible is ascertained, and the time-variability of soft excesses in pair cascade models is examined. It is established that the parameter space in which soft excesses appear encompasses the range of preferred input parameters for a recently development Compton reflection model of UV and X-ray emission from the central engine of an AGN.

The 60 Month All-Sky Burst Alert Telescope Survey of Active Galactic Nucleus and the Anisotropy of Nearby AGNs

NASA Technical Reports Server (NTRS)

Ajello, M.; Alexander, D. M.; Greiner, J.; Madejeski, G. M.; Gehrels, N.; Burlon, D.

2014-01-01

Surveys above 10 keV represent one of the best resources to provide an unbiased census of the population of active galactic nuclei (AGNs). We present the results of 60 months of observation of the hard X-ray sky with Swift/Burst Alert Telescope (BAT). In this time frame, BAT-detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGNs, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of approx. 2 larger over similarly complete sets of AGNs. Our sample contains (at least) 15 bona fide Compton-thick AGNs and 3 likely candidates. Compton-thick AGNs represent approx. 5% of AGN samples detected above 15 keV. We use the BAT data set to refine the determination of the log N-log S of AGNs which is extremely important, now that NuSTAR prepares for launch, toward assessing the AGN contribution to the cosmic X-ray background. We show that the log N-log S of AGNs selected above 10 keV is now established to approx. 10% precision. We derive the luminosity function of Compton-thick AGNs and measure a space density of 7.9(+4.1/-2.9)× 10(exp -5)/cubic Mpc for objects with a de-absorbed luminosity larger than 2 × 10(exp 42) erg / s. As the BAT AGNs are all mostly local, they allow us to investigate the spatial distribution of AGNs in the nearby universe regardless of absorption. We find concentrations of AGNs that coincide spatially with the largest congregations of matter in the local (much < 85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions..

Ionized Absorbers in AGN

NASA Technical Reports Server (NTRS)

Mathur, S.

1999-01-01

As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

SWIFT BAT Survey of AGN

NASA Technical Reports Server (NTRS)

Tueller, J.; Mushotzky, R. F.; Barthelmy, S.; Cannizzo, J. K.; Gehrels, N.; Markwardt, C. B.; Skinner, G. K.; Winter, L. M.

2008-01-01

We present the results1 of the analysis of the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGN) of 130 objects detected at [b] > 15deg and with significance > 4.8-delta. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the logN - log S distribution, and find the slope to be 1.42+/-0.14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity logL*(ergs/s)= 43.85+/-0.26. We obtain a mean photon index 1.98 in the 14-195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGN above 10(exp 41) erg/s of 2.4x10(exp -3) Mpc(sup -3), which is about 10% of the total luminous local galaxy density above M* = -19.75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log nH is essentially flat from nH = 10(exp 20)/sq cm to 10(exp 24)/sq cm, with 50% of the objects having column densities of less than 10(exp 22)/sq cm. BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log nH > 22.

Starburst or AGN dominance in submm-luminous candidate AGN

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Alexander, Dave; Aretxaga, Itziar; Blain, Andrew; Chapman, Scott; Clements, Dave; Dunlop, James; Dunne, Loretta; Dye, Simon; Farrah, Duncan; Hughes, David; Ivison, Rob; Kim, Sungeun; Menendez-Delmestre, Karin; Oliver, Sebastian; Page, Mat; Pope, Alexandra; Rowan-Robinson, Michael; Scott, Douglas; Smail, Ian; Swinbank, Mark; Vaccari, Mattia; van Kampen, Eelco

2008-03-01

It is widely believed that starbursts/ULIRGs and AGN activity are triggered by galaxy interactions and merging; and sub-mm selected galaxies (SMGs) seem to be simply high redshift ULIRGs, observed near the peak of activity. In this evolutionary picture every SMG would host an AGN, which would eventually grow a black hole strong enough to blow off all of the gas and dust leaving an optically luminous QSO. In order to probe this evolutionary sequence, a crucial sub-sample to focus on would be the 'missing link' sources, which demonstrate both strong starburst and AGN signatures and to determine if the starburst is the main power source even in SMGs when we have evidence that an AGN is present. The best way to determine if a dominant AGN is present is to look in the mid-IR for their signatures, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We have selected a sample of SMGs which are good candidates for harboring powerful AGN on the basis of their IRAC colours (S8um/S4.5um>2). Once we confirm these SMGs are AGN-dominated, we can then perform an audit of the energy balance between star-formation and AGN within this special sub-population of SMGs where the BH has grown appreciably to begin heating the dust emission. The proposed observations with IRS will probe the physics of how SMGs evolve from a cold-dust starburst-dominated ULIRG to an AGN/QSO by measuring the level of the mid-IR continuum, PAH luminosity, and Si absorption in these intermediate `transitory' AGN/SMGs.

AGN Clustering in the BAT Sample

NASA Astrophysics Data System (ADS)

Powell, Meredith; Cappelluti, Nico; Urry, Meg; Koss, Michael; BASS Team

2018-01-01

We characterize the environments of local growing supermassive black holes by measuring the clustering of AGN in the Swift-BAT Spectroscopic Survey (BASS). With 548 AGN in the redshift range 0.01AGN to date due to its hard X-ray selection (14-195 keV). By measuring the projected cross-correlation function between the AGN and 2MASS galaxies, we constrain the halo occupation distribution (HOD) of the full sample with unprecedented sensitivity, as well as in bins of obscuration with matched luminosity distributions. In doing so, we find that AGN tend to reside in galaxy groups, agreeing with previous studies of AGN throughout a large range of luminosity and redshift. We also find evidence that obscured AGN tend to reside in denser environments than unobscured AGN.

Multiwavelength Properties of the X-Ray Sources in the Groth-Westphal Strip Field

NASA Astrophysics Data System (ADS)

Miyaji, Takamitsu; Sarajedini, Vicki; Griffiths, Richard E.; Yamada, Toru; Schurch, Matthew; Cristóbal-Hornillos, David; Motohara, Kentaro

2004-06-01

We summarize the multiwavelength properties of X-ray sources detected in the 80 ks XMM-Newton observation of the Groth-Westphal strip, a contiguous strip of 28 Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images. Among the ~150 X-ray sources detected in the XMM-Newton field of view, 23 are within the WFPC2 fields. Ten spectroscopic redshifts are available from the Deep Extragalactic Evolutionary Probe and Canada-France Redshift Survey projects. Four of these show broad Mg II emission and can be classified as type 1 active galactic nuclei (AGNs). Two of those without any broad lines, nevertheless, have [Ne V] emission, which is an unambiguous signature of AGN activity. One is a narrow-line Seyfert 1 and the other a type 2 AGN. As a follow-up, we have made near-infrared spectroscopic observations using the OHS/CISCO spectrometer for five of the X-ray sources for which we found no indication of AGN activity in the optical spectrum. We have detected Hα+[N II] emission in four of them. A broad Hα component and/or a large [N II]/Hα ratio is seen, suggestive of AGN activity. Nineteen sources have been detected in the Ks band, and four of these are extremely red objects (EROs) (I814-Ks>4). The optical counterparts for the majority of the X-ray sources are bulge-dominated. The I814-Ks color of these bulge-dominated hosts are indeed consistent with evolving elliptical galaxies, while contaminations from star formation/AGNs seems to be present in their V606-I814 color. Assuming that the known local relations among the bulge luminosity, central velocity dispersion, and the mass of the central blackhole still hold at z~1, we compare the AGN luminosity with the Eddington luminosity of the central blackhole mass. The AGN bolometric luminosity to Eddington luminosity ratio ranges from 0.3% to 10%. Based on observations from the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA. Also based on data

The SIX survey: evolution and properties of AGN in the local universe

NASA Astrophysics Data System (ADS)

Bottacini, Eugenio

2014-07-01

Current most sensitive surveys at soft X-ray (~ 0.5-10 keV) energies by Chandra and XMM-Newton preferably sample AGN at high-redshift (z > 0.5). At low-redshift (z < 0.5), where AGN are supposed to be in their evolution end-stage, these sources are very sparsely sampled. The low-redshift universe is best fathomed at hard X-ray energies (> 15 keV) by the INTEGRAL and the Swift missions with their coded-mask telescopes IBIS/ISGRI and BAT respectively. These instruments have two major advantages: 1) they have a huge field of view, hence allowing to sample a large number of AGN at low-redshift; 2) they operate at energies above 15 keV, hence allowing detecting photons with enough power to efficiently pierce even through the Compton-thick torus of AGN. Estimates based on observations with PDS on board the BeppoSAX satellite predict that Compton-thick AGN should dominate over unabsorbed AGN in the local universe playing an important role in reproducing the shape and intensity of the cosmic X-ray background (CXB). However coded-mask detectors suffer from heavy systematic effects preventing them from reaching their theoretical limiting sensitivity. We overcome this limit with a new and alternative approach, which has been designed ad hoc to improve the sensitivity of hard X-ray surveys by using IBIS/ISGRI and BAT. Both telescopes are so close in design that their observations can be combined to obtain a more sensitive survey. The observations are combined with resampling, merging, and cross-calibration techniques. We are able to sample limiting fluxes of the order of ~3.3 times 10-12 erg cm-2 s-1 in the 18-55 keV energy range. This is called the SIX survey, that stands for Swift-INTEGRAL X-ray survey. The SIX survey extends over a wide sky area of 6200 deg2 and it is used to obtain a persistent sample of faint AGN. The source number density (log N - log S) is a factor of 3 better than current parent surveys of BAT and IBIS/ISGRI alone. I will present a study of the

AGN Science with AGIS

NASA Astrophysics Data System (ADS)

Coppi, Paolo

2009-05-01

AGIS, a proposed future gamma-ray telescope consisting of a square km array of 50 atmospheric Cherenkov telescopes, will provide a powerful new view of the high energy universe. The combination of its increased sensitivity (a factor 10 over current observatories), increased survey capabilities, and a low energy threshold (<30 GeV) that allows observations at energies not subject to absorption on extragalactic background light will result in a dramatic increase in the number of AGN accessible at high energies. The overall number of ``TeV blazar" AGN, those detected by current ground-based observatories, should increase by a factor 30 or more with a corresponding increase in the number of these that can be monitored at high statistical significance to test emission models rigorously. More excitingly, AGIS may also begin to pick up entirely new classes of AGN such as radio galaxies with X-ray emitting hotspots at large distances from the central engine, providing further insight into the outflows from AGN. The low AGIS threshold energy will also allow significant source overlap with objects detected by the recently launched Fermi gamma-ray space observatory at lower, GeV energies. AGIS will significantly improve on the localization and variability monitoring of the Fermi sources it sees.

Inflow Generated X-Ray Corona around Supermassive Black Holes and a Unified Model for X-Ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-02-01

Three-dimensional hydrodynamic simulations are performed, which cover the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass {10}8{M}⊙ , with detailed radiative cooling processes. The existence of a significant amount of shock heated, high temperature (≥slant {10}8 {{K}}) coronal gas in the inner (≤slant {10}4{r}{sch}) region is generally found. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures is in reasonable agreement with the overall ensemble spectrum of active galactic nuclei (AGNs) and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shapes, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

The Spectacular Radio-Near-IR-X-Ray Jet of 3C 111: the X-Ray Emission Mechanism and Jet Kinematics

NASA Technical Reports Server (NTRS)

Clautice, Devon; Perlman, Eric S.; Georganopoulos, Markos; Lister, Matthew L.; Tombesi, Francesco; Cara, Mihai; Marshall, Herman L.; Hogan, Brandon M.; Kazanas, Demos

2016-01-01

Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the subparsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near- IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio galaxies known. We discuss new, deep Chandra and Hubble Space Telescope (HST) observations that reveal both near-IR and X-ray emission from several components of the 3C 111 jet, as well as both the northern and southern hotspots. Important differences are seen between the morphologies in the radio, X-ray, and near-IR bands. The long (over 100 kpc on each side), straight nature of this jet makes it an excellent prototype for future, deep observations, as it is one of the longest such features seen in the radio, near-IR/optical, and X-ray bands. Several independent lines of evidence, including the X-ray and broadband spectral shape as well as the implied velocity of the approaching hotspot, lead us to strongly disfavor the EC/CMB model and instead favor a two-component synchrotron model to explain the observed X-ray emission for several jet components. Future observations with NuSTAR, HST, and Chandra will allow us to further constrain the emission mechanisms.

