Nearby galaxies in the LOFAR Two-metre Sky Survey. I. Insights into the non-linearity of the radio-SFR relation - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles Astronomy and Astrophysics - A&A Year : 2022

Nearby galaxies in the LOFAR Two-metre Sky Survey. I. Insights into the non-linearity of the radio-SFR relation

V. Heesen
  • Function : Author
M. Staffehl
  • Function : Author
A. Basu
  • Function : Author
R. Beck
  • Function : Author
M. Stein
  • Function : Author
F. S. Tabatabaei
  • Function : Author
M. J. Hardcastle
  • Function : Author
K. T. Chyży
  • Function : Author
T. W. Shimwell
  • Function : Author
B. Adebahr
  • Function : Author
R. Beswick
  • Function : Author
D. J. Bomans
  • Function : Author
A. Botteon
  • Function : Author
E. Brinks
  • Function : Author
M. Brüggen
  • Function : Author
R. -J. Dettmar
  • Function : Author
A. Drabent
  • Function : Author
F. de Gasperin
  • Function : Author
G. Gürkan
  • Function : Author
G. H. Heald
  • Function : Author
C. Horellou
  • Function : Author
B. Nikiel-Wroczynski
  • Function : Author
R. Paladino
  • Function : Author
J. Piotrowska
  • Function : Author
H. J. A. Röttgering
  • Function : Author
D. J. B. Smith
  • Function : Author

Abstract

Context. Cosmic rays and magnetic fields are key ingredients in galaxy evolution, regulating both stellar feedback and star formation. Their properties can be studied with low-frequency radio continuum observations that are free from thermal contamination.
Aims: We define a sample of 76 nearby (< 30 Mpc) galaxies with rich ancillary data in the radio continuum and infrared from the CHANG-ES and KINGFISH surveys, which will be observed with the LOFAR Two-metre Sky Survey (LoTSS) at 144 MHz.
Methods: We present maps for 45 of them as part of the LoTSS data release 2 (LoTSS-DR2), where we measure integrated flux densities and study integrated and spatially resolved radio spectral indices. We investigate the radio-star formation rate (SFR) relation using SFRs derived from total infrared and Hα + 24-μm emission.
Results: The radio-SFR relation at 144 MHz is clearly super-linear with L144 MHz ∝ SFR1.4−1.5. The mean integrated radio spectral index between 144 and ≈1400 MHz is ⟨α⟩= − 0.56 ± 0.14, in agreement with the injection spectral index for cosmic ray electrons (CREs). However, the radio spectral index maps show variation of spectral indices with flatter spectra associated with star-forming regions and steeper spectra in galaxy outskirts and, in particular, in extra-planar regions. We found that galaxies with high SFRs have steeper radio spectra; we find similar correlations with galaxy size, mass, and rotation speed.
Conclusions: Galaxies that are larger and more massive are better electron calorimeters, meaning that the CRE lose a higher fraction of their energy within the galaxies. This explains the super-linear radio-SFR relation, with more massive, star-forming galaxies being radio bright. We propose a semi-calorimetric radio-SFR relation that employs the galaxy mass as a proxy for the calorimetric efficiency.

Tables and fits maps are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/664/A83

Fichier principal
Vignette du fichier
aa42878-21.pdf (33.68 Mo) Télécharger le fichier
Origin Publisher files allowed on an open archive

Dates and versions

insu-03849380 , version 1 (11-11-2022)

Identifiers

Cite

V. Heesen, M. Staffehl, A. Basu, R. Beck, M. Stein, et al.. Nearby galaxies in the LOFAR Two-metre Sky Survey. I. Insights into the non-linearity of the radio-SFR relation. Astronomy and Astrophysics - A&A, 2022, 664, ⟨10.1051/0004-6361/202142878⟩. ⟨insu-03849380⟩
109 View
8 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More