The far- and mid-infrared/radio correlations in the Spitzer extragalactic first look survey

P. N. Appleton, D. T. Fadda, F. R. Marleau, D. T. Frayer, G. Helou, J. J. Condon, P. I. Choi, L. Yan, M. Lacy, G. Wilson, L. Armus, S. C. Chapman, F. Fang, I. Heinrichson, M. Im, B. T. Jannuzi, L. J. Storrie-Lombardi, D. Shupe, B. T. Soifer, G. SquiresH. I. Teplitz

Research output: Contribution to journalArticlepeer-review

260 Scopus citations


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 q70 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 924 shows significantly more dispersion than q70. 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 q24 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.

Original languageEnglish (US)
Pages (from-to)147-150
Number of pages4
JournalAstrophysical Journal, Supplement Series
Issue number1
StatePublished - Sep 2004


  • Cosmology: observations
  • Galaxies: evolution
  • Galaxies: high-redshift
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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