Publication Search Results

ID: 159608
Type: article
Authors: Jones, Mackenzie L.; Parker, Kieran; Fabbiano, G.; Elvis, Martin; Maksym, W. P.; Paggi, A.; Ma, Jingzhe; Karovska, M.; Siemiginowska, Aneta; Wang, Junfeng
Abstract: We present the spatial analysis of five Compton thick (CT) active galactic nuclei (AGNs), including MKN 573, NGC 1386, NGC 3393, NGC 5643, and NGC 7212, for which high-resolution Chandra observations are available. For each source, we find hard X-ray emission (>3 keV) extending to ∼kiloparsec scales along the ionization cone, and for some sources, in the cross-cone region. This collection represents the first, high-signal sample of CT AGN with extended hard X-ray emission for which we can begin to build a more complete picture of this new population of AGN. We investigate the energy dependence of the extended X-ray emission, including possible dependencies on host galaxy and AGN properties, and find a correlation between the excess emission and obscuration, suggesting a connection between the nuclear obscuring material and the galactic molecular clouds. Furthermore, we find that the soft X-ray emission extends farther than the hard X-rays along the ionization cone, which may be explained by a galactocentric radial dependence on the density of molecular clouds due to the orientation of the ionization cone with respect to the galactic disk. These results are consistent with other CT AGN with observed extended hard X-ray emission (e.g., ESO 428-G014 and the Ma et al. CT AGN sample), further demonstrating the ubiquity of extended hard X-ray emission in CT AGN.

ID: 159625
Type: article
Authors: Ma, Jingzhe; Maksym, W. Peter; Fabbiano, G.; Elvis, Martin; Storchi-Bergmann, Thaisa; Karovska, Margarita; Wang, Junfeng; Travascio, Andrea
Abstract: We present spatially resolved Baldwin-Phillips-Terlevich (BPT) mapping of the extended narrow-line regions (ENLRs) of seven nearby Seyfert 2 galaxies, using Hubble Space Telescope narrowband filter imaging. We construct the BPT diagrams using ≤0"1 resolution emission line images of [O III] λ5007, Hα, [S II] λλ6717, 6731, and Hβ. By mapping these diagnostic lines according to the BPT classification, we dissect the ENLR into Seyfert, low-ionization nuclear emission-line (LINER), and star-forming regions. The nucleus and ionization cones are dominated by Seyfert-type emission, which can be interpreted as predominantly photoionization by the active galactic nucleus (AGN). The Seyfert nucleus and ionization cones transition to and are surrounded by a LINER cocoon, extending up to ∼250 pc in thickness. The ubiquity of the LINER cocoon in Seyfert 2 galaxies suggests that the circumnuclear regions are not necessarily Seyfert-type, and LINER activity plays an important role in Seyfert 2 galaxies. We demonstrate that spatially resolved diagnostics are crucial to understanding the excitation mechanisms in different regions and the AGN-host galaxy interactions.

ID: 159632
Type: article
Authors: Yi, Huili; Wang, Junfeng; Shu, Xinwen; Fabbiano, Giuseppina; Pappalardo, Cirino; Wang, Chen; Yu, Hanbo
Abstract: We present imaging and spectral analysis of the combined ∼48 ks Chandra observations of Seyfert 2 galaxy NGC 4388. Compared with previous studies, three prominent extended X-ray structures around the nucleus on a kiloparsec-scale are well imaged, allowing an in-depth spatially resolved study. Both the extended hard continuum (4-6 keV) and the Fe Kα line (6.2-6.7 keV) show similar morphology, consistent with a scenario where the ionizing emission from the nucleus is reprocessed by circumnuclear cold gas, resulting in a weak reflection continuum and an associated neutral Fe Kα line. This has been seen in other Compton-thick active galactic nuclei (AGN), but NGC 4388 is one of the rare cases with a lower column density (N_H ²⁴ cm^-2) along the line of sight. Significant differences in equivalent width of the Fe Kα emission line (up to a factor of 3) are found for the nuclear and extended regions. Such a difference could be ascribed to different column densities or scattering angles with respect to the line of sight, rather than variations in iron abundances. The northeast and west extended structures appear to be aligned with the larger-scale galactic disk and dust lane in the HST V - H color map, and are located at the peak of molecular gas distribution. The morphology of remaining extended features likely traces edges of a known radio jet, indicating that the outflow at the kiloparsec-scale may have compressed the interstellar gas and produced clumps working as the reflector to enhance line emission. In addition, using [O IV] emission as a proxy of the AGN intrinsic luminosity, we find that both of the extended Fe Kα emission and reflection continuum are linearly correlated with the [O IV] luminosity, which indicates a connection between the central AGN and the extended emission.

