The recent Chandra discovery of extended $\sim$kpc-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 super massive 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 7 nearby ($0.006 < z < 0.013$) 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 $>$ 3$σ$ above the Chandra PSF with $\sim$12% to 22% of the total emission in the extended components. ESO 137-G034 and NGC 3281 display biconical ionization structures with extended hard X-ray emission reaching kpc-scales ($\sim$ 1.9 kpc and 3.5 kpc in diameter). The other three show extended hard X-ray emission above the PSF out to at least $\sim$360 pc in radius. We find a trend that a minimum 3-7 keV count rate of 0.01 cts/s and total excess fraction $>$20% is required to detect a prominent extended hard X-ray component. Given that this extended hard X-ray component appears to be relatively common in this uniformly selected CT AGN sample, we further discuss the implications for torus modeling and AGN feedback.
We investigate infrared colours and spectral energy distributions (SEDs) of 338 X-ray selected AGN from Swift-BAT 105-month survey catalogue that have AKARI detection, in order to find a new selection criteria for Compton-thick AGN. By combining data from Galaxy Evolution Explore (GALEX), Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14), Two Micron All Sky Survey (2MASS), Wide-field Infrared Survey Explorer (WISE), AKARI and Herschel for the first time we perform ultraviolet (UV) to far-infrared (FIR) SED fitting 158 Swift BAT AGN by CIGALE and constrain the AGN model parameters of obscu…
We present the analysis of simultaneous NuSTAR and XMM-Newton data of 8 Compton-thick (CT-) active galactic nuclei (AGN) candidates selected in the Swift-Burst Alert Telescope (BAT) 100 month survey. This work is part of an ongoing effort to find and characterize all CT-AGN in the local ($z\leq$0.05) Universe. We used two physically motivated models, MYTorus and borus02, to characterize the sources in the sample, finding 5 of them to be confirmed CT-AGN. These results represent an increase of $\sim19$% over the previous NuSTAR-confirmed, BAT-selected CT-AGN at $z\leq0.05$, bringing the total n…
The all-sky hard X-ray survey performed by Swift/BAT allowed the detection of many heavily obscured Compton-thick AGN. In our previous work, we have identified more than 50 candidate Compton-thick AGN in the local Universe, corresponding to an observed fraction of about 7% of the total AGN population. This number can be converted to the intrinsic Compton-thick AGN number density, only if we know the form of the Compton-thick AGN spectrum, that is the energy of their absorption turnover, photon-index and its cut-off energy at high energies, as well as the strength of the reflection component on…
We present X-ray spectral analysis of the brightest sources (f_{2-10 keV}>10^{-15}$ cgs) in the Chandra Deep Field North. Our sample consists of 222 sources; for the vast majority (171) either a spectroscopic or a photometric redshift is available. Our goal is to discover the Compton-thick AGN in a direct way i.e. through their X-ray spectra. Compton-thick AGN give away their presence in X-rays either directly through the absorption turnover redshifted in the Chandra passband, or through a flat, reflection-dominated, spectrum. The above selection criteria yield 10 Compton-thick AGN candidates …
We present a broad-band X-ray spectral analysis of the radio-loud active galactic nuclei NGC 612, 4C 73.08 and 3C 452, exploiting archival data from NuSTAR, XMM-Newton, Swift and INTEGRAL. These Compton-thick candidates are the most absorbed sources among the hard X-ray selected radio galaxies studied in Panessa et al. (2016). We find an X-ray absorbing column density in every case below $1.5 \times 10^{24}$ cm$^{-2}$, and no evidence for a strong reflection continuum or iron K $α$ line. Therefore, none of these sources is properly Compton-thick. We review other Compton-thick radio galaxies re…
