The halo concentration and mass relation traced by satellite galaxies

TL;DR

This study uses SDSS data to analyze the relation between dark matter halo concentration and mass by fitting satellite galaxy distributions, confirming an anti-correlation consistent with cosmological simulations.

Contribution

It provides a new observational measurement of the c-M relation over a wide mass range using satellite galaxy profiles from SDSS data.

Findings

Confirmed the anti-correlation between halo mass and concentration.

Results agree with galaxy dynamics and lensing for lower mass halos.

Red satellites are better tracers of dark matter distribution.

Abstract

We study the relation between halo concentration and mass (c-M relation) using the Seventh and Eighth Data Release of the Sloan Digital Sky Survey (SDSS DR7 and DR8) galaxy catalogue. Assuming that the satellite galaxies follow the distribution of dark matter, we derive the halo concentration by fitting the satellite radial profile with a Nararro Frank and White (NFW) format. The derived c-M relation covers a wide halo mass range from $10^{11.6}$ to $10^{14.1} \rm\ M_\odot$. We confirm the anti-correlation between the halo mass and concentration as predicted in cosmological simulations. Our results are in good agreement with those derived using galaxy dynamics and gravitational lensing for halos of $10^{11.6}-10^{12.9} \rm\ M_\odot$, while they are slightly lower for halos of $10^{12.9}-10^{14.1}\rm\ M_\odot$. It is because blue satellite galaxies are less concentrated, especially in the inner regions. Instead of using all satellite galaxies, red satellites could be better tracers of the underlying dark matter distribution in galaxy groups.