arXiv subjects

Yuichi Terashima

Publications and source records attributed to Yuichi Terashima.

At least 55 records · Page 3Linked to original sources

arXiv2015

A New Sample of Obscured AGNs Selected from the XMM-Newton and AKARI Surveys

We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90 micron) sources located at |b|>10 deg to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2-4.5 keV and 4.5-12 keV bands >-0.1 and (2) EPIC-PN count rate (CR) in the 0.2-12 keV to infrared flux ratio CR/F90<0.1 or CR/F18<1, where F18 and F90 are infrared fluxes at 18 and 90 micron in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of NH~10^{22-24} cm^-2, a very flat continuum, or a strong Fe-K emission line with an equivalent width of >700 eV is found in 26 objects. Six among them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18 micron condition is used. Of the 26 objects, 4 are optically classified as an HII nucleus and are new "elusive AGNs" in which star formation activity likely overwhelms AGN emission in the optical and infrared bands.

astro-ph.GA↗

arXiv2015

ALMA Observations of the Submillimeter Dense Molecular Gas Tracers in the Luminous Type-1 Active Nucleus of NGC 7469

We present ALMA Cycle 1 observations of the central kpc region of the luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.5$"$ $\times$ 0.4$"$ = 165 pc $\times$ 132 pc) at submillimeter wavelengths. Utilizing the wide-bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO$^+$(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 $μ$m continuum. The region consists of the central $\sim$ 1$"$ component and the surrounding starburst ring with a radius of $\sim$ 1.5$"$-2.5$"$. Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated towards the central $\sim$ 1$"$, suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anti-correlated with the optical one, indicating the existence of dust obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO$^+$(4-3) and HCN(4-3)/CS(7-6) are higher at the AGN position than at the starburst ring, which is consistent to our previous findings (submm-HCN enhancement). However, the HCN(4-3)/HCO$^+$(4-3) ratio at the AGN position of NGC 7469 (1.11$\pm$0.06) is almost half of the corresponding value of the low-luminosity type-1 Seyfert galaxy NGC 1097 (2.0$\pm$0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 ($\sim$ 1.5). Based on these results, we speculate that some other heating mechanisms than X-ray (e.g., mechanical heating due to AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.

astro-ph.GA↗

arXiv2015

Local instability signatures in ALMA observations of dense gas in NGC7469

We present an unprecedented measurement of the disc stability and local instability scales in the luminous infrared Seyfert 1 host, NGC7469, based on ALMA observations of dense gas tracers and with a synthesized beam of 165 x 132 pc. While we confirm that non-circular motions are not significant in redistributing the dense interstellar gas in this galaxy, we find compelling evidence that the dense gas is a suitable tracer for studying the origin of its intensely high-mass star forming ring-like structure. Our derived disc stability parameter accounts for a thick disc structure and its value falls below unity at the radii in which intense star formation is found. Furthermore, we derive the characteristic instability scale and find a striking agreement between our measured scale of ~ 180 pc, and the typical sizes of individual complexes of young and massive star clusters seen in high-resolution images.

astro-ph.GA↗

arXiv2015

Hyper-luminous Dust Obscured Galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

We present the photometric properties of a sample of infrared (IR) bright dust obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam (HSC) on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer (WISE), we discovered 48 DOGs with $i - K_\mathrm{s} > 1.2$ and $i - [22] > 7.0$, where $i$, $K_\mathrm{s}$, and [22] represent AB magnitude in the $i$-band, $K_\mathrm{s}$-band, and 22 $μ$m, respectively, in the GAMA 14hr field ($\sim$ 9 deg$^2$). Among these objects, 31 ($\sim$ 65 %) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show a NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma $z$ = 1.99 $\pm$ 0.45, we calculated their total IR luminosity using an empirical relation between 22 $μ$m luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5 $\pm$ 1.1) $\times$ $10^{13}$ L$_{\odot}$, which classifies them as hyper-luminous infrared galaxies (HyLIRGs). We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 $μ$m flux greater than 3.0 mJy and with $i$-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log $ϕ$ = -6.59 $\pm$ 0.11 [Mpc$^{-3}$]. The IR LF for DOGs including data obtained from the literature is well fitted by a double-power law. The derived lower limit for the IR LD for our sample is $ρ_{\mathrm{IR}}$ $\sim$ 3.8 $\times$ 10$^7$ [L$_{\odot}$ Mpc$^{-3}$] and its contributions to the total IR LD, IR LD of all ultra-luminous infrared galaxies (ULIRGs), and that of all DOGs are $>$ 3 %, $>$ 9 %, and $>$ 15 %, respectively.

