Bibcode
Tabatabaei, F. S.; Schinnerer, E.; Krause, M.; Dumas, G.; Meidt, S.; Damas-Segovia, A.; Beck, R.; Murphy, E. J.; Mulcahy, D. D.; Groves, B.; Bolatto, A.; Dale, D.; Galametz, M.; Sandstrom, K.; Boquien, M.; Calzetti, D.; Kennicutt, R. C.; Hunt, L. K.; De Looze, I.; Pellegrini, E. W.
Bibliographical reference
The Astrophysical Journal, Volume 836, Issue 2, article id. 185, 24 pp. (2017).
Advertised on:
2
2017
Journal
Citations
129
Refereed citations
111
Description
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}ν ∼
{ν }-{α {nt}}) and the thermal fraction
({f}{th}) with mean values of {α }{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 ∼3 orders of magnitude in the sample, 4.3×
{10}2 {L}ȯ < MRC < 3.9×
{10}5 {L}ȯ . The thermal emission is
responsible for ∼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 star-forming regions. This
particularly implies a decrease in the ratio at high redshifts, where
mostly luminous/star-forming galaxies are detected.
Related projects
Spiral Galaxies: Evolution and Consequences
Our small group is well known and respected internationally for our innovative and important work on various aspects of the structure and evolution of nearby spiral galaxies. We primarily use observations at various wavelengths, exploiting synergies that allow us to answer the most pertinent questions relating to what the main properties of
Johan Hendrik
Knapen Koelstra