Shuntaro A. Yoshida | Searcharxiv

arXiv2026

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

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 $q_ν$. 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 $γ=-0.63$. The ensemble-averaged $q_ν$ 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).

astro-ph.GA↗

arXiv2022

Galaxy Manifold: Characterizing and understanding galaxies with two parameters

We report the discovery of a two-dimensional Galaxy Manifold within the multi-dimensional luminosity space of local galaxies. The multi-dimensional luminosity space is constructed using 11 bands that span from far ultraviolet to near-infrared for redshift < 0.1 galaxies observed with GALEX, SDSS, and UKIDSS. The two latent parameters are sufficient to express 93.2% of the variance in the galaxy sample, suggesting that this Galaxy Manifold is one of the most efficient representations of galaxies. The transformation between the observed luminosities and the manifold parameters as an analytic mapping is provided. The manifold representation provides accurate (85%) morphological classifications with a simple linear boundary, and galaxy properties can be estimated with minimal scatter (0.12 dex and 0.04 dex for star formation rate and stellar mass, respectively) by calibrating with the two-dimensional manifold location. Under the assumption that the manifold expresses the possible parameter space of galaxies, the evolution on the manifold is considered. We find that constant and exponentially decreasing star formation histories form almost orthogonal modes of evolution on the manifold. Through these simple models, we understand that the two modes are closely related to gas content, which suggests the close relationship of the manifold to gas accretion. Without assuming a star formation history, a gas-regulated model reproduces an exponentially declining star formation history with a timescale of $\sim$1.2 Gyrs on the manifold. Lastly, the found manifold suggests a paradigm where galaxies are characterized by their mass/scale and specific SFR, which agrees with previous studies of dimensionality reduction.

astro-ph.GA↗