July
2010
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2010A&A...518L..31I
Authors
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Ivison, R. J.
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Magnelli, B.
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Ibar, E.
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Andreani, P.
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Elbaz, D.
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Altieri, B.
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Amblard, A.
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Arumugam, V.
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Auld, R.
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Aussel, H.
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Babbedge, T.
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Berta, S.
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Blain, A.
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Bock, J.
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Bongiovanni, A.
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Boselli, A.
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Buat, V.
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Burgarella, D.
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Castro-Rodríguez, N.
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Cava, A.
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Cepa, J.
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Chanial, P.
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Cimatti, A.
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Cirasuolo, M.
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Clements, D. L.
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Conley, A.
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Conversi, L.
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Cooray, A.
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Daddi, E.
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Dominguez, H.
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Dowell, C. D.
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Dwek, E.
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Eales, S.
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Farrah, D.
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Förster Schreiber, N.
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Fox, M.
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Franceschini, A.
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Gear, W.
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Genzel, R.
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Glenn, J.
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Griffin, M.
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Gruppioni, C.
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Halpern, M.
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Hatziminaoglou, E.
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Isaak, K.
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Lagache, G.
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Levenson, L.
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Lu, N.
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Lutz, D.
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Madden, S.
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Maffei, B.
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Magdis, G.
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Mainetti, G.
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Maiolino, R.
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Marchetti, L.
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Morrison, G. E.
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Mortier, A. M. J.
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Nguyen, H. T.
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Nordon, R.
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O'Halloran, B.
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Oliver, S. J.
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Omont, A.
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Owen, F. N.
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Page, M. J.
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Panuzzo, P.
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Papageorgiou, A.
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Pearson, C. P.
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Pérez-Fournon, I.
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Pérez García, A. M.
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Poglitsch, A.
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Pohlen, M.
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Popesso, P.
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Pozzi, F.
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Rawlings, J. I.
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Raymond, G.
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Rigopoulou, D.
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Riguccini, L.
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Rizzo, D.
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Rodighiero, G.
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Roseboom, I. G.
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Rowan-Robinson, M.
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Saintonge, A.
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Sanchez Portal, M.
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Santini, P.
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Schulz, B.
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Scott, D.
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Seymour, N.
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Shao, L.
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Shupe, D. L.
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Smith, A. J.
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Stevens, J. A.
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Sturm, E.
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Symeonidis, M.
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Tacconi, L.
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Trichas, M.
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Tugwell, K. E.
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Vaccari, M.
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Valtchanov, I.
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Vieira, J.
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Vigroux, L.
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Wang, L.
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Ward, R.
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Wright, G.
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Xu, C. K.
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Zemcov, M.
Abstract
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We set out to determine the ratio, qIR, of rest-frame 8-1000-μm flux, SIR, to monochromatic radio flux, S1.4 GHz, for galaxies selected at far-infrared (IR) and radio wavelengths, to search for signs that the ratio evolves with redshift, luminosity or dust temperature, Td, and to identify any far-IR-bright outliers - useful laboratories for exploring why the far-IR/radio correlation (FIRRC) is generally so tight when the prevailing theory suggests variations are almost inevitable. We use flux-limited 250-μm and 1.4-GHz samples, obtained using Herschel and the Very Large Array (VLA) in GOODS-North (-N). We determine bolometric IR output using ten bands spanning λobs = 24-1250 μm, exploiting data from PACS and SPIRE (PEP; HerMES), as well as Spitzer, SCUBA, AzTEC and MAMBO. We also explore the properties of an LIR-matched sample, designed to reveal evolution of qIR with redshift, spanning log LIR = 11-12 L⊙ and z = 0-2, by stacking into the radio and far-IR images. For 1.4-GHz-selected galaxies in GOODS-N, we see tentative evidence of a break in the flux ratio, qIR, at L1.4 GHz ~ 1022.7 W Hz-1, where active galactic nuclei (AGN) are starting to dominate the radio power density, and of weaker correlations with redshift and Td. From our 250-μm-selected sample we identify a small number of far-IR-bright outliers, and see trends of qIR with L1.4 GHz, LIR, Td and redshift, noting that some of these are inter-related. For our LIR-matched sample, there is no evidence that qIR changes significantly as we move back into the epoch of galaxy formation: we find qIR ∝(1+z)γ, where γ = -0.04±0.03 at z = 0-2; however, discounting the least reliable data at z < 0.5 we find γ = -0.26±0.07, modest evolution which may be related to the radio background seen by ARCADE 2, perhaps driven by <10-μJy radio activity amongst ordinary star-forming galaxies at z > 1.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
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