The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M$_∗$ plane up to z2

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 & 4 others D. Rosario, I. Roseboom, L. Wang, S. Wuyts

Research output: Contribution to journalArticle

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Abstract

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. qFIR) 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 Sν ∝ 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 deg2. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with M∗ > 1010 M⊙ and 0 <z< 2.3. We find that α1.4 GHz610 MHz 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) /SSFRMS(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, qFIR,displays a moderate but statistically significant redshift evolution as qFIR(z) = (2.35 ± 0.08) × (1 + z)−0.12 ± 0.04, consistent with some previous literature. Finally, we find no significant correlation between qFIR and Δlog (SSFR)MS, though a weak positive trend, as observed in one of our redshift bins (i.e. Δ [ qFIR ]/Δ [ Δlog (SSFR)MS ] = 0.22 ± 0.07 at 0.5 <z< 0.8), cannot be firmly ruled out using our dataset.
Original languageEnglish
Article numberA45
Number of pages18
JournalAstronomy & Astrophysics
Volume573
Early online date15 Dec 2014
DOIs
Publication statusPublished - 1 Jan 2015

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radio
galaxies
luminosity
flux density
stars
radio spectra
Very Large Array (VLA)
radio observation
index
radio telescopes
blanks
star formation rate
stellar mass
sky
observatories
synchrotrons
coverings
grids
methodology
radio wave

Keywords

  • galaxies: evolution
  • galaxies: formation
  • galaxies: starburst
  • galaxies: high-redshift
  • infrared: galaxies

Cite this

The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M$_∗$ plane up to z2. / Magnelli, B.; Ivison, R. J.; Lutz, D.; Valtchanov, I.; Farrah, D.; Berta, S.; Bertoldi, F.; Bock, J.; Cooray, A.; Ibar, E.; Karim, A.; Le Floc'h, E.; Nordon, R.; Oliver, S. J.; Page, M.; Popesso, P.; Pozzi, F.; Rigopoulou, D.; Riguccini, L.; Rodighiero, G.; Rosario, D.; Roseboom, I.; Wang, L.; Wuyts, S.

In: Astronomy & Astrophysics, Vol. 573, A45, 01.01.2015.

Research output: Contribution to journalArticle

Magnelli, B, Ivison, RJ, Lutz, D, Valtchanov, I, Farrah, D, Berta, S, Bertoldi, F, Bock, J, Cooray, A, Ibar, E, Karim, A, Le Floc'h, E, Nordon, R, Oliver, SJ, Page, M, Popesso, P, Pozzi, F, Rigopoulou, D, Riguccini, L, Rodighiero, G, Rosario, D, Roseboom, I, Wang, L & Wuyts, S 2015, 'The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M$_∗$ plane up to z2', Astronomy & Astrophysics, vol. 573, A45. https://doi.org/10.1051/0004-6361/201424937
Magnelli, B. ; Ivison, R. J. ; Lutz, D. ; Valtchanov, I. ; Farrah, D. ; Berta, S. ; Bertoldi, F. ; Bock, J. ; Cooray, A. ; Ibar, E. ; Karim, A. ; Le Floc'h, E. ; Nordon, R. ; Oliver, S. J. ; Page, M. ; Popesso, P. ; Pozzi, F. ; Rigopoulou, D. ; Riguccini, L. ; Rodighiero, G. ; Rosario, D. ; Roseboom, I. ; Wang, L. ; Wuyts, S. / The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M$_∗$ plane up to z2. In: Astronomy & Astrophysics. 2015 ; Vol. 573.
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abstract = "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. qFIR) 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 Sν ∝ 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 deg2. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with M∗ > 1010 M⊙ and 0 <z< 2.3. We find that α1.4 GHz610 MHz 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) /SSFRMS(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, qFIR,displays a moderate but statistically significant redshift evolution as qFIR(z) = (2.35 ± 0.08) × (1 + z)−0.12 ± 0.04, consistent with some previous literature. Finally, we find no significant correlation between qFIR and Δlog (SSFR)MS, though a weak positive trend, as observed in one of our redshift bins (i.e. Δ [ qFIR ]/Δ [ Δlog (SSFR)MS ] = 0.22 ± 0.07 at 0.5 <z< 0.8), cannot be firmly ruled out using our dataset.",
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T1 - The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M$_∗$ plane up to z2

AU - Magnelli, B.

AU - Ivison, R. J.

AU - Lutz, D.

AU - Valtchanov, I.

AU - Farrah, D.

AU - Berta, S.

AU - Bertoldi, F.

AU - Bock, J.

AU - Cooray, A.

AU - Ibar, E.

AU - Karim, A.

AU - Le Floc'h, E.

AU - Nordon, R.

AU - Oliver, S. J.

AU - Page, M.

AU - Popesso, P.

AU - Pozzi, F.

AU - Rigopoulou, D.

AU - Riguccini, L.

AU - Rodighiero, G.

AU - Rosario, D.

AU - Roseboom, I.

AU - Wang, L.

AU - Wuyts, S.

PY - 2015/1/1

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N2 - 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. qFIR) 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 Sν ∝ 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 deg2. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with M∗ > 1010 M⊙ and 0 <z< 2.3. We find that α1.4 GHz610 MHz 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) /SSFRMS(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, qFIR,displays a moderate but statistically significant redshift evolution as qFIR(z) = (2.35 ± 0.08) × (1 + z)−0.12 ± 0.04, consistent with some previous literature. Finally, we find no significant correlation between qFIR and Δlog (SSFR)MS, though a weak positive trend, as observed in one of our redshift bins (i.e. Δ [ qFIR ]/Δ [ Δlog (SSFR)MS ] = 0.22 ± 0.07 at 0.5 <z< 0.8), cannot be firmly ruled out using our dataset.

AB - 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. qFIR) 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 Sν ∝ 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 deg2. Using this methodology, we constrain the radio spectral index and FRC index of star-forming galaxies with M∗ > 1010 M⊙ and 0 <z< 2.3. We find that α1.4 GHz610 MHz 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) /SSFRMS(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, qFIR,displays a moderate but statistically significant redshift evolution as qFIR(z) = (2.35 ± 0.08) × (1 + z)−0.12 ± 0.04, consistent with some previous literature. Finally, we find no significant correlation between qFIR and Δlog (SSFR)MS, though a weak positive trend, as observed in one of our redshift bins (i.e. Δ [ qFIR ]/Δ [ Δlog (SSFR)MS ] = 0.22 ± 0.07 at 0.5 <z< 0.8), cannot be firmly ruled out using our dataset.

KW - galaxies: evolution

KW - galaxies: formation

KW - galaxies: starburst

KW - galaxies: high-redshift

KW - infrared: galaxies

UR - http://dx.doi.org/10.1051/0004-6361/201424937

U2 - 10.1051/0004-6361/201424937

DO - 10.1051/0004-6361/201424937

M3 - Article

VL - 573

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A45

ER -