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Constraining the Population of Compton-Thick AGN and N_H Distribution in the Local Universe

Annuar, Adlyka and Gandhi, Poshak and Alexander, Dave and Lansbury, George and Harrison, Fiona and Stern, Daniel (2015) Constraining the Population of Compton-Thick AGN and N_H Distribution in the Local Universe. In: International Conference on Space Science and Communication (IconSpace), 2015. IEEE , Piscataway, NJ, pp. 329-331. ISBN 978-1-4799-1939-0.

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Compton-thick active galactic nuclei (CTAGN) are defined as AGN that are obscured along our line-of-sight by absorbing gas with a column density of N_H ≳ 10^(24) cm^(-2). This is what makes it difficult to identify them at X-ray energies E <; 10 keV, where the direct emission from the AGN is severely absorbed by the obscuring gas. Because of this, a large fraction of the CTAGN population is believed to be missed by current low X-ray energy observations. In this paper, we present updated results from an ongoing project to form the most unbiased census of CTAGN population in the local universe, using a sample of mid-infrared (mid-IR) selected AGN within D <; 15 Mpc. We find that 20% of the AGN in the sample has been confirmed to be CT from current hard X-ray studies (E ≳ 10 keV). More candidates are then selected using multiwavelength techniques, i.e. optical [OIII]λ5007:X-ray and mid-IR:X-ray flux ratios. Based on these analyses, we initially find a further 25% of potential candidates. NuSTAR (Nuclear Spectroscopic Telescope Array) recently observed two of these candidates at high X-ray energies and is able to confirm one of them, NGC 5643, as a CTAGN and rule out the other one as an obscured AGN. This constrains the total CTAGN population in the sample to 25-40%, though it could also be as high as 65% accounting for those that we still lack data. Finally, we use these results to estimate the intrinsic Nu distribution of the local AGN population.

Item Type:Book Section
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URLURL TypeDescription
Annuar, Adlyka0000-0003-0387-1429
Gandhi, Poshak0000-0003-3105-2615
Alexander, Dave0000-0002-5896-6313
Lansbury, George0000-0002-5328-9827
Harrison, Fiona0000-0003-2992-8024
Stern, Daniel0000-0003-2686-9241
Alternate Title:Constraining the Population of Compton-Thick AGN and NH Distribution in the Local Universe
Additional Information:© 2015 IEEE. We thank D. Asmus and A. D. Goulding for providing extra data and information for some of the sources in the sample, and useful discussions carried out throughout this work. We acknowledge financial support from Majlis Amanah Rakyat (MARA) Malaysia (A.A), the Science and Technology Facilities Council (STFC) grant ST/J003697/1 (P.G), ST/I0015731/1 (D.M.A), ST/K501979/1 (G.B.L), and the Leverhulme Trust (D.M.A). NuSTAR is a project led by the California Institute of Technology (Caltech), managed by the Jet Propulsion Laboratory (JPL), and funded by the National Aeronautics and Space Administration (NASA). This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center (HEASARC) Online Service, provided by the NASA/Goddard Space Flight Center, and the NASA/IPAC extragalactic Database (NED) operated by JPL, Caltech under contract with NASA.
Group:NuSTAR, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Majlis Amanah Rakyat (MARA)UNSPECIFIED
Science and Technology Facilities Council (STFC)ST/J003697/1
Science and Technology Facilities Council (STFC)ST/I0015731/1
Science and Technology Facilities Council (STFC)ST/K501979/1
Leverhulme TrustUNSPECIFIED
Subject Keywords: Adaptive optics, Astrophysics, NASA, Sociology, Statistics, Telescopes
Record Number:CaltechAUTHORS:20161014-095514513
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Official Citation:A. Annuar, P. Gandhi, D. Alexander, G. Lansbury, F. Harrison and D. Stern, "Constraining the population of compton-thick AGN and NH distribution in the local universe," 2015 International Conference on Space Science and Communication (IconSpace), Langkawi, 2015, pp. 329-331. doi: 10.1109/IconSpace.2015.7283747
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71090
Deposited By: Ruth Sustaita
Deposited On:14 Oct 2016 19:53
Last Modified:11 Nov 2021 04:39

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