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Insights into galaxy evolution from mid-infrared wavelengths

Chary, Ranga-Ram (2007) Insights into galaxy evolution from mid-infrared wavelengths. In: At the edge of the universe: latest results from the deepest astronomical surveys. ASP Conference Series. No.380. Astronomical Society of the Pacific , San Francisco, pp. 375-385. ISBN 978-1-58381-323-2.

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In this paper, I have attempted to highlight key results from deep extragalactic surveys at mid-infrared wavelengths. I discuss advances in our understanding of dust enshrouded star-formation and AGN activity at 0 < z < 3 from IRAS, ISO and Spitzer. The data seem to indicate that about 70% of the co-moving star-formation rate density at 0.5 < z < 3 is obscured by dust and that AGN, including obscured sources, account for <20% of the co-moving bolometric luminosity density. There is tentative evidence that the mode of star-formation changes as a function of redshift; star-formation at z ~ 2 is preferentially in massive, ultraluminous infrared galaxies (ULIRGs) while z ~ 1 sources are luminous infrared galaxies (LIRGs) which are about 1 mag fainter than ULIRGs in the near-infrared. This evolution of the star-formation mode, is similar to the evolution of the redshift distribution of X-ray sources as a function of X-ray luminosity and would suggest an extension of the downsizing hypothesis to include both AGN and star-forming galaxies. Measuring dust-enshrouded star-formation at z > 3 will become possible only with future facilities like ALMA. Currently, the presence of dust can only be assessed in a small fraction of the youngest starbursts at z > 5 by looking for redshifted large equivalent width Hα emission in broadband filters like the IRAC 4.5μm passband. Hα to UV ratios in these objects are a tracer of dust extinction and measuring this ratio in GOODS galaxies indicate dust in ~20% of star-forming galaxies at z > 5. Finally, implications for reionization based on the measured stellar mass density and star-formation rates of galaxies at these redshifts are discussed.

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Chary, Ranga-Ram0000-0001-7583-0621
Additional Information:© 2007 Astronomical Society of the Pacific. I wish to thank the organizers for a very productive and enjoyable meeting. I would like to acknowledge contributions from various members of the GOODS team which resulted in the material presented in this paper. This work is partly funded by NASA through Contract Number 1224666 issued by JPL/Caltech under NASA contract 1407.
Group:Infrared Processing and Analysis Center (IPAC)
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Series Name:ASP Conference Series
Issue or Number:380
Record Number:CaltechAUTHORS:20100820-131420255
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19560
Deposited By: Tony Diaz
Deposited On:20 Aug 2010 20:41
Last Modified:14 Dec 2019 06:00

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