Estimating Galaxy Star Formation Rates from Murchison Widefield Array Radio Continuum Emission

Abstract

We investigate the frequency dependence of the low-frequency infrared (IR)--radio correlation for nearby galaxies drawn from the {\sl Herschel} Reference Survey (HRS), using radio continuum observations from the GaLactic and Extragalactic All-sky MWA (GLEAM) survey obtained with the Murchison Widefield Array (MWA). The GLEAM survey provides densely sampled flux densities across 20 sub-bands spanning 72--231 MHz, allowing detailed characterization of the low-frequency radio spectral energy distribution (SED). We analyze 18 nearby galaxies detected by GLEAM and examine the frequency dependence of the IR--radio correlation coefficient $q_\nu$. Among these galaxies, three sources show Seyfert or LINER signatures and may contain non-negligible AGN contributions to the radio continuum emission. We therefore use the remaining 15 predominantly star-forming galaxies as the primary sample for deriving the main calibration results. For the majority of the sample, the low-frequency radio continuum is well described by a single power-law spectral model from the GLEAM frequency range up to 1.5 GHz, with a median spectral index of $\gamma=-0.63$. The ensemble-averaged $q_\nu$ relation and its intrinsic scatter provide a practical calibration for converting low-frequency radio luminosities into star formation rates (SFRs), while explicitly quantifying the associated systematic uncertainty. Our results indicate that the low-frequency IR--radio correlation remains stable across the MWA bands for nearby star-forming galaxies, supporting the use of low-frequency radio continuum as a dust-unbiased tracer of star formation in the local Universe. These results provide a local benchmark for interpreting low-frequency radio continuum surveys and for future studies of radio-based SFR tracers with next-generation facilities such as the Square Kilometre Array (SKA).