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Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy

Oda, Saeko and Tanimoto, Atsushi and Ueda, Yoshihiro and Imanishi, Masatoshi and Terashima, Yuichi and Ricci, Claudio (2017) Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy. Astrophysical Journal, 835 (2). Art. no. 179. ISSN 0004-637X. doi:10.3847/1538-4357/835/2/179.

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We report the broadband X-ray spectra of the ultraluminous infrared galaxy (ULIRG) UGC 5101 in the 0.25–100 keV band observed with the Swift/Burst Alert Telescope (BAT), Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM-Newton, and Chandra. A Compton-thick active galactic nucleus (AGN) obscured with a hydrogen column density of ≈ 1.3 × 10^(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°, 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 ≈ 1.4× 10^(43) erg s^(‑1), which is ≈ 2.5 times larger than the previous estimate using only data below 10 keV with a simple spectral model. We find that UGC 5101 shows the ratio between the [O iv] 26 μm line and 2–10 keV luminosities similar to those of normal Seyfert galaxies, along with other ULIRGs observed with NuSTAR, indicating that a significant portion of local ULIRGs are not really “X-ray faint” with respect to the flux of forbidden lines originating from the narrow-line region. We propose a possible scenario that (1) the AGN in UGC 5101 is surrounded not only by Compton-thick matter located close to the equatorial plane but also by Compton-thin (N_H ∼ 10^(21) cm^(‑2)) matter in the torus-hole region and (2) it is accreting at a high Eddington rate with a steep UV to X-ray spectral energy distribution. Nevertheless, we argue that AGNs in many ULIRGs do not look extraordinary (i.e., extremely X-ray faint), as suggested by recent works, compared with normal Seyferts.

Item Type:Article
Related URLs:
URLURL TypeDescription
Tanimoto, Atsushi0000-0002-0114-5581
Ueda, Yoshihiro0000-0001-7821-6715
Imanishi, Masatoshi0000-0001-6186-8792
Terashima, Yuichi0000-0003-1780-5481
Ricci, Claudio0000-0001-5231-2645
Additional Information:© 2017. The American Astronomical Society. Received 2016 September 28; revised 2016 December 10; accepted 2016 December 18; published 2017 January 30. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy, and the California Institute of Technology [Caltech], USA). Part of this work was financially supported by the Grant-in-Aid for Scientific Research 26400228 (Y.U.), 15K05030 (M.I.), and 15H02070 (Y.T.) from the Japan Society for the Promotion of Science (JSPS), and by the CONICYT-Chile grants "EMBIGGEN" Anillo ACT1101 (C.R.), FONDECYT 1141218 (C.R.), and Basal-CATA PFB–06/2007 (C.R.). C.R. acknowledges support from the China-CONICYT fund.
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)26400228
Japan Society for the Promotion of Science (JSPS)15K05030
Japan Society for the Promotion of Science (JSPS)15H02070
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)ACT1101
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Subject Keywords:galaxies: active; galaxies: individual (UGC 5101) ; X-rays: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20170331-102221840
Persistent URL:
Official Citation:Saeko Oda et al 2017 ApJ 835 179
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75577
Deposited By: Joy Painter
Deposited On:31 Mar 2017 17:36
Last Modified:15 Nov 2021 16:34

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