New Research links Dust, Gas, and light Blockage in Spiral Galaxies
Geneva, Switzerland - A new study published September 1, 2025, on the arXiv preprint server details a comprehensive inquiry into how dust and gas affect the visibility of light within nearby spiral galaxies. Researchers,led by Evangelos Dimitrios Paspaliaris,have mapped the distribution of dust and gas alongside measurements of optical attenuation – the dimming of light – to understand how these elements interact across galactic discs at resolutions smaller than 0.5 kpc. The findings offer crucial insights into star formation processes and the evolution of galaxies.
This research addresses a fundamental challenge in astronomy: accurately measuring star formation rates. Dust and gas obscure light, making stars appear dimmer and cooler than they are. By precisely quantifying this “attenuation,” astronomers can better estimate the true energy output of stars and, consequently, the rate at which new stars are born. The study focuses on five nearby star-forming spirals, utilizing data spanning the ultraviolet to sub-millimeter wavelengths, combined with optical integral-field spectroscopy and gas density maps.
The team employed the CIGALE SED-fitting code to determine dust mass surface density ($Sigmamathrm{dust}$) and optical attenuation ($A{V,mathrm{SED}}$) for diffrent stellar populations.They then independently calculated attenuation using the Balmer decrement ($A{V,mathrm{BD}}$) for each pixel within the galaxies. The analysis revealed that both dust distribution and Balmer decrement-derived attenuation correlate more strongly with molecular and total gas mass than with atomic gas alone. Researchers observed that as the proportion of molecular gas increases, atomic gas surface densities – often indicative of molecular gas shielding – decrease, and the overall dust-to-gas ratio increases from galaxy to galaxy.
Notably, the attenuation measured for young stars ($A^mathrm{young}{V,mathrm{SED}}$) closely matched the values derived from the Balmer decrement ($A{V,mathrm{BD}}$), suggesting the SED-fitting method can reliably estimate attenuation even in galaxies lacking detailed spectroscopic data. The ratio of $A{V,mathrm{BD}}$ to total stellar $A_{V,mathrm{SED}}$ was found to be slightly higher than previously reported.
Further investigation into dust distribution models showed that attenuation affecting older stars aligns with expectations for a mixed stellar and dust configuration, typical of galactic discs. Though, attenuation impacting younger stars and measured via the Balmer decrement fell between the predictions for a simple foreground dust screen and a fully mixed scenario, indicating a more complex interplay between dust and star-forming regions. This work, documented in paper [2509.01803],provides a valuable framework for interpreting observations of star-forming galaxies and refining our understanding of galactic evolution.
