Detailed star formation histories in the outskirts of the Andromeda galaxy
by
Edouard Bernard(Institute for Astronomy, Royal Observatory Edinburgh)
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Europe/Stockholm
FA31
FA31
Description
In the past decade, very wide-field observations of the Andromeda galaxy have revealed that its outer disk and halo were dominated by substructure, in the form of streams, clumps and shelves. However, understanding the nature and origin of these structures is not straightforward from these observations alone. I will present the quantitative star formation history (SFH) of a dozen fields located in the outskirts of the Andromeda galaxy, calculated from deep HST/ACS color-magnitude diagrams. These fields probe different stellar substructures between 12 and 24 kpc in projected radius, and can be broadly separated into two categories based on their SFH: disk-like fields have formed about 65% of their mass since z~1 and resemble the stellar populations of the thin disk, while stream-like fields have generally older stars, similar to the populations of the Giant Stellar Stream. I will discuss the possible implications of these results for the interaction and merger history of the Andromeda galaxy.