English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Context. Cosmic rays and magnetic fields are key ingredients in galaxyevolution, regulating both stellar feedback and star formation. Theirproperties can be studied with low-frequency radio continuum observations, freefrom thermal contamination. Aims. We define a sample of 76 nearby (< 30 Mpc)galaxies, with rich ancillary data in the radio continuum and infrared from theCHANG-ES and KINGFISH surveys, which will be observed with the LOFAR Two-metreSky Survey (LoTSS) at 144 MHz. Methods. We present maps for 45 of them as partof the LoTSS data release 2 (LoTSS-DR2), where we measure integrated fluxdensities and study integrated and spatially resolved radio spectral indices.We investigate the radio-SFR relation, using star-formation rates (SFR) fromtotal infrared and H $\alpha$ + 24-$\mu$m emission. Results. The radio-SFRrelation at 144 MHz is clearly super-linear with $L_{144} \proptoSFR^{1.4-1.5}$. The mean integrated radio spectral index between 144 and$\approx$1400 MHz is $\langle \alpha\rangle = -0.56 \pm 0.14$, in agreementwith the injection spectral index for cosmic ray electrons (CRE). However, theradio spectral index maps show a variation of spectral indices with flatterspectra associated with star-forming regions and steeper spectra in galaxyoutskirts and, in particular, in extra-planar regions. We found that galaxieswith high star-formation rates (SFR) have steeper radio spectra; we findsimilar 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 thegalaxies. This explains the super-linear radio-SFR relation, with more massive,star-forming galaxies being radio bright. We propose a semi-calorimetricradio-SFR relation, which employs the galaxy mass as a proxy for thecalorimetric efficiency.

Nearby galaxies in LoTSS-DR2: insights into the non-linearity of the radio-SFR relation