We perform a systematic X-ray spectroscopic analysis of 57 local ultra/luminous infrared galaxy systems (containing 84 individual galaxies) observed with Nuclear Spectroscopic Telescope Array and/or Swift/BAT. Combining soft X-ray data obtained with
Chandra, XMM-Newton, Suzaku and/or Swift/XRT, we identify 40 hard ($>$10 keV) X-ray detected active galactic nuclei (AGNs) and constrain their torus parameters with the X-ray clumpy torus model XCLUMPY (Tanimoto et al. 2019). Among the AGNs at $z < 0.03$, for which sample biases are minimized, the fraction of Compton-thick ($N_{rm H} geq 10^{24}$ cm$^{-2}$) AGNs reaches 64$^{+14}_{-15}$% (6/9 sources) in late mergers, while 24$^{+12}_{-10}$% (3/14 sources) in early mergers, consistent with the tendency reported by Ricci et al. (2017). We find that the bolometric AGN luminosities derived from the infrared data increase, but the X-ray to bolometric luminosity ratios decrease, with merger stage. The X-ray weak AGNs in late mergers ubiquitously show massive outflows at sub-pc to kpc scales. Among them, the most luminous AGNs ($L_{rm bol,AGN} sim 10^{46}$ erg s$^{-1}$) have relatively small column densities of $lesssim$10$^{23}$ cm$^{-2}$ and almost super-Eddington ratios ($lambda_{rm Edd} sim$ 1.0). Their torus covering factors ($C_{rm T}^{rm (22)} sim 0.6$) are larger than those of Swift/BAT selected AGNs with similarly high Eddington ratios. These results suggest a scenario that, in the final stage of mergers, multiphase strong outflows are produced due to chaotic quasi-spherical inflows and the AGN becomes extremely X-ray weak and deeply buried due to obscuration by inflowing and/or outflowing material.
We construct a new catalog of extragalactic X-ray binaries (XRBs) by matching the latest Chandra source catalog with local galaxy catalogs. Our XRB catalog contains 4430 XRBs hosted by 237 galaxies within ~130 Mpc. As XRBs dominate the X-ray activity
in galaxies, the catalog enables us to study the correlations between the total X-ray luminosity of a galaxy $L_{X,rm tot}$, star formation rate $dot{rho}_star$, and stellar mass $M_star$. As previously reported, $L_{X,rm tot}$ is correlated with $dot{rho}_star$ and $M_star$. In particular, we find that there is a fundamental plane in those three parameters as $log L_{X,rm tot}={38.80^{+0.09}_{-0.12}}+log(dot{rho}_star + alpha M_star)$, where $alpha = {(3.36pm1.40)times10^{-11}} {rm yr^{-1}}$. In order to investigate this relation, we construct a phenomenological binary population synthesis model. We find that the high mass XRB and low mass XRB fraction in formed compact object binary systems is ~9% and ~0.04%, respectively. Utilizing the latest XMM-Newton, and Swift X-ray source catalog data sets, additional XRB candidates are also found resulting in 5757 XRBs hosted by 311 galaxies.
The location of the obscuring torus in an active galactic nucleus (AGN) is still an unresolved issue. The line widths of X-ray fluorescence lines originated from the torus, particularly Fe K$alpha$, carry key information on the radii of line emitting
regions. Utilizing XCLUMPY (Tanimoto et al. 2019), an X-ray clumpy torus model, we develop a realistic model of emission line profiles from an AGN torus where we take into account line broadening due to the Keplerian motion around the black hole. Then, we apply the updated model to the best available broadband spectra (3-100 keV) of the Circinus galaxy observed with Suzaku, XMM-Newton, Nuclear Spectroscopic Telescope Array (NuSTAR), and Chandra, including 0.62 Ms Chandra/HETG data. We confirm that the torus is Compton-thick (hydrogen column-density along the equatorial plane is $N_mathrm{H}^mathrm{Equ}=2.16^{+0.24}_{-0.16}times 10^{25} mathrm{cm}^{-2}$), geometrically thin (torus angular width $sigma=10.3^{+0.7}_{-0.3} mathrm{degrees}$), viewed edge-on (inclination $i=78.3^{+0.4}_{-0.9} mathrm{degrees}$), and has super-solar abundance ($1.52^{+0.04}_{-0.06}$ times solar). Simultaneously analyzing the Chandra/HETG first, second, and third order spectra with consideration of the spatial extent of the Fe K$alpha$ line emitting region, we constrain the inner radius of the torus to be $1.9^{+3.1}_{-0.8}times 10^5$ times the gravitational radius, or $1.6^{+1.5}_{-0.9}times 10^{-2} mathrm{pc}$ for a black hole mass of $(1.7pm 0.3)times 10^6 M_{odot}$. This is about 3 times smaller than that estimated from the dust sublimation radius, suggesting that the inner side of the dusty region of the torus is composed of dust-free gas.
