Far-ultraviolet diffuse emission as a tracer of Galactic extinction at the North Galactic Pole
Year: 2026
Type: article
Abstract: ABSTRACT Interstellar extinction at high Galactic latitude is often traced by thermal dust emission, but conversion of infrared surface brightness to reddening is sensitive to grain properties and temperature. We test dust-scattered far-ultraviolet (FUV) and near-ultraviolet (NUV) diffuse emission as a high-resolution extinction tracer towards the North Galactic Pole, where $E(B\!-\!V)\lt 0.1$ mag. We build 6-arcmin resolution FUV and NUV diffuse maps over $b \gt 70^\circ$ and compare them with the Planck $E(B\!-\!V)$ map at matched resolution. Direct pixel-to-pixel regression gives only moderate correlations ($\rho = 0.536$ for FUV, 0.243 for NUV), owing to scatter from $\mathrm{H_2}$ fluorescence, line emission, and photon-counting noise. We therefore construct per-pixel Galaxy Evolution Explorer (GALEX) uncertainty maps and fit the mean intensity in bins of $E(B\!-\!V)$, with iterative sigma-clipping, recovering tight relations ($\rho = 0.993$ for FUV, 0.976 for NUV): FUV $= 2285.3 E(B\!-\!V) + 278.6$ and NUV $= 1517.6 E(B\!-\!V) + 547.2$ ($\mathrm{photon\, cm^{-2}\, s^{-1}\, sr^{-1}\, \mathring{A}^{-1}}$ per $6\,\mathrm{arcmin}\,\times 6\,\mathrm{arcmin}$ pixel). Inverting these yields a $601 \times 601$ GALEX reddening map, which correlates strongly with HI4PI $\mathrm{ H}\,{\small I}$ column density ($\rho = 0.991$). Against Sloan Digital Sky Survey quasar extinctions, the GALEX and Planck maps agree (correlation 0.99, slope 0.986). Relative to the Pan-STARRS1 stellar reddening map of GALEX-based values show a smaller mean difference (0.039 mag) than Planck-based values (0.064 mag). Dust-scattered FUV emission is thus a viable alternative to thermal-dust extinction maps at high Galactic latitude.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
OpenAlex ID: W7214737511