ID: 158817
Type: article
Authors: Fabbiano, Giuseppina; Paggi, A.; Karovska, Margarita; Elvis, Martin; Nardini, E.; Wang, Junfeng
Abstract: We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5-5.9 keV), the redshifted Fe I Ka line (6.0-6.4 keV), and the redshifted Fe XXV line (6.4-6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches-(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images-we are able to resolve structures extending from ˜1 kpc to <200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ˜2" (˜1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120-210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe I Ka emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240.

ID: 155843
Type: article
Authors: Feruglio, C.; Fabbiano, Giuseppina; Bischetti, M.; Elvis, Martin; Travascio, A.; Fiore, F.
Abstract: We present ALMA 230 GHz continuum and CO(2─1) observations of the nearby Compton-thick Seyfert galaxy ESO428─G14, with angular resolution 0"7 (78 pc). CO(2─1) is distributed in clumpy spiral arms, a lopsided circumnuclear ring (CNR) with ∼200 pc radius, and a transverse gas lane with size _dyn = 5 × 10⁹ M_☉ within ∼1 kpc. We detect off-plane gas motions with respect to the main disk plane which likely trace a molecular outflow with rate ${\dot{M}}_{\mathrm{of}}\approx 0.1\mbox{--}0.3\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , along a biconical structure with radius 700 pc. The CO outflow smoothly joins the warm molecular outflow detected in SINFONI/Very Large Telescope data in the central 170 pc, suggesting that the outflow may cool with increasing distance. Our dynamical modeling of the inner 100 pc region suggests a warped disk or bar, and of fast gas streams which may trace an inflow toward the AGN. The inner warped disk overlaps with the most obscured, CT region seen in X-rays. There, we derive a column density $N({{\rm{H}}}_{2})\approx 2\times {10}^{23}\,{\mathrm{cm}}^{-2}$ , suggesting that molecular gas may contribute significantly to the AGN obscuration. Most of the hard X-ray emitting nuclear region is deprived of cold molecular gas and shows a CO-cavity. The CO-cavity is filled with warm molecular gas traced by H₂, confirming that the 3─6 keV continuum and Fe Kα emission are due to scattering from dense ISM clouds.

ID: 156368
Type: article
Authors: Jones, Mackenzie L.; Fabbiano, Giuseppina; Elvis, Martin; Paggi, A.; Karovska, Margarita; Maksym, W. Peter; Siemiginowska, Aneta; Raymond, John
Abstract: Recent observations of nearby Compton thick (CT) active galactic nuclei (AGNs) with Chandra have resolved hard (>3 keV) X-ray emission extending out from the central supermassive black hole to kiloparsec scales, challenging the long-held belief that the characteristic hard X-ray continuum and fluorescent Fe K lines originate in the inner ∼parsec due to the excitation of obscuring material. In this paper we present the results of the most recent Chandra ACIS-S observations of NGC 7212, a CT AGN in a compact group of interacting galaxies, with a total effective exposure of ∼150 ks. We find ∼20% of the observed emission is found outside of the central kiloparsec, with ∼17% associated with the soft X-rays, and ∼3% with hard X-ray continuum and Fe K line. This emission is extended both along the ionization cone and in the cross-cone direction up to ∼3.8 kpc scales. The spectrum of NGC 7212 is best represented by a mixture of thermal and photoionization models that indicate the presence of complex gas interactions. These observations are consistent with what is observed in other CT AGN (e.g., ESO 428-G014, NGC 1068), providing further evidence that this may be a common phenomenon. High-resolution observations of extended CT AGN provide an especially valuable environment for understanding how AGN feedback impacts host galaxies on galactic scales.

