The GLEAM 200-MHz local radio luminosity function for AGN and star-forming galaxies

Abstract The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76–227 MHz of the entire southern sky (Declination $<\!{+}30^{\circ}$ ) with an angular resolution ${\approx}2$ arcmin. In this paper, we combine GLEAM data optical spectroscopy from 6dF Galaxy Survey to construct sample 1 590 local (median $z \approx 0.064$ sources $S_{200\,\mathrm{MHz}} > 55$ mJy across area ${\approx}16\,700\,\mathrm{deg}^{2}$ . From spectra, identify dominant physical process responsible for emission each galaxy: 73% are fuelled by active galactic nucleus (AGN) 27% star formation. We present luminosity function AGN star-forming (SF) galaxies 200 characterise typical spectra these two populations between 76 ${\sim}1$ GHz. For AGN, median spectral index GHz, $\alpha_{\mathrm{high}}$ , $-0.600 \pm 0.010$ (where $S \propto \nu^{\alpha}$ within band, $\alpha_{\mathrm{low}}$ $-0.704 0.011$ SF galaxies, value $-0.650 $-0.596 0.015$ Among population, flat-spectrum more common lower luminosity, suggesting existence significant population weak that remain core-dominated even low frequencies. However, around 4% have ultra-steep frequencies ( $\alpha_{\mathrm{low}} < -1.2$ ). These ultra-steep-spectrum span wide range in further work needed clarify their nature.