THE SPECTACULAR RADIO-NEAR-IR-X-RAY JET OF 3C 111: THE X-RAY EMISSION MECHANISM AND JET KINEMATICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clautice, Devon; Perlman, Eric S.; Georganopoulos, Markos

2016-08-01

Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the sub-parsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near-IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio galaxies known. We discuss new,more » deep Chandra and Hubble Space Telescope ( HST ) observations that reveal both near-IR and X-ray emission from several components of the 3C 111 jet, as well as both the northern and southern hotspots. Important differences are seen between the morphologies in the radio, X-ray, and near-IR bands. The long (over 100 kpc on each side), straight nature of this jet makes it an excellent prototype for future, deep observations, as it is one of the longest such features seen in the radio, near-IR/optical, and X-ray bands. Several independent lines of evidence, including the X-ray and broadband spectral shape as well as the implied velocity of the approaching hotspot, lead us to strongly disfavor the EC/CMB model and instead favor a two-component synchrotron model to explain the observed X-ray emission for several jet components. Future observations with NuSTAR , HST , and Chandra will allow us to further constrain the emission mechanisms.« less

Prospects for AGN Science using the ART-XC on the SRG Mission

NASA Technical Reports Server (NTRS)

Swartz, Douglas A.; Elsner, Ronald F.; Gubarev, Mikhail V.; O'Dell, Stephen L.; Ramsey, Brian D.; Bonamente, Massimiliano

2012-01-01

The enhanced hard X-ray sensitivity provided by the Astronomical Roentgen Telescope to the Spectrum Roentgen Gamma mission facilitates the detection of heavily obscured and other hard-spectrum cosmic X-ray sources. The SRG all-sky survey will obtain large, statistically-well-defined samples of active galactic nuclei (AGN) including a significant population of local heavily-obscured AGN. In anticipation of the SRG all-sky survey, we investigate the prospects for refining the bright end of the AGN luminosity function and determination of the local black hole mass function and comparing the spatial distribution of AGN with large-scale structure defined by galaxy clusters and groups. Particular emphasis is placed on studies of the deep survey Ecliptic Pole regions.

Active Galaxy Unification in the Era of X-Ray Polarimetry

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.

2010-01-01

Active galactic nuclei (AGNs), Seyfert galaxies, and quasars are powered by luminous accretion and often accompanied by winds that are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes that are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption (warm absorbers). Here, we show that such gas will have a distinct signature when viewed in polarized X-rays. Observations of such polarization can test models for the geometry of the flow and the gas responsible for launching and collimating it. We present calculations that show that the polarization depends on the hydrodynamics of the flow, the quantum mechanics of resonance-line scattering, and the transfer of polarized X-ray light in the highly ionized moving gas. The results emphasize the three-dimensional nature of the wind for modeling spectra. We show that the polarization in the 0.1-10 keV energy range is dominated by the effects of resonance lines. We predict a 5%-25% X-ray polarization signature of type-2 objects in this energy range. These results are generalized to flows that originate from a cold torus-like structure, located approximately 1 pc from the BH, which wraps the BH and is ultimately responsible for the apparent dichotomy between type 1 and type 2 AGNs. Such signals will be detectable by future dedicated X-ray polarimetry space missions, such as the NASA Gravity and Extreme Magnetism Small Explorer SMEX, "GEMS" Swank et al. (2008).

Seeing Through the Clouds: AGN Geometry with the Swift BAT Sample

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Urry, M.; Schawinski, K.; Koss, M. J.; Winter, L. M.; Elitzur, M.; Wilkin, W. H.

2011-01-01

We investigate the intrinsic structure of the clouds surrounding AGN which give rise to their X-ray and optical emission properties. Using a complete sample of Swift BAT AGN selected in hard X-rays (14-195 keV), which is unbiased with respect to obscuration and extinction, we compute the reddening in the broad line region along the line of sight to the nucleus of each source using Balmer decrement from the ratio of the broad components of H-alpha/H-beta. We compare reddening from dust in the broad line clouds to the hydrogen column density (NH) obtained from their X-ray spectra. The distribution of the gas-to-dust ratios over many lines of sight allow us to test models of AGN structure and probe the immediate environment of the accreting supermassive black holes.

X-ray variability and the inner region in active galactic nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohan, P.; Mangalam, A., E-mail: prashanth@iiap.res.in, E-mail: mangalam@iiap.res.in

2014-08-20

We present theoretical models of X-ray variability attributable to orbital signatures from an accretion disk including emission region size, quasi-periodic oscillations (QPOs), and its quality factor Q, and the emergence of a break frequency in the power spectral density shape. We find a fractional variability amplitude of F{sub var}∝M{sub ∙}{sup −0.4}. We conduct a time series analysis on X-ray light curves (0.3-10 keV) of a sample of active galactic nuclei (AGNs). A statistically significant bend frequency is inferred in 9 of 58 light curves (16%) from 3 AGNs for which the break timescale is consistent with the reported BH spinmore » but not with the reported BH mass. Upper limits of 2.85 × 10{sup 7} M {sub ☉} in NGC 4051, 8.02 × 10{sup 7} M {sub ☉} in MRK 766, and 4.68 × 10{sup 7} M {sub ☉} in MCG-6-30-15 are inferred for maximally spinning BHs. For REJ 1034+396 where a QPO at 3733 s was reported, we obtain an emission region size of (6-6.5) M and a BH spin of a ≲ 0.08. The relativistic inner region of a thin disk, dominated by radiation pressure and electron scattering, is likely to host the orbital features as the simulated Q ranges from 6.3 × 10{sup –2} to 4.25 × 10{sup 6}, containing the observed Q. The derived value of Q ∼ 32 for REJ 1034+396 therefore suggests that the AGN hosts a thin disk.« less

X-Ray Polarimetry with GEMS

NASA Technical Reports Server (NTRS)

Strohmayer, Tod

2011-01-01

The polarization properties of cosmic X-ray sources are still largely unexplored. The Gravity and Extreme Magnetism SMEX (GEMS) will carry out the first sensitive X-ray polarization survey of a wide range of sources including; accreting compact objects (black holes and neutron stars), AGN, supernova remnants, magnetars and rotation-powered pulsars. GEMS employs grazing-incidence foil mirrors and novel time-projection chamber (TPC) polarimeters leveraging the photoelectric effect to achieve high polarization sensitivity in the 2 - 10 keV band. I will provide an update of the project status, illustrate the expected performance with several science examples, and provide a brief overview of the data analysis challenges

Accretion Properties of a Sample of Hard X-Ray (<60 keV) Selected Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Wang, J.; Mao, Y. F.; Wei, J. Y.

2009-02-01

We examine the accretion properties in a sample of 42 hard (3-60 keV) X-ray selected nearby broad-line active galactic nuclei (AGNs). The energy range in the sample is harder than that usually used in similar previous studies. These AGNs are mainly complied from the RXTE All Sky Survey, and complemented by the released INTEGRAL AGN catalog. The black hole masses, bolometric luminosities of AGN, and Eddington ratios are derived from their optical spectra in terms of the broad Hβ emission line. The tight correlation between the hard X-ray (3-20 keV) and bolometric/line luminosity is well identified in our sample. Also identified is a strong inverse Baldwin relationship of the Hβ emission line. In addition, all of these hard X-ray AGNs are biased toward luminous objects with a high Eddington ratio (mostly between 0.01 and 0.1) and a low column density (<1022 cm-2), which is most likely due to the selection effect of the surveys. The hard X-ray luminosity is consequently found to be strongly correlated with the black hole mass. We believe the sample completeness will be improved in the next few years by the ongoing Swift and the International Gamma-Ray Astrophysics Laboratory missions, and by the next advanced missions, such as NuSTAR, Simbol-X, and NeXT. Finally, the correlation between RFe (= optical Fe II/Hβ) and disk temperature as assessed by T vprop (L/L Edd)M -1 BH leads us to suggest that the strength of the Fe II emission is mainly determined by the shape of the ionizing spectrum.

X-ray-ing the Low Luminosity Supermassive Black Hole Accretion: the Crucial Role of Public Serendipitous Catalogs.

NASA Astrophysics Data System (ADS)

Constantin, Anca; Green, Paul; Haggard, Daryl

2018-01-01

For most of the nearby active galaxies, a mix of processes including emission from star-forming regions, other ionization sources (shocks, turbulence, etc.), nuclear obscuration, as well as host galaxy starlight obfuscate the true nature of their dominant ionization mechanism. X-ray emission is one of the most reliable primary signatures of accretion activity, and with the advent of the public catalogs, it became one of the most effective diagnostics as well. Working with large and significantly less biased samples that only serendipitous X-ray catalogs are able to provide, we were able to: 1) provide the most accurate estimates of the AGN fraction as a function of a diverse set of parameters; 2) confirm with X-rays a sequence from star-forming to active to passive galaxies that matches trends in both optical host galaxy characteristics and in the large scale environment; 3) discover intriguing similarities between accretion onto supermassive and stellar size black holes, with direct consequences for the physical significance of the Gamma-L/Ledd relation for AGN of both type I and II in the local universe. This presentation will summarize these exciting results, and will also report on novel extended efforts to decipher the link between the water megamaser emission and galactic nuclear activity, which are made possible only by the availability of the large sample statistics of carefully curated X-ray measurements uniquely offered by the combined Chandra and XMM catalogs.

THE GLOBAL IMPLICATIONS OF THE HARD EXCESS. II. ANALYSIS OF THE LOCAL POPULATION OF RADIO-QUIET AGNs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatum, M. M.; Turner, T. J.; Reeves, J. N.

2016-02-10

Active galactic nuclei (AGNs) show evidence for reprocessing gas, outflowing from the accreting black hole. The combined effects of absorption and scattering from the circumnuclear material likely explain the “hard excess” of X-ray emission above 20 keV, compared with the extrapolation of spectra from lower X-ray energies. In a recent Suzaku study, we established that the ubiquitous hard excess in hard, X-ray-selected, radio-quiet type 1 AGNs is consistent with a reprocessing of the X-ray continuum in an ensemble of clouds, located tens to hundreds of gravitational radii from the nuclear black hole. Here we add hard X-ray-selected, type 2 AGNsmore » to extend our original study and show that the gross X-ray spectral properties of the entire local population of radio-quiet AGNs may be described by a simple unified scheme. We find a broad, continuous distribution of spectral hardness ratio and Fe Kα equivalent width across all AGN types, which can be reproduced by varying the observer's sightline through a single, simple model cloud ensemble, provided that the radiative transfer through the model cloud distribution includes not only photoelectric absorption but also three-dimensional (3D) Compton scattering. Variation in other parameters of the cloud distribution, such as column density or ionization, should be expected between AGNs, but such variation is not required to explain the gross X-ray spectral properties.« less

On the relation of optical obscuration and X-ray absorption in Seyfert galaxies

NASA Astrophysics Data System (ADS)

Burtscher, L.; Davies, R. I.; Graciá-Carpio, J.; Koss, M. J.; Lin, M.-Y.; Lutz, D.; Nandra, P.; Netzer, H.; Orban de Xivry, G.; Ricci, C.; Rosario, D. J.; Veilleux, S.; Contursi, A.; Genzel, R.; Schnorr-Müller, A.; Sternberg, A.; Sturm, E.; Tacconi, L. J.

2016-02-01

The optical classification of a Seyfert galaxy and whether it is considered X-ray absorbed are often used interchangeably. There are many borderline cases, however, and also numerous examples where the optical and X-ray classifications appear to be in disagreement. In this article we revisit the relation between optical obscuration and X-ray absorption in active galactic nuclei (AGNs). We make use of our "dust colour" method to derive the optical obscuration AV, and consistently estimated X-ray absorbing columns using 0.3-150 keV spectral energy distributions. We also take into account the variable nature of the neutral gas column NH and derive the Seyfert subclasses of all our objects in a consistent way. We show in a sample of 25 local, hard-X-ray detected Seyfert galaxies (log LX/ (erg / s) ≈ 41.5-43.5) that there can actually be a good agreement between optical and X-ray classification. If Seyfert types 1.8 and 1.9 are considered unobscured, the threshold between X-ray unabsorbed and absorbed should be chosen at a column NH = 1022.3 cm-2 to be consistent with the optical classification. We find that NH is related to AV and that the NH/AV ratio is approximately Galactic or higher in all sources, as indicated previously. However, in several objects we also see that deviations from the Galactic ratio are only due to a variable X-ray column, showing that (1) deviations from the Galactic NH/AV can be simply explained by dust-free neutral gas within the broad-line region in some sources; that (2) the dust properties in AGNs can be similar to Galactic dust and that (3) the dust colour method is a robust way to estimate the optical extinction towards the sublimation radius in all but the most obscured AGNs.

X-ray cavities in a sample of 83 SPT-selected clusters of galaxies: Tracing the evolution of AGN feedback in clusters of galaxies out to z = 1.2

DOE PAGES

Hlavacek-Larrondo, J.; McDonald, M.; Benson, B. A.; ...

