Heavier galaxies cluster more in denser regions of the Universe

The near-infrared 6dF Galaxy Survey (6dFGS; UK Schmidt Telescope in Siding Spring Observatory) is one of the largest (76,833 galaxies) and most complete (92% on average) galaxy surveys to study galaxy formation in the local Universe (median redshift of z = 0.05). A team of researchers in Australia and the US used 6dFGS data to analyse how the clustering of galaxies depends on stellar mass (Monthly Notices of the Royal Astronomical Society 429). Clustering was estimated relative to a random, unclustered distribution which followed the same angular and redshift selection function as the galaxy sample. Selecting four volume-limited sub-samples of 6dFGS galaxies, they found that more massive dark matter halos tend to host galaxies with higher stellar mass.

Ex-ICRAR/UWA PhD student Florian Beutler and his supervisors, CAASTRO Chief Investigators Chris Blake and Lister Staveley-Smith, and other colleagues further examined the relationship between dark matter halo mass and satellite galaxies. Using the Halo Occupation Distribution model, they determined that the satellite fraction of 6dFGS galaxies declines with increasing stellar mass. In their simulations, only those dark matter halos that already contained a central galaxy could host a satellite galaxy.

The researchers also tested the predictions made by previously published models (‘Munich model’ by Croton et al. 2006 and ‘Durham model’ by Bower et al. 2006) that are based on the ‘Millennium Simulation’ and take gas cooling, star formation, and feedback processes into account. All of the ‘mock’ 6dFGS catalogues created by these two models contained about 40% fewer galaxies than the real data with ‘Munich’ under-predicting and ‘Durham’ slightly over-predicting the satellite fraction.

Publication details:

F. Beutler, C. Blake, M. Colless, D. H. Jones, L. Staveley-Smith, L. Campbell, Q. Parker, W. Saunders, F. Watson in MNRAS 429 "The 6df Galaxy Survey: Dependence of halo occupation on stellar mass"