University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Monday, November 24th 2014
12:15 pm:
Speaker: Annalisa Pillepich, Center for Astrophysics
Subject: New insights on the Stellar Haloes and the Assembly of Galaxies with Eris and the Illustris Simulations

Can we theoretically predict the imprint of different accretion, merger and star formation histories on the stellar components of galaxies, across a wide range of galaxy masses and types? Can we reliably reconstruct the assembly of our Galaxy from the distribution and properties of the stellar mass across its halo, in light of the upcoming, exquisitely detailed stellar maps of the Milky Way e.g. with Rave and Gaia?
To these aims, I use state-of-the-art numerical simulations of individual galaxies (the Eris Simulation) and large cosmological volumes (the Illustris Simulation) to gain insight on the build up of galaxies, with particular focus on their lowest surface brightness components - the stellar haloes - and on Milky-Way-like objects.
For example, in the first work of a series based on ~5’000 Illustris galaxies spanning a variety of morphologies and halo masses (3×10^11 < Mvir < 10^14 Msun), we show that the solely logarithmic slope of the 3D stellar halo density profile encodes a plethora of quantitative information. We find a strong trend between stellar halo slope and total halo mass, where more massive objects have shallower stellar haloes than the less massive ones. At fixed halo mass, disk-like, blue, young, and more massive galaxies are surrounded by significantly steeper stellar haloes than elliptical, red, older, and less massive galaxies. Finally, DM haloes which formed more recently, or which accreted larger fractions of stellar mass from infalling satellites, exhibit shallower stellar haloes than their older analogs with similar masses. Our findings, combined with the most recent measurements of the strikingly different stellar power-law indexes for M31 and the Milky Way, appear to favor a massive M31, and a Milky Way characterized by a much quieter accretion history over the past 10 Gyrs than its companion.

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