2015-05-18

X-ray cavities are key tracers of mechanical (or radio mode) heating arising from the active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). Here, we report on a survey for X-ray cavities in 83 massive, high-redshift (more » $$0.4\\lt z\\lt 1.2$$) clusters of galaxies selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. Based on Chandra X-ray images, we find a total of six clusters having symmetric pairs of surface brightness depressions consistent with the picture of radio jets inflating X-ray cavities in the intracluster medium (ICM). Furthermore, the majority of these detections are of relatively low significance and require deeper follow-up data in order to be confirmed. Further, this search will miss small (<10 kpc) X-ray cavities that are unresolved by Chandra at high ($$z\\gtrsim 0.5$$) redshift. Despite these limitations, our results suggest that the power generated by AGN feedback in BCGs has remained unchanged for over half of the age of the universe ($$\\gt 7$$ Gyr at $$z\\sim 0.8$$). On average, the detected X-ray cavities have powers of $$(0.8-5)\\times {{10}^{45}}\\ {\\rm erg}\\ {{{\\rm s}}^{-1}}$$, enthalpies of $$(3-6)\\times {{10}^{59}}\\ {\\rm erg}$$, and radii of ~17 kpc. Integrating over 7 Gyr, we find that the supermassive black holes in BCGs may have accreted 108 to several $${{10}^{9}}\\;{{M}_{\\odot }}$$ of material to power these outflows. This level of accretion indicates that significant supermassive black hole growth may occur not only at early times, in the quasar era, but at late times as well. We also find that X-ray cavities at high redshift may inject an excess heat of 0.1–1.0 keV per particle into the hot ICM above and beyond the energy needed to offset cooling. Though our result needs to be confirmed, we note that the magnitude of excess heating is similar to the energy needed to preheat clusters, break self-similarity, and explain the excess entropy in hot atmospheres.« less

Suzaku View of the Swift/BAT Active Galactic Nuclei (I): Spectral Analysis of Six AGNs and Evidence for Two Types of Obscured Population

NASA Technical Reports Server (NTRS)

Eguchi, Satoshi; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.; Tueller, Jack

2009-01-01

We present a systematic spectral analysis with Suzaku of six AGNs detected in the Swift/BAT hard X-ray (15-200 keV) survey, Swift J0138.6-4001, J0255.2-0011, J0350.1-5019, J0505.7-2348, J0601.9-8636, and J1628.1-5145. This is considered to be a representative sample of new AGNs without X-ray spectral information before the BAT survey. We find that the 0.5-200 keV spectra of these sources can be uniformly fit with a base model consisting of heavily absorbed (log NH >23.5/sq cm) transmitted components, scattered lights, a reflection component, and an iron-K emission line. There are two distinct groups, three "new type" AGNs (including the two sources reported by Ueda et al. 2007) with an extremely small scattered fraction (f(sub scat) < 0:5%) and strong reflection component (R = omega/2pi > or equal to 0.8 where omega is the solid angle of the reflector), and three "classical type" ones with f(sub scat > 0.5% and R < or approx. 0.8. The spectral parameters suggest that the new type has an optically thick torus for Thomson scattering (N(sub H) approx. 10(exp 25)/sq cm) with a small opening angle theta approx. 20deg viewed in a rather face-on geometry, while the classical type has a thin torus (N(sub H) approx. 10(exp 23-24)/sq cm) with theta > or approx. 30deg. We infer that a significant number of new type AGNs with an edge-on view is missing in the current all-sky hard X-ray surveys. Subject headings: galaxies: active . gamma rays: observations . X-rays: galaxies . X-rays: general

A WISE Selection of MIR AGN in Different Environments

NASA Astrophysics Data System (ADS)

Cheeseboro, Belinda D.; Norman, Dara J.

2015-01-01

This study was undertaken to understand the role of large scale environment in the evolution of MIR-selected AGN. In this study we examine AGN candidates in two types of environments: 7 clusters and 6 blank fields. Two types of clusters were studied in this project: 3 virialized and 4 non-virialized. The redshift of the clusters ranged 0.22≤z≤0.28. We used the mid-infrared WISE All-Sky database to identify AGN, applying various methods to refine our AGN candidate selection. To ascertain if there is an excess or deficit of MIR AGN in galaxy clusters vs. blank fields, we compared the AGN candidate distributions in virialized vs. non-virialized clusters to the blank fields. After close examination and comparison of the results to X-ray selected AGN from the Gilmour et al. (2009) study, we concluded that we do not detect an excess or deficit of MIR AGN in our clusters whether the cluster was virialized or non-virialized. This contrasted the conclusion of the Gilmour et al. (2009) study where there was an excess of X-Ray selected AGN in clusters.We also note an interesting feature in our WISE color-color plots that might be used for further investigation.Cheeseboro was supported by the NOAO/KPNO ResearchExperiences for Undergraduates (REU) Program which is funded by theNational Science Foundation Research Experiences for UndergraduatesProgram (AST-1262829).

Extragalactic gamma-ray background from AGN winds and star-forming galaxies in cosmological galaxy-formation models

NASA Astrophysics Data System (ADS)

Lamastra, A.; Menci, N.; Fiore, F.; Antonelli, L. A.; Colafrancesco, S.; Guetta, D.; Stamerra, A.

2017-10-01

We derive the contribution to the extragalactic gamma-ray background (EGB) from active galactic nuclei (AGN) winds and star-forming galaxies by including a physical model for the γ-ray emission produced by relativistic protons accelerated by AGN-driven and supernova-driven shocks into a state-of-the-art semi-analytic model of galaxy formation. This is based on galaxy interactions as triggers of AGN accretion and starburst activity and on expanding blast waves as the mechanism to communicate outwards the energy injected into the interstellar medium by the active nucleus. We compare the model predictions with the latest measurement of the EGB spectrum performed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) in the range between 100 MeV and 820 GeV. We find that AGN winds can provide 35 ± 15% of the observed EGB in the energy interval Eγ = 0.1-1 GeV, for 73 ± 15% at Eγ = 1-10 GeV, and for 60 ± 20% at Eγ ≳10 GeV. The AGN wind contribution to the EGB is predicted to be larger by a factor of 3-5 than that provided by star-forming galaxies (quiescent plus starburst) in the hierarchical clustering scenario. The cumulative γ-ray emission from AGN winds and blazars can account for the amplitude and spectral shape of the EGB, assuming the standard acceleration theory, and AGN wind parameters that agree with observations. We also compare the model prediction for the cumulative neutrino background from AGN winds with the most recent IceCube data. We find that for AGN winds with accelerated proton spectral index p = 2.2-2.3, and taking into account internal absorption of γ-rays, the Fermi-LAT and IceCube data could be reproduced simultaneously.

BAT AGN Spectroscopic Survey - III. An Observed Link Between AGN Eddington Ratio and Narrow-Emission-Line Ratios

NASA Technical Reports Server (NTRS)

Oh, Kyuseok; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny; Lamperti, Isabella; Ricci, Claudio; Mushotzky, Richard; Veilleux, Sylvain; Berney, Simon; Crenshaw, D. Michael;

THE X-RAY SPECTRUM OF THE COOLING-FLOW QUASAR H1821+643: A MASSIVE BLACK HOLE FEEDING OFF THE INTRACLUSTER MEDIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, Christopher S.; Lohfink, Anne M.; Babul, Arif

2014-09-10

We present a deep Suzaku observation of H1821+643, an extremely rare example of a powerful quasar hosted by the central massive galaxy of a rich cooling-core cluster of galaxies. Informed by previous Chandra studies of the cluster, we achieve a spectral separation of emission from the active galactic nucleus (AGN) and the intracluster medium (ICM). With a high degree of confidence, we identify the signatures of X-ray reflection/reprocessing by cold and slowly moving material in the AGN's immediate environment. The iron abundance of this matter is found to be significantly sub-solar (Z ≈ 0.4 Z {sub ☉}), an unusual findingmore » for powerful AGN but in line with the idea that this quasar is feeding from the ICM via a Compton-induced cooling flow. We also find a subtle soft excess that can be described phenomenologically (with an additional blackbody component) or as ionized X-ray reflection from the inner regions of a high inclination (i ≈ 57°) accretion disk around a spinning (a > 0.4) black hole. We describe how the ionization state of the accretion disk can be used to constrain the Eddington fraction of the source. Applying these arguments to our spectrum implies an Eddington fraction of 0.25-0.5, with an associated black hole mass of 3--6×10{sup 9} M{sub ⊙}.« less

Spectral evolution of active galactic nuclei: A unified description of the X-ray and gamma

NASA Technical Reports Server (NTRS)

Leiter, D.; Boldt, E.

1982-01-01

A model for spectral evolution is presented whereby active galactic nuclei (AGN) of the type observed individually emerge from an earlier stage at z approx = 4 in which they are the thermal X-ray sources responsible for most of the cosmic X-ray background (CXB). The conjecture is pursued that these precursor objects are initially supermassive Schwarzschild black holes with accretion disks radiating near the Eddington luminosity limit. It is noted that after approx. 10 to the 8th power years these central black holes are spun-up to a canonical Kerr equilibrium state (A/M = 0.998; Thorne 1974) and shown how they then can lead to spectral evolution involving non-thermal emission extending to gamma rays, at the expense of reduced thermal disk radiation. That major portion of the CXB remaining after the contribution of usual AGN are considered, while a superposition of AGN sources at z 1 can account for the gamma ray background. Extensive X-ray measurements carried out with the HEAO 1 and 2 missions as well as gamma ray and optical data are shown to compare favorably with principal features of this model.

Longterm AGN variability in the BASS sample

NASA Astrophysics Data System (ADS)

Sartori, Lia; Schawinski, Kevin; Koss, Michael; Treister, Ezequiel

2018-01-01

The study of AGN variability on different timescales can provide important information about black hole accretion physics, as well as the black hole – host galaxy interaction and coevolution. Galaxies with extended AGN photoionised clouds, e.g. IC 2497 and “Hanny’s Voorwerp”, are a great laboratory to study AGN variability over 100 kyr timescales, especially in the case where the AGN is currently dropping in luminosity. Based on a large sample of optically elusive AGN in the BASS sample we suggest that AGN may ‘flicker’ on and off 100-1000 times on ~10^5 yr timescales, and that optically elusive AGN may provide information about the switching on phase. In this talk I will show how longslit and IFU observations of BASS sources, combined with high quality hard X-ray observations and black hole demographic information, can help constraining the AGN lifecycle, and ultimately what is the physics driving AGN variability.

On the X-ray spectra of luminous, inhomogeneous accretion flows

NASA Astrophysics Data System (ADS)

Merloni, A.; Malzac, J.; Fabian, A. C.; Ross, R. R.

2006-08-01

We discuss the expected X-ray spectral and variability properties of black hole accretion discs at high luminosity, under the hypothesis that radiation-pressure-dominated discs are subject to violent clumping instabilities and, as a result, have a highly inhomogeneous two-phase structure. After deriving the full accretion disc solutions explicitly in terms of the parameters of the model, we study their radiative properties both with a simple two-zone model, treatable analytically, and with radiative transfer simulations which account simultaneously for energy balance and Comptonization in the hot phase, together with reflection, reprocessing, ionization and thermal balance in the cold phase. We show that, if not only the density, but also the heating rate within these flows is inhomogeneous, then complex reflection-dominated spectra can be obtained for a high enough covering fraction of the cold phase. In general, large reflection components in the observed X-ray spectra should be associated with strong soft excesses, resulting from the combined emission of ionized atomic emission lines. The variability properties of such systems are such that, even when contributing to a large fraction of the hard X-ray spectrum, the reflection component is less variable than the power-law-like emission originating from the hot Comptonizing phase, in agreement with what is observed in many Narrow Line Seyfert 1 galaxies and bright Seyfert 1. Our model falls within the family of those trying to explain the complex X-ray spectra of bright AGN with ionized reflection, but presents an alternative, specific, physically motivated, geometrical set-up for the complex multiphase structure of the inner regions of near-Eddington accretion flows.

VizieR Online Data Catalog: Mid-infrared-X-ray correlation for local AGNs (Asmus+, 2015)

NASA Astrophysics Data System (ADS)

Asmus, D.; Gandhi, P.; Honig, S. F.; Smette, A.; Duschl, W. J.

2018-01-01

We start with the total sample from the AGN MIR atlas of 253 objects (Asmus et al. 2014, J/MNRAS/439/1648). Note that sample is a combination of a hard X-ray (14-195 keV) selected and a quasi-MIR selected sample as explained in Asmus et al. (2014, J/MNRAS/439/1648). The MIR continuum fluxes are the unresolved nuclear fluxes extracted from ground-based multifilter photometry obtained with the instruments VISIR (Lagage et al. 2004Msngr.117...12L), T-ReCS (Telesco et al. 1998SPIE.3354..534T), Michelle (Glasse, Atad-Ettedgui & Harris 1997SPIE.2871.1197G), and COMICS; (Kataza et al. 2000SPIE.4008.1144K). We collect observed 14-195 keV fluxes, Fobs(14-195 keV), measured with Swift/BAT (Burst Alert Telescope) by combining the data of the 54 and 70 month source catalogues with preference for the latter (Cusumano et al. 2010, J/A+A/524/A64; Baumgartner et al. 2013, J/ApJS/207/19). (2 data files).

NASA's Future X-ray Missions: From Constellation-X to Generation-X

NASA Technical Reports Server (NTRS)

Hornschemeier, A.

2006-01-01

Among the most important topics in modern astrophysics are the formation and evolution of supermassive black holes in concert with galaxy bulges, the nature of the dark energy equation of state, and the self-regulating symmetry imposed by both stellar and AGN feedback. All of these topics are readily addressed with observations at X-ray wavelengths. NASA's next major X-ray observatory is Constellation-X, which is being developed to perform spatially resolved high-resolution X-ray spectroscopy. Con-X will directly measure the physical properties of material near black holes' last stable orbits and the absolute element abundances and velocities of hot gas in clusters of galaxies. The Con-X mission will be described, as well as its successor, Generation-X (anticipated to fly approx.1 decade after Con-X). After describing these missions and their driving science areas, the talk will focus on areas in which Chandra observing programs may enable science with future X-ray observatories. These areas include a possible ultra-deep Chandra imaging survey as an early Universe pathfinder, a large program to spatially resolve the hot intracluster medium of massive clusters to aid dark energy measurements, and possible deep spectroscopic observations to aid in preparatory theoretical atomic physics work needed for interpreting Con-X spectra.

