Local AGN survey (LASr): I. Galaxy sample, infrared colour selection, and predictions for AGN within 100 Mpc
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 ( $90{{\ \rm per\ cent}}$ 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 ${\sim}20{{\ \rm per\ cent}}$ of known luminous AGN. These 49k galaxies serve as parent sample for LASr, called LASr-GPS. It contains 4.3k already known AGN, $\ge 82{{\ \rm per\ cent}}$ of these are estimated to have $L^\mathrm{nuc}(12\, \mu \mathrm{m})\lt 10^{42.3}$ 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 $L^\mathrm{nuc}(12\, \mu \mathrm{m})\ge 10^{42.3}$ erg s-1 to host an AGN at $90{{\ \rm per\ cent}}$ 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 $L^\mathrm{int}(\rm {2-10\,keV})\ge 10^{42}$ erg s-1 in the volume to be $362^{+145}_{-116}$ ( $8.6^{+3.5}_{-2.8}\, \times$ 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.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2020
- DOI:
- arXiv:
- arXiv:2003.05959
- Bibcode:
- 2020MNRAS.494.1784A
- Keywords:
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- galaxies: active;
- galaxies: Seyfert;
- infrared: galaxies;
- X-rays: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in MNRAS. 30 pages, 19 figures. For full, digital versions of Table 1, 2 and 3, see: https://my.pcloud.com/publink/show?code=kZiqWnkZgyLixKFSgruXOsYYglos20Y3kB6V