EVOLUTION OF THE HIGH-MASS END OF THE STELLAR INITIAL MASS FUNCTIONS IN STARBURST GALAXIES

We investigate the time evolution and spatial variation of the stellar initial mass function (IMF) in star-forming disk galaxies by using chemodynamical simulations with an IMF model depending both on local densities and metallicities ([Fe/H]) of the interstellar medium (ISM). We find that the slope...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2013-03, Vol.765 (1), p.1-5
Main Authors: Bekki, Kenji, Meurer, Gerhardt R
Format: Article
Language:English
Subjects:
Approximation
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
DENSITY
Disk galaxies
EVOLUTION
FEEDBACK
GALAXIES
INTERACTIONS
LUMINOSITY
MASS
SIMULATION
Slopes
Star formation
SUPERNOVAE
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Summary:We investigate the time evolution and spatial variation of the stellar initial mass function (IMF) in star-forming disk galaxies by using chemodynamical simulations with an IMF model depending both on local densities and metallicities ([Fe/H]) of the interstellar medium (ISM). We find that the slope ( alpha ) of a power-law IMF (N(m) [proportional, variant] m super(- alpha )) for stellar masses larger than 1 M sub([middot in circle]) evolves from the canonical Salpeter IMF ( alpha [approximate] 2.35) to be moderately top-heavy one ( alpha [approximate] 1.9) in the simulated disk galaxies with starbursts triggered by galaxy interaction. We also find that alpha in star-forming regions correlates with star formation rate densities ( capital sigma sub(SFR) in units of M sub([middot in circle]) yr super(-1) kpc super(-2)). Feedback effects of Type Ia and II supernovae are found to prevent IMFs from being too top-heavy ( alpha < 1.5). The simulation predicts alpha [approximate] 0.23 log capital sigma sub(SFR) + 1.7 for log capital sigma sub(SFR) [> or =, slanted] -2 (i.e., more top-heavy in higher capital sigma sub(SFR)), which is reasonably consistent with corresponding recent observational results. The present study also predicts that inner regions of starburst disk galaxies have smaller alpha and thus are more top-heavy (d alpha /dR ~ 0.07 kpc super(-1) for R [< or =, slant] 5 kpc). The predicted radial alpha gradient can be tested against future observational studies of the alpha variation in star-forming galaxies.
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/765/1/L22