The X-ray evolution of inflows and outflows in active galactic nuclei

NASA Astrophysics Data System (ADS)

Saez, Cristian

The evolution of the space density of AGNs might have spectral counterparts which could be observable in X-rays. The main objective of this thesis is to study the spectral properties of AGNs in X-rays in order to increase our current knowledge of AGN evolution. In chapter 2, we present results from a statistical analysis of 173 bright radio-quiet AGNs selected from the Chandra Deep Field-North and Chandra Deep Field-South surveys (hereafter, CDFs) in the redshift range of 0.1 ≲z≲ 4. We find that the X-ray power-law photon index (Gamma) of radio-quiet AGNs is correlated with their 2--10 keV rest-frame X-ray luminosity ( LX) at the > 99.5% confidence level in two redshift bins, 0.3 ≲z≲ 0.96, and 1.5 ≲z≲ 3.3 and is slightly less significant in the redshift bin 0.96 ≲z≲ 1.5. The X-ray spectral slope steepens as the X-ray luminosity increases for AGNs in the luminosity range 1042 to 1045 erg s-1. Combining our results from the CDFs with those from previous studies in the redshift range 1.5 ≲z≲ 3.3, we find that the Gamma -- L X correlation has a null-hypothesis probability of 1.6 x 10 -9. We investigate the redshift evolution of the correlation between the power-law photon index and the hard X-ray luminosity and find that the slope and offset of a linear fit to the correlation change significantly (at the > 99.9% confidence level) between redshift bins of 0.3 ≲z≲ 0.96 and 1.5 ≲z≲ 3.3. We explore physical scenarios explaining the origin of this correlation and its possible evolution with redshift in the context of steady corona models focusing on its dependency on variations of the properties of the hot corona with redshift. In chapter 3, we present results from three Suzaku observations of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. We detect strong and broad absorption at rest-frame energies of ≲ 2 keV (low-energy) and 7--12 keV (high-energy). The detection of these features confirms the results of

Chandra survey in the AKARI North Ecliptic Pole Deep Field - I. X-ray data, point-like source catalogue, sensitivity maps, and number counts

NASA Astrophysics Data System (ADS)

Krumpe, M.; Miyaji, T.; Brunner, H.; Hanami, H.; Ishigaki, T.; Takagi, T.; Markowitz, A. G.; Goto, T.; Malkan, M. A.; Matsuhara, H.; Pearson, C.; Ueda, Y.; Wada, T.

2015-01-01

We present data products from the 300 ks Chandra survey in the AKARI North Ecliptic Pole Deep Field. This field has a unique set of nine-band infrared photometry covering 2-24 μm from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ˜15 μm, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z ˜ 1. We design a source detection procedure, which performs joint maximum likelihood PSF (point spread function) fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 deg2. The procedure has been highly optimized and tested by simulations. We provide a point source catalogue with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5-7, 0.5-2, 2-7, 2-4, and 4-7 keV bands. The catalogue contains 457 X-ray sources and the spurious fraction is estimated to be ˜1.7 per cent. Sensitivity and 90 per cent confidence upper flux limits maps in all bands are provided as well. We search for optical-MIR counterparts in the central 0.25 deg2, where deep Subaru Suprime-Cam multiband images exist. Among the 377 X-ray sources detected there, ˜80 per cent have optical counterparts and ˜60 per cent also have AKARI MIR counterparts. We cross-match our X-ray sources with MIR-selected AGN from Hanami et al. Around 30 per cent of all AGN that have MIR SEDs purely explainable by AGN activity are strong Compton-thick AGN candidates.

Compton thick AGN in the NuSTAR era

NASA Astrophysics Data System (ADS)

Marchesi, Stefano; Ajello, Marco; Marcotulli, Lea; Comastri, Andrea

2017-08-01

The recent launch of the Nuclear Spectroscopic Telescope Array (NuSTAR), the first telescope with focusing optics at >10 keV, represented a major breakthrough in the study of obscured active galactic nuclei (AGN). In this talk, I present the results of the 0.3-100 keV spectral analysis of the 30 Compton thick (CT-; i.e., those sources having column density NH>1E24 cm-2) AGN detected within z~0.1 in the BAT 100-month survey with available NuSTAR data. Particularly, I will focus on how adding NuSTAR data to the 0.3-10 keV information helps to characterize the CT-AGN population, significantly improving the measurements of important X-ray spectral parameters such as the photon index, the intrinsic absorption, the intensity of the Iron K alpha line at 6.4 keV and the obscuring torus opening angle. Finally, I will discuss the role of these objects in the context of obscured AGN accretion physics, and their contribution to the cosmic X-ray background.

Chandra and NuSTAR Follow-up Observations of Swift-BAT-selected AGNs

NASA Astrophysics Data System (ADS)

Marchesi, S.; Tremblay, L.; Ajello, M.; Marcotulli, L.; Paggi, A.; Cusumano, G.; La Parola, V.; Segreto, A.

2017-10-01

Based on current models of the cosmic X-ray background (CXB), heavily obscured active galactic nuclei (AGNs) are expected to make up ˜10% of the peak emission of the CXB and ˜20% of the total population of AGNs, yet few of these sources have been recorded and characterized in current surveys. Here we present the Chandra follow-up observation of 14 AGNs detected by Swift-BAT. For five sources in the sample, NuSTAR observations in the 3-80 keV band are also available. The X-ray spectral fitting over the 0.3-150 keV energy range allows us to determine the main X-ray spectral parameters, such as the photon index and the intrinsic absorption, of these objects and to make hypotheses on the physical structures responsible for the observed spectra. We find that 13 of the 14 objects are absorbed AGNs, and one is a candidate Compton-thick AGN, having intrinsic absorption {N}{{H}}> {10}24 cm-2. Finally, we verified that the use of NuSTAR observations is strategic to strongly constrain the properties of obscured AGNs, since the best-fit values we obtained for parameters such as the power-law photon index Γ and the intrinsic absorption {N}{{H}} changed sometimes significantly fitting the spectra with and without the use of NuSTAR data.

Spatial clustering and halo occupation distribution modelling of local AGN via cross-correlation measurements with 2MASS galaxies

NASA Astrophysics Data System (ADS)

Krumpe, Mirko; Miyaji, Takamitsu; Coil, Alison L.; Aceves, Hector

2018-02-01

We present the clustering properties and halo occupation distribution (HOD) modelling of very low redshift, hard X-ray-detected active galactic nuclei (AGN) using cross-correlation function measurements with Two-Micron All Sky Survey galaxies. Spanning a redshift range of 0.007 < z < 0.037, with a median z = 0.024, we present a precise AGN clustering study of the most local AGN in the Universe. The AGN sample is drawn from the SWIFT/BAT 70-month and INTEGRAL/IBIS eight year all-sky X-ray surveys and contains both type I and type II AGN. We find a large-scale bias for the full AGN sample of b=1.04^{+0.10}_{-0.11}, which corresponds to a typical host dark matter halo mass of M_h^typ=12.84^{+0.22}_{-0.30} h^{-1} M_{⊙}. When split into low and high X-ray luminosity and type I and type II AGN subsamples, we detect no statistically significant differences in the large-scale bias parameters. However, there are differences in the small-scale clustering, which are reflected in the full HOD model results. We find that low and high X-ray luminosity AGN, as well as type I and type II AGN, occupy dark matter haloes differently, with 3.4σ and 4.0σ differences in their mean halo masses, respectively, when split by luminosity and type. The latter finding contradicts a simple orientation-based AGN unification model. As a by-product of our cross-correlation approach, we also present the first HOD model of 2MASS galaxies.

Optical Time-Domain and Radio Imaging Analyses of the Dynamic Hearts of AGN

NASA Astrophysics Data System (ADS)

Smith, Krista Lynne

Active galactic nuclei (AGN) are among the most extreme objects in the universe: galaxies with a central supermassive black hole feeding on gas from a hot accretion disk. Despite their potential as powerful tools to study topics ranging from relativity to cosmology, they remain quite mysterious. In the first portion of this thesis, we explore how an AGN may influence the formation of stars in its host galaxy. Using high-resolution 22 GHz radio imaging of an X-ray selected sample of radio-quiet AGN, we find that the far-infrared radio correlation for normal star forming galaxies remains valid within a few hundred parsecs of the central engine. Because the core flux is often spatially isolated from star formation, we can also determine that the radio emission in radio-quiet AGN is consistent with both coronal and disk-jet coupling models. Finally, we find that AGN with jet-like radio morphologies have suppressed star formation, possibly indicating ongoing feedback. The second portion of this thesis uses optical AGN light curves to study the physics of accretion. The Kepler spacecraft produces groundbreaking light curves, but its fixed field of view only contained a handful of known AGN. We conduct an X-ray survey of this field, yielding 93 unique X-ray sources identified by optical follow-up spectroscopy as a mixture of AGN and stars. For the AGN, we spectroscopically measure black hole masses and accretion rates. We then analyze a sample of 22 Kepler AGN light curves. We develop a customized pipeline for AGN science with Kepler, a necessary step since the initial data was optimized for the unique goal of exoplanet detection. The light curves display an astonishing variety of behaviors in a new regime of optical variability inaccessible with previous facilities. We find power spectral slopes inconsistent with the damped random walk model, characteristic variability timescales, correlations of variability properties with physical parameters, and bimodal flux

On the Importance of Very Light Internally Subsonic AGN Jets in Radio-mode AGN Feedback

NASA Astrophysics Data System (ADS)

Guo, Fulai

2016-07-01

Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light (η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonic jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations by internally subsonic and internally supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.

MHD Wind Models in X-Ray Binaries and AGN

NASA Astrophysics Data System (ADS)

Behar, Ehud; Fukumura, Keigo; Kazanas, Demosthenes; Shrader, Chris R.; Tombesi, Francesco; Contopoulos, Ioannis

2017-08-01

Self-similar magnetohydrodynamic (MHD) wind models that can explain both the kinematics and the ionization structure of outflows from accretion sources will be presented.The X-ray absorption-line properties of these outflows are diverse, their velocity ranging from 0.001c to 0.1c, and their ionization ranging from neutral to fully ionized.We will show how the velocity structure and density profile of the wind can be tightly constrained, by finding the scaling of the magnetic flux with the distance from the center that best matches observations, and with no other priors.It will be demonstrated that the same basic MHD wind structure that successfully accounts for the X-ray absorber properties of outflows from supermassive black holes, also reproduces the high-resolution X-ray spectrum of the accreting stellar-mass black hole GRO J1655-40 for a series of ions between ~1A and ~12A.These results support both the magnetic nature of these winds, as well as the universal nature of magnetic outflows across all black hole sizes.

Confinement and diffusion time-scales of CR hadrons in AGN-inflated bubbles

NASA Astrophysics Data System (ADS)

Prokhorov, D. A.; Churazov, E. M.

2017-09-01

While rich clusters are powerful sources of X-rays, γ-ray emission from these large cosmic structures has not been detected yet. X-ray radiative energy losses in the central regions of relaxed galaxy clusters are so strong that one needs to consider special sources of energy, likely active galactic nucleus (AGN) feedback, to suppress catastrophic cooling of the gas. We consider a model of AGN feedback that postulates that the AGN supplies the energy to the gas by inflating bubbles of relativistic plasma, whose energy content is dominated by cosmic-ray (CR) hadrons. If most of these hadrons can quickly escape the bubbles, then collisions of CRs with thermal protons in the intracluster medium (ICM) should lead to strong γ-ray emission, unless fast diffusion of CRs removes them from the cluster. Therefore, the lack of detections with modern γ-ray telescopes sets limits on the confinement time of CR hadrons in bubbles and CR diffusive propagation in the ICM.

The X-Ray Polarization of the Accretion Disk Coronae of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Beheshtipour, Banafsheh; Krawczynski, Henric; Malzac, Julien

2017-11-01

Hard X-rays observed in Active Galactic Nuclei (AGNs) are thought to originate from the Comptonization of the optical/UV accretion disk photons in a hot corona. Polarization studies of these photons can help to constrain the corona geometry and the plasma properties. We have developed a ray-tracing code that simulates the Comptonization of accretion disk photons in coronae of arbitrary shapes, and use it here to study the polarization of the X-ray emission from wedge and spherical coronae. We study the predicted polarization signatures for the fully relativistic and various approximate treatments of the elemental Compton scattering processes. We furthermore use the code to evaluate the impact of nonthermal electrons and cyclo-synchrotron photons on the polarization properties. Finally, we model the NuSTAR observations of the Seyfert I galaxy Mrk 335 and predict the associated polarization signal. Our studies show that X-ray polarimetry missions such as NASA’s Imaging X-ray Polarimetry Explorer and the X-ray Imaging Polarimetry Explorer proposed to ESA will provide valuable new information about the physical properties of the plasma close to the event horizon of AGN black holes.

