http://arxiv.org/abs/1705.08442
There is increasing observational and theoretical evidence for a tight correlation between the metallicity and total mass of accreted stellar halos for galaxies with Milky Way-like stellar masses. Using the Illustris cosmological hydrodynamical simulations, we explore this relationship for central galaxies spanning a broad range in dark matter halo masses. We find that there exists a general accreted metallicity-stellar mass relationship over 3 orders of magnitude in accreted stellar mass. This arises due to the accreted stellar metallicity being set by the dominant accreted progenitor, which also contributes the bulk of its stellar material. We show that the scatter in accreted metallicity at a fixed accreted stellar mass encodes information about the stellar mass of the dominant progenitor, while the density and metallicity gradients of the accreted stellar halo provides information about the time of accretion of the dominant progenitor. We demonstrate that the total accreted stellar metallicity and accreted stellar mass can be reconstructed from aperture measurements along the minor axis of edge-on disk galaxies. These correlations highlight the potential for observational studies of stellar halos to quantify our understanding of the most dominant events in the growth history of galaxies. We explore the implication of our models for our understanding of the accretion histories of the Milky Way, M31 and NGC 5128. In particular, a relatively late and massive accretion is favoured for M31; additionally, we provide a first estimate of the accreted stellar mass for NGC 5128.
R. DSouza and E. Bell
Wed, 24 May 17
67/70
Comments: 20 pages, submitted to MNRAS, Comments welcome