CHILLING: Continuum Halos in LVHIS Local Irregular Nearby Galaxies

Radio continuum spectral behavior of dwarf galaxies

¹ Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB) Universitätsstraße 150 44801 Bochum, Germany
² Ruhr Astroparticle and Plasma Physics Center (RAPP Center) 44780 Bochum, Germany
³ CSIRO Space and Astronomy PO Box 1130 Bentley WA 6102, Australia
⁴ National Science Foundation, 2415 Eisenhower Avenue Alexandria VA 22314, USA
⁵ Department of Physics, University of Maryland Baltimore County 1000 Hilltop Circle Baltimore MD 21250, USA
⁶ SKA Observatory, SKA-Low Science Operations Centre 26 Dick Perry Avenue Kensington WA 6151, Australia
⁷ National Radio Astronomy Observatory 1011 Lopezville Road Socorro NM 87801, USA
⁸ National Radio Astronomy Observatory 520 Edgemont Road Charlottesville VA 22903, USA
⁹ International Centre for Radio Astronomy Research, Curtin University Bentley WA, Australia

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 12 September 2025
Accepted: 15 December 2025

Abstract

Context. Dwarf galaxies, due to their shallow gravitational potentials, provide critical environments for studying feedback mechanisms from star formation and its impacts on dwarf galaxy evolution. In particular, radio continuum (RC) observations offer valuable insights into cosmic ray dynamics, which play a significant role in shaping these processes.

Aims. This study investigates the detectability and spectral characteristics of RC emission in a sample of 15 dwarf galaxies (11 gas-rich, star-forming dwarfs and four blue compact dwarfs) spanning a broad range of stellar masses and star formation histories.

Methods. Using multi-band RC data (L/S-, C-, and X-band) from the Australia Telescope Compact Array, we analyse the physical conditions responsible for RC emission and explore the dominant emission mechanisms within these systems.

Results. RC emission is detected in 11 out of the 15 galaxies. Our results indicate that RC emission correlates strongly with star formation rate, far-infrared, and stellar mass, while dynamic parameters such as HI and rotational velocity exhibit no significant correlation with RC detectability. Spectral analysis reveals that the RC spectral energy distribution in these galaxies frequently deviate from a simple power-law behaviour, instead displaying curvature that suggests more complex underlying physical processes. Statistical model comparison confirms that a single power-law model is inadequate to capture the observed spectral shapes, emphasising the necessity of more sophisticated approaches. Additionally, the observed radio–far-infrared correlation indicates that cosmic ray electrons in lower-mass dwarf galaxies cool more rapidly than they can escape (e.g. via galactic winds), resulting in a measurable RC deficit.