Storm in a Teacup: X-Ray View of an Obscured Quasar and Superbubble

NASA Astrophysics Data System (ADS)

Lansbury, George B.; Jarvis, Miranda E.; Harrison, Chris M.; Alexander, David M.; Del Moro, Agnese; Edge, Alastair C.; Mullaney, James R.; Thomson, Alasdair P.

2018-03-01

We present the X-ray properties of the “Teacup AGN” (SDSS J1430+1339), a z = 0.085 type 2 quasar that is interacting dramatically with its host galaxy. Spectral modeling of the central quasar reveals a powerful, highly obscured active galactic nucleus (AGN) with a column density of N H = (4.2–6.5) × 1023 cm‑2 and an intrinsic luminosity of L 2–10 keV = (0.8–1.4) × 1044 erg s‑1. The current high bolometric luminosity inferred (L bol ≈1045–1046 erg s‑1) has ramifications for previous interpretations of the Teacup as a fading/dying quasar. High-resolution Chandra imaging data reveal a ≈10 kpc loop of X-ray emission, cospatial with the “eastern bubble” previously identified in luminous radio and ionized gas (e.g., [O III] line) emission. The X-ray emission from this structure is in good agreement with a shocked thermal gas, with T = (4–8) × 106 K, and there is evidence for an additional hot component with T ≳ 3 × 107 K. Although the Teacup is a radiatively dominated AGN, the estimated ratio between the bubble power and the X-ray luminosity is in remarkable agreement with observations of ellipticals, groups, and clusters of galaxies undergoing AGN feedback.

AGN host galaxy mass function in COSMOS. Is AGN feedback responsible for the mass-quenching of galaxies?

NASA Astrophysics Data System (ADS)

Bongiorno, A.; Schulze, A.; Merloni, A.; Zamorani, G.; Ilbert, O.; La Franca, F.; Peng, Y.; Piconcelli, E.; Mainieri, V.; Silverman, J. D.; Brusa, M.; Fiore, F.; Salvato, M.; Scoville, N.

2016-04-01

We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate, that is, λSAR, the distribution function (SARDF), up to z ~ 2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best-fit model characterizes the SARDF as a double power-law with mass-dependent but redshift-independent break, whose low λSAR slope flattens with increasing redshift while the normalization increases. This implies that for a given stellar mass, higher λSAR objects have a peak in their space density at earlier epoch than the lower λSAR objects, following and mimicking the well-known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with an almost constant M∗⋆ and a low-mass slope α that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that up to log (M⋆/M⊙) ~ 11.5, the ratio of AGN host galaxies to star-forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, M⋆ > 1010.7 M⊙, feedback from luminous AGN (log Lbol ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

X-Ray Polarization from High Mass X-Ray Binaries

NASA Technical Reports Server (NTRS)

Kallman, T.; Dorodnitsyn, A.; Blondin, J.

2015-01-01

X-ray astronomy allows study of objects which may be associated with compact objects, i.e. neutron stars or black holes, and also may contain strong magnetic fields. Such objects are categorically non-spherical, and likely non-circular when projected on the sky. Polarization allows study of such geometric effects, and X-ray polarimetry is likely to become feasible for a significant number of sources in the future. A class of potential targets for future X-ray polarization observations is the high mass X-ray binaries (HMXBs), which consist of a compact object in orbit with an early type star. In this paper we show that X-ray polarization from HMXBs has a distinct signature which depends on the source inclination and orbital phase. The presence of the X-ray source displaced from the star creates linear polarization even if the primary wind is spherically symmetric whenever the system is viewed away from conjunction. Direct X-rays dilute this polarization whenever the X-ray source is not eclipsed; at mid-eclipse the net polarization is expected to be small or zero if the wind is circularly symmetric around the line of centers. Resonance line scattering increases the scattering fraction, often by large factors, over the energy band spanned by resonance lines. Real winds are not expected to be spherically symmetric, or circularly symmetric around the line of centers, owing to the combined effects of the compact object gravity and ionization on the wind hydrodynamics. A sample calculation shows that this creates polarization fractions ranging up to tens of percent at mid-eclipse.

Constraining AGN triggering mechanisms through the clustering analysis of active black holes

NASA Astrophysics Data System (ADS)

Gatti, M.; Shankar, F.; Bouillot, V.; Menci, N.; Lamastra, A.; Hirschmann, M.; Fiore, F.

2016-02-01

The triggering mechanisms for active galactic nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disc instabilities (DIs). Using an advanced semi-analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modelling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: (I) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the centre of haloes with Mh > 1013.5 h-1 M⊙. On the contrary, the IT scenario predicts abundance of active central galaxies that generally agrees well with observations at every halo mass. (II) The relative number of satellite AGN in DIs at intermediate-to-low luminosities is always significantly higher than in IT models, especially in groups and clusters. The low AGN satellite fraction predicted for the IT scenario might suggest that different feeding modes could simultaneously contribute to the triggering of satellite AGN. (III) Both scenarios are quite degenerate in matching large-scale clustering measurements, suggesting that the sole average bias might not be an effective observational constraint. (IV) Our analysis suggests the presence of both a mild luminosity and a more consistent redshift dependence in the AGN clustering, with AGN inhabiting progressively less massive dark matter haloes as the redshift increases. We also discuss the impact of different observational selection cuts in measuring AGN clustering, including possible discrepancies between optical and X-ray surveys.

Seeing Red and Shooting Blanks: A Study of Red Quasars and Blank Field X-Ray Sources

NASA Technical Reports Server (NTRS)

Elvis, Martin; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

We have identified a population of 'blank field sources' (or 'blanks') among the ROSAT (Roentgen Satellite) bright unidentified X-ray sources with faint optical counterparts. The extreme X-ray over optical flux ratio of blank field sources is not compatible with the main classes of X-ray emitters except for extreme BL Lacertae objects at fx/fv is equal to or less than 35. From the analysis of ROSAT archival data we found evidence for only three sources, out of 16, needing absorption in excess of the Galactic value and no indication of variability. We also found evidence for an extended nature for only one of the five blanks with a serendipitous HRI (High Resolution Imager) detection; this source (1WGA J1226.9+3332) was confirmed as a z=0.89 cluster of galaxies. Palomar images reveal the presence of a red (O - E is equal to or greater than 2) counterpart in the X-ray error circle for six blanks. The identification process brought to the discovery of another high z cluster of galaxies, one (possibly extreme) BL Lac and two apparently normal type 1 AGNs (Active Galactic Nuclei). These AGNs, together with four more AGN-like objects seem to form a well defined group: they present type 1 X-ray spectra but red Palomar counterparts. We discuss the possible explanations for the discrepancy between the X-ray and optical data, among which: a suppressed big blue bump emission, an extreme dust to gas (approximately 40 - 60 the Galactic ratio) ratio value and a high redshift (z is greater than or equal to 3.5) QSO (Quasi-Stellar Object) nature. These AGN-like blanks seem to be the bright (and easier to study) analogs of the sources which are being found in deep Chandra observations. Five more blanks have a still an unknown nature.

Broadband X-Ray Spectral Analysis of the Double-nucleus Luminous Infrared Galaxy Mrk 463

NASA Astrophysics Data System (ADS)

Yamada, Satoshi; Ueda, Yoshihiro; Oda, Saeko; Tanimoto, Atsushi; Imanishi, Masatoshi; Terashima, Yuichi; Ricci, Claudio

2018-05-01

We present a broadband (0.4–70 keV) X-ray spectral analysis of the luminous infrared galaxy (LIRG) system Mrk 463 observed with Nuclear Spectroscopic Telescope Array (NuSTAR), Chandra, and XMM-Newton, which contains double active galactic nuclei (AGNs; Mrk 463E and Mrk 463W) with a separation of ∼3.8 kpc. Detecting their transmitted hard X-ray >10 keV continua with NuSTAR, we confirm that Mrk 463E and Mrk 463W have AGNs with intrinsic luminosities of (1.6–2.2) × 1043 and (0.5–0.6) × 1043 erg s‑1 (2–10 keV) obscured by hydrogen column densities of 8 × 1023 and 3 × 1023 cm‑2, respectively. Both nuclei show strong reflection components from cold matter. The luminosity ratio between X-ray (2–10 keV) and [O IV] 25.89 μm of Mrk 463E is ∼5 times smaller than those of normal Seyfert galaxies, suggesting that the intrinsic SED is X-ray weak relative to the UV luminosity. In fact, the bolometric AGN luminosity of Mrk 463E estimated from L‧-band (3.8 μm), [O IV] 25.89 μm, and [Ne V] 14.32 μm lines indicate a large bolometric-to-X-ray luminosity ratio, κ 2–10 keV ≈ 110–410, and a high Eddington ratio, λ Edd ∼ 0.4–0.8. We suggest that the merger triggered a rapid growth of the black hole in Mrk 463E, which is not yet deeply “buried” by circumnuclear dust. By contrast, the L‧-band luminosity of Mrk 463W is unusually small relative to the X-ray luminosity, suggesting that the Eddington ratio is low (<10‑3) and it might be still in an early phase of merger-driven AGN activity.

Identifying the subtle signatures of feedback from distant AGN using ALMA observations and the EAGLE hydrodynamical simulations

NASA Astrophysics Data System (ADS)

Scholtz, J.; Alexander, D. M.; Harrison, C. M.; Rosario, D. J.; McAlpine, S.; Mullaney, J. R.; Stanley, F.; Simpson, J.; Theuns, T.; Bower, R. G.; Hickox, R. C.; Santini, P.; Swinbank, A. M.

2018-03-01

We present sensitive 870 μm continuum measurements from our ALMA programmes of 114 X-ray selected active galactic nuclei (AGN) in the Chandra Deep Field-South and Cosmic Evolution Survey fields. We use these observations in combination with data from Spitzer and Herschel to construct a sample of 86 X-ray selected AGN, 63 with ALMA constraints at z = 1.5-3.2 with stellar mass >2 × 1010 M⊙. We constructed broad-band spectral energy distributions in the infrared band (8-1000 μm) and constrain star-formation rates (SFRs) uncontaminated by the AGN. Using a hierarchical Bayesian method that takes into account the information from upper limits, we fit SFR and specific SFR (sSFR) distributions. We explore these distributions as a function of both X-ray luminosity and stellar mass. We compare our measurements to two versions of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations: the reference model with AGN feedback and the model without AGN. We find good agreement between the observations and that predicted by the EAGLE reference model for the modes and widths of the sSFR distributions as a function of both X-ray luminosity and stellar mass; however, we found that the EAGLE model without AGN feedback predicts a significantly narrower width when compared to the data. Overall, from the combination of the observations with the model predictions, we conclude that (1) even with AGN feedback, we expect no strong relationship between the sSFR distribution parameters and instantaneous AGN luminosity and (2) a signature of AGN feedback is a broad distribution of sSFRs for all galaxies (not just those hosting an AGN) with stellar masses above ≈1010 M⊙.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2017-01-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z~5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z≈0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z≈0.9 quasars may be commonly hosted by haloes with Mh ~ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

Energy Feedback from X-ray Binaries in the Early Universe

NASA Technical Reports Server (NTRS)

Fragos, T.; Lehmer, B..; Naoz, S.; Zezas, A.; Basu-Zych, A.

2013-01-01

X-ray photons, because of their long mean-free paths, can easily escape the galactic environments where they are produced, and interact at long distances with the intergalactic medium, potentially having a significant contribution to the heating and reionization of the early universe. The two most important sources of X-ray photons in the universe are active galactic nuclei (AGNs) and X-ray binaries (XRBs). In this Letter we use results from detailed, large scale population synthesis simulations to study the energy feedback of XRBs, from the first galaxies (z (redshift) approximately equal to 20) until today.We estimate that X-ray emission from XRBs dominates over AGN at z (redshift) greater than or approximately equal to 6-8. The shape of the spectral energy distribution of the emission from XRBs shows little change with redshift, in contrast to its normalization which evolves by approximately 4 orders of magnitude, primarily due to the evolution of the cosmic star-formation rate. However, the metallicity and the mean stellar age of a given XRB population affect significantly its X-ray output. Specifically, the X-ray luminosity from high-mass XRBs per unit of star-formation rate varies an order of magnitude going from solar metallicity to less than 10% solar, and the X-ray luminosity from low-mass XRBs per unit of stellar mass peaks at an age of approximately 300 Myr (million years) and then decreases gradually at later times, showing little variation for mean stellar ages 3 Gyr (Giga years, or billion years). Finally, we provide analytical and tabulated prescriptions for the energy output of XRBs, that can be directly incorporated in cosmological simulations.

Spatial Fluctuations in the Diffuse Cosmic X-Ray Background. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Shafer, R. A.

1983-01-01

The bright, essentially isotropic, X-ray sky flux above 2 keV yields information on the universe at large distances. However, a definitive understanding of the origin of the flux is lacking. Some fraction of the total flux is contributed by active galactic nuclei and clusters of galaxies, but less than one percent of the total is contributed by the or approximately 3 keV band resolved sources, which is the band where the sky flux is directly observed. Parametric models of AGN (quasar) luminosity function evolution are examined. Most constraints are by the total sky flux. The acceptability of particular models hinges on assumptions currently not directly testable. The comparison with the Einstein Observatory 1 to keV low flux source counts is hampered by spectral uncertainties. A tentative measurement of a large scale dipole anisotropy is consistent with the velocity and direction derived from the dipole in the microwave background. The impact of the X-ray anisotropy limits for other scales on studies of large-scale structure in the universe is sketched. Models of the origins of the X-ray sky flux are reviewed, and future observational programs outlined.

