Initial mass function variability from the integrated light of diverse stellar systems
Monthly Notices of the Royal Astronomical Society, vol. 526, pp. 4004–4023
Abstract
ABSTRACT We present a uniform analysis of the stellar initial mass function (IMF) from integrated light spectroscopy of 15 compact stellar systems (11 globular clusters in M31 and 4 ultra compact dwarfs in the Virgo cluster, UCDs) and two brightest Coma cluster galaxies (BCGs), covering a wide range of metallicities (−1.7 < [Fe/H] < 0.01) and velocity dispersions (7.4 km s−1 <σ < 275 km s−1). The S/N ∼100 Å−1 Keck LRIS spectra are fitted over the range 4000 < λ/Å < 10 000 with flexible full-spectrum stellar population synthesis models. We use the models to fit simultaneously for ages, metallicities, and individual elemental abundances of the population, allowing us to decouple abundance variations from variations in IMF slope. We show that compact stellar systems do not follow the same trends with physical parameters that have been found for early-type galaxies. Most globular clusters in our sample have an IMF consistent with that of the Milky Way, over a wide range of [Fe/H] and [Mg/Fe]. There is more diversity among the UCDs, with some showing evidence for a bottom-heavy IMF, but with no clear correlation with metallicity, abundance, or velocity dispersion. The two Coma BCGs have similar velocity dispersion and metallicity, but we find the IMF of NGC 4874 is consistent with that of the Milky Way while NGC 4889 presents evidence for a significantly bottom-heavy IMF. For this sample, the IMF appears to vary between objects in a way that is not explained by a single metallicity-dependent prescription.
Authors 7
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Leiden University · University of Waterloo · Leiden Observatory
Affiliation as printed
Department of Physics and Astronomy, University of Waterloo , Waterloo, Ontario N2L 3G1 , Canada
Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden , The Netherlands
Waterloo Centre for Astrophysics, University of Waterloo , Waterloo, Ontario N2L 3G1 , Canada
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Affiliation as printed
Department of Physics and Astronomy, University of Waterloo , Waterloo, Ontario N2L 3G1 , Canada
Waterloo Centre for Astrophysics, University of Waterloo , Waterloo, Ontario N2L 3G1 , Canada
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Affiliation as printed
Department of Physics and Astronomy, University of Waterloo , Waterloo, Ontario N2L 3G1 , Canada
Waterloo Centre for Astrophysics, University of Waterloo , Waterloo, Ontario N2L 3G1 , Canada
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University of California, Santa Cruz · University of California Observatories · Swinburne University of Technology
Affiliation as printed
Centre for Astrophysics and Supercomputing, Swinburne University of Technology , 1 John St, Hawthorn VIC 3122 , Australia
University of California Observatories, University of California , Santa Cruz, CA 95060 , USA
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Universidad de La Laguna · Instituto de Astrofísica de Canarias
Affiliation as printed
Departamento de Astrofísica, Universidad de La Laguna , E-38205 La Laguna, Tenerife , Spain
Instituto de Astrofísica de Canarias , Vía Láctea s/n, E-38205 La Laguna, Tenerife , Spain
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University of California, Santa Cruz · University of California Observatories · San Jose State University
Affiliation as printed
Department of Astronomy & Astrophysics, University of California Santa Cruz , 1156 High Street, Santa Cruz, CA 95604 , USA
Department of Physics & Astronomy, San José State University , One Washington Square, San Jose, CA 95192 , USA
University of California Observatories , 1156 High Street, Santa Cruz, CA 95064 , USA
Department of Astronomy & Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95604, USA
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Affiliation as printed
Astronomy Department, Yale University , 52 Hillhouse Ave, New Haven, CT 06511 , USA
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