How much dark matter is there inside early-type galaxies?

Abstract

We study the luminous mass as a function of the dynamical mass inside the effective radius (r_e) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. 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 perform Monte Carlo (MC) simulations of galaxy samples and compare them with real samples. The main results are: i) MC simulations show that the distribution of the dynamical vs. luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is approximately 7% +- 22%. iii) This amount of dark matter is lower than the minimum estimate (10%) found in the literature and four times lower than the average (30%) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.

24 pages, 12 figures. MNRAS accepted

References in corpus (7)

• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• A systematic variation of the stellar initial mass function in early-type galaxies
• Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies
• Curvature in the scaling relations of early-type galaxies
• The Baryon Fractions and Mass-to-Light Ratios of Early-Type Galaxies
• The Kormendy Relation for early-type galaxies. Dependence on the magnitude range
• The Fundamental Plane for early-type galaxies. Dependence on the magnitude range

Cited by in corpus (3)

• Dark matter in galaxies
• Dark matter inside early-type galaxies as function of mass and redshift
• The quantity of dark matter in early-type galaxies and its relation to the environment