The Swift/BAT Hard X-Ray Survey

NASA Technical Reports Server (NTRS)

Tueller, Jack; Markwardt, C. B.; Mushotzky, R. F.; Barthelmy, S. D.; Gehrels, N.; Krimm, H. A.; Skinner, G. K.; Falcone, A.; Kennea, J. A.

2006-01-01

The BAT instrument on Swift is a wide field (70 deg. '100 deg.) coded aperture instrument with a CdZnTe detector array sensitive to energies of 14-200 keV. Each day, the BAT survey typically covers 60% of the sky to a detection limit of 30 millicrab. BAT makes hard X-ray light curves of similar sensitivity and coverage to the X-ray light curves from XTE/ASM, but in an energy range where sources show remarkably different behavior. Integrating the BAT data produces an all sky map with a source detection limit at 15 months of a few 10(exp -11) ergs per square centimeter per second, depending on the exposure. This is the first uniform all-sky survey at energies high enough to be unaffected by absorption since HEAO 1 in 1977-8. BAT has detected greater than 200 AGN and greater than 180 galactic sources. At high galactic latitudes, the BAT sources are usually easy to identify, but many are heavily absorbed and there are a few quite surprising identifications. The BAT selected galaxies can be used to calculate LogN/LogS and the luminosity function for AGN which are complete and free from common systematics. Several crucial parameters for understanding the cosmic hard x-ray background are now determined.

Two Active States of the Narrow-Line Gamma-Ray-Loud AGN GB 1310 + 487

NASA Technical Reports Server (NTRS)

Sokolovsky, K. V.; Schinzel, F. K.; Tanaka, Y. T.; Abolmasov, P. K.; Angelakis, E.; Bulgarelli, A.; Carrasco, L.; Cenko, S. B.; Cheung, C. C.; Clubb, K. I.;

Two active states of the narrow-line gamma-ray-loud AGN GB 1310+487

DOE PAGES

Sokolovsky, K. V.

2014-04-28

Context. Previously unremarkable, the extragalactic radio source GB1310+487 showed a γ-ray flare on 2009 November 18, reaching a daily flux of ~ 10 -6 photons cm -2 s -1 at energies E > 100MeV and became one of the brightest GeV sources for about two weeks. Its optical spectrum shows strong forbidden-line emission while lacking broad permitted lines, which is not typical for a blazar. Instead, the spectrum resembles those of narrow emission-line galaxies. Aims. We investigate changes in the object’s radio-to-GeV spectral energy distribution (SED) during and after the prominent γ-ray flare with the aim of determining the naturemore » of the object and of constraining the origin of the variable high-energy emission. Methods. The data collected by the Fermi and AGILE satellites at γ-ray energies; Swift at X-ray and ultraviolet (UV); the Kanata, NOT, and Keck telescopes at optical; OAGH andWISE at infrared (IR); and IRAM30m, OVRO 40m, Effelsberg 100m, RATAN-600, and VLBA at radio are analyzed together to trace the SED evolution on timescales of months. Results. The γ-ray/radio-loud narrow-line active galactic nucleus (AGN) is located at redshift z = 0.638. It shines through an unrelated foreground galaxy at z = 0.500. The AGN light is probably amplified by gravitational lensing. The AGN SED shows a two-humped structure typical of blazars and γ-ray-loud narrow-line Seyfert 1 galaxies, with the high-energy (inverse-Compton) emission dominating by more than an order of magnitude over the low-energy (synchrotron) emission during γ-ray flares. The difference between the two SED humps is smaller during the low-activity state. Fermi observations reveal a strong correlation between the γ-ray flux and spectral index, with the hardest spectrum observed during the brightest γ-ray state. The γ-ray flares occurred before and during a slow rising trend in the radio, but no direct association between γ-ray and radio flares could be established. Conclusions. If the γ-ray

X-ray emission associated with radio galaxies in the Perseus cluster

NASA Technical Reports Server (NTRS)

Rhee, George; Burns, Jack O.; Kowalski, Michael P.

1994-01-01

In this paper, we report on new x-ray observations of the Perseus cluster made using four separate pointings of the Roentgen Satellite (ROSAT) Positron Sensitive Proportional Counter (PSPC). We searched for x-ray emission associated with 16 radio galaxies and detected six above 3 sigma. We made use of the PSPC spectra to determine if the x-ray emission associated with radio galaxies in Perseus is thermal or nonthermal in origin (i.e., hot gas or an active galactic nuclei (AGN)). For the head-tail radio galaxy IC 310, we find that the data are best fit by a power law model with an unusually large spectral index alpha = 2.7. This is consistent with its unresolved spatial structure. On the other hand, a second resolved x-ray source associated with another radio galaxy 2.3 Mpc from the Perseus center (V Zw 331) is best fit by a thermal model. For three sources with insufficient flux for a full spectral analysis, we calculated hardness ratios. On this basis, the x-ray emission associated with the well known head-tail source NGC 1265 is consistent with thermal radiation. The x-ray spectra of UGC 2608 and UGC 2654 probably arise from hot gas, although very steep power-law spectra (alpha greater than 3.2) are also possible. The spectrum of NGC 1275 is quite complex due to the presence of an AGN and the galaxy's location at the center of a cluster cooling flow.

Transient iron fluorescence: new clues on the AGN disk/corona?

NASA Astrophysics Data System (ADS)

Nardini, E.

2017-10-01

Deep X-ray observations of the so-called `bare' active galaxies represent the most effective means of probing the physical conditions in the immediate surroundings of a radiatively efficient supermassive black hole, thus aiding our understanding of the emission processes in AGN. Indeed, the structure and properties of the putative X-ray corona, and the nature of coupling with the disk, are still largely unknown. The recent, surprising discovery of transient iron fluorescence on timescales of 10-15 hours during the 7.5 days of XMM-Newton monitoring of Ark 120, the nearest and X-ray brightest bare AGN, poses several challenges to the commonly adopted X-ray emission paradigm of a very compact corona. Such a rapid variability implies that the inner accretion flow is highly dynamic and inhomogeneous, involving the presence of orbiting hotspots, density gradients, or other forms of clumpiness and instability. Whatever the case, these results offer a compelling glimpse of what could be achieved in the future with Athena's capabilities.

Steps Toward Unveiling the True Population of AGN: Photometric Selection of Broad-Line AGN

NASA Astrophysics Data System (ADS)

Schneider, Evan; Impey, C.

2012-01-01

We present an AGN selection technique that enables identification of broad-line AGN using only photometric data. An extension of infrared selection techniques, our method involves fitting a given spectral energy distribution with a model consisting of three physically motivated components: infrared power law emission, optical accretion disk emission, and host galaxy emission. Each component can be varied in intensity, and a reduced chi-square minimization routine is used to determine the optimum parameters for each object. Using this model, both broad- and narrow-line AGN are seen to fall within discrete ranges of parameter space that have plausible bounds, allowing physical trends with luminosity and redshift to be determined. Based on a fiducial sample of AGN from the catalog of Trump et al. (2009), we find the region occupied by broad-line AGN to be distinct from that of quiescent or star-bursting galaxies. Because this technique relies only on photometry, it will allow us to find AGN at fainter magnitudes than are accessible in spectroscopic surveys, and thus probe a population of less luminous and/or higher redshift objects. With the vast availability of photometric data in large surveys, this technique should have broad applicability and result in large samples that will complement X-ray AGN catalogs.

X-Ray Spectral Study of AGN Sources Content in Some Deep Extragalactic XMM-Newton Fields

NASA Astrophysics Data System (ADS)

Hassan, M. A.; Korany, B. A.; Misra, R.; Issa, I. A. M.; Ahmed, M. K.; Abdel-Salam, F. A.

2012-06-01

We undertake a spectral study of a sample of bright X-ray sources taken from six XMM-Newton fields at high galactic latitudes, where AGN are the most populous class. These six fields were chosen such that the observation had an exposure time more than 60 ksec, had data from the EPIC-pn detector in the full-Frame mode and lying at high galactic latitude | b|>25°. The analysis started by fitting the spectra of all sources with an absorbed power-law model, and then we fitted all the spectra with an absorbed power-law with a low energy black-body component model.The sources for which we added a black body gave an F-test probability of 0.01 or less (i.e. at 99% confidence level), were recognized as sources that display soft excess. We perform a comparative analysis of soft excess spectral parameters with respect to the underlying power-law one for sources that satisfy this criterion. Those sources, that do not show evidence for a soft excess, based on the F-test probability at a 99% confidence level, were also fitted with the absorbed power-law with a low energy black-body component model with the black-body temperature fixed at 0.1 and 0.2 keV. We establish upper limits on the soft excess flux for those sources at these two temperatures. Finally we have made use of Aladdin interactive sky atlas and matching with NASA/IPAC Extragalactic Database (NED) to identify the X-ray sources in our sample. For those sources which are identified in the NED catalogue, we make a comparative study of the soft excess phenomenon for different types of systems.

Mid-IR Properties of an Unbiased AGN Sample of the Local Universe. 1; Emission-Line Diagnostics

NASA Technical Reports Server (NTRS)

Weaver, K. A.; Melendez, M.; Muhotzky, R. F.; Kraemer, S.; Engle, K.; Malumuth. E.; Tueller, J.; Markwardt, C.; Berghea, C. T.; Dudik, R. P.;

The Cosmic History of Hot Gas Cooling and Radio AGN Activity in Massive Early-Type Galaxies

NASA Technical Reports Server (NTRS)

Danielson, A. L. R.; Lehmer, B. D.; Alexander, D. M.; Brandt, W. M.; Luo, B.; Miller, N.; Xue, Y. Q.; Stott, J. P.

2012-01-01

We study the X-ray properties of 393 optically selected early-type galaxies (ETGs) over the redshift range of z approx equals 0.0-1.2 in the Chandra Deep Fields. To measure the average X-ray properties of the ETG population, we use X-ray stacking analyses with a subset of 158 passive ETGs (148 of which were individually undetected in X-ray). This ETG subset was constructed to span the redshift ranges of z = 0.1-1.2 in the approx equals 4 Ms CDF-S and approx equals 2 Ms CDF-N and z = 0.1-0.6 in the approx equals 250 ks E-CDF-S where the contribution from individually undetected AGNs is expected to be negligible in our stacking. We find that 55 of the ETGs are detected individually in the X-rays, and 12 of these galaxies have properties consistent with being passive hot-gas dominated systems (i.e., systems not dominated by an X-ray bright Active Galactic Nucleus; AGN). On the basis of our analyses, we find little evolution in the mean 0.5-2 keY to B-band luminosity ratio (L(sub x) /L(sub Beta) varies as [1 +z]) since z approx equals 1.2, implying that some heating mechanism prevents the gas from cooling in these systems. We consider that feedback from radio-mode AGN activity could be responsible for heating the gas. We select radio AGNs in the ETG population using their far-infrared/radio flux ratio. Our radio observations allow us to constrain the duty cycle history of radio AGN activity in our ETG sample. We estimate that if scaling relations between radio and mechanical power hold out to z approx equals 1.2 for the ETG population being studied here, the average mechanical power from AGN activity is a factor of approx equals1.4 -- 2.6 times larger than the average radiative cooling power from hot gas over the redshift range z approx equals 0-1.2. The excess of inferred AGN mechanical power from these ETGs is consistent with that found in the local Universe for similar types of galaxies.

Chandra Resolves Cosmic X-ray Glow and Finds Mysterious New Sources

NASA Astrophysics Data System (ADS)

2000-01-01

-energy X-ray background, showing that it arose in very faraway galaxies with extremely bright cores, called quasars or Active Galactic Nuclei (AGN). The Chandra team sampled a region of the sky about one-fifth the angular area of a full moon and resolved about 80 percent of the more-energetic X-ray background into discrete sources. Stretched across the entire sky, this would account for approximately 70 million sources, most of which would be identified with galaxies. Their analysis confirms that a significant fraction of the X-ray background cannot be due to diffuse radiation from hot, intergalactic gas. Combined X-ray and optical observations showed that nearly one third of the sources are galaxies whose cores are very bright in X rays yet emit virtually no optical light from the core. The observation suggests that these "veiled galactic nuclei" galaxies may number in the tens of millions over the whole sky. They almost certainly harbor a massive black hole at their core that produces X rays as the gas is pulled toward it at nearly the speed of light. Their bright X-ray cores place these galaxies in the AGN family. Because these numerous AGN are bright in X rays, but optically dim, the Chandra observation implies that optical surveys of AGN are very incomplete. A second new class of objects, comprising approximately one-third of the background, is assumed to be "ultra-faint galaxies." Mushotzky said that these sources may emit little or no optical light, either because the dust around the galaxy blocks the light totally or because the optical light is eventually absorbed by relatively cool gas during its long journey across the universe. In the latter scenario, Mushotzky said that these sources would have a redshift of 6 or higher, meaning that they are well over 14 billion light years away and thus the earliest, most distant objects ever identified. "This is a very exciting discovery," said Dr. Alan Bunner, Director of NASA's Structure and Evolution of the universe

ON THE IMPORTANCE OF VERY LIGHT INTERNALLY SUBSONIC AGN JETS IN RADIO-MODE AGN FEEDBACK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Fulai, E-mail: fulai@shao.ac.cn

Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light ( η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonicmore » jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations by internally subsonic and internally supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.« less

The 5-10 keV AGN luminosity function at 0.01 < z < 4.0

NASA Astrophysics Data System (ADS)

Fotopoulou, S.; Buchner, J.; Georgantopoulos, I.; Hasinger, G.; Salvato, M.; Georgakakis, A.; Cappelluti, N.; Ranalli, P.; Hsu, L. T.; Brusa, M.; Comastri, A.; Miyaji, T.; Nandra, K.; Aird, J.; Paltani, S.

