Lingjian Chen

Saint Mary’s University

My research is a galactic environment study. Dense galactic environment, such as galaxy groups and clusters, are thought to be formed through hierarchical mergers. The spatial distribution of satellite galaxies can be a good indicator of galaxy evolution in such an environment. We study the radial distribution of satellites around isolated massive central galaxies using data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP) and the CFHT Large Area U-band Deep Survey (CLAUDS). Thanks to the large area, 6-band photometry, and good depth of the combined survey, we were able to identify ~5000 centrals in a redshift range of. 0.3<z<0.9 and also identify satellites around them down to the stellar mass of 10^9.5 solar mass. Our results show that satellite number density distribution can be described by an NFW profile (Navarro+1995, usually for mass density profile in dark matter halos) on scales greater than 100 kpc but deviates from it within that scale. This feature is seen out to z=0.9, it was previously found in studies at low redshift (e.g. Tal+2012). We have also investigated the dependence of the distribution on satellite and central properties such as mass and star-forming level. We concluded that the mechanism of shaping satellite distribution can probably be related to a combination of dynamic friction and tidal stripping when they are orbiting in the dark matter halo, but more detailed simulation or modeling are needed to understand better the physical process.

This shows our satellite galaxy selection. Central galaxy is indicated by the yellow circle, potential satellites are circled in green, and red circle indicates our selection radius for satellites (700kpc). Central galaxies were identified by mass and isolation criteria. Satellites were selected by photo-z difference and a circular aperture (basically a cylindrical selection centred on central galaxy). Number of satellites selected here were then corrected for contaminating background objects.

This shows surface number density of satellite galaxies (averaged) around one central galaxy, after correction for background objects. The solid line is the best fit curve and can be separated into NFW component on large scale and Sersic component on small scale (dotted and dashed lines).