ID: 155834
Type: article
Authors: Kim, Dong-Woo; Traynor, Liam; Paggi, Alessandro; O'Sullivan, Ewan; Anderson, Craig; Burke, Douglas; D'Abrusco, Raffaele; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer; McCollough, Michael; Morgan, Douglas; Mossman, Amy; Vrtilek, Saeqa; Trinchieri, Ginevra
Abstract: Using the data products of the Chandra Galaxy Atlas (Kim et al.), we have investigated the radial profiles of the hot gas temperature in 60 early-type galaxies (ETGs). Considering the characteristic temperature and radius of the peak, dip, and break (when scaled by the gas temperature and virial radius of each galaxy), we propose a universal temperature profile of the hot halo in ETGs. In this scheme, the hot gas temperature peaks at R_MAX = 35 ± 25 kpc (or ∼0.04 R_VIR) and declines both inward and outward. The temperature dips (or breaks) at R_MIN (or R_BREAK) = 3-5 kpc (or ∼0.006 R_VIR). The mean slope between R_MIN (R_BREAK) and R_MAX is 0.3 ± 0.1. Allowing for selection effects and observational limits, we find that the universal temperature profile can describe the temperature profiles of 72 per cent (possibly up to 82 per cent) of our ETG sample. The remaining ETGs (18 per cent) with irregular or monotonically declining profiles do not fit the universal profile and require another explanation. The temperature gradient inside R_MIN (R_BREAK) varies widely, indicating different degrees of additional heating at small radii. Investigating the nature of the hot core (HC with a negative gradient inside R_MIN), we find that HC is most clearly visible in small galaxies. Searching for potential clues associated with stellar, active galactic nucleus (AGN) feedback, and gravitational heating, we find that HC may be related to recent star formation. But we see no clear evidence that AGN feedback and gravitational heating play any significant role for HC.

ID: 158791
Type: article
Authors: Lusso, E.; Risaliti, G.; Nardini, E.; Bargiacchi, G.; Benetti, M.; Bisogni, S.; Capozziello, S.; Civano, Francesca; Eggleston, L.; Elvis, Martin; Fabbiano, Giuseppina; Gilli, R.; Marconi, A.; Paolillo, M.; Piedipalumbo, E.; Salvestrini, F.; Signorini, M.; Vignali, C.
Abstract: We present a new catalogue of ˜2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM-Newton. The sample can be used to investigate the non-linear relation between the ultraviolet (UV) and X-ray luminosity of quasars as well as to build a Hubble diagram up to a redshift of z ˜ 7.5. We selected sources that are neither reddened by dust in the optical and UV nor obscured by gas in the X-rays, and whose X-ray fluxes are free from flux-limit-related biases. After checking for any possible systematics, we confirm, in agreement with our previous works, that the X-ray to UV relation provides distance estimates matching those from supernovae up to z ˜ 1.5, and its slope shows no redshift evolution up to z ˜ 5. We provide a full description of the methodology for testing cosmological models, further supporting a trend whereby the Hubble diagram of quasars is well reproduced by the standard flat cold dark matter model up to z ˜ 1.5-2, but strong deviations emerge at higher redshifts. Since we have minimised all non-negligible systematic effects and proven the stability of the L_X - L_UV relation at high redshifts, we conclude that an evolution of the expansion rate of the Universe should be considered as a possible explanation for the observed deviation, rather than some systematic (redshift-dependent) effect associated with high-redshift quasars.
Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/642/A150

ID: 157684
Type: article
Authors: Ma, Jingzhe; Elvis, Martin; Fabbiano, Giuseppina; Baloković, Mislav; Maksym, W. Peter; Jones, Mackenzie L.; Risaliti, Guido
Abstract: The recent Chandra discovery of extended ∼kiloparsec-scale hard (>3 keV) X-ray emission in nearby Compton-thick (CT) active galactic nuclei (AGN) opens a new window to improving AGN torus modeling and investigating how the central supermassive black hole interacts with and impacts the host galaxy. Since there are only a handful of detections so far, we need to establish a statistical sample to determine the ubiquity of the extended hard X-ray emission in CT AGN and quantify the amount and extent of this component. In this paper, we present the spatial analysis results of a pilot Chandra imaging survey of seven nearby ( $0.006\lt z\lt 0.013$ ) CT AGN selected from the Swift-BAT spectroscopic AGN survey. We find that five out of the seven CT AGN show extended emission in the 3-7 keV band detected at >3σ above the Chandra point-spread function (PSF), with ∼12%-22% of the total emission in the extended components. ESO 137-G034 and NGC 3281 display biconical ionization structures with extended hard X-ray emission reaching kiloparsec scales (∼1.9 and 3.5 kpc in diameter). The other three show extended hard X-ray emission above the PSF out to at least ∼360 pc in radius. We find a trend that a minimum 3-7 keV count rate of 0.01 counts s^-1 and total excess fraction >20% are required to detect a prominent extended hard X-ray component. Given that this extended hard X-ray component appears to be relatively common in this uniformly selected CT AGN sample, we further discuss the implications for torus modeling and AGN feedback.