2016-03-01

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

The Origin of the Extra-nuclear X-ray Emission in the Seyfert Galaxy NGC 2992

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.; Strickland, D. K.; Veilleux, S.; Weaver, K. A.

2004-12-01

We present an analysis of a Chandra ACIS observation of the edge-on Seyfert galaxy NGC 2992. We find extended X-ray emission with Lx(total) in excess of 10**40 erg/s. The brightest nebula is positioned a few 100 pc from the X-ray core, and is spatially coincident with optical line and radio emission. This emission nebula may be energized by the AGN, as opposed to a nuclear starburst. The expected kpc-scale X-ray emission due to a starburst-driven wind is larger than a few 10**39 erg/s, and we present large-scale X-ray emission that may be associated with such an outflow. The extra-nuclear emission has a very soft spectrum. Chandra and XMM spectra of the total nuclear region show a very prominent ``soft excess'' below 2-3 keV. We shall discuss the spectral properties of this soft excess, and will compare with the results from the spatial analysis, and with AGN and starburst models for extranuclear X-ray nebulae.

The Presence of Thermally Unstable X-Ray Filaments and the Production of Cold Gas in the NGC 5044 Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Laurence P.; Vrtilek, Jan; O’Sullivan, Ewan

We present the results of a deep Chandra observation of the X-ray bright moderate-cooling flow group NGC 5044 along with the observed correlations between the ionized, atomic, and molecular gas in this system. The Chandra observation shows that the central AGN has undergone two outbursts in the past 10{sup 8} years, based on the presence of two pairs of nearly bipolar X-ray cavities. The molecular gas and dust within the central 2 kpc is aligned with the orientation of the inner pair of bipolar X-ray cavities, suggesting that the most recent AGN outburst had a dynamical impact on the molecularmore » gas. NGC 5044 also hosts many X-ray filaments within the central 8 kpc, but there are no obvious connections between the X-ray and H α filaments and the more extended X-ray cavities that were inflated during the prior AGN outburst. Using the line width of the blended Fe-L line complex as a diagnostic for multiphase gas, we find that the majority of the multiphase thermally unstable gas in NGC 5044 is confined within the X-ray filaments. While the cooling time and entropy of the gas within the X-ray filaments are very similar, not all filaments show evidence of gas cooling or an association with H α emission. We suggest that the various observed properties of the X-ray filaments are suggestive of an evolutionary sequence where thermally unstable gas begins to cool, becomes multiphased, develops H α emitting plasma, and finally produces cold gas.« less

Compton-thick AGNs in the NuSTAR Era

NASA Astrophysics Data System (ADS)

Marchesi, S.; Ajello, M.; Marcotulli, L.; Comastri, A.; Lanzuisi, G.; Vignali, C.

2018-02-01

We present the 2–100 keV spectral analysis of 30 candidate Compton-thick-(CT-)active galactic nuclei (AGNs) selected in the Swift-Burst Alert Telescope (BAT) 100 month survey. The average redshift of these objects is < z> ∼ 0.03, and they all lie within ∼500 Mpc. We used the MyTorus model to perform X-ray spectral fittings both without and with the contribution of the Nuclear Spectroscopic Telescope Array (NuSTAR) data in the 3–50 keV energy range. When the NuSTAR data are added to the fit, 13 out of 30 of these objects (43% of the whole sample) have intrinsic absorption N H < 1024 cm‑2 at the >3σ confidence level, i.e., they are reclassified from Compton thick to Compton thin. Consequently, we infer an overall observed fraction of the CT-AGN, with respect to the whole AGN population, lower than the one reported in previous works, as low as ∼4%. We find evidence that this overestimation of N H is likely due to the low quality of a subsample of spectra, either in the 2–10 keV band or in the Swift-BAT one.

X-Ray Spectroscopy of Photoionized Plasmas

NASA Technical Reports Server (NTRS)

Kallman, Tim

2008-01-01

Spectroscopy allows study of sources on small spatial scales, and can provide detailed diagnostic information about elemental abundances, temperature, density and gas dynamics. For compact sources such as accreting black holes in active galactic nuclei (AGN) and X-ray binaries X-ray spectra provide truly unique insight. Observations using Chandra and XMM have revealed components of gas in these systems which were previously unknown or poorly studied. Interpretation of these data presents modeling and analysis challenges, and requires an understanding of atomic physics, ionization and spectrum formation in a radiation-dominated environment. In this talk I will discuss examples, and how they have contributed to our understanding of accreting sources and the nearby gas.

THE LONGEST TIMESCALE X-RAY VARIABILITY REVEALS EVIDENCE FOR ACTIVE GALACTIC NUCLEI IN THE HIGH ACCRETION STATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Youhong, E-mail: youhong.zhang@mail.tsinghua.edu.cn

2011-01-01

The All Sky Monitor (ASM) on board the Rossi X-ray Timing Explorer has continuously monitored a number of active galactic nuclei (AGNs) with similar sampling rates for 14 years, from 1996 January to 2009 December. Utilizing the archival ASM data of 27 AGNs, we calculate the normalized excess variances of the 300-day binned X-ray light curves on the longest timescale (between 300 days and 14 years) explored so far. The observed variance appears to be independent of AGN black-hole mass and bolometric luminosity. According to the scaling relation of black-hole mass (and bolometric luminosity) from galactic black hole X-ray binariesmore » (GBHs) to AGNs, the break timescales that correspond to the break frequencies detected in the power spectral density (PSD) of our AGNs are larger than the binsize (300 days) of the ASM light curves. As a result, the singly broken power-law (soft-state) PSD predicts the variance to be independent of mass and luminosity. Nevertheless, the doubly broken power-law (hard-state) PSD predicts, with the widely accepted ratio of the two break frequencies, that the variance increases with increasing mass and decreases with increasing luminosity. Therefore, the independence of the observed variance on mass and luminosity suggests that AGNs should have soft-state PSDs. Taking into account the scaling of the break timescale with mass and luminosity synchronously, the observed variances are also more consistent with the soft-state than the hard-state PSD predictions. With the averaged variance of AGNs and the soft-state PSD assumption, we obtain a universal PSD amplitude of 0.030 {+-} 0.022. By analogy with the GBH PSDs in the high/soft state, the longest timescale variability supports the standpoint that AGNs are scaled-up GBHs in the high accretion state, as already implied by the direct PSD analysis.« less

X-Ray Weak Broad-Line Quasars: Absorption or Intrinsic X-Ray Weakness

NASA Technical Reports Server (NTRS)

Risaliti, Guido; Mushotzky, Richard F. (Technical Monitor)

2004-01-01

XMM observations of X-ray weak quasars have been performed during 2003. The data for all but the last observation are now available (there has been a delay of several months on the initial schedule, due to high background flares which contaminated the observations: as a consequence, most of them had to be rescheduled). We have reduced and analyzed these data, and obtained interesting preliminary scientific results. Out of the eight sources, 4 are confirmed to be extrimely X-ray weak, in agreement with the results of previous Chandra observations. 3 sources are confirmed to be highly variable both in flux (by factors 20-50) and in spectral properties (dramatic changes in spectral index). For both these groups of objects, an article is in preparation. Preliminary results have been presented at an international workshop on AGN surveys in December 2003, in Cozumel (Mexico). In order to further understand the nature of these X-ray weak quasars, we submitted proposals for spectroscopy at optical and infrared telescopes. We obtained time at the TNG 4 meter telescope for near-IR observations, and at the Hobby-Eberly Telescope for optical high-resolution spectroscopy. These observations will be performed in early 2004, and will complement the XMM data, in order to understand whether the X-ray weakness of these sources is an intrinsic property or is due to absorption by circumnuclear material.

The mm-wave compact component of AGN

NASA Astrophysics Data System (ADS)

Behar, Ehud; Vogel, Stuart; Baldi, Ranieri D.; Smith, Krista L.; Mushotzky, Richard F.

2018-05-01

mm-wave emission from Active Galactic Nuclei (AGN) may hold the key to understanding the physical origin of their radio cores. The correlation between radio/mm and X-ray luminosity may suggest a similar physical origin of the two sources. Since synchrotron self absorption decreases with frequency, mm-waves probe smaller length scales than cm-waves. We report on 100 GHz (3 mm) observations with CARMA of 26 AGNs selected from the hard X-ray Swift/BAT survey. 20/26 targets were detected at 100 GHz down to the 1 mJy (3σ) sensitivity, which corresponds to optically thick synchrotron source sizes of 10-4 - 10-3 pc. Most sources show a 100 GHz flux excess with respect to the spectral slope extrapolated from low frequencies. This mm spectral component likely originates from smaller scales than the few-GHz emission. The measured mm sources lie roughly around the Lmm (100 GHz) ˜10-4LX (2-10 keV) relation, similar to a few previously published X-ray selected sources, and hinting perhaps at a common coronal origin.

Tending the Fire, A Legacy Survey of Molecular Gas Fueling in Powerful Nearby AGN

NASA Astrophysics Data System (ADS)

Koss, Michael; BASS Team

2018-01-01

Over the last 30 years the importance of host galaxy molecular gas for growing black holes has been intensely debated. We have observed a a volume-limited sample of over 200 nearby powerful AGN (0.01 < z < 0.05, Lbol;AGN > 10^44 erg/s) using the CO 2-1 line with the JCMT and APEX telescopes to definitively address this issue. The AGN are selected from the Swift-BAT all sky hard X-ray survey which is superior to optical or IR selection since high energy X-rays (14-195 keV) are almost independent of host galaxy properties and obscuration. We compare our samples molecular gas properties to inactive galaxies selected with the IRAM 30m COLD GASS survey to understand the general trends with AGN activity.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2016-04-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of AGN evolution stretching back to z˜5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function - all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is demonstrated at z ≈0 and 0.9, and clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z. The results support the idea that there are at least two different modes of AGN triggering: one, at high luminosity, that only occurs in high mass, highly biased haloes, and one that can occur over a wide range of halo masses and leads to luminosities that are correlated with halo mass. This latter mode dominates at z<0.9. The CLFs for Type 2 and Type 1 AGNs are also constrained at z ≈0, and we find evidence that unobscured quasars are more likely to be found in higher mass halos than obscured quasars. Thus, the AGN unification model seems to fail at quasar luminosities.

X-ray beamsplitter

DOEpatents

Ceglio, Natale M.; Stearns, Daniel S.; Hawryluk, Andrew M.; Barbee, Jr., Troy W.

1989-01-01

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5-50 pairs of alternate Mo/Si layers with a period of 20-250 A. The support membrane is 10-200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window.

Multiwavelength observations of Active Galactic Nuclei from the radio to the hard X-rays

NASA Astrophysics Data System (ADS)

Beuchert, Tobias

2017-07-01

Active Galaxies form a peculiar type of galaxies. Their cores, the so-called "Active Galactic Nuclei" (AGN), are the most persistent luminous objects in the universe. Accretion of several solar masses per year onto black holes of Millions to Billions of solar masses drive the immense energy output of these systems, which can exceed that of the entire galaxy. The compact energy source, however, only measures about one over a Billion times that of the entire galaxy. Subject of my thesis are observations of the two main channels of energy release of selected AGN systems, both of which are encompassed by profound and yet unanswered questions. These channels are on the one hand the pronounced X-ray emission of the hot and compact accreting environment in close vicinity of the black hole, and on the other hand the radio synchrotron emission of magnetically collimated jets that are fed by portions of the accreted matter. These jets also function as effective accelerators and drive the injected matter deep into the intergalactic medium. As the circumnuclear environment of AGN is too compact to be spatially resolved in the X-rays, I show how X-ray spectroscopy can be used to: (1) understand the effects of strong gravity to trace the geometry and physics of the X-ray source and (2) more consistently quantify matter that surrounds and dynamically absorbs our direct line of sight towards the X-ray source. Second, I unveil the valuable information contained in the polarized radio light being emitted from magnetized jet outflows. In contrast to the X-ray emitting region, I am able to spatially resolve the inner parts of the jet of a prominent galaxy with help of the Very Long Baseline Array, a large network of radio telescopes. The resulting polarization maps turn out to be exceptionally promising in answering fundamental questions related to jet physics.

Ensemble X-ray variability of active galactic nuclei. II. Excess variance and updated structure function

NASA Astrophysics Data System (ADS)

Vagnetti, F.; Middei, R.; Antonucci, M.; Paolillo, M.; Serafinelli, R.

