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arXiv · 1504.02120

A Global Star Forming Episode in M31 2-4 Gyr Ago

Benjamin F. Williams·Julianne J. Dalcanton·Andrew E. Dolphin·Daniel R. Weisz·Alexia R. Lewis·Dustin Lang·Eric F. Bell·Martha Boyer·Morgan Fouesneau·Karoline M. Gilbert·Antonela Monachesi·Evan Skillman
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Abstract

We have identified a major global enhancement of star formation in the inner M31 disk that occurred between 2-4 Gyr ago, producing $\sim$60% of the stellar mass formed in the past 5 Gyr. The presence of this episode in the inner disk was discovered by modeling the optical resolved star color-magnitude diagrams of low extinction regions in the main disk of M31 (3$<$R$<$20 kpc) as part of the Panchromatic Hubble Andromeda Treasury. This measurement confirms and extends recent measurements of a widespread star formation enhancement of similar age in the outer disk, suggesting that this burst was both massive and global. Following the galaxy-wide burst, the star formation rate of M31 has significantly declined. We briefly discuss possible causes for these features of the M31 evolutionary history, including interactions with M32, M33 and/or a merger.

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Benjamin F. Williams, Julianne J. Dalcanton, Andrew E. Dolphin, Daniel R. Weisz, Alexia R. Lewis, Dustin Lang, Eric F. Bell, Martha Boyer, Morgan Fouesneau, Karoline M. Gilbert, Antonela Monachesi, Evan Skillman. 2015-04-08. A Global Star Forming Episode in M31 2-4 Gyr Ago. https://doi.org/10.1088/0004-637x%2F806%2F1%2F48

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