2012/07/31 by C. Tortora, Crescenzo Tortora, Aaron J. Romanowsky +2 · 2 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Initial mass function #Milky Way #Physics #Star formation #Stars #Stellar mass #Stellar, planetary, and galactic studies #Velocity dispersion #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/765/1/8
8 pages, 5 figures, 1 table, accepted for publication on ApJ. This version includes further updates and, a new subsection and a figure on late-type galaxies are added
arxiv created 2012/12/10 · openalex publication_date 2013/02/11 · arxiv updated 2015/06/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as our own new findings from combined stellar population synthesis (SPS) and Jeans dynamical analyses of data on ∼4500 early-type galaxies (ETGs) from the SPIDER project. We focus on the mass-to-light ratio mismatch relative to the Milky Way IMF, δ IMF , correlated against the central stellar velocity dispersion, σ ⋆ . We find a strong correlation between δ IMF and σ ⋆ , for a wide set of dark matter (DM) model profiles. These results are robust if a uniform halo response to baryons is adopted across the sample. The overall normalization of δ IMF and the detailed DM profile are less certain, but the data are consistent with standard cold DM halos and a central DM fraction that is roughly constant with σ ⋆ . For a variety of related studies in the literature, using SPS, dynamics, and gravitational lensing, similar results are found. Studies based solely on spectroscopic line diagnostics agree on a Salpeter-like IMF at high σ ⋆ but differ at low σ ⋆ . Overall, we find that multiple independent lines of evidence appear to be converging on a systematic variation in the IMF, such that high-σ ⋆ ETGs have an excess of low-mass stars relative to spirals and low-σ ⋆ ETGs. Robust verification of super-Salpeter IMFs in the highest-σ ⋆ galaxies will require additional scrutiny of scatter and systematic uncertainties. The implications for the distribution of DM are still inconclusive.