Computer Science
Scientific paper
Jan 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008phdt.........1j&link_type=abstract
Proquest Dissertations And Theses 2008. Section 0054, Part 0606 157 pages; [Ph.D. dissertation].United States -- New York: Colu
Computer Science
Galaxies, Star Formation, Surveys, Dust
Scientific paper
The meaningful comparison of models of galaxy evolution to observations is critically dependent on the accurate treatment of dust attenuation. To investigate dust absorption and emission in galaxies we have assembled a sample of ~1000 galaxies from the ultrviolet (UV) through the Infrared (IR) by the GALEX, SDSS, and Spitzer observatories. The ratio of IR to UV emission (IRX) is used to constrain the dust attenuation in galaxies. We consider this measure in optically red galaxies making several simplfying assumptions we estimate the fraction of IR emission due to the heating of by old stars to be as much as 99%. We use the 4000Å break as a robust and useful, though coarse, indicator of star formation history (SFH).
Dust attenuation and star formation history (SFH) are the dominant factors affecting the color of galaxies. We explore the empirical relation between SFH, attenuation, and color (especially the UV color) for a wide range of galaxies, including early types. This relation is compared to models that separately predict the effects of dust and SFH on color. We perform fits to the relation between SFH, attenuation, and color, which links the production of starlight and its absorption by dust to the subsequent reemmision of the absorbed light in the IR. Galaxy models that self-consistently treat dust absorption and emission as well as stellar populations will need to reproduce these fitted relations in the low-redshift universe.
We construct estimates of dust attenuation and star formation rate (SFR) from the UV and IR photmetry and compare them to optical indicators, including the SFR b of Brinchmann et al. (2004). We find that there is a significant trend of the ratio of SFR b to the IR+UV luminosity with D n (4000) that cannot be explained as due to the additional IR emission from dust heatred by old stars. We find that the dust attenuation inferred from the ratio of optical emission lines is ~ 2-3 times higher than that inferred from IRX for a wide range of galaxies, consistent with the the interpretation that very young stars are enshrouded by more dust than slightly older stars.
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