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The radio spectral energy distribution and star-formation rate calibration in galaxies

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Abstract
We study the spectral energy distribution (SED) of the radio continuum (RC) emission from the Key Insight in Nearby Galaxies Emitting in Radio (KINGFISHER) sample of nearby galaxies to understand the energetics and origin of this emission. Effelsberg multi-wavelength observations at 1.4, 4.8, 8.4, and 10.5 GHz combined with archive data allow us, for the first time, to determine the mid-RC (1-10 GHz, MRC) bolometric luminosities and further present calibration relations versus the monochromatic radio luminosities. The 1-10 GHz radio SED is fitted using a Bayesian Markov Chain Monte Carlo technique leading to measurements for the nonthermal spectral index (S-nu similar to nu(-alpha nt)) and the thermal fraction (f(th)) with mean values of alpha(nt)= 0.97 +/- 0.16(0.79 +/- 0.15 for the total spectral index) and f(th) = (10 +/- 9)% at 1.4 GHz. The MRC luminosity changes over similar to 3 orders of magnitude in the sample, 4.3 x 10(2) L-circle dot < MRC < 3.9 x 10(5) L-circle dot. The thermal emission is responsible for similar to 23% of the MRC on average. We also compare the extinction-corrected diagnostics of the. star-formation rate (SFR) with the thermal and nonthermal radio tracers and derive the first star-formation calibration relations using the MRC radio luminosity. The nonthermal spectral index flattens with increasing SFR surface density, indicating the effect of the star-formation feedback on the cosmic-ray electron population in galaxies. Comparing the radio and IR SEDs, we find that the FIR-to-MRC ratio could decrease with SFR, due to the amplification of the magnetic fields in starforming regions. This particularly implies a decrease in the ratio at high redshifts, where mostly luminous/starforming galaxies are detected.
Keywords
galaxies:ISM, galaxies: star formation, infrared: galaxies, radio continuum: galaxies, surveys Supporting material: machine-readable tables, FAR-INFRARED/RADIO CORRELATION, FORMATION RATE INDICATORS, MAGNETIC-FIELD STRUCTURE, SMALL-MAGELLANIC-CLOUD, SHAPLEY-AMES GALAXIES, NRAO PMN SURVEYS, NEARBY GALAXIES, SPIRAL GALAXIES, CONTINUUM SURVEY, NONTHERMAL RADIO

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Please use this url to cite or link to this publication:

Chicago
Tabatabaei, FS, E Schinnerer, M Krause, G Dumas, S Meidt, A Damas-Segovia, R Beck, et al. 2017. “The Radio Spectral Energy Distribution and Star-formation Rate Calibration in Galaxies.” Astrophysical Journal 836 (2).
APA
Tabatabaei, F., Schinnerer, E., Krause, M., Dumas, G., Meidt, S., Damas-Segovia, A., Beck, R., et al. (2017). The radio spectral energy distribution and star-formation rate calibration in galaxies. ASTROPHYSICAL JOURNAL, 836(2).
Vancouver
1.
Tabatabaei F, Schinnerer E, Krause M, Dumas G, Meidt S, Damas-Segovia A, et al. The radio spectral energy distribution and star-formation rate calibration in galaxies. ASTROPHYSICAL JOURNAL. 2017;836(2).
MLA
Tabatabaei, FS, E Schinnerer, M Krause, et al. “The Radio Spectral Energy Distribution and Star-formation Rate Calibration in Galaxies.” ASTROPHYSICAL JOURNAL 836.2 (2017): n. pag. Print.
@article{8549939,
  abstract     = {We study the spectral energy distribution (SED) of the radio continuum (RC) emission from the Key Insight in Nearby Galaxies Emitting in Radio (KINGFISHER) sample of nearby galaxies to understand the energetics and origin of this emission. Effelsberg multi-wavelength observations at 1.4, 4.8, 8.4, and 10.5 GHz combined with archive data allow us, for the first time, to determine the mid-RC (1-10 GHz, MRC) bolometric luminosities and further present calibration relations versus the monochromatic radio luminosities. The 1-10 GHz radio SED is fitted using a Bayesian Markov Chain Monte Carlo technique leading to measurements for the nonthermal spectral index (S-nu similar to nu(-alpha nt)) and the thermal fraction (f(th)) with mean values of alpha(nt)= 0.97 +/- 0.16(0.79 +/- 0.15 for the total spectral index) and f(th) = (10 +/- 9)\% at 1.4 GHz. The MRC luminosity changes over similar to 3 orders of magnitude in the sample, 4.3 x 10(2) L-circle dot {\textlangle} MRC {\textlangle} 3.9 x 10(5) L-circle dot. The thermal emission is responsible for similar to 23\% of the MRC on average. We also compare the extinction-corrected diagnostics of the. star-formation rate (SFR) with the thermal and nonthermal radio tracers and derive the first star-formation calibration relations using the MRC radio luminosity. The nonthermal spectral index flattens with increasing SFR surface density, indicating the effect of the star-formation feedback on the cosmic-ray electron population in galaxies. Comparing the radio and IR SEDs, we find that the FIR-to-MRC ratio could decrease with SFR, due to the amplification of the magnetic fields in starforming regions. This particularly implies a decrease in the ratio at high redshifts, where mostly luminous/starforming galaxies are detected.},
  articleno    = {185},
  author       = {Tabatabaei, FS and Schinnerer, E and Krause, M and Dumas, G and Meidt, S and Damas-Segovia, A and Beck, R and Murphy, EJ and Mulcahy, DD and Groves, B and Bolatto, A and Dale, D and Galametz, M and Sandstrom, K and Boquien, M and Calzetti, D and Kennicutt, RC and Hunt, LK and De Looze, Ilse and Pellegrini, EW},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  language     = {eng},
  number       = {2},
  pages        = {24},
  title        = {The radio spectral energy distribution and star-formation rate calibration in galaxies},
  url          = {http://dx.doi.org/10.3847/1538-4357/836/2/185},
  volume       = {836},
  year         = {2017},
}

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