* Astronomy

Title: SGAS 143845.1+145407: A Big, Cool Starburst at Redshift 0.816
Authors: Michael D. Gladders, Jane R. Rigby, Keren Sharon, Eva Wuyts, Louis E. Abramson, Hakon Dahle, S.E. Persson, Andrew J. Monson, Daniel D. Kelson, Dominic J. Benford, David Murphy, Matthew B. Bayliss, Keely D. Finkelstein, Benjamin P. Koester, Alissa Bans, Eric J. Baxter, Jennifer E. Helsby

We present the discovery and a detailed multi-wavelength study of a strongly-lensed luminous infrared galaxy at z=0.816. Unlike most known lensed galaxies discovered at optical or near-infrared wavelengths, this lensed source is red, which the data presented here demonstrate is due to ongoing dusty star formation. The overall lensing magnification (a factor of 17) facilitates observations from the blue optical through to 500 micron, fully capturing both the stellar photospheric emission as well as the re-processed thermal dust emission. We also present optical and near-IR spectroscopy. These extensive data show that this lensed galaxy is in many ways typical of IR-detected sources at z~1, with both a total luminosity and size in accordance with other (albeit much less detailed) measurements in samples of galaxies observed in deep fields with the Spitzer telescope. Its far-infrared spectral energy distribution is well--fit by local templates that are an order of magnitude less luminous than the lensed galaxy; local templates of comparable luminosity are too hot to fit. Its size (D~7 kpc) is much larger than local luminous infrared galaxies, but in line with sizes observed for such galaxies at z~1. The star formation appears uniform across this spatial scale. Thus, this lensed galaxy, which appears representative of vigorously star--forming z~1 galaxies, is forming stars in a fundamentally different mode than is seen at z~0.

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