We present the 2--78 keV spectral analysis of the deep NuSTAR and XMM-Newton observation of a nearby Seyfert 2 galaxy, ESO 116-G018, which is selected as a candidate Compton-thick (CT-) active galactic nucleus (AGN) based on a previous Chandra-Swift/BAT study. Through our analysis, the source is for the first time confirmed to be a CT-AGN at a $>$3 $σ$ confidence level, with the 'line-of-sight' column density N$_{\rm H,Z}$ = [2.46-2.76] $\times$ $10^{24}$ cm$^{-2}$. The 'global average' column density of the obscuring torus is N$_{\rm H,S}$ = [0.46-0.62] $\times$ $10^{24}$ cm$^{-2}$, which sug…
We present a new metric that uses the spectral curvature (SC) above 10 keV to identify Compton-thick AGN in low-quality Swift BAT X-ray data. Using NuSTAR, we observe nine high SC-selected AGN. We find that high-sensitivity spectra show the majority are Compton-thick (78% or 7/9) and the remaining two are nearly Compton-thick (NH~5-8x10^23 cm^-2). We find the SC_bat and SC_nustar measurements are consistent, suggesting this technique can be applied to future telescopes. We tested the SC method on well-known Compton-thick AGN and find it is much more effective than broad band ratios (e.g. 100% …
We present results of our analysis of NuSTAR data of the luminous infrared galaxy Mrk 266, which contains two nuclei, SW and NE, resolved in previous Chandra imaging. Combining with the Chandra data, we intepret the hard X-ray spectrum obtained from a NuSTAR observation as resulting from steeply rising flux from a Compton-thick AGN in the SW nucleus which is very faint in the Chandra band, confirming the previous claim of Mazzarella et al. (2012). This hard X-ray component is dominated by reflection, and its intrinsic 2-10 keV luminosity is likely to be ~1e43 erg/s. Although it is bright in so…
The 70-month Swift/BAT catalogue provides a sensitive view of the extragalactic X-ray sky at hard energies (>10 keV) containing about 800 Active Galactic Nuclei. We explore its content in heavily obscured, Compton-thick AGN by combining the BAT (14-195 keV) with the lower energy XRT (0.3-10 keV) data. We apply a Bayesian methodology using Markov chains to estimate the exact probability distribution of the column density for each source. We find 53 possible Compton-thick sources (with probability 3 to 100%) translating to a ~7% fraction of the AGN in our sample. We derive the first parametric l…
Recently, Boorman et al. (2018) reported on the discovery of the Iwasawa-Taniguchi (I-T) effect (a.k.a. X-ray Baldwin effect) for Compton-thick AGN. They measured a decrease of the 6.4 keV iron line equivalent width with the 12mu luminosity, assumed as a proxy for the intrinsic X-ray luminosity, which in Compton-thick AGN is not directly observable. One of the most popular explanations of the classic I-T effect is the so-called receding torus model, i.e. the decrease of the covering factor of the molecular `torus' with X-ray luminosity. In this paper we show that an I-T effect for Compton-thic…
We present the combined NuSTATR and XMM-Newton 0.6-79 keV spectral analysis of a Seyfert 2 galaxy, NGC 1358, which we selected as a candidate Compton thick (CT-) active galactic nucleus (AGN) on the basis of previous Swift/BAT and Chandra studies. According to our analysis, NGC 1358 is confirmed to be a CT-AGN using physical motivated models, at >3 $σ$ confidence level. Our best-fit shows that the column density along the 'line-of-sight' of the obscuring material surrounding the accreting super-massive black hole is N$\rm _H$ = [1.96--2.80] $\times$ 10$^{24}$ cm$^{-2}$. The high-quality data f…
Most of the optically classified low ionisation narrow emission-line regions (LINERs) nuclei host an active galactic nuclei (AGN). However, how they fit into the unified model (UM) of AGN is still an open question. The aims of this work are to study at mid-infrared (mid-IR) (1) the Compton-thick nature of LINERs; and (2) the disappearance of the dusty torus in LINERs predicted from theoretical arguments. We have compiled all the available low spectral resolution mid-IR spectra of LINERs from the IRS/Spitzer (40 LINERs). We have complemented this sample with Spitzer/IRS spectra of PGQSOs, S1s, …
Warm absorbers are found in many AGN and consist of clouds moving at moderate radial velocities, showing complex ionization structures and having moderate to large column densities. Using 1D numerical calculations, we confirm earlier suggestions that the energy released by an AGN pushes the surrounding gas outward in a bubble until this reaches transparency. Typical AGN episode durations of $5\times 10^4$ yr supply enough energy for this, except in very gas-rich and/or very compact galaxies, such as those in the early Universe. In those galaxies, the AGN might remain hidden for many periods of…