ID: 158809
Type: article
Authors: Maksym, W. Peter; Schmidt, Judy; Keel, William C.; Fabbiano, Giuseppina; Fischer, Travis C.; Bland-Hawthorn, Joss; Barth, Aaron J.; Elvis, Martin; Oosterloo, Tom; Ho, Luis C.; Kim, Minjin; Hwang, Hyunmo; Mayer, Evan
Abstract: On Earth near sunset, the Sun may cast "crepuscular rays" such that clouds near the horizon obscure the origin of light scattered in bright rays. In principle, active galactic nuclei (AGN) should be able to produce similar effects. Using new Hubble Space Telescope (HST) near-infrared and optical observations, we show that the active galaxy IC 5063 contains broad radial rays extending to ?11 kpc from the nucleus. We argue that the bright rays may arise from dusty scattering of continuum emission from the active nucleus, while the dark rays are due to shadowing near the nucleus, possibly by a warped torus. We also consider alternative AGN-related and stellar origins for the extended light. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with programs #15444 and #15609.

ID: 154627
Type: article
Authors: Fabbiano, Giuseppina; Elvis, Martin
Abstract: We report the detection in Chandra Advanced CCD Imaging Spectrometer archival data of an elongated soft (⁴⁰ erg s^-1. We infer an [O III]/soft-X-ray ratio in the range of ̃200, consistent with the highest values measured in some of the clouds of NGC 4151. Overall, given the uncertainties, Hanny's Voorwerp appears to be a feature consistent with the ionization cone emission of nearby AGNs. We estimate an X-ray recombination time of ̃2 × 10⁷ yr, longer than the [O III] recombination time (̃8000 yr). This suggests that extended soft X-ray components may be a better diagnostic of overall long-term activity, while detection of an [O III] HV would point to a time-limited activity burst.

ID: 155158
Type: article
Authors: Fabbiano, Giuseppina; Paggi, A.; Elvis, Martin
Abstract: A recent Atacama Large Millimeter/submillimeter Array study of the Seyfert 2 active galactic nucleus (AGN) NGC 2110 by Rosario et al. has reported a remarkable lack of CO 2-1 emission from the circumnuclear region, where optical lines and H₂ emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. As interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report the discovery of an extra-nuclear ∼1″ (∼170 pc) feature in the soft ( emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. As interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report the discovery of an extra-nuclear ∼1″ (∼170 pc) feature in the soft (₂ emission in this region, which is devoid of CO 2-1 emission. The Chandra image completes the emerging picture of a multiphase circumnuclear medium excited by the X-rays from the AGN, with dense warm molecular clouds emitting in H₂ but depleted of CO 2-1 line emission.

ID: 150426
Type: article
Authors: Fabbiano, Giuseppina; Siemiginowska, Aneta; Paggi, Alessandro; Elvis, Martin; Volonteri, M.; Mayer, L.; Karovska, Margarita; Maksym, W. Peter; Risaliti, G.; Wang, Junfeng
Abstract: We report the results of high-resolution subpixel imaging of the hard continuum and Fe Kα line of the Compton-thick (CT) active galactic nucleus (AGN) ESO 428-G014, observed with Chandra ACIS. While the 3–4 keV emission is dominated by an extended component, a single nuclear point source is prominent in the 4–6 keV range. Instead, two peaks of similar intensity, separated by ∼36 pc in projection on the plane of the sky are detected in the Fe Kα emission. The SE knot could be marginally associated with the heavily obscured hard continuum source. We discuss four possible interpretations of the nuclear morphology. (1) Given the bolometric luminosity and likely black hole mass of ESO 428-G014, we may be imaging two clumps of the CT obscuring torus in the Fe Kα line. (2) The Fe Kα knots may be connected with the fluorescent emission from the dusty bicone, or (3) with the light echo of a nuclear outburst. (4) We also explore the less likely possibility that we may be detecting the rare signature of merging nuclei. Considering the large-scale kiloparsec-size extent of the hard continuum and Fe Kα emission (Papers I and II), we conclude that the AGN in ESO 428-G014 has been active for at least 10⁴ yr. Comparison with the models of Czerny et al. suggests high accretion rates during this activity.

