A New Compton-thick AGN in Our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR

作者：Annuar, A.^*; Alexander, D. M.; Gandhi, P.; Lan**ury, G. B.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Goulding, A. D.; Hailey, C. J.; Harrison, F. A.; Koss, M. J.; LaMassa, S. M.; Murray, S. S.; Ricci, C.; Rosario, D. J.; Stanley, F.; Stern, D.; Zhang, W.

来源：Astrophysical Journal, 2017, 836(2): 165.

DOI：10.3847/1538-4357/836/2/165

• galaxies: active
• galaxies: nuclei
• techniques: spectroscopic
• X-rays: galaxies
• X-rays: individual (NGC 1448)

NGC 1448 is one of the nearest luminous galaxies (L-8-1000(mu m) > 10(9) L-circle dot) to ours (z = 0.00390), and yet the active galactic nucleus (AGN) it hosts was only recently discovered, in 2009. In this paper, we present an analysis of the nuclear source across three wavebands: mid-infrared (MIR) continuum, optical, and X-rays. We observed the source with the Nuclear Spectroscopic Telescope Array (N(u)STAR), and combined these data with archival Chandra data to perform broadband X-ray spectral fitting (approximate to 0.5-40 keV) of the AGN for the first time. Our X-ray spectral analysis reveals that the AGN is buried under a Compton-thick (CT) column of obscuring gas along our line of sight, with a column density of N-H(los)greater than or similar to 2.5 x 10(24) cm(-2). The best-fitting torus models measured an intrinsic 2-10 keV luminosity of L-2-10, int = (3.5-7.6). x. 10(40)erg s(-1), making NGC 1448 one of the lowest luminosity CTAGNs known. In addition to the NuSTAR observation, we also performed optical spectroscopy for the nucleus in this edge-on galaxy using the European Southern Observatory New Technology Telescope. We reclassify the optical nuclear spectrum as a Seyfert on the basis of the Baldwin-Philips-Terlevich diagnostic diagrams, thus identifying the AGN at optical wavelengths for the first time. We also present high spatial resolution MIR observations of NGC 1448 with Gemini/T-ReCS, in which a compact nucleus is clearly detected. The absorption-corrected 2-10 keV luminosity measured from our X-ray spectral analysis agrees with that predicted from the optical [O III]lambda 5007 angstrom emission line and the MIR 12 mu m. continuum, further supporting the CT nature of the AGN.

• 出版日期2017-2-20
• 单位Virginia Tech; 北京大学; 美国弗吉尼亚理工大学(Virginia Tech)