Stellar populations of stellar halos: Results from the Illustris simulation

Abstract

The influence of both major and minor mergers is expected to significantly affect gradients of stellar ages and metallicities in the outskirts of galaxies. Measurements of observed gradients are beginning to reach large radii in galaxies, but a theoretical framework for connecting the findings to a picture of galactic build-up is still in its infancy. We analyze stellar populations of a statistically representative sample of quiescent galaxies over a wide mass range from the Illustris simulation. We measure metallicity and age profiles in the stellar halos of quiescent Illustris galaxies ranging in stellar mass from $10^{10}$ to $10^{12}{M}_{\odot }$, accounting for observational projection and luminosity-weighting effects. We find wide variance in stellar population gradients between galaxies of similar mass, with typical gradients agreeing with observed galaxies. We show that, at fixed mass, the fraction of stars born in-situ within galaxies is correlated with the metallicity gradient in the halo, confirming that stellar halos contain unique information about the build-up and merger histories of galaxies.

6 pages, 2 figures, proceedings of IAU Symposium 317: "The General Assembly of Galaxy Halos: Structure, Origin and Evolution"

References in corpus (11)

• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• Properties of galaxies reproduced by a hydrodynamic simulation
• Introducing the Illustris Project: the evolution of galaxy populations across cosmic time
• The merger rate of galaxies in the Illustris Simulation: a comparison with observations and semi-empirical models
• The accretion origin of the Milky Way's stellar halo
• Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies
• Synthetic Galaxy Images and Spectra from the Illustris Simulation
• First results from the Dragonfly Telephoto Array: the apparent lack of a stellar halo in the massive spiral galaxy M101
• The stellar accretion origin of stellar population gradients in massive galaxies at large radii
• The SLUGGS survey: Exploring the metallicity gradients of nearby early-type galaxies to large radii
• Systematic Problems With Using Dark Matter Simulations to Model Stellar Halos