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A Far-infrared Characterization of 24 μm Selected Galaxies at 0 < z < 2.5 using Stacking at 70 μm and 160 μm in the COSMOS Field

Lee, Nicholas and Le Floc'h, Emeric and Sanders, D. B. and Frayer, D. T. and Arnouts, Stephane and Ilbert, Olivier and Aussel, Herve and Salvato, Mara and Scoville, N. Z. and Kartaltepe, Jeyhan S. (2010) A Far-infrared Characterization of 24 μm Selected Galaxies at 0 < z < 2.5 using Stacking at 70 μm and 160 μm in the COSMOS Field. Astrophysical Journal, 717 (1). pp. 175-182. ISSN 0004-637X. doi:10.1088/0004-637X/717/1/175.

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We present a study of the average properties of luminous infrared galaxies detected directly at 24 μm in the COSMOS field using a median stacking analysis at 70 μm and 160 μm. Over 35,000 sources spanning 0 ≤ z ≤ 3 and 0.06 mJy ≤ S_(24) ≤ 3.0 mJy are stacked, divided into bins of both photometric redshift and 24 μm flux. We find no correlation of S_(70)/S_(24) flux density ratio with S_(24), but find that galaxies with higher S_(24) have a lower S_(160)/S_(24) flux density ratio. These observed ratios suggest that 24 μm selected galaxies have warmer spectral energy distributions (SEDs) at higher mid-IR fluxes, and therefore have a possible higher fraction of active galactic nuclei. Comparisons of the average S_(70)/S_(24) and S_(160)/S_(24) colors with various empirical templates and theoretical models show that the galaxies detected at 24 μm are consistent with "normal" star-forming galaxies and warm mid-IR galaxies such as Mrk 231, but inconsistent with heavily obscured galaxies such as Arp 220. We perform a χ^2 analysis to determine best-fit galactic model SEDs and total IR luminosities for each of our bins. We compare our results to previous methods of estimating L IR and find that previous methods show considerable agreement over the full redshift range, except for the brightest S_(24) sources, where they overpredict the bolometric IR luminosity at high redshift, most likely due to their warmer dust SED. We present a table that can be used as a more accurate and robust method for estimating bolometric infrared luminosity from 24 μm flux densities.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sanders, D. B.0000-0002-1233-9998
Frayer, D. T.0000-0003-1924-1122
Ilbert, Olivier0000-0002-7303-4397
Aussel, Herve0000-0002-1371-5705
Salvato, Mara0000-0001-7116-9303
Scoville, N. Z.0000-0002-0438-3323
Kartaltepe, Jeyhan S.0000-0001-9187-3605
Additional Information:© 2010 The American Astronomical Society. Received 2010 February 17; accepted 2010 May 7; published 2010 June 9. It is a pleasure to acknowledge the contribution from all our colleagues in the COSMOS collaboration. More information on the COSMOS survey is available at This work is based on observations made with the Spitzer Space Telescope, a facility operated by NASA/JPL. Financial supports were provided by NASA through contracts 1289085, 1310136, 1282612, and 1298231 issued by the Jet Propulsion Laboratory. We are grateful to Herve Dole for insightful discussions on stacking techniques.
Funding AgencyGrant Number
Subject Keywords:galaxies: evolution; galaxies: high-redshift; galaxies: statistics; infrared: galaxies
Issue or Number:1
Classification Code:PACS: 98.54.Ep; 98.54.Cm; 98.62.Py; 98.62.Qz; 98.62.Ai
Record Number:CaltechAUTHORS:20100714-135827342
Persistent URL:
Official Citation:Nicholas Lee et al 2010 ApJ 717 175. doi: 10.1088/0004-637X/717/1/175
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19047
Deposited By: Tony Diaz
Deposited On:15 Jul 2010 20:56
Last Modified:08 Nov 2021 23:49

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