A GNIRS (Gemini South) study identifies a surprising class of distant massive galaxies with strongly suppressed star formation.
An international team led by Mariska Kriek of Leiden Observatory (Holland) and Yale University has found that 45% of a small sample (20) of massive high-redshift galaxies exhibit very low or no star formation activity. The existence of "red and dead" massive galaxies at a time when the universe was between 1/4 to a 1/3 of its current age is surprising.
During the past few years our knowledge of galaxy formation evolution has grown significantly. Several recent papers indicate that most of the stars in high-mass galaxies were formed at a higher redshift (earlier in the history of the universe) than those of low mass galaxies. This newly published work puts a new twist on the growing evidence that most massive galaxies formed at an extremely early epoch in the universe.
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Title: SPECTROSCOPIC IDENTIFICATION OF MASSIVE GALAXIES AT Z ~ 2.3 WITH STRONGLY SUPPRESSED STAR FORMATION
Authors: Mariska Kriek, Pieter G. van Dokkum, Marijn Franx, Ryan Quadri, Eric Gawiser, David Herrera,Garth D. Illingworth, Ivo Labb´e, Paulina Lira, Danilo Marchesini, Hans-Walter Rix, Gregory Rudnick, Edward N. Taylor, Sune Toft, C. Megan Urry, and Stijn Wuyts
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The equivalent width of Hα vs. the specific SFR derived from our model fits to the spectra. Filled red circles are galaxies with no detected Hα emission and purple squares are emission line galaxies in our sample. yellow crosses are UV-selected galaxies by Erb et al. (2006a,b,c). DRGs are indicated by open green diamonds. Upper limits for H and the specific SFR are 2σ. Expected relations between WH and specific SFR are derived from the Bruzual & Charlot (2003) and Kennicutt (1998) models and drawn for a τ100Myr (gray dotted line) and a τ1000Myr (gray dashed line) model for the first 3 Gyr. Both Hα measurements and the independent SED modelling demonstrate that in 9 out of 20 galaxies in our sample the star formation has been strongly suppressed.
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22-September-2006, 12:23 AM
Distant galaxies with suppressed star formation
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