Journal
ASTROPHYSICAL JOURNAL
Volume 799, Issue 2, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/0004-637X/799/2/125
Keywords
galaxies: evolution; galaxies: formation; galaxies: kinematics and dynamics; galaxies: stellar content; galaxies: structure
Categories
Funding
- Netherlands Foundation for Research (NWO), the Leids Kerkhoven-Bosscha Fonds
- NASA/ESA HST [GO 12177, 12328]
- NASA [NAS5-26555]
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We explore the relation between the dynamical mass-to-light ratio (M/L) and rest-frame color of massive quiescent galaxies out to z similar to 2. We use a galaxy sample with measured stellar velocity dispersions in combination with Hubble Space Telescope and ground-based multi-band photometry. Our sample spans a large range in log M-dyn/L-g (of 1.6 dex) and log M-dyn/L-K (of 1.3 dex). There is a strong, approximately linear correlation between the M/L for different wavebands and rest-frame color. The root-mean-square scatter in log M-dyn/L residuals implies that it is possible to estimate the M/L with an accuracy of similar to 0.25 dex from a single rest-frame optical color. Stellar population synthesis (SPS) models with a Salpeter stellar initial mass function (IMF) cannot simultaneously match M-dyn/L-g versus (g-z)(rest) (frame) and M-dyn/L-K versus (g-K)(rest) (frame). By changing the slope of the IMF we are still unable to explain the M/L of the bluest and reddest galaxies. We find that an IMF with a slope between alpha = 2.35 and alpha = 1.35 provides the best match. We also explore a broken IMF with a Salpeter slope at M < 1M(circle dot) and M > 4M(circle dot) and a slope alpha in the intermediate region. The data favor a slope of alpha = 1.35 over alpha = 2.35. Nonetheless, our results show that variations between different SPS models are comparable to the IMF variations. In our analysis we assume that the variation in M/L and color is driven by differences in age, and that other contributions (e.g., metallicity evolution, dark matter) are small. These assumptions may be an important source of uncertainty as galaxies evolve in more complex ways.
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