A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments

By N. Bastian, K. Covey, Michael R. Meyer IoA, Cambridge, Cornell, Harvard-Smithsonian Cfa, E. Zurich, S. Observatory. 2010

811 citations recorded by the source corpus.

Whether the stellar initial mass function (IMF) is universal or is instead sensitive to environmental conditions is of critical importance: The IMF influences most observable properties of stellar populations and thus galaxies, and detecting variations in the IMF could provide deep insights into the star formation process. This review critically examines reports of IMF variations, with a view toward whether other explanations are sufficient given the evidence. Studies of the field, young clusters and associations, and old globular clusters suggest that the vast majority were drawn from a universal system IMF: a power law of Salpeter index (Γ = 1.35) above a few solar masses, and a log normal or shallower power law (Γ ∼ 0–0.25) for lower mass stars. The shape and universality of the substellar IMF is still under investigation. Observations of resolved stellar populations and the integrated properties of most galaxies are also consistent with a universal IMF, suggesting no gross variations over much of cosm...

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e8cba1872384fcadbf107583560c241071f538d2

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Citations in the corpus

• Dusty Star Forming Galaxies at High Redshift (2014, methodology): “Finally, the flat IMF that galform requires in order to match the observed SMG number counts and evolution in the galaxy mid-IR luminosity function has not been observed in any nearby environment (see the recent review by Bastian et al., 2010).”
• The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “(20 4) and Bastian et al. (2010)), but for the purposes of this review I have mostly limited myself to those issues about which there is some consensus; where I make controversial claims about the observations that are not universallyaccepted, I will attempt to make this clear.”
• Double neutron stars: merger rates revisited (2017, background): “…C C+P NK2 Rlocal;BHBH [ Gpc−3 yr−1]: 32 [310] 695 [695] 190 [1072] trends in the form of the IMF with redshift or metallicity (Massey 2003; Bastian et al. 2010; Offner et al. 2014), apart from local deviations (e.g. top-heavy IMF found in some globular clusters, see Kroupa et al. 2013).”
• The stellar and sub-stellar IMF of simple and composite populations (2011, result): “3 in Bastian et al. 2010), Fig.”
• Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Variations in the IMF with environment are plausible, but convincing evidence for variation remains elusive (Bastian et al. 2010).”
• FURTHER DEFINING SPECTRAL TYPE “Y” AND EXPLORING THE LOW-MASS END OF THE FIELD BROWN DWARF MASS FUNCTION (2012, result): “Although doubts about the universality of the initial mass function persist, Andersen et al. (2008) found that this assumption is credible and, having combined observational results in seven star formation regions and open clusters in the mass range 0.03-1.0 M⊙ – including the Pleiades, the Orion Ne”
• Systematic variation of the stellar initial mass function with velocity dispersion in early-type galaxies (2012, background): “For a recent review on the IMF and its possible variations, see Bastian et al. (2010).”
• Production of dust by massive stars at high redshift (2011, background): “A fundamental debate regarding the IMF is whether there is a systematic variation of the IMF with some physical conditions of star formation or whether it is universal (see Bastian et al, 2010, for a review).”
• The dynamical state of stellar structure in star‐forming regions (2011, background): “…(see the review by McKee & Ostriker 2007) to the fundamental properties of young star clusters (e.g. McMillan et al. 2007; Allison et al. 2009a; Moeckel & Bonnell 2009), or possibly even the global stellar mass assembly of galaxies (see e.g. Pflamm-Altenburg et al. 2007; Bastian et al. 2010).”
• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars (2014, background): “Inferences about the initial mass function (IMF; Bastian et al. 2010) and variation of the star-formation rate through cosmic time (Hopkins & Beacom 2006, Madau et al. 1998) hinge upon converting reprocessed massive star UV luminosity to a collective star-formation rate.”
• THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT (2013, background): “The IMF is fundamental to all calculations of star formation rates and galaxy stellar masses (for reviews see Bastian et al. 2010; Kroupa et al. 2011).”
• STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, positive): “In this work, we shall assume that the IMF of stars is universal in galactic disks when averaged over large regions of space and long intervals of time (Bastian et al. 2010).”