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

Ivison, R. J., Alexander, David M., Biggs, Andy D., Brandt, W. N., Chapin, Edward L., Coppin, Kristen E. K., Devlin, Mark J., Dickinson, Mark, Dunlop, James, Dye, Simon, Eales, Stephen Anthony ORCID:, Frayer, David T., Halpern, Mark, Hughes, David H., Ibar, Edo, Kovács, A., Marsden, Gaelen, Moncelsi, Lorenzo, Netterfield, Calvin B., Pascale, Enzo ORCID:, 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, Marco P., Walter, Fabian, Weiß, Axel, Weibe, Donald V. and Xue, Y. Q. 2010. BLAST: the far-infrared/radio correlation in distant galaxies. Monthly Notices of the Royal Astronomical Society 402 (1) , pp. 245-258. 10.1111/j.1365-2966.2009.15918.x

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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 and the Giant Metre-wave Radio Telescope (GMRT) in the Extended Chandra Deep Field South (ECDFS). For a catalogue of BLAST 250-μm-selected galaxies, we remeasure the 70–870-μm flux densities at the positions of their most likely 24-μm counterparts, which have a median [interquartile] redshift of 0.74 [0.25, 1.57]. From these, we determine the monochromatic flux density ratio, q250(= log10[S250 μm/S1400 MHz]), and the bolometric equivalent, qIR. At z≈ 0.6, where our 250-μm filter probes rest-frame 160-μm emission, we find no evolution relative to q160 for local galaxies. We also stack the FIR and submm images at the positions of 24-μm- and radio-selected galaxies. The difference between qIR seen for 250-μm- and radio-selected galaxies suggests that star formation provides most of the IR luminosity in ≲100-μJy radio galaxies, but rather less for those in the mJy regime. For the 24-μm sample, the radio spectral index is constant across 0 < z < 3, but qIR exhibits tentative evidence of a steady decline such that qIR∝ (1 +z)−0.15±0.03– significant evolution, spanning the epoch of galaxy formation, with major implications for techniques that rely on the FIR/radio correlation. We compare with model predictions and speculate that we may be seeing the increase in radio activity that gives rise to the radio background.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: galaxies: evolution; infrared: galaxies; radio continuum: galaxies
Additional Information: Pdf uploaded in accordance with publisher's policy at (accessed 20/02/2014).
Publisher: Royal Astronomical Society
ISSN: 0035-8711
Date of First Compliant Deposit: 30 March 2016
Last Modified: 26 May 2023 15:59

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