AuthorWilliams, Benjamin F.
Dolphin, Andrew E.
Dalcanton, Julianne J.
Weisz, Daniel R.
Bell, Eric F.
Lewis, Alexia R.
AffiliationUniv Arizona, Steward Observ
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationPHAT. XIX. The Ancient Star Formation History of the M31 Disk 2017, 846 (2):145 The Astrophysical Journal
JournalThe Astrophysical Journal
Rights© 2017. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractWe map the star formation history across M31 by fitting stellar evolution models to color-magnitude diagrams of each 83 '' x 83 '' (0.3 x 1.4 kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost 6' x 12' portion. We find that most of the star formation occurred prior to similar to 8 Gyr ago, followed by a relatively quiescent period until similar to 4 Gyr ago, a subsequent star formation episode about 2 Gyr ago, and a return to relative quiescence. There appears to be little, if any, structure visible for populations with ages older than 2 Gyr, suggesting significant mixing since that epoch. Finally, assuming a Kroupa initial mass function from 0.1 to 100 M-circle dot, we find that the total amount of star formation over the past 14 Gyr in the area over which we have fit models is 5 x 10(10) M-circle dot. Fitting the radial distribution of this star formation and assuming azimuthal symmetry, (1.5 +/- 0.2). x 10(11) M-circle dot of stars has formed in the M31 disk as a whole, (9 +/- 2) x 10(10). M-circle dot of which has likely survived to the present after accounting for evolutionary effects. This mass is about one-fifth of the total dynamical mass of M31.
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