ID: 155313
Type: article
Authors: Kim, Dong-Woo; Anderson, Craig S.; Burke, Douglas J.; D'Abrusco, Raffaele; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer; McCollough, Michael; Morgan, Douglas; Mossman, Amy; O'Sullivan, Ewan; Paggi, Alessandro; Vrtilek, Saeqa; Trinchieri, Ginevra
Abstract: The hot interstellar medium (ISM) in early-type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. The structural features of the hot gas identified by Chandra observations point to key evolutionary mechanisms, (e.g., active galactic nuclei, AGN, and stellar feedback, merging history). In our Chandra Galaxy Atlas (CGA) project, taking full advantage of the Chandra capabilities, we systematically analyzed the archival Chandra data of 70 ETGs and produced uniform data products for the hot gas properties. The primary data products are spatially resolved 2D spectral maps of the hot gas from individual galaxies. We emphasize that new features can be identified in the spectral maps that are not readily visible in the surface brightness maps. The high-level images can be viewed at the dedicated CGA website, and the CGA data products can be downloaded to compare with data at other wavelengths and to perform further analyses. Using our data products, we address a few focused science topics.

ID: 154435
Type: article
Authors: Kim, Dong-Woo; James, Nicholas; Fabbiano, Giuseppina; Forbes, Duncan; Alabi, Adebusola
Abstract: Using globular cluster kinematics and photometry data, we calibrate the scaling relation between the total galaxy mass (M_TOT, including dark matter) and total globular cluster system mass (M_GCS) in a sample of 30 early-type galaxies (ETGs), confirming a nearly linear relationship between the two physical parameters. Using samples of 83 and 57 ETGs, we investigate this scaling relation in conjunction with the previously known relations between M_TOT and the interstellar medium (ISM) X-ray luminosity and temperature, respectively. We confirm that M_GCS can be effectively used as a proxy of M_TOT. We further find that the L_X,GAS-M_TOT relation is far tighter in the subsample of core ETGs when compared to cusp ETGs. In core ETGs (old, passively evolving stellar systems) M_TOT is significantly larger than the total stellar mass M_STAR and the correlation with the hot gas properties is driven by their dark matter mass M_DM. Cusp ETGs typically have lower L_X,GAS than core ETGs. In cusp ETGs, for a given M_DM, higher L_X,GAS is associated with higher M_STAR, suggesting stellar feedback as an important secondary factor for heating the ISM. Using the M_GCS-M_TOT scaling relations we compare 272 ETGs with previous estimates of the stellar-to-halo-mass relation of galaxies. Our model-independent estimate of M_TOT results in a good agreement around halo masses of 10¹² M_☉, but suggests higher star formation efficiency than usually assumed both at the low- and at the high-halo-mass ends.

ID: 150511
Type: article
Authors: Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Raymond, John; Wang, Junfeng; Storchi-Bergmann, Thaisa; Risaliti, Guido
Abstract: We present spatially resolved Chandra narrow-band imaging and imaging spectroscopy of NGC 3393. This galaxy hosts a Compton-thick Seyfert 2 active galactic nucleus (AGN) with sub-kpc bipolar outflows that are strongly interacting with the circumnuclear gas. We identify narrow-band excess emission associated with the Ne IX 0.905 keV transition (with likely contributions due to intermediate-state iron emission) that points to strong shocks driven by AGN feedback. Imaging spectroscopy resolves outflow-interstellar medium (ISM) interaction sites and the surrounding ISM at ∼100 pc scales, and suggests the presence of a hot AGN wind above the plane at radii beyond the shock sites. The cross-cone shows evidence for reprocessing of photoionization that has passed through gaps in the torus, and also for collisionally excited plasma that may be powered by a shock-confined equatorial outflow. Deep X-ray observations at subarcsecond resolution (such as may be performed very efficiently by Lynx, which would also energetically resolve the complex line emission) are necessary to eliminate model degeneracies and reduce uncertainties in local feedback properties.