We revisit the dependence of covering factor (CF) of dust torus on physical properties of active galactic nuclei (AGNs) by taking into account an AGN polar dust emission. The CF is converted from a ratio of infrared (IR) luminosity contributed from A
GN dust torus ($L_{rm IR}^{rm torus}$) and AGN bolometric luminosity ($L_{rm bol}$), by assuming a non-linear relation between luminosity ratio and intrinsic CF. We select 37,181 type 1 quasars at $z < 0.7$ from the Sloan Digital Sky Survey Data Release 16 quasar catalog. Their $L_{rm bol}$, black hole mass ($M_{rm BH}$), and Eddington ratio ($lambda_{rm Edd}$) are derived by spectral fitting with QSFit. We conduct spectral energy distribution decomposition by using X-CIGALE with clumpy torus and polar dust model to estimate $L_{rm IR}^{rm torus}$ without being affected by the contribution of stellar and AGN polar dust to IR emission. For 5720 quasars whose physical quantities are securely determined, we perform a correlation analysis on CF and (i) $L_{rm bol}$, (ii) $M_{rm BH}$, and (iii) $lambda_{rm Edd}$. As a result, anti-correlations for CF-$L_{rm bol}$, CF-$M_{rm BH}$, and CF-$lambda_{rm Edd}$ are confirmed. We find that incorporating the AGN polar dust emission makes those anti-correlations stronger which are compared to those without considering it. This indicates that polar dust wind provably driven by AGN radiative pressure is one of the key components to regulate obscuring material of AGNs.
We investigate the relation of black hole mass versus host stellar mass and that of mass accretion rate versus star formation rate (SFR) in moderately luminous ($log L_{rm bol} sim 44.5-46.5 {rm erg s^{-1}}$), X-ray selected broad-line active galacti
c nuclei (AGNs) at $z=1.18-1.68$ in the Subaru/XMM-Newton Deep Field. The far-infrared to far-ultraviolet spectral energy distributions of 85 AGNs are reproduced with the latest version of Code Investigating GALaxy Emission ({tt CIGALE}), where the AGN clumpy torus model {tt SKIRTOR} is implemented. Most of their hosts are confirmed to be main-sequence star-forming galaxies. We find that the mean ratio of the black hole mass ($M_{rm BH}$) to the total stellar mass ($M_{rm stellar}$) is $log M_{rm BH}/M_{rm stellar} = -2.2$, which is similar to the local black hole-to-bulge mass ratio. This suggests that if the host galaxies of these moderately luminous AGNs at $zsim1.4$ are dominated by bulges, they already established the local black hole mass-bulge mass relation; if they are disk dominant, their black holes are overmassive relative to the bulges. AGN bolometric luminosities and SFR show a good correlation with ratios higher than that expected from the local black hole-to-bulge mass relation, suggesting that these AGNs are in a SMBH-growth dominant phase.
We have analyzed the broadband X-ray spectra of active galactic nuclei (AGNs) in two non-merging luminous infrared galaxies (LIRGs) UGC 2608 and NGC 5135, utilizing the data of NuSTAR, Suzaku, XMM-Newton, and Chandra. Applying the X-ray clumpy-torus
model (XCLUMPY: Tanimoto et al. 2019), we find that both sources have similar spectra characterized by Compton-thick (CT) absorption ($N_{rm H} sim$ 5-7 $times$ $10^{24}$ cm$^{-2}$) and small torus angular width ($sigma$ $<$ 20$^{circ}$). The intrinsic 2-10 keV luminosities are $3.9^{+2.2}_{-1.7}$ $times$ $10^{43}$ erg s$^{-1}$ (UGC 2608) and $2.0^{+3.3}_{-1.0}$ $times$ $10^{43}$ erg s$^{-1}$ (NGC 5135). The [O IV]-to-nuclear-12 $mu$m luminosity ratios are larger than those of typical Seyferts, which are consistent with the torus covering factors ($C_{rm T} lesssim$ 0.7) estimated from the torus angular widths and column densities by X-ray spectroscopy. The torus covering factors and Eddington ratios ($lambda_{rm Edd} sim$ 0.1) follow the relation found by Ricci et al. (2017c) for local AGNs, implying that their tori become geometrically thin due to significant radiation pressure of the AGN that blows out some part of the tori. These results indicate that the CT AGNs in these non-merger LIRGs are just a normal AGN population seen edge-on through a large line-of-sight column density. They are in contrast to the buried CT AGNs in late-stage mergers that have large torus covering factors even at large Eddington ratios.
