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Published January 2015 | Published + Submitted
Journal Article Open

Evolution of the dust emission of massive galaxies up to z = 4 and constraints on their dominant mode of star formation


We aim to measure the average dust and molecular gas content of massive star-forming galaxies (>3 × 10^(10)M_⊙) up to z = 4 in the COSMOS field to determine if the intense star formation observed at high redshift is induced by major mergers or is caused by large gas reservoirs. Firstly, we measured the evolution of the average spectral energy distributions as a function of redshift using a stacking analysis of Spitzer, Herschel, LABOCA, and AzTEC data for two samples of galaxies: normal star-forming objects and strong starbursts, as defined by their distance to the main sequence. We found that the mean intensity of the radiation field ⟨ U ⟩ heating the dust (strongly correlated with dust temperature) increases with increasing redshift up to z = 4 in main-sequence galaxies. We can reproduce this evolution with simple models that account for the decrease in the gas metallicity with redshift. No evolution of ⟨ U ⟩ with redshift is found in strong starbursts. We then deduced the evolution of the molecular gas fraction (defined here as M_(mol)/(M_(mol)+M_⋆)) with redshift and found a similar, steeply increasing trend for both samples. At z ~ 4, this fraction reaches ~60%. The average position of the main-sequence galaxies is on the locus of the local, normal star-forming disks in the integrated Schmidt-Kennicutt diagram (star formation rate versus mass of molecular gas), suggesting that the bulk of the star formation up to z = 4 is dominated by secular processes.

Additional Information

© 2015 ESO. Received: 19 September 2014. Accepted: 11 November 2014. Published online 07 January 2015. We thank the anonymous referee for providing constructive comments. We acknowledge Morgane Cousin, Nick Lee, Nick Scoville, and Christian Maier for their interesting discussions/suggestions, Laure Ciesla for providing an electronic table of the physical properties of the HRS sample, and Amélie Saintonge for providing her compilation of data. We gratefully acknowledge the contributions of the entire COSMOS collaboration consisting of more than 100 scientists. The HST COSMOS program was supported through NASA grant HST-GO-09822. More information on the COSMOS survey is available at http://www.astro.caltech.edu/cosmos. ased on data obtained from the ESO Science Archive Facility. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO programme ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the Ultra VISTA consortium. M.B., E.D., and M.S. acknowledge the support of the ERC-StG UPGAL 240039 and ANR-08-JCJC-0008 grants. A.K. acknowledges support by the Collaborative Research Council 956, sub-project A1, funded by the Deutsche Forschungsgemeinschaft (DFG).

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Submitted - 1409.5796v2.pdf

Published - aa25031-14.pdf


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August 20, 2023
August 20, 2023