ID: 154538
Type: article
Authors: Nardini, E.; Lusso, E.; Risaliti, G.; Bisogni, S.; Civano, Francesca; Elvis, Martin; Fabbiano, Giuseppina; Gilli, R.; Marconi, A.; Salvestrini, F.; Vignali, C.
Abstract: We present the X-ray analysis of 30 luminous quasars at z ≃ 3.0 - 3.3 with pointed XMM-Newton observations (28-48 ks) originally obtained by our group to test the suitability of active galactic nuclei as standard candles for cosmological studies. The sample was selected in the optical from the Sloan Digital Sky Survey Data Release 7 to be representative of the most luminous, intrinsically blue quasar population, and by construction boasts a high degree of homogeneity in terms of optical and UV properties. In the X-rays, only four sources are too faint for a detailed spectral analysis, one of which is formally undetected. Neglecting one more object later found to be radio-loud, the other 25 quasars are, as a whole, the most X-ray luminous ever observed, with rest-frame 2-10 keV luminosities of 0.5 - 7 × 10⁴⁵ erg s^-1. The continuum photon index distribution, centred at Γ ̃ 1.85, is in excellent agreement with those in place at lower redshift, luminosity, and black-hole mass, confirming the universal nature of the X-ray emission mechanism in quasars. Even so, when compared against the well-known L_X-L_UV correlation, our quasars show an unexpectedly varied behaviour, splitting into two distinct subsets. About two-thirds of the sources are clustered around the relation with a minimal scatter of 0.1 dex, while the remaining one-third appear to be X-ray underluminous by factors of > 3-10. Such a large incidence (≈25%) of X-ray weakness has never been reported in radio-quiet, non- broad absorption line (BAL) quasar samples. Several factors could contribute to enhancing the X-ray weakness fraction among our z ≃ 3 blue quasars, including variability, mild X-ray obscuration, contamination from weak-line quasars, and missed BALs. However, the X-ray weak objects also have, on average, flatter spectra, with no clear evidence of absorption. Indeed, column densities in excess of a few ×10²² cm^-2 can be ruled out for most of the sample. We suggest that, at least in some of our X-ray weak quasars, the corona might experience a radiatively inefficient phase due to the presence of a powerful accretion-disc wind, which substantially reduces the accretion rate through the inner disc and therefore also the availability of seed photons for Compton up-scattering. The origin of the deviations from the L_X-L_UV relation will be further investigated in a series of future studies.

ID: 146154
Type: article
Authors: Fabbiano, G.; Paggi, A.; Karovska, M.; Elvis, M.; Maksym, W. Peter; Risaliti, G.; Wang, Junfeng
Abstract: We present a deep Chandra spectral and spatial study of the kpc-scale diffuse X-ray emission of the Compton-thick (CT) active galactic nucleus (AGN) ESO 428-G014. The entire spectrum is best fit with composite photoionization + thermal models. The diffuse emission is more extended at lower energies (³⁸ erg s^‑1, is roughly consistent with the thermal component suggested by the spectral fits in the 170–900 pc annulus.

ID: 149403
Type: article
Authors: Fabbiano, Giuseppina; Paggi, Alessandro; Karovska, Margarita; Elvis, Martin; Maksym, W. Peter; Wang, Junfeng
Abstract: We have analyzed the deep Chandra observation (∼155 ks) of the Compton thick active galactic nucleus ESO 428-G014, to study in detail the morphology of the diffuse X-ray emission in the inner ∼500 pc radius region. Comparing different X-ray energy bands we find localized differences in the absorbing column and in the emission processes. Collisional ionization may be prevalent in the area of most intense optical line emission (Hα and [O III]). There is a good correspondence between optical line, radio continuum, and soft (3 keV, the extended emission in the central 1.″5 (170 pc) radius circumnuclear region amounts to ∼70%–30% of the contribution of a point source in that area (or ∼40%–25% of the total counts in the region). Within a 5″ radius, the contribution from extended emission overcomes that from a nuclear point source in the 3–4 keV band. This extended emission suggests scattering of nuclear photons by dense molecular clouds in the inner galactic disk of ESO 428-G014. Its presence may adversely bias the torus modeling of spectra from X-ray telescopes with inferior angular resolution compared to that of Chandra, such as NuSTAR and XMM-Newton.

ID: 150189
Type: article
Authors: Fabbiano, Giuseppina; Paggi, Alessandro; Siemiginowska, Aneta; Elvis, Martin
Abstract: We report a clumpy elongated feature found with deep Chandra Advanced CCD Imaging Spectrometer high-resolution imaging of the Fe Kα line emission in the nuclear region of the Compton-thick active galactic nucleus galaxy NGC 5643. This feature extends for ˜65 pc north to south (N-S). No corresponding feature is seen in the 3.0–6.0 keV continuum. The Fe Kα feature is spatially consistent with the N-S elongation found in the CO(2–1) high-resolution imaging with the Atacama Large Millimeter/submillimeter Array, but slightly more extended than the rotating molecular disk of diameter 26 pc indicated by the kinematics of the CO(2–1) line. The Chandra detection of a corresponding north to south structure in the neutral Fe Kα line would argue for both CO and Fe Kα emission originating from the obscuring torus.