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

Local AGN Survey (LASr): I. Galaxy sample, infrared colour selection and predictions for AGN within 100 Mpc
Local AGN Survey (LASr): I. Galaxy sample, infrared colour selection and predictions for AGN within 100 Mpc
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(12μm)≥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(2−10keV)≥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.
0035-8711
1784–1816
Asmus, D.
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Greenwell, C.L.
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Gandhi, P.
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Boorman, P.G.
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Aird, J.
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Alexander, D.M.
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Assef, R.J.
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Baldi, R.D.
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Davies, R.I.
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Hönig, S.F.
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Ricci, C.
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Rosario, D.J.
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Salvato, M.
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Shankar, F.
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Stern, D.
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Asmus, D.
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Greenwell, C.L.
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Gandhi, P.
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Boorman, P.G.
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Aird, J.
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Alexander, D.M.
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Assef, R.J.
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Baldi, R.D.
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Davies, R.I.
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Hönig, S.F.
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Ricci, C.
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Rosario, D.J.
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Salvato, M.
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Shankar, F.
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Stern, D.
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Asmus, D., Greenwell, C.L., Gandhi, P., Boorman, P.G., Aird, J., Alexander, D.M., Assef, R.J., Baldi, R.D., Davies, R.I., Hönig, S.F., Ricci, C., Rosario, D.J., Salvato, M., 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), 1784–1816. (doi:10.1093/mnras/staa766).

Record type: Article

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(12μm)≥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(2−10keV)≥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.

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More information

Accepted/In Press date: 12 March 2020
e-pub ahead of print date: 18 March 2020
Published date: May 2020

Identifiers

Local EPrints ID: 441751
URI: http://eprints.soton.ac.uk/id/eprint/441751
ISSN: 0035-8711
PURE UUID: 10bb7242-ecb0-4974-85d8-c99f536324e9
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615
ORCID for P.G. Boorman: ORCID iD orcid.org/0000-0001-9379-4716

Catalogue record

Date deposited: 25 Jun 2020 16:48
Last modified: 07 Oct 2020 02:06

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Contributors

Author: D. Asmus
Author: C.L. Greenwell
Author: P. Gandhi ORCID iD
Author: P.G. Boorman ORCID iD
Author: J. Aird
Author: D.M. Alexander
Author: R.J. Assef
Author: R.D. Baldi
Author: R.I. Davies
Author: S.F. Hönig
Author: C. Ricci
Author: D.J. Rosario
Author: M. Salvato
Author: F. Shankar
Author: D. Stern

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