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 distribution (SED) fitting with CIGALE to derive its stellar mass, star formation rate, and infrared luminosity. The estimated Eddington ratio based on stellar mass and integration of the best-fit SED of AGN component is $lambda_{rm Edd}$ = 0.70, which suggests that WISE0825+3002 harbors an actively growing black hole behind a large amount of gas and dust. We found that the relationship between luminosity ratio of X-ray and 6 $mu$m, and Eddington ratio follows an empirical relation for AGNs reported by Toba et al. (2019a).
We construct an X-ray spectral model from the clumpy torus in an active galactic nucleus (AGN), designated as XCLUMPY, utilizing the Monte Carlo simulation for Astrophysics and Cosmology framework (MONACO: Odaka et al. 2011, 2016). The adopted geomet
ry of the torus is the same as that in Nenkova et al. (2008), who assume a power law distribution of clumps in the radial direction and a normal distribution in the elevation direction. We investigate the dependence of the X-ray continuum and Fe K$alpha$ fluorescence line profile on the torus parameters. Our model is compared with other torus models: MYTorus model (Murphy & Yaqoob 2009), Ikeda model (Ikeda et al. 2009), and CTorus model (Liu & Li 2014). As an example, we also present the results applied to the broadband X-ray spectra of the Circinus galaxy observed with XMM-Newton, Suzaku, and NuSTAR. Our model can well reproduce the data, yielding a hydrogen column density along the equatorial plane $N_{mathrm{H}}^{mathrm{Equ}} = 9.08_{-0.08}^{+0.14} times 10^{24}$ cm$^{-2}$, a torus angular width $sigma = 14.7_{-0.39}^{+0.44}$ degree, and a 2--10 keV luminosity $log L_{2-10}/mathrm{erg s^{-1}} = 42.8$. These results are discussed in comparison with the observations in other wavelengths.
We propose new diagnostics that utilize the [O IV] 25.89 $mu$m and nuclear (subarcsecond scale) 12 $mu$m luminosity ratio for identifying whether an AGN is deeply `buried in their surrounding material. Utilizing a sample of 16 absorbed AGNs at redshi
fts lower than 0.03 in the Swift/BAT catalog observed with Suzaku, we find that AGNs with small scattering fractions ($<$0.5%) tend to show weaker [O IV]-to-12 $mu$m luminosity ratios than the average of Seyfert 2 galaxies. This suggests that this ratio is a good indicator for identifying buried AGNs. Then, we apply this criterion to 23 local ultra/luminous infrared galaxies (U/LIRGs) in various merger stages hosting AGNs. We find that AGNs in most of mid- to late-stage mergers are buried, while those in earlier stage ones (including non-merger) are not. This result suggests that the fraction of buried AGNs in U/LIRGs increases as the galaxy-galaxy interaction becomes more significant.
We revisit the correlation between the mid-infrared (6 $mu$m) and hard X-ray (2--10 keV) luminosities of active galactic nuclei (AGNs) to understand the physics behind it. We construct an X-ray flux-limited sample of 571 type 1 AGNs with $f_{0.5-2.0
,{rm keV}} > 2.4 times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$, drawn from the ROSAT Bright Survey catalog. Cross-matching the sample with infrared data taken from Wide-field Infrared Survey Explorer, we investigate the relation between the rest-frame 6 $mu$m luminosity ($L_{rm 6}$) and the rest-frame 2--10 keV luminosity ($L_{rm X}$), where $L_{rm 6}$ is corrected for the contamination of host galaxies by using the spectral energy distribution fitting technique. We confirm that $L_{rm 6}$ and $L_{rm X}$ are correlated over four orders of magnitude, in the range of $L_{rm X} = 10^{42-46}$ erg s$^{-1}$. We investigate what kinds of physical parameters regulate this correlation. We find that $L_{rm X}$/$L_{rm 6}$ clearly depends on the Eddington ratio ($lambda_{rm Edd}$) as $log lambda_{rm Edd} = -(0.56 pm 0.10) log , (L_{rm X}/L_{rm 6}) - (1.07 pm 0.05)$, even taking into account quasars that are undetected by ROSAT as well as those detected by XMM-Newton in the literature. We also add hyper-luminous quasars with $L_{rm 6}$ $>$ 10$^{46}$ erg s$^{-1}$ in the literature and perform a correlation analysis. The resultant correlation coefficient is $-0.41 pm 0.07$, indicating a moderately tight correlation between $L_{rm X}$/$L_{rm 6}$ and $lambda_{rm Edd}$. This means that AGNs with high Eddington ratios tend to have lower X-ray luminosities with respect to the mid-infrared luminosities. This dependence can be interpreted as a change in the structure of the accretion flow.