We present the multi-epoch monitoring with NuSTAR and XMM-Newton of NGC 1358, a nearby Seyfert 2 galaxy whose properties made it a promising candidate X-ray changing look AGN, i.e., a source whose column density could transition from its 2017 Compton-thick (CT-, having line-of-sight Hydrogen column density NH,los>10^24 cm^-2) state to a Compton-thin (NH,los<10^24 cm^-2) one. The multi-epoch X-ray monitoring confirmed the presence of significant NH,los variability over time-scales as short as weeks, and allowed us to confirm the "changing look" nature of NGC 1358, which has most recently been o…
The archival data of 3C 345, a type 1 quasar at $z = 0.5928$, obtained with Suzaku and Swift/BAT are analysed. Though previous studies of this source applied only a simple broken power law model, a heavily obscuring material is found to be required by considering Akaike information criteria. The application of the numerical torus model by Murphy & Yaqoob (2009) surprisingly reveals the existence of Compton thick type 2 nucleus with the line-of-sight hydrogen column density of the torus of $N_{\rm H} = 10^{24.5}$ cm$^{-2}$ and the inclination angle of $θ_{\rm inc} = 90^{\circ}$. However, this m…
We present the results of the broadband X-ray spectral analysis of simultaneous NuSTAR and XMM-Newton observations of four nearby Compton-thick active galactic nuclei (AGN) candidates selected from the Swift-Burst Alert Telescope (BAT) 150-month catalog. This work is part of a larger effort to identify and characterize all Compton-thick (NH >= 10^24 cm^-2) AGN in the local Universe (z < 0.05). We used three physically motivated models -- MYTorus, borus02, and UXClumpy -- to fit and characterize these sources. Of the four candidates analyzed, 2MASX J02051994-0233055 was found to be an unobscure…
We performed near-diffraction-limited (~0.4 FWHM) N-band imaging of one of the nearest Active Galactic Nucleus (AGN) in M51 with 8.2m Subaru telescope to study the nuclear structure and spectral energy distribution (SED) at 8-13 um. We found that the nucleus is composed of an unresolved core (at ~13 pc resolution, or intrinsic size corrected for the instrumental effect of <6 pc) and an extended halo (at a few tens pc scale), and each of their SEDs is almost flat. We examined the SED by comparing with the archival Spitzer IRS spectrum processed to mimic our chopping observation of the nucleus, …
Mid-infrared (MIR) spectra observed with Gemini/Michelle were used to study the nuclear region of the Compton-thick Seyfert 2 (Sy 2) galaxy Mrk 3 at a spatial resolution of $\sim$200 pc. No polycyclic aromatic hydrocarbons (PAHs) emission bands were detected in the N-band spectrum of Mrk 3. However, intense [Ar III] 8.99 $μ$m, [S IV] 10.5 $μ$m and [Ne II] 12.8 $μ$m ionic emission-lines, as well as silicate absorption feature at 9.7$μ$m have been found in the nuclear extraction ($\sim$200 pc). We also present subarcsecond-resolution Michelle N-band image of Mrk 3 which resolves its circumnuclea…
We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local (D$\sim$44 Mpc) 12$μ$m-selected Seyfert 2 galaxy, enshrouded within Compton-thick layers of obscuring gas. We find no evidence of variability between the Chandra and NuSTAR observations (separated by 2 years), and between the two NuSTAR observations (separated by 10 months). Using self-consistent X-ray models, we rule out the scenario where the obscuring medium is nearly spherical and uniform, contradicting the results implied by the $<$10 keV Chandra spectrum. The line-of-sight column density, from intervening matter b…
We present X-ray observations of the active galactic nucleus (AGN) in NGC 4785. The source is a local Seyfert 2 which has not been studied so far in much detail. It was recently detected with high significance in the 15-60 keV band in the 66 month Swift/BAT all sky survey, but there have been no prior pointed X-ray observations of this object. With Suzaku, we clearly detect the source below 10 keV, and find it to have a flat continuum and prominent neutral iron fluorescence line with equivalent width >~1 keV. Fitting the broadband spectra with physical reflection models shows the source to be …
