2009/11/17 by Tommaso Treu, T. Treu, M. W. Auger +7 · 413 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Dark matter #Dark matter halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Initial mass function #Metallicity #Physics #Star formation #Stellar mass #Stellar population #Stellar, planetary, and galactic studies #Velocity dispersion #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/709/2/1195
published in The Astrophysical Journal 709(2), 1195-1202 (IOP Publishing) · 10 pages 4 figures. Resubmitted to ApJ taking into account referee's comments
arxiv created 2009/11/17 · openalex publication_date 2010/01/12 · arxiv updated 2014/11/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We determine an absolute calibration of the initial mass function (IMF) of early-type galaxies, by studying a sample of 56 gravitational lenses identified by the Sloan Lenses ACS Survey. Under the assumption of standard Navarro, Frenk, and White dark matter halos, a combination of lensing, dynamical, and stellar population synthesis models is used to disentangle the stellar and dark matter contribution for each lens. We define an "IMF mismatch" parameter α≡ M LD *,Ein / M SPS *,Ein as the ratio of stellar mass inferred by a joint lensing and dynamical model ( M LD *,Ein ) to the current stellar mass inferred from stellar populations synthesis models ( M SPS *,Ein ). We find that a Salpeter IMF provides stellar masses in agreement with those inferred by lensing and dynamical models (〈log α〉 = −0.00 ± 0.03 ± 0.02), while a Chabrier IMF underestimates them (〈log α〉 = 0.25 ± 0.03 ± 0.02). A tentative trend is found, in the sense that α appears to increase with galaxy velocity dispersion. Taken at face value, this result would imply a non-universal IMF, perhaps dependent on metallicity, age, or abundance ratios of the stellar populations. Alternatively, the observed trend may imply non-universal dark matter halos with inner density slope increasing with velocity dispersion. While the degeneracy between the two interpretations cannot be broken without additional information, the data imply that massive early-type galaxies cannot have both a universal IMF and universal dark matter halos.