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

Abstract

NGC 1448 is one of the nearest luminous galaxies ($L_{8-1000\mu m}>$ 10${}^9{L}_{\odot }$) 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 ($\approx$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 $N_{\mathrm{H}}$(los) $\gtrsim$ 2.5 $\times$ 10${}^{24}$ cm${}^{-2}$. The best-fitting torus models measured an intrinsic 2-10 keV luminosity of $L_{2-10,\mathrm{int}}$ $=$ (3.5-7.6) $\times$ 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 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]$\lambda$5007Å emission line and the MIR 12$\mu$m continuum, further supporting the CT nature of the AGN.

Accepted for publication in ApJ on Dec. 27th, 2016; 14 pages; 9 figures and 2 tables

References in corpus (15)

• The Host Galaxies and Classification of Active Galactic Nuclei
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies
• Cosmic X-ray Surveys of Distant Active Galaxies: The Demographics, Physics, and Ecology of Growing Supermassive Black Holes
• Suzaku Observations of Active Galactic Nuclei Detected in the Swift/BAT Survey: Discovery of "New Type" of Buried Supermassive Black Holes
• Size and properties of the narrow-line region in Seyfert-1 galaxies from spatially-resolved optical spectroscopy
• AGN dust tori at low and high luminosities
• The mid IR -- hard X-ray correlation in AGN and its implications for dusty torus models
• The NuSTAR View of Nearby Compton-thick AGN: The Cases of NGC 424, NGC 1320 and IC 2560
• The variable hard X-ray emission of NGC4945 as observed by NuSTAR
• NuSTAR unveils a Compton-thick Type 2 quasar in Mrk 34
• Determining the covering factor of Compton-thick active galactic nuclei with NuSTAR
• The central parsecs of active galactic nuclei: challenges to the torus
• A Compton thick AGN in the barred spiral NGC 4785

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• Variability-selected intermediate mass black hole candidates in dwarf galaxies from ZTF and WISE
• BASS XXVIII: Near-infrared Data Release 2, High-Ionization and Broad Lines in Active Galactic Nuclei
• A hard look at local, optically-selected, obscured Seyfert galaxies
• The demographics of obscured AGN from X-ray spectroscopy guided by multiwavelength information
• NuSTAR Uncovers an Extremely Local Compton-thick AGN in NGC 4968
• $NuSTAR$ Observations of Four Nearby X-ray Faint AGN: Low Luminosity or Heavy Obscuration?
• A Low Incidence of Mid-Infrared Variability in Dwarf Galaxies
• Consistent extinction model for type Ia supernovae in Cepheid-based calibration galaxies and its impact on $H_0$
• Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data
• The highly obscured Seyfert 2 nucleus in NGC 1448 observed with MUSE
• Nuclear Activity and Host Galaxy Properties of Low-Luminosity AGN Identified from VLA Observations