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Constraining AGN triggering mechanisms through the clustering analysis of active black holes

Constraining AGN triggering mechanisms through the clustering analysis of active black holes
Constraining AGN triggering mechanisms through the clustering analysis of active black holes
The triggering mechanisms for active galactic nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disc instabilities (DIs). Using an advanced semi-analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modelling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: (i) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the centre of haloes with Mh > 1013.5?h?1?M?. On the contrary, the IT scenario predicts abundance of active central galaxies that generally agrees well with observations at every halo mass. (ii) The relative number of satellite AGN in DIs at intermediate-to-low luminosities is always significantly higher than in IT models, especially in groups and clusters. The low AGN satellite fraction predicted for the IT scenario might suggest that different feeding modes could simultaneously contribute to the triggering of satellite AGN. (iii) Both scenarios are quite degenerate in matching large-scale clustering measurements, suggesting that the sole average bias might not be an effective observational constraint. (iv) Our analysis suggests the presence of both a mild luminosity and a more consistent redshift dependence in the AGN clustering, with AGN inhabiting progressively less massive dark matter haloes as the redshift increases. We also discuss the impact of different observational selection cuts in measuring AGN clustering, including possible discrepancies between optical and X-ray surveys.
0035-8711
1073-1092
Gatti, M.
be9e1f3e-3cb4-4cc3-9d64-01bc9547d290
Shankar, F.
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Boillot, V.
89921bb7-a68b-48a2-9123-7bf3af1d8baf
Menci, N.
ccf9bf08-c993-4e53-9b2c-fc2f71a57698
Lamastra, A.
3f85bac3-f39c-46ce-9934-78214faef6e7
Hirschmann, M.
f17a9f7e-058a-40a9-8391-befe977c8670
Fiore, F.
7178d030-3909-4d1d-9334-720d219b0634
Gatti, M.
be9e1f3e-3cb4-4cc3-9d64-01bc9547d290
Shankar, F.
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Boillot, V.
89921bb7-a68b-48a2-9123-7bf3af1d8baf
Menci, N.
ccf9bf08-c993-4e53-9b2c-fc2f71a57698
Lamastra, A.
3f85bac3-f39c-46ce-9934-78214faef6e7
Hirschmann, M.
f17a9f7e-058a-40a9-8391-befe977c8670
Fiore, F.
7178d030-3909-4d1d-9334-720d219b0634

Gatti, M., Shankar, F., Boillot, V., Menci, N., Lamastra, A., Hirschmann, M. and Fiore, F. (2016) Constraining AGN triggering mechanisms through the clustering analysis of active black holes. Monthly Notices of the Royal Astronomical Society, 456 (1), 1073-1092. (doi:10.1093/mnras/stv2754).

Record type: Article

Abstract

The triggering mechanisms for active galactic nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disc instabilities (DIs). Using an advanced semi-analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modelling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: (i) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the centre of haloes with Mh > 1013.5?h?1?M?. On the contrary, the IT scenario predicts abundance of active central galaxies that generally agrees well with observations at every halo mass. (ii) The relative number of satellite AGN in DIs at intermediate-to-low luminosities is always significantly higher than in IT models, especially in groups and clusters. The low AGN satellite fraction predicted for the IT scenario might suggest that different feeding modes could simultaneously contribute to the triggering of satellite AGN. (iii) Both scenarios are quite degenerate in matching large-scale clustering measurements, suggesting that the sole average bias might not be an effective observational constraint. (iv) Our analysis suggests the presence of both a mild luminosity and a more consistent redshift dependence in the AGN clustering, with AGN inhabiting progressively less massive dark matter haloes as the redshift increases. We also discuss the impact of different observational selection cuts in measuring AGN clustering, including possible discrepancies between optical and X-ray surveys.

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Accepted/In Press date: 19 November 2015
e-pub ahead of print date: 18 December 2015
Published date: 11 February 2016
Organisations: Astronomy Group

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Local EPrints ID: 394759
URI: http://eprints.soton.ac.uk/id/eprint/394759
ISSN: 0035-8711
PURE UUID: 89b58620-983d-4a5e-aa2d-0d73948bd3ae

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Date deposited: 24 May 2016 09:00
Last modified: 16 Dec 2019 19:55

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