Colloquium

What can we learn about how the Milky Way and similar galaxies came to be?

With the advent of large surveys of stars in the Milky Way, it is becoming increasingly relevant to understand how the Milky Way fits in with the larger population of galaxies with similar broad scale characteristics (e.g., stellar mass). In this presentation, I discuss efforts to understand the growth history of galaxies of approximately Milky Way mass. I will start by critically examining studies of plausible Milky Way progenitors --- galaxies with similar comoving space density to Milky Way-mass galaxies at the present day --- with the aid of models of galaxy evolution in a cosmological context and the HST/CANDELS dataset. We have learned that scatter in the growth history of Milky Way mass galaxies may lead to considerable contamination and incompleteness in the pool of candidate 'Milky Way progenitors', and that diversity in the present-day galaxy population at Milky Way masses complicates interpretation of the evolution of average properties of plausible Milky Way progenitor galaxies as a function of redshift. I then discuss insights into the evolution of Milky Way mass galaxies which can be gleaned from their low density outskirts (i.e., their stellar halos), reporting on the considerable diversity of halos at masses comparable to the Milky Way's. We highlight the possible importance of both tidal disruption of satellites and the thickening/disruption of stellar disks from the same satellite accretion events in moving stars into the outer parts of galaxies.

Followed by wine and cheese in Pupin 1402

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