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The far-infrared/radio correlation and radio spectral index of galaxies in the SFR–M_∗ plane up to z ∼ 2

Magnelli, B. and Ivison, R. J. and Lutz, D. and Valtchanov, I. and Farrah, D. and Berta, S. and Bertoldi, F. and Bock, J. and Cooray, A. and Ibar, E. and Karim, A. and Le Floc'h, E. and Nordon, R. and Oliver, S. J. and Page, M. and Pozzi, F. and Rigopoulou, D. and Riguccini, L. and Rodighiero, G. and Rosario, D. and Roseboom, I. and Wang, L. and Wuyts, S. (2015) The far-infrared/radio correlation and radio spectral index of galaxies in the SFR–M_∗ plane up to z ∼ 2. Astronomy and Astrophysics, 573 . Art. No. A45. ISSN 0004-6361.

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We study the evolution of the radio spectral index and far-infrared/radio correlation (FRC) across the star-formation rate – stellar masse (i.e. SFR–M_∗) plane up to z ~ 2. We start from a stellar-mass-selected sample of galaxies with reliable SFR and redshift estimates. We then grid the SFR–M_∗ plane in several redshift ranges and measure the infrared luminosity, radio luminosity, radio spectral index, and ultimately the FRC index (i.e. q_(FIR)) of each SFR–M_∗–z bin. The infrared luminosities of our SFR–M_∗–z bins are estimated using their stacked far-infrared flux densities inferred from observations obtained with the Herschel Space Observatory. Their radio luminosities and radio spectral indices (i.e. α, where S_ν ∝ ν^(−α)) are estimated using their stacked 1.4 GHz and 610 MHz flux densities from the Very Large Array and Giant Metre-wave Radio Telescope, respectively. Our far-infrared and radio observations include the most widely studied blank extragalactic fields – GOODS-N, GOODS-S, ECDFS, and COSMOS – covering a total sky area of ~2.0 deg^2. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with M_∗ > 10^(10) M_⊙ and 0 <z< 2.3. We find that α^(1.4GHz)_(610MHz) does not evolve significantly with redshift or with the distance of a galaxy with respect to the main sequence (MS) of the SFR–M∗ plane (i.e. Δlog (SSFR)_(MS) = log  [ SSFR(galaxy) /SSFR_(MS)(M_∗,z) ]). Instead, star-forming galaxies have a radio spectral index consistent with a canonical value of 0.8, which suggests that their radio spectra are dominated by non-thermal optically thin synchrotron emission. We find that the FRC index, q_(FIR), displays a moderate but statistically significant redshift evolution as q_(FIR)(z) = (2.35 ± 0.08) × (1 + z)^(−0.12 ± 0.04), consistent with some previous literature. Finally, we find no significant correlation between q_(FIR) and Δlog (SSFR)_(MS), though a weak positive trend, as observed in one of our redshift bins (i.e. Δ [q_(FIR)]/Δ [Δlog (SSFR)_(MS)] = 0.22 ± 0.07 at 0.5 <z< 0.8), cannot be firmly ruled out using our dataset.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Magnelli, B.0000-0002-6777-6490
Ivison, R. J.0000-0001-5118-1313
Lutz, D.0000-0003-0291-9582
Valtchanov, I.0000-0001-9930-7886
Farrah, D.0000-0003-1748-2010
Berta, S.0000-0002-0320-1532
Bertoldi, F.0000-0002-1707-1775
Bock, J.0000-0002-5710-5212
Cooray, A.0000-0002-3892-0190
Karim, A.0000-0002-8414-9579
Oliver, S. J.0000-0001-7862-1032
Page, M.0000-0002-6689-6271
Rigopoulou, D.0000-0001-6854-7545
Rodighiero, G.0000-0002-9415-2296
Additional Information:© 2014 ESO. Received: 6 September 2014. Accepted: 21 October 2014. Published online 15 December 2014. We thank the anonymous referee for suggestions which greatly enhanced this work. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAF-IFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain). SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including University of Lethbridge (Canada), NAOC (China), CEA, LAM (France), IFSI, University of Padua (Italy), IAC (Spain), Stockholm Observatory (Sweden), Imperial College London, RAL, UCL-MSSL, UKATC, University of Sussex (UK), Caltech, JPL, NHSC, University of Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA). Support for BM was provided by the DFG priority programme 1573 The physics of the interstellar medium. R.J.I. acknowledges support from the European Research Council in the form of Advanced Grant, cosmicism. E.I. acknowledges funding from CONICYT/FONDECYT postdoctoral project N◦:3130504. F.B. and A.K. acknowledge support by the Collaborative Research Council 956, sub-project A1, funded by the Deutsche Forschungsgemeinschaft (DFG).
Funding AgencyGrant Number
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Ministerio de Ciencia Y Tecnologia (MCYT)UNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
National Astronomical Observatories, Chinese Academy of Sciences (NAOC)UNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Ministerio de Ciencia e Innovación (MCINN)UNSPECIFIED
Swedish National Space Board (SNSB)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
European Research Council (ERC)COSMICISM
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)3130504
Commissariat à l'énergie atomique (CEA)UNSPECIFIED
United Kingdom Space Agency (UKSA)UNSPECIFIED
Comisión Interministerial de Ciencia y Tecnología (CICYT)UNSPECIFIED
Subject Keywords:galaxies: evolution, galaxies: formation, galaxies: starburst galaxies: high-redshift, infrared: galaxies
Record Number:CaltechAUTHORS:20150317-091500633
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Official Citation:The far-infrared/radio correlation and radio spectral index of galaxies in the SFR–M∗ plane up to z~2 B. Magnelli, R. J. Ivison, D. Lutz, I. Valtchanov, D. Farrah, S. Berta, F. Bertoldi, J. Bock, A. Cooray, E. Ibar, A. Karim, E. Le Floc’h, R. Nordon, S. J. Oliver, M. Page, P. Popesso, F. Pozzi, D. Rigopoulou, L. Riguccini, G. Rodighiero, D. Rosario, I. Roseboom, L. Wang and S. Wuyts A&A 573 A45 (2015) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55835
Deposited By: Ruth Sustaita
Deposited On:17 Mar 2015 17:13
Last Modified:09 Mar 2020 13:19

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