astro-ph.GA↗

arXiv2015

Infrared and X-Ray Evidence of an AGN in the NGC 3256 Southern Nucleus

We investigate signs of Active Galactic Nucleus (AGN) in the luminous infrared galaxy NGC 3256 at both infrared and X-ray wavelengths. NGC 3256 has double, the Northern and Southern, nuclei (hereafter, N and S nuclei, respectively). We show that the Spitzer IRAC colors extracted at the S nucleus are AGN-like, and the Spitzer IRS spectrum is bluer at <6um than at the N nucleus. We built for the S nucleus an AGN-starburst composite model with a heavily absorbed AGN to successfully reproduce not only the IRAC and IRS specrophotometries at ~3arcsec but also the very deep silicate 9.7um absorption observed at 0.36" scale by Diaz-Santos et al. We found a 2.2um compact source at the S nucleus in a HST NICMOS image and identified its unresolved core (at 0.26" resolution) with the compact core in previous mid-infrared observations at comparable resolution. The flux of the 2.2umm core is consistent with our AGN spectral energy distribution model. We also analyzed a deeper than ever Chandra X-ray spectrum of the unresolved (at 0.5" resolution) source at the S nucleus. We found that a dual-component power-law model (for primary and scattered ones) fits an apparently very hard spectrum with a moderately large absorption on the primary component. Together with a limit on equivalent width of a fluorescent Fe-K emission line at 6.4 keV, the X-ray spectrum is consistent with a typical Compton-thin Seyfert 2. We therefore suggest that the S nucleus hosts a heavily absorbed low-luminosity AGN.

astro-ph.GA↗

arXiv2014

Suzaku observation of IRAS 00521-7054, a peculiar type-II AGN with a very broad feature at 6 keV

IRAS 00521$-$7054 is the first Seyfert 2 in which the presence of an extremely large Fe K$α$ line has been claimed. We report here on the analysis of a 100 ks Suzaku observation of the source. We confirm the existence of a very strong excess over the power-law X-ray continuum at $E\sim6$ keV ($EW\simeq 800$ eV), extending down to $\sim 4.5$ keV, and found that the X-ray spectrum of the source can be explained by two different models. i) An absorption scenario, in which the X-ray source is obscured by two fully-covering ionized absorbers, with a strong reflection component from neutral material ($R\sim 1.7$), a black body component and four narrow Gaussian lines (corresponding to Fe K$α$, Fe K$β$, Fe xxv and Fe xxvi). ii) A reflection scenario, in which the X-ray spectrum is dominated by an obscured ($\log N_{\rm\,H}\sim 22.9$) blurred reflection produced in an ionized disk around a rotating supermassive black hole with a spin of $a \geq 0.73$, and affected by light-bending ($R\sim 2.7$), plus two narrow Gaussian lines (corresponding to Fe K$α$ and Fe K$β$). The narrow Fe K$α$ and K$β$ lines are consistent with being produced by ionized iron, and in particular by Fe xiv-Fe xvi and Fe xii-Fe xvi for the absorption and reflection scenario, respectively. While the X-ray continuum varies significantly during the observation, the intensity of the broad feature appears to be constant, in agreement with both the absorption and reflection scenarios. For both scenarios we obtained a steep power-law emission ($Γ\sim 2.2-2.3$), and we speculate that the source might be an obscured narrow-line Seyfert 1.

astro-ph.HE↗

arXiv2014

Tracking the Complex Absorption in NGC 2110 with Two Suzaku Observations

We present spectral analysis of two Suzaku observations of the Seyfert 2 galaxy, NGC 2110. This source has been known to show complex, variable absorption which we study in depth by analyzing these two observations set seven years apart and by comparing to previously analyzed observations with the XMM-Newton and Chandra observatories. We find that there is a relatively stable, full-covering absorber with a column density of ~3$\times 10 ^{22}$ cm$^{-2}$, with an additional patchy absorber that is likely variable in both column density and covering fraction over timescales of years, consistent with clouds in a patchy torus or in the broad line region. We model a soft emission line complex, likely arising from ionized plasma and consistent with previous studies. We find no evidence for reflection from an accretion disk in this source with no contribution from relativistically broadened Fe Ka line emission nor from a Compton reflection hump.

