The quantity of dark matter in early-type galaxies and its relation to the environment

Abstract

We study the behavior of the dynamical and stellar mass inside the effective radius of early-type galaxies (ETGs) as a function of environment considering Newtonian dynamics, different surface--brightness profiles, different initial mass functions (IMF) and different redshift ranges. We use several samples of ETGs --ranging from 19,000 to 98,000 objects-- from the ninth data release of the Sloan Digital Sky Survey. We assume that any difference between the dynamical and stellar mass is due to dark matter and/or a non-universal IMF. The main results, considering samples in the redshift range 0.0024 $\le z\le$ 0.35 are: (i) the amount of dark matter inside ETGs depends on the environment; (ii) ETGs in low density environments span a wider dark matter range than ETGs in dense environments; (iii) the amount of dark matter inside ETGs in the most dense environments will be less than approximately 55\%--75\% of the dynamical mass; (iv) the accurate value of this upper limit depends on the impact of the IMF on the stellar mass estimation; (v) in the case of an ETGs sample which is approximately complete for log$({\mathbf{M}}_{\mathbf{Virial}}/{\mathbf{M}}_{\mathbf{Sun}})>10.5$ and in the redshift range 0.04 $\le z\le$ 0.08 we find that the amount of dark matter in the most dense environments will be less than approximately 60\%--65\% of the dynamical mass.

15 pages, 7 figures. Accepted by MNRAS

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Cited by in corpus (5)

• On the environmental influence of groups and clusters of galaxies beyond the virial radius: Galactic conformity at few Mpc scales
• Inferring galaxy dark halo properties from visible matter with Machine Learning
• The central dark matter fraction of massive early-type galaxies
• Late growth of early-type galaxies in low-z massive clusters
• Dynamics of Companion Galaxies of Early-Type Galaxies