THE HIGH-MASS STELLAR INITIAL MASS FUNCTION IN M31 CLUSTERS

We have undertaken the largest systematic study of the high-mass stellar initial mass function (IMF) to date using the optical color-magnitude diagrams (CMDs) of 85 resolved, young (4 Myr < t < 25 Myr), intermediate mass star clusters (10 super(3)-10 super(4) M sub([middot in circle])), observ...

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Bibliographic Details
Published in:The Astrophysical journal 2015-06, Vol.806 (2), p.1-13
Main Authors: Weisz, Daniel R, Johnson, L Clifton, eman-Mackey, Daniel, Dolphin, Andrew E, Beerman, Lori C, Williams, Benjamin F, Dalcanton, Julianne J, Rix, Hans-Walter, Hogg, David W, Fouesneau, Morgan
Format: Article
Language:English
Subjects:
AGE DEPENDENCE
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Clusters
COMPUTERIZED SIMULATION
Galaxies
Initial mass function
Local group (astronomy)
LUMINOSITY
MASS
MASS SPECTRA
Mathematical models
MILKY WAY
Slopes
STAR CLUSTERS
STARS
UNIVERSE
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Summary:We have undertaken the largest systematic study of the high-mass stellar initial mass function (IMF) to date using the optical color-magnitude diagrams (CMDs) of 85 resolved, young (4 Myr < t < 25 Myr), intermediate mass star clusters (10 super(3)-10 super(4) M sub([middot in circle])), observed as part of the Panchromatic Hubble Andromeda Treasury program. The lack of an age dependence suggests that the MF slope has not significantly evolved over the first ~25 Myr and provides direct observational evidence that the measured MF represents the IMF. Taken together, this analysis-based on an unprecedented large sample of young clusters, homogeneously constructed CMDs, well-defined selection criteria, and consistent principled modeling-implies that the high-mass IMF slope in M31 clusters is universal. The increased steepness in the M31 high-mass IMF slope implies that commonly used UV- and H alpha -based star formation rates should be increased by a factor of ~1.3-1.5 and the number of stars with masses >8 M sub([middot in circle]) is ~25% fewer than expected for a Salpeter/Kroupa IMF.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/806/2/198