Wolf-Rayet Galaxies in the Sloan Digital Sky Survey: the metallicity dependence of the initial mass function

Abstract

We use a large sample of 174 Wolf-Rayet (WR) galaxies drawn from the Sloan Digital Sky Survey to study whether and how the slope of the stellar initial mass function depends on metallicity. We calculate for each object its oxygen abundance according to which we divide our sample into four metallicity subsamples. For each subsample, we then measure three quantities: the equivalent width of \hb emission line, the equivalent width of WR bump around 4650Å, and the WR bump-to-\hb intensity ratio, and compare to the predictions of the same quantities by evolutionary synthesis models of Schaerer & Vacca. Such comparisons lead to a clear dependence of the slope of initial mass function ($\alpha$) on metallicity in that galaxies at higher metallicities tend to have steeper initial mass functions, with the slope index ranging from $\alpha \sim$1.00 for the lowest metallicity of $Z=0.001$ to $\alpha \sim$3.30 for the highest metallicity $Z=0.02$. We have carefully examined the possible sources of systematic error either in models or in our observational measurements and shown that these sources do not change this result.

12 pages, 6 figures, ApJ accepted

References in corpus (1)

• Balmer and Paschen jump temperature determinations in low-metallicity emission-line galaxies

Cited by in corpus (6)

• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• The galaxy-wide stellar initial mass function in the presence of cluster-to-cluster IMF variations
• Wolf-Rayet galaxies in SDSS-IV MaNGA. II. Metallicity dependence of the high-mass slope of the stellar initial mass function
• Witnessing a Transformation to Blue-cored Dwarf Early-type Galaxies in Filaments and the Cluster Outskirts: Gas-phase Abundances and Internal Kinematics Perspectives
• Massive stars in the nuclei and arms of spirals
• Clustering Property of Wolf-Rayet Galaxies in the SDSS