astro-ph.HE↗

arXiv2013

Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC 1097

We present the first 100 pc scale view of the dense molecular gas in the central ~ 1.3 kpc region of the type-1 Seyfert NGC 1097 traced by HCN (J=4-3) and HCO+ (J=4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we study the characteristics of the dense gas around this AGN and search for the mechanism of HCN enhancement. We find a high HCN (J=4-3) to HCO+ (J=4-3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (v2=1^{1f}, J=4-3) to HCN (J=4-3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J=4-3) to CS (J=7-6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined from similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J=4-3 and 1-0 data from ALMA, and J=3-2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 < [HCN]/[HCO+] < 20: non-LTE analysis) in the nucleus, and that the high-J lines (J=4-3 and 3-2) are emitted from dense (10^{4.5} < n_H2 [/cc] < 10^6), hot (70 < Tkin [K] < 550) regions. Finally we propose that the high temperature chemistry is more plausible to explain the observed enhanced HCN emission in NGC 1097 than the pure gas phase PDR/XDR chemistry.

astro-ph.GA↗

arXiv2013

Suzaku View of the Swift/BAT Active Galactic Nuclei. V. Torus Structure of Two Luminous Radio-loud AGNs (3C 206 and PKS 0707-35)

We present the results from broad-band X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku and Swift/BAT, two of the most luminous unobscured and obscured radio-loud active galactic nuclei with hard X-ray luminosities of 10^{45.5} erg s^{-1} and 10^{44.9} erg s^{-1} (14--195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant (~ 60% in the 14--195 keV band) contribution from the jet, while it is negligible in PKS 0707-35. We can successfully model the spectra with the jet component (for 3C 206), the transmitted emission, and two reflection components from the torus and the accretion disk. The reflection strengths from the torus are found to be R_{torus} (= Ω/2π) = 0.29 +- 0.18 and 0.41 +- 0.18 for 3C 206 and PKS 0707-35, respectively, which are smaller than those in typical Seyfert galaxies. Utilizing the torus model by Ikeda et al. (2009), we quantify the relation between the half opening angle of a torus (θ_{oa}) and the equivalent width of an iron-K line. The observed equivalent width of 3C 206, < 71 eV, constrain the column density in the equatorial plane to N_{H}^{eq} < 10^{23} cm^{-2}, or the half opening angle to θ_{oa} > 80^\circ if N_{H}^{eq} = 10^{24} cm^{-2} is assumed. That of PKS 0707-35, 72 +- 36 eV, is consistent with N_{H}^{eq} ~ 10^{23} cm^{-2}. Our results suggest that the tori in luminous radio-loud AGNs are only poorly developed. The trend is similar to that seen in radio-quiet AGNs, implying that the torus structure is not different between AGNs with jets and without jets.

astro-ph.HE↗

arXiv2013

Broad Band X-Ray Spectra of Two Low-luminosity Active Galactic Nuclei NGC 1566 and NGC 4941

We report the first broad band X-ray spectra of the low luminosity active galactic nuclei (LLAGN) NGC 1566 (type 1.5) and NGC 4941 (type 2) observed with Suzaku and Swift/BAT covering the 0.5-195 keV band. Both targets have hard X-ray luminosities of ~ 10^{41-42} ergs/s in the 15-55 keV band. The spectra of the nucleus are well reproduced by a sum of partially or fully covered transmitted emission and its reflection from the accretion disk, reprocessed emission from the torus accompanied by a strong narrow iron-Kαline, and a scattered component (for NGC 4941). We do not significantly detect a broad iron-Kαline from the inner accretion disk in both targets, and obtain an upper limit on the corresponding solid angle of Ω/2π< 0.3 in NGC 1566. The reflection strength from the torus is moderate, Ω/2π=0.45^{+0.13}_{-0.10} in NGC 1566 and Ω/2π=0.64^{+0.69}_{-0.27} in NGC 4941. Comparison of the equivalent width of the narrow iron-Kαline with a model prediction based on a simple torus geometry constrains its half-opening angle to be θ_oa ~ 60-70 degree in NGC 4941. These results agree with the obscured AGN fraction obtained from hard X-ray and mid-infrared selected samples at similar luminosities. Our results support the implication that the averaged covering fraction of AGN tori is peaked at L 10^{42-43} ergs/s but decreases toward lower luminosities.

astro-ph.GA↗

arXiv2012

The Low-mass, Highly Accreting Black Hole Associated with the Active Galactic Nucleus 2XMM J123103.2+110648