We report a clumpy elongated feature found with deep Chandra ACIS high-resolution imaging of the Fe Kα line emission in the nuclear region of the Compton Thick Active Galactic Nucleus (CT AGN) galaxy NGC 5643. This feature extends for ~65 pc 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 ALMA (Alonso-Herrero et al 2018), but slightly more extended than the rotating molecular disk of r=26 pc indicated by the kinematics of the CO(2-1) line. The Chandra detectio…
Compton Thick (CT) AGN are a key ingredient of Cosmic X-ray Background (CXB) synthesis models, but are still an elusive component of the AGN population beyond the local Universe. Multi-wavelength surveys are the only way to find them at z > 0.1, and a deep X-ray coverage is crucial in order to clearly identify them among star forming galaxies. As an example, the deep and wide COSMOS survey allowed us to select a total of 34 CT sources. This number is computed from the 64 nominal CT candidates, each counted for its N H probability distribution function. For each of these sources, rich multi-wav…
We present X-ray spectral analyses for three Seyfert 2 active galactic nuclei, NGC 424, NGC 1320, and IC 2560, observed by NuSTAR in the 3-79 keV band. The high quality hard X-ray spectra allow detailed modeling of the Compton reflection component for the first time in these sources. Using quasi-simultaneous NuSTAR and Swift/XRT data, as well as archival XMM-Newton data, we find that all three nuclei are obscured by Compton-thick material with column densities in excess of ~5 x $10^{24}$ cm$^{-2}$, and that their X-ray spectra above 3 keV are dominated by reflection of the intrinsic continuum …
The detailed study of nuclear regions of galaxies is important because it can help understanding the active galactic nucleus (AGN) feedback mechanisms, the connections between the nuclei and their host galaxies, and ultimately the galaxy formation processes. We present the analysis of an optical data cube of the central region of the galaxy NGC 2442, obtained with the integral field unit (IFU) of the Gemini Multi-Object Spectrograph (GMOS). We also performed a multiwavelength analysis, with Chandra data, XMM--Newton and NuSTAR spectra, and Hubble Space Telescope (HST) images. The analysis reve…
We examine the host morphologies of heavily obscured active galactic nuclei (AGN) at $z\sim1$ to test whether obscured supermassive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGN with $N_{\rm H}>10^{23.5}$ cm$^{-2}$ and $z<1.5$. Using visual classifications, we compare the morphologies of these AGN to control samples of moderately obscured ($10^{22}$ cm$^{-2}$ $<N_{\rm H}< 10^{23.5}$ cm$^{-2}$) and unobscured ($N_{\rm H}<10^{22}$ cm$^{-2}$) AGN. These control AGN are matched in redshift and intrinsic X-ray luminosity to our h…
We present the joint Chandra, XMM-Newton and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of ten low redshift ($z \le 0.05$), candidates Compton-thick Active Galactic Nuclei (AGN) selected in the 15-150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically-motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N$_{H,S}$) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N$_{H,z}$=[…
We present the systematic broadband X-ray spectral analysis of 52 Compton-thick ($24 \leq \log N_{\mathrm{H}}^{\mathrm{LOS}}/\mathrm{cm}^{-2}$) active galactic nucleus (CTAGN) candidates selected by the Swift/BAT all-sky hard X-ray survey observed with Chandra, XMM--Newton, Swift/XRT, Suzaku, and NuSTAR. The XMM--Newton data of 10 objects and the NuSTAR data of 15 objects are published for the first time. We use an X-ray spectral model from a clumpy torus (XClumpy) to determine the torus properties. As a result, the hydrogen column density along the line of sight $N_{\mathrm{H}}^{\mathrm{LOS}}…
XRISM Resolves the Circum-nuclear Environment of NGC 4945
