Journal Article

Major dry mergers in early-type brightest cluster galaxies

F. S. Liu, Shude Mao, Z. G. Deng, X. Y. Xia and Z. L. Wen

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 4, pages 2003-2010
Published in print July 2009 | ISSN: 0035-8711
Published online July 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14907.x
Major dry mergers in early-type brightest cluster galaxies

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We search for ongoing major dry mergers in a well-selected sample of local brightest cluster galaxies (BCGs) from the C4 cluster catalogue. 18 out of 515 early-type BCGs with redshift between 0.03 and 0.12 are found to be in major dry mergers, which are selected as pairs (or triples) with r-band magnitude difference δmr < 1.5 and projected separation rp < 30 kpc, and showing signatures of interaction in the form of significant asymmetry in residual images. We find that the fraction of BCGs in major dry mergers increases with the richness of the clusters, consistent with the fact that richer clusters usually have more massive (or luminous) BCGs. We estimate that present-day early-type BCGs may have experienced on average ∼0.6 (tmerge/0.3 Gyr)−1 major dry mergers and through this process increases their luminosity (mass) by 15 per cent (tmerge/0.3 Gyr)−1 (fmass/0.5) on average since z= 0.7, where tmerge is the merging time-scale and fmass is the mean mass fraction of companion galaxies added to the central ones. We also find that major dry mergers do not seem to elevate radio activities in BCGs. Our study shows that major dry mergers involving BCGs in clusters of galaxies are not rare in the local Universe, and they are an important channel for the formation and evolution of BCGs.

Keywords: galaxies: clusters: general; galaxies: elliptical and lenticular, cD; galaxies: photometry

Journal Article.  5688 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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