2016-09-01

Context. Most investigations of the X-ray variability of active galactic nuclei (AGN) have been concentrated on the detailed analyses of individual, nearby sources. A relatively small number of studies have treated the ensemble behaviour of the more general AGN population in wider regions of the luminosity-redshift plane. Aims: We want to determine the ensemble variability properties of a rich AGN sample, called Multi-Epoch XMM Serendipitous AGN Sample (MEXSAS), extracted from the fifth release of the XMM-Newton Serendipitous Source Catalogue (XMMSSC-DR5), with redshift between ~0.1 and ~5, and X-ray luminosities in the 0.5-4.5 keV band between ~1042 erg/s and ~1047 erg/s. Methods: We urge caution on the use of the normalised excess variance (NXS), noting that it may lead to underestimate variability if used improperly. We use the structure function (SF), updating our previous analysis for a smaller sample. We propose a correction to the NXS variability estimator, taking account of the light curve duration in the rest frame on the basis of the knowledge of the variability behaviour gained by SF studies. Results: We find an ensemble increase of the X-ray variability with the rest-frame time lag τ, given by SF ∝ τ0.12. We confirm an inverse dependence on the X-ray luminosity, approximately as SF ∝ LX-0.19. We analyse the SF in different X-ray bands, finding a dependence of the variability on the frequency as SF ∝ ν-0.15, corresponding to a so-called softer when brighter trend. In turn, this dependence allows us to parametrically correct the variability estimated in observer-frame bands to that in the rest frame, resulting in a moderate (≲15%) shift upwards (V-correction). Conclusions: Ensemble X-ray variability of AGNs is best described by the structure function. An improper use of the normalised excess variance may lead to an underestimate of the intrinsic variability, so that appropriate corrections to the data or the models must be applied to prevent

Deep X-ray Observations of an Ongoing Merger and 400 Myr of AGN Activity in Cygnus A

NASA Astrophysics Data System (ADS)

Wise, Michael W.; De Vries, Martijn; Nulsen, Paul; Snios, Bradford; Birkinshaw, Mark; Worrall, Diana; Duffy, Ryan; Halbesma, Timo; Donnert, Julius; Hardcastle, Martin

2017-08-01

We present a detailed spatial and spectral analysis of the large-scale X-ray emission associated with the merging cluster of galaxies containing the powerful Cygnus A radio galaxy. Using a new 1 Msec exposure from the ongoing Chandra XVP project, we have mapped the large-scale structure, temperature and abundance of the ICM in a 1 Mpc x 1 Mpc region surrounding Cygnus A. This new, deep exposure resolves unprecedented detail in the jets, lobes, and cocoon shock associated with Cygnus A, and provides new insights into the emission mechanisms that produce these features as well as implications for the ongoing activity of the central AGN. On larger scales, these new data reveal complex and dramatic temperature, pressure, entropy and metallicity structure in the ICM surrounding Cygnus A. We confirm the presence of large-scale X-ray emission associated with the two merging cluster components seen previously in lower resolution data. The temperature structure on the scale of the merger exhibits an asymmetric enhancement to the NW consistent with projected hotter gas from the merger shock. Using the derived density and temperature profiles in the two merging sub-cluster components as inputs, we have constructed a grid of hydro-dynamical simulations to constrain the geometry of the merger system. These models imply a pre-merger system with a 1:1 mass ratio at the virial radius with an inclination toward the line of sight of 35-45 deg. In addition to the merger-induced temperature asymmetry, we find evidence for additional surface brightness and temperature features indicative of previous outburst activity in Cygnus A over the past 400 Myr. Based on the location and strength of these features, we derive the energy associated with these previous outbursts and place constraints on the growth of the black hole in Cygnus A over that timescale.

X-ray beamsplitter

DOEpatents

Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.W. Jr.

1987-08-07

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5--50 pairs of alternate Mo/Si layers with a period of 20--250 A. The support membrane is 10--200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window. 6 figs.

Extended X-ray emission in PKS 1718-649

NASA Astrophysics Data System (ADS)

Beuchert, T.; Rodríguez-Ardila, A.; Moss, V. A.; Schulz, R.; Kadler, M.; Wilms, J.; Angioni, R.; Callingham, J. R.; Gräfe, C.; Krauß, F.; Kreikenbohm, A.; Langejahn, M.; Leiter, K.; Maccagni, F. M.; Müller, C.; Ojha, R.; Ros, E.; Tingay, S. J.

2018-04-01

PKS 1718-649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718-649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton, we are able to study the detailed physics of the environment of PKS 1718-649. Not only can we confirm that the bulk of the ≲kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate.

OSSE Observations of Seyfert AGN

NASA Astrophysics Data System (ADS)

Johnson, W. N.; Grove, J. E.; Kinzer, R. L.; Kroeger, R. A.; Kurfess, J. D.; Strickman, M. S.; McNaron-Brown, K.; Grabelsky, D. A.; Purcell, W. R.; Ulmer, M. P.; Jung, G. V.; Cameron, R. A.

1993-12-01

In the first two years of the Compton Gamma Ray Observatory mission, the Oriented Scintillation Spectrometer Experiment (OSSE) has observed about two dozen Seyfert active galactic nuclei (AGN) selected from the HEAO-1 list (Rothschild et al. 1983) and intense X-ray sources detected by EXOSAT and Ginga. The OSSE observations in the 50 keV - 10 MeV range indicate spectra which, on average, are significantly softer than the power law photon index of Gamma =1.7 which is generally reported in the Xray band. The average spectrum is well described by exponential or thermal Comptonization models indicating a break in the spectrum near 100 keV. We summarize the OSSE observations of AGN and present the average Seyfert spectrum above 50 keV. Rothschild, R.E., et al. 1983, Ap. J., 269, 423.

The invisible AGN catalogue: a mid-infrared-radio selection method for optically faint active galactic nuclei

NASA Astrophysics Data System (ADS)

Truebenbach, Alexandra E.; Darling, Jeremy

2017-06-01

A large fraction of active galactic nuclei (AGN) are 'invisible' in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared (IR)-bright AGN is predicted by models of galaxy-supermassive black hole coevolution and is required to explain the observed X-ray and IR backgrounds. Recently, IR colour cuts with Wide-field Infrared Survey Explorer have identified a portion of this missing population. However, as the host galaxy brightness relative to that of the AGN increases, it becomes increasingly difficult to differentiate between IR emission originating from the AGN and from its host galaxy. As a solution, we have developed a new method to select obscured AGN using their 20-cm continuum emission to identify the objects as AGN. We created the resulting invisible AGN catalogue by selecting objects that are detected in AllWISE (mid-IR) and FIRST (20 cm), but are not detected in SDSS (optical) or 2MASS (near-IR), producing a final catalogue of 46 258 objects. 30 per cent of the objects are selected by existing selection methods, while the remaining 70 per cent represent a potential previously unidentified population of candidate AGN that are missed by mid-IR colour cuts. Additionally, by relying on a radio continuum detection, this technique is efficient at detecting radio-loud AGN at z ≥ 0.29, regardless of their level of dust obscuration or their host galaxy's relative brightness.

X-ray flares from runaway pair production in active galactic nuclei

NASA Technical Reports Server (NTRS)

Kirk, J. G.; Mastichiadis, A.

1992-01-01

The hard X-ray spectrum of AGNs is nonthermal, probably arising from an electron-positron pair cascade, with some emission reflected off relatively cold matter. There has been interest in models on which protons are accelerated and create relativistic electrons on interaction with a local radiation field. It is shown here that a sufficient column density of protons can lead to runaway pair production: photons generated by the relativistic pairs are the targets for the protons to produce more pairs. This can produce X-ray fluxes with the characteristics observed in AGN. The model predicts the maximum ratio of luminosity to source size as well as their spectrum in the early phases. The same mechanism may also be able to create the knots of synchrotron-radiating pair plasma seen in sources such as 3C273.

The NuSTAR Serendipitous Survey: The 40-month Catalog and the Properties of the Distant High-Energy X-Ray Source Population

NASA Technical Reports Server (NTRS)

Lansbury, G. B.; Stern, D.; Aird, J.; Alexander, D. M.; Fuentes, C.; Harrison, F. A.; Treister, E.; Bauer, F. E.; Tomsick, J. A.; Balokovic, M.;

Soft X-ray properties of Seyfert galaxies. I - Spectra

NASA Technical Reports Server (NTRS)

Kruper, J. S.; Canizares, C. R.; Urry, C. M.

1990-01-01

Results are presented from a study of soft X-ray spectra of 75 Seyfert galaxies observed by the Einstein Observatory IPC. The spectra in this sample (mostly high-luminosity Seyfert type 1s) are found to be consistent with a single power-law index alpha = 81. The AGN spectra observed with the IPC are compared with those from higher energy experiments, where AGN spectra have power law indices alpha = 0.7. It is found that the IPC spectra are systematically steeper than the HEAO 1 A-2 spectra of the same Seyfert galaxies, indicating a flattening toward higher energies.

Simulation and Laboratory results of the Hard X-ray Polarimeter: X-Calibur

NASA Astrophysics Data System (ADS)

Guo, Qingzhen; Beilicke, M.; Kislat, F.; Krawczynski, H.

2014-01-01

X-ray polarimetry promises to give qualitatively new information about high-energy sources, such as binary black hole (BH) systems, Microquasars, active galactic nuclei (AGN), GRBs, etc. We designed, built and tested a hard X-ray polarimeter 'X-Calibur' to be flown in the focal plane of the InFOCuS grazing incidence hard X-ray telescope in 2014. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20- 80 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the E field orientation. X-Calibur achieves a high detection efficiency of order unity. We optimized of the design of the instrument based on Monte Carlo simulations of polarized and unpolarized X-ray beams and of the most important background components. We have calibrated and tested X-Calibur extensively in the laboratory at Washington University and at the Cornell High-Energy Synchrotron Source (CHESS). Measurements using the highly polarized synchrotron beam at CHESS confirm the polarization sensitivity of the instrument. In this talk we report on the optimization of the design of the instrument based on Monte Carlo simulations, as well as results of laboratory calibration measurements characterizing the performance of the instrument.

AGN-enhanced outflows of low-ionization gas in star-forming galaxies at 1.7 < z < 4.6*

NASA Astrophysics Data System (ADS)

Talia, M.; Brusa, M.; Cimatti, A.; Lemaux, B. C.; Amorin, R.; Bardelli, S.; Cassarà, L. P.; Cucciati, O.; Garilli, B.; Grazian, A.; Guaita, L.; Hathi, N. P.; Koekemoer, A.; Le Fèvre, O.; Maccagni, D.; Nakajima, K.; Pentericci, L.; Pforr, J.; Schaerer, D.; Vanzella, E.; Vergani, D.; Zamorani, G.; Zucca, E.

2017-11-01

Fast and energetic winds are invoked by galaxy formation models as essential processes in the evolution of galaxies. These outflows can be powered either by star formation (SF) and/or active galactic nucleus (AGN) activity, but the relative dominance of the two mechanisms is still under debate. We use spectroscopic stacking analysis to study the properties of the low-ionization phase of the outflow in a sample of 1330 star-forming galaxies (SFGs) and 79 X-ray-detected (1042 < LX < 1045 erg s-1) Type 2 AGN at 1.7 < z < 4.6 selected from a compilation of deep optical spectroscopic surveys, mostly zCOSMOS-Deep and VIMOS Ultra Deep Survey (VUDS). We measure mean velocity offsets of ˜- 150 km s-1 in the SFGs, while in the AGN sample the velocity is much higher (˜- 950 km s-1), suggesting that the AGN is boosting the outflow up to velocities that could not be reached only with the SF contribution. The sample of X-ray AGN has on average a lower SF rate than non-AGN SFGs of similar mass: this, combined with the enhanced outflow velocity in AGN hosts, is consistent with AGN feedback in action. We further divide our sample of AGN into two X-ray luminosity bins: we measure the same velocity offsets in both stacked spectra, at odds with results reported for the highly ionized phase in local AGN, suggesting that the two phases of the outflow may be mixed only up to relatively low velocities, while the highest velocities can be reached only by the highly ionized phase.

Classification of X-ray sources in the direction of M31

NASA Astrophysics Data System (ADS)

Vasilopoulos, G.; Hatzidimitriou, D.; Pietsch, W.

2012-01-01

M31 is our nearest spiral galaxy, at a distance of 780 kpc. Identification of X-ray sources in nearby galaxies is important for interpreting the properties of more distant ones, mainly because we can classify nearby sources using both X-ray and optical data, while more distant ones via X-rays alone. The XMM-Newton Large Project for M31 has produced an abundant sample of about 1900 X-ray sources in the direction of M31. Most of them remain elusive, giving us little signs of their origin. Our goal is to classify these sources using criteria based on properties of already identified ones. In particular we construct candidate lists of high mass X-ray binaries, low mass X-ray binaries, X-ray binaries correlated with globular clusters and AGN based on their X-ray emission and the properties of their optical counterparts, if any. Our main methodology consists of identifying particular loci of X-ray sources on X-ray hardness ratio diagrams and the color magnitude diagrams of their optical counterparts. Finally, we examined the X-ray luminosity function of the X-ray binaries populations.

Long term multiwavelength studies of the corona/disc connection in AGN