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

Journal
Date Issued
2020
Author(s)
Asmus, D.
•
Greenwell, C. L.
•
Gandhi, P.
•
Boorman, P. G.
•
Aird, J.
•
Alexander, D. M.
•
Assef, R. J.
•
•
Davies, R. I.
•
Hönig, S. F.
•
Ricci, C.
•
Rosario, D. J.
•
Salvato, M.
•
Shankar, F.
•
Stern, D.
DOI
Abstract
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 per cent 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 per cent of known luminous AGN. These 49k galaxies serve as parent sample for LASr, called LASr-GPS. It contains 4.3k already known AGN, 82 per cent 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 (12 μm) ≥ 1042.3 erg s-1 to host an AGN at 90 per cent reliability. This includes 61 new AGN candidates and implies an optical type 2 fraction of 50-71 per cent. 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 per cent 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.
Volume
494
Issue
2
Start page
1784
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2020MNRAS.494.1784A
Rights
open.access
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