Max Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）；Cahill Center for Astrophysics, California Institute of Technology（加州理工学院卡希尔天体物理学中心）；Department of Physics & Astronomy, Faculty of Physical Sciences and Engineering, University of Southampton（南安普顿大学物理与天文系，物理科学与工程学部）；Department of Astronomy, Kyoto University（京都大学天文学系）；European Space Agency (ESA), European Space Research and Technology Centre (ESTEC)（欧洲空间局（ESA），欧洲空间研究与技术中心（ESTEC））；Department of Astronomy, University of Geneva（日内瓦大学天文学系）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学柯文利天体物理与天文研究所）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
研究以近邻康普顿厚AGN NGC 4945为对象，利用XRISM/Resolve开展高分辨率X射线光谱分析，提出解耦双遮蔽体模型，揭示其核周遮蔽几何，为遥远同类AGN的研究提供参考。
We report on the torus constraints of the Compton-thick AGN with double-peaked optical narrow line region (NLR) emission lines, ANEPD-CXO245, at z=0.449 in the AKARI NEP Deep Field. The unique infrared data on this field, including those from the nine-band photometry over 2-24 $μ$m with the AKARI Infrared Camera (IRC), and the X-ray spectrum from Chandra allow us to constrain torus parameters such as the torus optical depth, X-ray absorbing column, torus angular width ($σ$) and viewing angle ($i$). We analyze the X-ray spectrum as well as the UV-optical-infrared spectral energy distribution (U…
Molecular Outflows in the Nucleus of the Nearby Compton-thick AGN NGC 3079
University of Toledo（托莱多大学）；Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)（中央研究院天文及天文物理研究所）；Max–Planck–Institut für extraterrestrische Physik（马克斯·普朗克地外物理学研究所）；Institut de Radioastronomie Millimétrique (IRAM)（毫米波射电天文学研究所）；National Radio Astronomy Observatory（美国国家射电天文台）；University of Virginia（弗吉尼亚大学）；Universidad de Alcalá（阿尔卡拉大学）
Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGN) is difficult to measure. A statistically significant correlation between the Eddington ratio, λ$_{Edd}$, and the X-ray power-law index, Γ, observed in unobscured AGN offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line-of-sight to the central engine is heavily obscured, the recovery of the intrinsic Γ is challenging. Here we study a sam…
Investigations of H$_2$O maser galaxies at X-ray energies reveal that most AGN associated with water masers are characterized by high levels of absorption. With the aim of finding new maser sources for possible interferometric follow-ups, we have searched for water maser emission in a well-defined sample of heavily absorbed AGN ($N_{\rm H} > 10^{23}$ cm$^{-2}$), including Compton-thick (CT) sources. All the galaxies in the sample were already searched for 22 GHz water maser emission in previous surveys. With the goal of providing a detection or a stringent upper limit on the H$_2$O luminosity,…
We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona-fide Compton-thick (N_H > 1.5 x 10^24 cm^-2) AGN with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at lambda~9.7um in archival low-resolution (R~57-127) Spitzer Infrared Spectrograph (IRS) spectroscopy, and show that only a minority (~45%) of nearby Compton-thick AGN have strong Si-absorption features (S_9.7 = ln(f_{int}/f_{obs}) > 0.5) which would indicate significant dust attenuation. The majority (~60%) are star-formation dominated (…
We present the joint NuSTAR and XMM-Newton spectral analysis in the 0.6-70 keV band of three candidate Compton thick (CT-) AGN selected in the 100-month Swift-BAT catalog. These objects were previously classified as CT-AGNs based on low quality Swift-XRT and Swift-BAT data, and had soft photon indices (Gamma>2.2) that suggested a potential overestimation of the line of sight column density. Thanks to the high-quality NuSTAR and XMM-Newton data we were able to determine that in all three objects the photon index was significantly overestimated, and two out of three sources are reclassified from…
A recent analysis of black hole scaling relations, used to estimate the local mass density in black holes, has indicated that the normalization of the scaling relations should be increased by approximately a factor of five. The local black hole mass density is connected to the mean radiative efficiency of accretion through the time integral of the quasar volume density. The correspondence between this estimate of the radiative efficiency and that expected theoretically from thin-disk accretion has long been used as an argument that most of the growth in black holes occurs via luminous accretio…
