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Local AGN Survey (LASr) : I. Galaxy sample, infrared colour selection and predictions for AGN within 100 Mpc.

Asmus, D. and Greenwell, C.L. and Gandhi, P. and Boorman, P.G. and Aird, J. and Alexander, D.M. and Assef, R.J. and Baldi, R.D. and Davies, R.I. and Hönig, S.F. and Ricci, C. and Rosario, D.J. and Salvato, M. and Shankar, F. and Stern, D. (2020) 'Local AGN Survey (LASr) : I. Galaxy sample, infrared colour selection and predictions for AGN within 100 Mpc.', Monthly notices of the Royal Astronomical Society., 494 (2). pp. 1784-1816.


To answer major questions on supermassive black hole (SMBH) and galaxy evolution, a complete census of SMBH growth, i.e., active galactic nuclei (AGN), is required. Thanks to all-sky surveys by the Wide-field Infrared Survey Explorer (WISE) and the Spectrum-Roentgen-Gamma (SRG) missions, this task is now feasible in the nearby Universe. We present a new survey, the Local AGN Survey (LASr), with the goal of identifying AGN unbiased against obscuration and determining the intrinsic Compton-thick (CT) fraction. We construct the most complete all-sky galaxy sample within 100 Mpc (90% completeness for log (M*/M⊙) ∼ 9.4), four times deeper than the current reference, the Two Micron All-Sky Survey Redshift Survey (2MRS), which misses ∼20% of known luminous AGN. These 49k galaxies serve as parent sample for LASr, called LASr-GPS. It contains 4.3k already known AGN, ≥82% of these are estimated to have Lnuc(12μm) < 1042.3 erg s−1, i.e., are low-luminosity AGN. As a first method for identifying Seyfert-like AGN, we use WISE-based infrared colours, finding 221 galaxies at Lnuc(12μm) ≥ 1042.3 erg s−1 to host an AGN at 90% reliability. This includes 61 new AGN candidates and implies and optical type 2 fraction of 50–71%. We quantify the efficiency of this technique and estimate the total number of AGN with Lint(2-10  keV) ≥ 1042 erg s−1 in the volume to be 362+145−116 (⁠8.6+3.5−2.8× 10−5 Mpc−3). X-ray brightness estimates indicate the CT fraction to be 40–55% to explain the Swift non-detections of the infrared selected objects. One third of the AGN within 100 Mpc remain to be identified, and we discuss the prospects for the eROSITA all-sky survey to detect them.

Item Type:Article
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:12 March 2020
Date deposited:18 March 2020
Date of first online publication:18 March 2020
Date first made open access:18 March 2020

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