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Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?

Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?
Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?
Which mechanism(s) are mainly driving nuclear activity in the centres of galaxies is a major unsettled question. In this study, we investigate the statistical relevance of galaxy mergers for fuelling gas onto the central few kpc of a galaxy, potentially resulting in an active galactic nucleus (AGN). To robustly address that, we employ large-scale cosmological hydrodynamic simulations from the Magneticum Pathfinder set, including models for black hole accretion and AGN feedback. Our simulations predict that for luminous AGN (LAGN >1045ergs−1) at z = 2, more than 50 per cent of their host galaxies have experienced a merger in the last 0.5 Gyr. These high merger fractions, however, merely reflect the intrinsically high merger fractions of massive galaxies at z = 2, in which luminous AGN preferentially occur. Apart from that, our simulations suggest that merger events are not the statistically dominant fuelling mechanism for nuclear activity over a redshift range z = 0 − 2: irrespective of AGN luminosity, less than 20 per cent of AGN hosts have on average undergone a recent merger, in agreement with a number of observational studies. The central interstellar medium conditions required for inducing AGN activity can be, but are not necessarily caused by a merger. Despite the statistically minor relevance of mergers, at a given AGN luminosity and stellar mass, the merger fractions of AGN hosts can be by up to three times higher than that of inactive galaxies. Such elevated merger fractions still point towards an intrinsic connection between AGN and mergers, consistent with our traditional expectation.
0035-8711
341-360
Steinborn, Lisa K
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Hirschmann, Michaela
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Dolag, Klaus
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Shankar, Francesco
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Juneau, Stéphanie
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Krumpe, Mirko
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Remus, Rhea-silvia
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Teklu, Adelheid F
a6d7aeaa-2574-41cb-a279-bf8508b8c4bd
Steinborn, Lisa K
6c73c808-0848-468e-87e8-5daba5a324d9
Hirschmann, Michaela
a3004aff-e242-49d0-890c-aff36446c037
Dolag, Klaus
d2a1346f-d354-4ab4-b4cb-b428acbc81e3
Shankar, Francesco
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Juneau, Stéphanie
7dd27837-dc12-4eec-85a1-fdf13e70a3a4
Krumpe, Mirko
247403ee-f0cb-47e0-bda7-1d3c193b22a8
Remus, Rhea-silvia
68cd8bb2-c7fb-4a07-a295-e8030137a322
Teklu, Adelheid F
a6d7aeaa-2574-41cb-a279-bf8508b8c4bd

Steinborn, Lisa K, Hirschmann, Michaela, Dolag, Klaus, Shankar, Francesco, Juneau, Stéphanie, Krumpe, Mirko, Remus, Rhea-silvia and Teklu, Adelheid F (2018) Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity? Monthly Notices of the Royal Astronomical Society, 481 (1), 341-360. (doi:10.1093/mnras/sty2288).

Record type: Article

Abstract

Which mechanism(s) are mainly driving nuclear activity in the centres of galaxies is a major unsettled question. In this study, we investigate the statistical relevance of galaxy mergers for fuelling gas onto the central few kpc of a galaxy, potentially resulting in an active galactic nucleus (AGN). To robustly address that, we employ large-scale cosmological hydrodynamic simulations from the Magneticum Pathfinder set, including models for black hole accretion and AGN feedback. Our simulations predict that for luminous AGN (LAGN >1045ergs−1) at z = 2, more than 50 per cent of their host galaxies have experienced a merger in the last 0.5 Gyr. These high merger fractions, however, merely reflect the intrinsically high merger fractions of massive galaxies at z = 2, in which luminous AGN preferentially occur. Apart from that, our simulations suggest that merger events are not the statistically dominant fuelling mechanism for nuclear activity over a redshift range z = 0 − 2: irrespective of AGN luminosity, less than 20 per cent of AGN hosts have on average undergone a recent merger, in agreement with a number of observational studies. The central interstellar medium conditions required for inducing AGN activity can be, but are not necessarily caused by a merger. Despite the statistically minor relevance of mergers, at a given AGN luminosity and stellar mass, the merger fractions of AGN hosts can be by up to three times higher than that of inactive galaxies. Such elevated merger fractions still point towards an intrinsic connection between AGN and mergers, consistent with our traditional expectation.

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Cosmological simulations of black hole growth II: How (in)significant are merger events for fuelling nuclear activity? - Accepted Manuscript
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Accepted/In Press date: 15 August 2018
e-pub ahead of print date: 23 August 2018
Published date: 21 November 2018

Identifiers

Local EPrints ID: 425562
URI: http://eprints.soton.ac.uk/id/eprint/425562
ISSN: 0035-8711
PURE UUID: b8bee113-c209-4905-8172-a17cedf06508

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Date deposited: 24 Oct 2018 16:30
Last modified: 25 Nov 2021 22:37

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Contributors

Author: Lisa K Steinborn
Author: Michaela Hirschmann
Author: Klaus Dolag
Author: Stéphanie Juneau
Author: Mirko Krumpe
Author: Rhea-silvia Remus
Author: Adelheid F Teklu

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