The existence of a large population of Compton thick (CT, $N_{H}>10^{24} cm^{-2}$) AGN is a key ingredient of most Cosmic X-ray background synthesis models. However, direct identification of these sources, especially at high redshift, is difficult due to the flux suppression and complex spectral shape produced by CT obscuration. We explored the Chandra COSMOS Legacy point source catalog, comprising 1855 sources, to select via X-ray spectroscopy, a large sample of CT candidates at high redshift. Adopting a physical model to reproduce the toroidal absorber, and a Monte-Carlo sampling method, we …
Compton-thick AGN in the NuSTAR Era. XI. Analyzing 11 CT-AGN Candidates Selected with Machine Learning
NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；Southeastern Universities Research Association（东南大学研究协会）；University of Minnesota（明尼苏达大学）；University of Virginia（弗吉尼亚大学）；Clemson University（克莱姆森大学）；Università di Bologna（博洛尼亚大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；University of Maryland Baltimore County（马里兰大学巴尔的摩县分校）
3C 223 is a radio loud, Type 2 quasar at $z=0.1365$ with an intriguing XMM-Newton spectrum that implicated it as a rare, Compton-thick ($N_{\rm H} \gtrsim 1.25 \times 10^{24}$ cm$^{-2}$) active galactic nucleus (AGN). We obtained contemporaneous XMM-Newton and NuSTAR spectra to fit the broad-band X-ray spectrum with the physically-motivated MYTorus and borus02 models. We confirm earlier results that the obscuring gas is patchy with both high (though not Compton-thick) levels of obscuration ($N_{\rm H} > 10^{23}$ cm$^{-2}$) and gas clouds with column densities up to an order of magnitude lower.…
The cold disk/torus gas surrounding active galactic nuclei (AGN) emits fluorescent lines when irradiated by hard X-ray photons. The fluorescent lines of elements other than Fe and Ni are rarely detected due to their relative faintness. We report the detection of K$α$ lines of neutral Si, S, Ar, Ca, Cr, and Mn, along with the prominent Fe K$α$, Fe K$β$, and Ni K$α$ lines, from the deep Chandra observation of the low-luminosity Compton-thick AGN in M51. The Si K$α$ line at 1.74 keV is detected at $\sim3σ$, the other fluorescent lines have a significance between 2 and 2.5 $σ$, while the Cr line h…
We report on the discovery of a dramatic X-ray spectral variability event observed in a $z\sim 1$ broad line type-1 QSO. The XMM-Newton spectrum from the year 2000 is characterized by an unobscured power-law spectrum with photon index of $Γ\sim 2$, a column density of $N_{\mathrm{H}}\sim 5\times 10^{20}\,\mathrm{cm^{-2}}$, and no prominent reflection component. Five years later, Chandra captured the source in a heavily-obscured, reflection-dominated state. The observed X-ray spectral variability could be caused by a Compton-thick cloud with $N_{\mathrm{H}}\sim 2\times 10^{24}\,\mathrm{cm^{-2}}…
A relationship between the water maser detection rate and large nuclear column densities in AGN has often been cited in the literature. Indeed, detailed studies of luminous water masers, typically associated with the nuclear activity, allow us to investigate the innermost regions of AGN, with an impact on the still debated Unified Model for this class of objects.We have recently entertained a search for maser emission in a well-defined sample of Compton-thick AGN aimed at investigating, on firm statistical bases, the aforementioned relationship. While the survey is still ongoing, and is matter…
We present the first study of an Iwasawa-Taniguchi/X-ray Baldwin effect for Compton-thick active galactic nuclei (AGN). We report a statistically significant anti-correlation between the rest-frame equivalent width (EW) of the narrow core of the neutral Fe K$α$ fluorescence emission line, ubiquitously observed in the reflection spectra of obscured AGN, and the mid-infrared 12$\,μ$m continuum luminosity (taken as a proxy for the bolometric AGN luminosity). Our sample consists of 72 Compton-thick AGN selected from pointed and deep-field observations covering a redshift range of $z\sim0.0014-3.7$…
Galaxy clusters in the local universe descend from high-redshift overdense regions known as protoclusters. The large gas reservoirs and high rate of galaxy interaction in protoclusters are expected to trigger star-formation activity and luminous SMBH accretion in the host galaxies. We investigated the AGN content of a gas-rich and starbursting protocluster at $z=4$, known as the Distant Red Core (DRC). We observed with Chandra (139 ks) the 13 identified members of the structure, and searched for luminous and possibly obscured AGN among them. We also tested whether a hidden AGN can power the $L…