Optical spectra and images taken with the Baade 6.5 meter Magellan telescope confirm that 2XMM J123103.2+110648, a highly variable X-ray source with an unusually soft spectrum, is indeed associated with a type 2 (narrow-line) active nucleus at a redshift of z = 0.11871. The absence of broad Halpha or Hbeta emission in an otherwise X-ray unabsorbed source suggests that it intrinsically lacks a broad-line region. If, as in other active galaxies, the ionized gas and stars in J1231+1106 are in approximate virial equilibrium, and the black hole mass versus stellar velocity dispersion relation holds, the exceptionally small velocity dispersion of 33.5 km/s for [O III] 5007 implies that the black hole mass is approximately 10^5 solar masses, among the lowest ever detected. Such a low black hole mass is consistent with the general characteristics of the host, a small, low-luminosity, low-mass disk galaxy. We estimate the Eddington ratio of the black hole to be > 0.5, in good agreement with expectations based on the X-ray properties of the source.

astro-ph.CO↗

arXiv2012

Mid and Far Infrared Properties of a Complete Sample of Local AGNs

We investigate the mid- (MIR) to far-infrared (FIR) properties of a nearly complete sample of local Active Galactic Nuclei (AGNs) detected in the Swift/BAT all sky hard X-ray (14-195 keV) survey, based on the cross correlation with the AKARI infrared survey catalogs complemented by those with IRAS and WISE. Out of 135 non-blazer AGNs in the Swift/BAT 9 month catalog, we obtain the MIR photometric data for 128 sources either in the 9, 12, 18, 22, and/or 25 um band. We find good correlation between their hard X-ray and MIR luminosities over 3 orders of magnitude (42< log lambda L_{lambda}(9, 18 um)< 45), which is tighter than that with the FIR luminosities at 90 um. This suggests that thermal emission from hot dusts irradiated by the AGN emission dominate the MIR fluxes. Both X-ray unabsorbed and absorbed AGNs follow the same correlation, implying isotropic infrared emission, as expected in clumpy dust tori rather than homogeneous ones. We find excess signals around 9 um in the averaged infrared spectral energy distribution from heavy obscured "new type" AGNs with small scattering fractions in the X-ray spectra. This could be attributed to the PAH emission feature, suggesting that their host galaxies have strong starburst activities.

astro-ph.GA↗

arXiv2012

A New Sample of Candidate Intermediate-Mass Black Holes Selected by X-ray Variability

We present the results of X-ray variability and spectral analysis of a sample of 15 new candidates for active galactic nuclei with relatively low-mass black holes (BHs). They are selected from the Second XMM-Newton Serendipitous Source Catalogue based on strong variability quantified by normalized excess variances. Their BH masses are estimated to be 1.1-6.6x10^6 M_solar by using a correlation between excess variance and BH mass. Seven sources have estimated BH masses smaller than 2x10^6 M_solar, which are in the range for intermediate-mass black holes. Eddington ratios of sources with known redshifts range from 0.07 to 0.46 and the mean Eddington ratio is 0.24. These results imply that some of our sources are growing supermassive black holes, which are expected to have relatively low masses with high Eddington ratios. X-ray photon indices of the 15 sources are in the range of ~0.57-2.57, and 5 among them have steep (>2) photon indices, which are the range for narrow-line Seyfert 1s. Soft X-ray excess is seen in 12 sources, and is expressed by a blackbody model with kT~83-294 eV. We derive a correlation between X-ray photon indices and Eddington ratios, and find that the X-ray photon indices of about a half of our sources are flatter than the positive correlation suggested previously.

astro-ph.HE↗

arXiv2012

A Candidate Active Galactic Nucleus with a Pure Soft Thermal X-ray Spectrum

We report the discovery of a candidate active galactic nucleus (AGN), 2XMM J123103.2+110648 at z = 0.13, with an X-ray spectrum represented purely by soft thermal emission reminiscent of Galactic black hole (BH) binaries in the disk-dominated state. This object was found in the second XMM serendipitous source catalogue as a highly variable X-ray source. In three separate observations, its X-ray spectrum can be represented either by a multicolor disk blackbody model with an inner temperature of kT_in~0.16-0.21 keV or a Wien spectrum Comptonized by an optically thick plasma with kT~0.14-0.18 keV. The soft X-ray luminosity in the 0.5--2 keV band is estimated to be (1.6-3.8)x10^42 erg/s. Hard emission above ~2 keV is not detected. The ratio of the soft to hard emission is the strongest among AGNs observed thus far. Spectra selected in high/low flux time intervals are examined in order to study spectral variability. In the second observation with the highest signal-to-noise ratio, the low energy (below 0.7 keV) spectral regime flattens when the flux is high, while the shape of the high energy part (1-1.7 keV) remains unchanged. This behavior is qualitatively consistent with being caused by strong Comptonization. Both the strong soft excess and spectral change consistent with Comptonization in the X-ray spectrum imply that the Eddington ratio is large, which requires a small BH mass (smaller than ~10^5M_solar.

