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Published September 2004 | Published + Erratum + Submitted
Journal Article Open

The Far- and Mid-Infrared/Radio Correlations in the Spitzer Extragalactic First Look Survey


Using the Spitzer Space Telescope and the Very Large Array (VLA), we present the first direct evidence that the well-known far-infrared/radio correlation is valid to cosmologically significant redshift. We also confirm, with improved statistics compared with previous surveys, a similar result for the mid-IR/radio correlation. We explore the dependence of monochromatic q_(24) and q_(70) on z. The results were obtained by matching Spitzer sources at 24 and 70 μm with VLA 1.4 GHz microjansky radio sources obtained for the Spitzer First Look Survey (FLS). Spectroscopic redshifts have been obtained for over 500 matched IR/radio sources using observations at WIYN and Keck, and archival Sloan Digital Sky Survey (SDSS) data extending out to z > 2. We find that q_(24) shows significantly more dispersion than q_(70). By comparing the observed fluxes at 70, 24, and 4.5 μm with a library of SED templates, we find that the larger dispersion in q_(24) is predictable in terms of systematic variations in spectral energy distribution (SED) shape throughout the population. Although the models are not able to encompass the full range of observed behavior (both the presence of either extremely flat or extremely steep IR SEDs), the fitting parameters were used to "k-correct" the higher z galaxies, which resulted in a reduced scatter in q. For comparison, we also corrected these data using the SED for M82. The results for 24 and 70 μm provide strong consistent evidence for the universality of the mid- and far-IR/radio correlations out to redshifts of at least z = 1.

Additional Information

© 2004 The American Astronomical Society. Received 2004 March 27; accepted 2004 May 5. This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. The authors wish to thank V. Charmandaris (Cornell University), D. Dale (University of Wyoming), and an anonymous referee for helpful contributions to this work.

Attached Files

Published - Appleton_2004_ApJS_154_147.pdf

Submitted - 0406030.pdf

Erratum - Appleton_2005_ApJS_156_111.pdf


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