BLAST : the far-infrared/radio correlation in distant galaxies

Ivison, R.J., Alexander, David M., Biggs, Andy D., Brandt, W.N., Chapin, E.L., Coppin, Kristen, Devlin, Mark J., Dickinson, Mark, Dunlop, James, Dye, Simon, Eales, Stephen A., Frayer, David T., Halpern, Mark, Hughes, David H., Ibar, Edo, Kovacs, A., Marsden, Gaelen, Moncelsi, L., Netterfield, Calvin B., Pascale, Enzo, Patanchon, Guillaume, Rafferty, D. A., Rex, Marie, Schinnerer, Eva, Scott, Douglas, Semisch, C., Smail, Ian, Swinbank, A. M., Truch, Matthew D.P., Tucker, Gregory S., Viero, M.P., Walter, Fabian, Weiss, Axel, Wiebe, Donald V. and Xue, Y.Q. (2010) BLAST : the far-infrared/radio correlation in distant galaxies. Monthly Notices of the Royal Astronomical Society (MNRAS), 402 (1). pp. 245-58. ISSN 0035-8711

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We investigate the correlation between far-infrared (FIR) and radio luminosities in distant galaxies, a lynchpin of modern astronomy. We use data from the Balloon-borne Large Aperture Submillimetre Telescope (BLAST), Spitzer, the Large Apex BOlometer CamerA (LABOCA), the Very Large Array (VLA) and the Giant Metre-wave Radio Telescope (GMRT) in the Extended Chandra Deep Field South (ECDFS). For a catalogue of BLAST 250-micron-selected galaxies, we re-measure the 70--870-micron flux densities at the positions of their most likely 24-micron counterparts, which have a median [interquartile] redshift of 0.74 [0.25, 1.57]. From these, we determine the monochromatic flux density ratio, q_250 = log_10 (S_250micron / S_1400MHz), and the bolometric equivalent, q_IR. At z ~= 0.6, where our 250-micron filter probes rest-frame 160-micron emission, we find no evolution relative to q_160 for local galaxies. We also stack the FIR and submm images at the positions of 24-micron- and radio-selected galaxies. The difference between q_IR seen for 250-micron- and radio-selected galaxies suggests star formation provides most of the IR luminosity in ~