CHANG-ES: XXXVI. The thin and thick radio discs
arXiv:2505.13713 · doi:10.1051/0004-6361/202554046
Abstract
Context. Edge-on spiral galaxies give us an outsiders' view of the radio halo, which envelops these galaxies. The radio halos are caused by extra-planar cosmic-ray electrons that emit synchrotron emission in magnetic fields. Aims. We aim to study the origin of radio halos around galaxies and infer the role of cosmic-rays in supporting the gaseous discs. We would like to test the influence of star formation as the main source of cosmic rays as well as other fundamental galaxy properties such as mass and size. Methods. We present a study of radio continuum scale heights in 22 nearby edge-on galaxies from the CHANG-ES survey. We employ deep observations with the Jansky Very Large Array in the S-band (2-4 GHz), imaging at 7" angular resolution. We measure scale heights in three strips within the effective radio continuum radius, correcting for the influence of angular resolution and inclination angle. We include only galaxies where a distinction between the two disc components can be made in at least one of the strips, providing us with robust measurements of both scale heights. Results. We find a strong positive correlation between scale heights of the thin and thick discs and star-forming radius as well as star-formation rate (SFR); moderately strong correlations are found for the mass surface density and the ratio of SFR-to-mass surface density; no correlation is found with SFR surface density alone. Yet the SFR surface density plays a role as well: galaxies with high SFR surface densities have a rather roundish shape, whereas galaxies with little star formation show only a relatively small vertical extent in comparison to their size. Conclusions. Thick gaseous discs are partially supported by cosmic-ray pressure. Our results are a useful benchmark for simulations of galaxy evolution that include cosmic rays.
Accepted for publication in Astronomy & Astrophysics, section "4. Extragalactic astronomy"
References in corpus (21)
- The Circumgalactic Medium
- CASA, the Common Astronomy Software Applications for Radio Astronomy
- WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
- HyperLEDA. III. The catalogue of extragalactic distances
- The LOFAR Two-metre Sky Survey Deep fields: The star formation rate - radio luminosity relation at low frequencies
- CHANG-ES XXII: Coherent Magnetic Fields in the Halos of Spiral Galaxies
- Nearby galaxies in LoTSS-DR2: insights into the non-linearity of the radio-SFR relation
- CHANG-ES XIII: Transport processes and the magnetic fields of NGC 4666 - indication of a reversing disk magnetic field
- Cosmic rays and non-thermal emission in simulated galaxies. I. Electron and proton spectra compared to Voyager-1 data
- The NOD3 software package: A graphical user interface-supported reduction package for single-dish radio continuum and polarisation observations
- CHANG-ES XXI. Transport processes and the X-shaped magnetic field of NGC 4217: off-center superbubble structure
- CHANG-ES XX. High Resolution Radio Continuum Images of Edge-on Galaxies and their AGNs -- Data Release 3
- CHANG-ES XXIII: Influence of a galactic wind in NGC 5775
- CHANG-ES XXVI: Insights into cosmic-ray transport from radio halos in edge-on galaxies
- CHANG-ES XIV: Cosmic-ray propagation and magnetic field strengths in the radio halo of NGC 4631
- Nearby galaxies in the LOFAR Two-metre Sky Survey II. The magnetic field-gas relation
- eDIG-CHANGES I: Extended Hα Emission from the Extraplanar Diffuse Ionized Gas (eDIG) around CHANG-ES Galaxies
- CHANG-ES XXXII: Spatially Resolved Thermal/Nonthermal Separation from Radio Data Alone -- New Probes into NGC 3044 and NGC 5775
- A spatially resolved radio spectral study of the galaxy M 51
- CHANG-ES XXXIV: a 20 kpc radio bubble in the halo of the star-forming galaxy NGC 4217
- CHANG-ES XXXIV: Magnetic Field Structure in Edge-On Galaxies Characterising large-scale magnetic fields in galactic halos