To fully understand cosmic black hole growth we need to constrain the population of heavily obscured active galactic nuclei (AGN) at the peak of cosmic black hole growth ($z\sim$1-3). Sources with obscuring column densities higher than $\mathrm{10^{24}}$ atoms $\mathrm{cm^{-2}}$, called Compton-thick (CT) AGN, can be identified by excess X-ray emission at $\sim$20-30 keV, called the "Compton hump". We apply the recently developed Spectral Curvature (SC) method to high-redshift AGN (2<z<5) detected with Chandra. This method parametrizes the characteristic "Compton hump" feature cosmologically r…
X-ray fluorescent lines are unique features of the reflection spectrum of the torus when irradiated by the central AGN. Their intrinsic line width can be used to probe the line-emitting region. Previous studies have focused on the Fe Ka line at 6.4 keV, which is the most prominent fluorescent line. These studies, however, are limited by the spectral resolution of currently available instruments, the best of which is $\sim1860$ km s$^{-1}$ afforded by the Chandra High-Energy Grating (HEG). The HEG spectral resolution is improved by a factor of 4 at 1.74 keV, where the Si Ka line is located. We …
We report the broadband X-ray spectra of the ultra-luminous infrared galaxy (ULIRG) UGC 5101 in the 0.25-100 keV band observed with Swift/Burst Alert Telescope (BAT), NuSTAR, Suzaku, XMM-Newton, and Chandra. A Compton-thick AGN obscured with a hydrogen column density of $\approx 1.3\times10^{24}$ cm$^{-2}$ is detected above 10 keV. A spectral fit with a numerical torus model favors a large half opening angle of the torus, $>41$ degrees, suggesting that the covering fraction of material heavily obscuring the X-ray source is moderate. The intrinsic 2-10 keV luminosity is determined to be $\appro…
The nature of the ASCA/INTEGRAL source AX J183039-1002: a new Compton-thick AGN?
我们报告的X/软γ射线源AX J183039-1002检测ASCA和INTEGRAL/IBIS的识别。该源的观测通量为8.6 x 10^-11 erg/cm^2/s，在20-100 keV范围内，位于一个弥散射电超新星遗迹（SNR）内，在空间上与一个致密射电源重合。我们分析了钱德拉和XMM-牛顿观测的档案，以确定ASCA/INTEGRAL源。一个点状的钱德拉X射线天体被发现与致密射电源的位置重合，并且在ASCA和INTEGRAL源的误差圆内。虽然致密的射电/X射线源与射电超新星遗迹的关联可能表明脉冲星风星云（PWN），但XMM-牛顿X射线谱与吸收的Seyfert-2活动星系核兼容，因为它提供了约1 keV等效宽度的铁发射线的证据;此外，X射线源谱与其他康普顿厚活动星系核相似，其中<2 keV data are associated to a warm reflector and the >10 keV的辐射源是冷反射体。
We report the discovery of a Compton-thick (CT) dust-obscured galaxy (DOG) at $z$ = 0.89, WISE J082501.48+300257.2 (WISE0825+3002), observed by Nuclear Spectroscopic Telescope Array (NuSTAR). X-ray analysis with the XCLUMPY model revealed that hard X-ray luminosity in the rest-frame 2-10 keV band of WISE0825+3002 is $L_{\rm X}$ (2-10 keV) = $4.2^{+2.8}_{-1.6} \times 10^{44}$ erg s$^{-1}$ while its hydrogen column density is $N_{\rm H}$ = $1.0^{+0.8}_{-0.4} \times 10^{24}$ cm$^{-2}$, indicating that WISE0825+3002 is a mildly CT active galactic nucleus (AGN). We performed the spectral energy dis…
Current measurements show that the observed fraction of Compton-thick (CT) AGN is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC 5347 ($z=0.00792,\, D =35.5 \rm ~Mpc $) have alternately suggested a CT and Compton-thin source. Combining archival data from $Suzaku$, $Chandra$, and - most importantly - new data from $NuSTAR$, and using three distinct families of models, we show that NGC 5347 is an obscured CTAGN ($N_{\rm H} > 2.23\times 10^{24}~\rm cm^{-2}$). Its 2-30~keV spectrum is dominated by …
We present the infrared (IR) and X-ray properties of a sample of 33 mid-IR luminous quasars ($ν$L(6 micron)>6x10$^{44}$ erg/s) at redshift z~1-3, identified through detailed spectral energy distribution analyses of distant star-forming galaxies, using the deepest IR data from Spitzer and Herschel in the GOODS-Herschel fields. The aim is to constrain the fraction of obscured, and Compton-thick (CT, N$_H$>1.5x10$^{24}$ cm$^{-2}$) quasars at the peak era of nuclear and star-formation activities. Despite being very bright in the mid-IR band, ~30% of these quasars are not detected in the extremely …
