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

Annuar, A.; Alexander, D.M.; Gandhi, P.; Lansbury, 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.

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


Authors

A. Annuar

P. Gandhi

G.B. Lansbury

D. Asmus

D.R. Ballantyne

F.E. Bauer

S.E. Boggs

P.G. Boorman

W.N. Brandt

M. Brightman

F.E. Christensen

W.W. Craig

D. Farrah

A.D. Goulding

C.J. Hailey

F.A. Harrison

M.J. Koss

S.M. LaMassa

S.S. Murray

C. Ricci

D.J. Rosario

F. Stanley

D. Stern

W. Zhang



Abstract

NGC 1448 is one of the nearest luminous galaxies (L8−1000μm> 109L⊙) 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 (NuSTAR), and combined this data with archival Chandra data to perform broadband X-ray spectral fitting (≈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 NH(los) ≳ 2.5 × 1024 cm−2. The best-fitting torus models measured an intrinsic 2-10 keV luminosity of L2−10,int = (3.5-7.6) × 1040 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 re-classify 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 [OIII]λ5007\AA\ emission line and the MIR 12μm continuum, further supporting the CT nature of the AGN.

Journal Article Type Article
Acceptance Date Dec 27, 2016
Online Publication Date Feb 17, 2017
Publication Date Feb 17, 2017
Deposit Date Jan 19, 2017
Publicly Available Date Jan 26, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 836
Issue 2
Article Number 165
DOI https://doi.org/10.3847/1538-4357/836/2/165
Public URL https://durham-repository.worktribe.com/output/1365888
Related Public URLs https://arxiv.org/abs/1701.00497

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© 2017. The American Astronomical Society. All rights reserved.






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