Speaker
Description
The Conditional Colour-Magnitude Distribution (CCMD) is a comprehensive model of the colour-magnitude-halo mass distribution of present day galaxies. It reproduces well the observed galaxy abundance and clustering of galaxies defined by arbitrary luminosity and colour cuts. We present a comprehensive comparison of the galaxy colour--magnitude--halo mass relation from the CCMD galaxy mocks and from the galaxy group catalogues of the Sloan Digital Sky Survey DR7. When the same galaxy group finder is applied to both the mocks and data, the same systematic errors in group-finding and mass assignment are inherited to both the resulting CCMD groups and SDSS groups. We adopt two group finders to eliminate any potential dependence of comparison on the group finder. Regardless of which group finder is used, we find nice agreement in the conditional luminosity function, the conditional colour function, and the conditional colour-magnitude distribution inferred from the CCMD and SDSS group catalogues, suggesting that the CCMD mocks are accurate representations of the reality in terms of galaxy colour and luminosity.Within two external central galaxy catalogues whose host halo mass has been calibrated by galaxy lensing measurements, we find their colour-magnitude distribution showing two distinct and orthogonal components, in line with the prediction of the CCMD model. The CCMD galaxy mocks provide the ideal control samples for accessing the statistical significance of any inference from group catalogues.The halo and CCMD mock catalogues are available to the public.
