PHAT. XIX. The Ancient Star Formation History of the M31 Disk

We map the star formation history across M31 by fitting stellar evolution models to color-magnitude diagrams of each 83″ × 83″ (0.3 × 1.4 kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost portion. We find that most of the star formation occ...

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Bibliographic Details
Published inThe Astrophysical journal Vol. 846; no. 2; pp. 145 - 180
Main Authors Williams, Benjamin F., Dolphin, Andrew E., Dalcanton, Julianne J., Weisz, Daniel R., Bell, Eric F., Lewis, Alexia R., Rosenfield, Philip, Choi, Yumi, Skillman, Evan, Monachesi, Antonela
Format Journal Article
LanguageEnglish
Published Philadelphia The American Astronomical Society 10.09.2017
IOP Publishing
Subjects
Andromeda Galaxy
Astronomical models
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
GALAXIES
galaxies: evolution
galaxies: individual (M31)
galaxies: stellar content
Initial mass function
MASS
Radial distribution
SPATIAL DISTRIBUTION
Star & galaxy formation
STAR EVOLUTION
Star formation
STARS
Stars & galaxies
Stellar evolution
Stellar models
SYMMETRY
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Summary:We map the star formation history across M31 by fitting stellar evolution models to color-magnitude diagrams of each 83″ × 83″ (0.3 × 1.4 kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost portion. We find that most of the star formation occurred prior to ∼8 Gyr ago, followed by a relatively quiescent period until ∼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 , 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 × 1010 M . Fitting the radial distribution of this star formation and assuming azimuthal symmetry, (1.5 0.2) × 1011 M of stars has formed in the M31 disk as a whole, (9 2) × 1010 M 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.
Bibliography:Galaxies and Cosmology
AAS05203
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aa862a