Oral Presentation

Using member galaxy luminosities as halo mass proxies of galaxy groups

Yi Lu (SHAO)

Reliable halo mass estimation for a given galaxy system plays an important
role both in cosmology and galaxy formation studies. Here we set out to
find the way that can improve the halo mass estimation for those galaxy
systems with limited brightest member galaxies been observed. Using four
mock galaxy samples constructed from semi-analytical formation models, the
subhalo abundance matching method and the conditional luminosity functions,
respectively, we find that the luminosity gap between the brightest and the
second brightest member galaxies in a halo (group) can be used to
significantly reduce the scatter in the halo mass estimation based on the
luminosity of the brightest galaxy alone. Further studies about luminosity
gaps between the brightest and the other fainter member galaxies show somewhat
enhanced effect: involving more fainter member galaxies can give slightly
tighter relationship between halo mass and brightest galaxies in a group.
Fitting formulae as a function of brightest galaxy luminosity and luminosity
gaps are provided to correct for the halo mass estimations. Tests show that
these corrections can significantly reduce the error in the halo mass
estimations by $\sim 50\%$ to $\sim 70\%$ in massive halos depending on
which member galaxies are considered.