Oral Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Galaxy and Mass Assembly (GAMA): Testing galaxy formation models through the most massive objects in the universe (#6)

Paola Oliva-Altamirano 1 , Sarah Brough 2 , Chris Lidman 2 , Warrick Couch 1 , Edward Taylor 3
  1. Swinburne University of Technology, Hawthorn east, VIC, Australia
  2. Australian Astronomical Observatory, Sydney, Australia
  3. University of Melbourne, Melbourne, VIC, Australia
Brightest Cluster Galaxies (BCGs) represent the most luminous systems known at present epochs. The extent to which such extreme galaxies have acquired their particular properties from their privileged location at the centres of clusters and/or their high density environment is of key astrophysical interest. Unfortunately, the assembly history and evolution of these giant galaxies is still poorly understood.

We analyse the growth of BCGs in the last 3.5 billion years using a large sample from the Galaxy and Mass Assembly Survey (GAMA), 1220 BCGs/BGGs, and compare our results with the Semi-Analytic Models (SAMs) of De Lucia \& Blaizot (2007) and Tonini et al. (2012). The growth is analyse taking into account the BCG Stellar Mass-Halo Mass correlation, in other words, we compare the BCG stellar mass of like-to-like clusters. We find no significant growth between redshifts 0.3 and 0, whereas SAMs predict that BCGs have acquired 30\% of their stellar mass over this period of cosmic time. 
We also examine the position of the BCGs with respect to their Dark Matter Halo and find that around 14\% of the BCGs are not lying at the centre of the dark matter halo potential well and this could be an indicator of recent cluster mergers. In a further analysis, we find that around 40\% of the BCGs harbor on-going star formation, with rates in a range 0-4 M$_{\odot}$ per year, in agreement with the new recipes used in Tonini et al. (2012). While BCGs might not be completely dormant, the fraction of their mass being converted into new stars is still very low.