astro-ph.HE↗

arXiv2012

Infrared and hard X-ray diagnostics of AGN identification from the Swift/BAT and AKARI all-sky surveys

We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) properties for local active galactic nuclei (AGN). The Swift/Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray detected AGN. Cross-correlating the 22-month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGN detected by the AKARI instruments. We find a strong correlation for most AGN between the infrared (9, 18, and 90 micron) and hard X-ray (14-195 keV) luminosities, and quantify the correlation for various subsamples of AGN. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1s, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity vs. infrared color diagram, in which type 1 radio-loud AGN are well isolated from the others in the sample. The other uses the X-ray vs. infrared color as a useful redshift-independent indicator for identifying Compton-thick AGN. Importantly, Compton-thick AGN and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.

astro-ph.HE↗

arXiv2011

Suzaku View of the Swift/Bat Active Galactic Nuclei. IV. Nature of Two Narrow-Line Radio Galaxies (3C 403 and IC 5063)

We report the results of Suzaku broad band X-ray observations of the two narrow-line radio galaxies (NLRGs), 3C 403 and IC 5063. Combined with the Swift/BAT spectra averaged for 58 months, we are able to accurately constrain their spectral properties over the 0.5--200 keV band. The spectra of both nuclei are well represented with an absorbed cut-off power law, an absorbed reflection component from cold matter with an iron-K emission line, and an unabsorbed soft component, which gives a firm upper limit for the scattered emission. The reflection strength normalized to the averaged BAT flux is R = Ω/2π~ 0.6 in both targets, implying that their tori have a sufficiently large solid angle to produce the reprocessed emission. A numerical torus model with an opening angle of ~ 50 deg well reproduces the observed spectra. We discuss the possibility that the amount of the normal gas responsible for Thomson scattering is systematically smaller in radio galaxies compared with Seyfert galaxies.

astro-ph.HE↗

arXiv2010

Suzaku View of the Swift/BAT Active Galactic Nuclei. III. Application of Numerical Torus Models to Two Nearly Compton Thick AGNs (NGC 612 and NGC 3081)

The broad band spectra of two Swift/BAT AGNs obtained from Suzaku follow-up observations are studied: NGC 612 and NGC 3081. Fitting with standard models, we find that both sources show similar spectra characterized by a heavy absorption with $N_{\rm{H}} \simeq 10^{24} \ \rm{cm}^{-2}$, the fraction of scattered light is $f_{\rm{scat}} = 0.5-0.8%$, and the solid angle of the reflection component is $Ω/2π= 0.4-1.1$. To investigate the geometry of the torus, we apply numerical spectral models utilizing Monte Carlo simulations by Ikeda et al. (2009) to the Suzaku spectra. We find our data are well explained by this torus model, which has four geometrical parameters. The fit results suggest that NGC 612 has the torus half opening-angle of $\simeq 60^{\circ}-70^{\circ}$ and is observed from a nearly edge-on angle with a small amount of scattering gas, while NGC 3081 has a very small opening angle $\simeq 15^\circ$ and is observed on a face-on geometry, more like the deeply buried "new type" AGNs found by Ueda et al. (2007). We demonstrate the potential power of direct application of such numerical simulations to the high quality broad band spectra to unveil the inner structure of AGNs.

astro-ph.CO↗

arXiv2010

Suzaku Observation of the Brightest Broad-Line Radio Galaxy 4C 50.55 (IGR J 21247+5058)

We report the results from a deep Suzaku observation of 4C 50.55 (IGR J 21247+5058), the brightest broad-line radio galaxy in the hard X-ray (> 10 keV) sky. The simultaneous broad band spectra over 1-60 keV can be represented by a cut-off power law with two layers of absorption and a significant reflection component from cold matter with a solid angle of Ω/2π\approx 0.2. A rapid flux rise by ~ 20% over 2 \times 10^4 sec is detected in the 2-10 keV band. The spectral energy distribution suggests that there is little contribution to the total X-ray emission from jets. Applying a thermal Comptonization model, we find that corona is optically thick (τ_e \approx 3) and has a relatively low temperature (kT_e \approx 30 keV). The narrow iron-K emission line is consistent with a picture where the standard disk is truncated and/or its inner part is covered by optically thick Comptonizing corona smearing out relativistic broad line features. The inferred disk structure may be a common feature of accretion flows onto black holes that produce powerful jets.

astro-ph.HE↗