Journal Article

On merger bias and the clustering of quasars

Silvia Bonoli, Francesco Shankar, Simon D. M. White, Volker Springel and J. Stuart B. Wyithe

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 1, pages 399-408
Published in print May 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI:
On merger bias and the clustering of quasars

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We use the large catalogues of haloes available for the Millennium Simulation to test whether recently merged haloes exhibit stronger large-scale clustering than other haloes of the same mass. This effect could help us to understand the very strong clustering of quasars at high redshift. However, we find no statistically significant excess bias for recently merged haloes over the redshift range 2 ≤z≤ 5, with the most massive haloes showing an excess of at most ∼5 per cent. We also consider galaxies extracted from a semi-analytic model built on the Millennium Simulation. At fixed stellar mass, we find an excess bias of ∼20–30 per cent for recently merged objects, decreasing with increasing stellar mass. The fact that recently merged galaxies are found in systematically more massive subhaloes than other galaxies of the same stellar mass accounts for about half of this signal, and perhaps more for high-mass galaxies. The weak merger bias of massive systems suggests that objects of merger-driven nature do not cluster significantly differently from other objects of the same characteristic mass over the range 5 < r < 25 h−1 Mpc. We discuss the implications of these results for the interpretation of quasar clustering data with respect to quasar duty cycles, visibility times and evolution in the black hole–host mass relation.

Keywords: galaxies: formation; galaxies: high-redshift; quasars: general; cosmology: theory; dark matter

Journal Article.  8236 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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