Radio continuum halos in nearby galaxies and the CHANG-ES project

About a decade ago, the upgrade from the classic Very Large Array into the EVLA, i.e. the Karl G. Jansky Very Large Array (VLA), made it possible to observe fainter radio continuum emission than ever before. The project Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES, PI: J. Irwin) has allowed us to probe gaseous halos of 35 edge-on galaxies with arcsecond details and faint microJansky/beam sensitivities, and to begin answering questions such as: What is the nature, prevalence and origin of radio halos? What happens at the interface between the disk and the halo? What is the role of magnetic fields in the halos? What can we learn from how the halo radio emission correlates with emission at other frequencies? A variety of angular scales (VLA’s B, C and D configurations) illuminate both faint diffuse emission and distinct filamentary structures in the halos. The wide bandwidths of the VLA (L, S and C bands, i.e. 1.2-7 GHz) in all Stokes products not only increase the sensitivity, but has allowed us to bring forth multi-frequency images, spectral index maps, and use rotation measure synthesis to study the magnetic fields (with great images as a result - to be shown!). While the magnetic field of the disk can be well explained by dynamo action, the 3D structure of the magnetic field in the halo region and its physical nature are still unclear, but we have now been able to probe these halo magnetic fields and start to study their role in the galaxy outskirts. In order to fill in the gap between the initial L and C-band we also observed S-band (5-7 GHz, 2020-2022), to study polarisation in the transition zone between Faraday thick and thin regimes. Like our previous data releases, the products from these new data will be made publicly available.

In this talk, I will describe the CHANG-ES project, its data products and exciting findings brought forth by the consortium members thanks to these data, as well as the continued journey and future prospects taking upcoming radio facilities into consideration.

20/06/2023 - 12:30
Theresa Wiegert