Testing galaxy formation scenarios with a new mass estimator

TL;DR

This paper introduces a new mass estimator for pressure-supported stellar systems, enabling tests of galaxy formation models across a wide luminosity range, revealing consistent halo masses for dwarf galaxies and a U-shaped mass-to-light ratio relation.

Contribution

It applies the Wolf et al. (2009) mass estimator to various stellar systems, providing new insights into their dark matter halos and the mass-to-light ratio trends across galaxy types.

Findings

Milky Way dwarf spheroidals formed in ~3 x 10^9 Msun halos.

Faint dwarf spheroidals have similar halo masses as brighter ones.

Mass-to-light ratio exhibits a U-shape across galaxy types.

Abstract

We present the recently derived Wolf et al. (2009) mass estimator, which is applicable for spherical pressure-supported stellar systems spanning over ten orders of magnitude in luminosity, as a tool to test galaxy formation theories. We show that all of the Milky Way dwarf spheroidal galaxies (MW dSphs) are consistent with having formed within a halo of mass approximately 3 x 10^9 Msun in LCDM cosmology. The faintest MW dSphs seem to have formed in dark matter halos that are at least as massive as those of the brightest MW dSphs, despite the almost five orders of magnitude spread in luminosity. We expand our analysis to the full range of observed pressure-supported stellar systems and examine their half-light I-band mass-to-light ratios. The M/L vs. half-light mass M_1/2 relation for pressure-supported galaxies follows a U-shape, with a broad minimum near M/L ~ 3 that spans dwarf elliptical galaxies to normal ellipticals, a steep rise to M/L ~ 3,200 for ultra-faint dSphs, and a more shallow rise to M/L ~ 800 for galaxy cluster spheroids.