WALLABY Pre-pilot Survey: The Effects of Tidal Interaction on Radial Distribution of Color in Galaxies of the Eridanus Supergroup

We study the tidal interaction of galaxies in the Eridanus supergroup, using H I data from the pre-pilot survey of the Widefield ASKAP L-band Legacy All-sky Blind surveY. We obtain optical photometric measurements and quantify the strength of tidal perturbation using a tidal parameter S _sum. For low-mass galaxies of M _* ≲ 10⁹ M _⊙, we find a dependence of decreasing H I to optical disk size ratio with increasing S _sum, but no dependence of H I spectral line asymmetry with S _sum. This is consistent with the behavior expected under tidal stripping. We confirm that the color profile shape and color gradient depend on the stellar mass, but there is an additional correlation of low-mass galaxies having their color gradients within 2R ₅₀ increasing with higher S _sum. For these low-mass galaxies, the dependence of color gradients on S _sum is driven by the color becoming progressively redder in the inner disk when tidal perturbations are stronger. For high-mass galaxies, there is no dependence of color gradients on S _sum, and we find a marginal reddening throughout the disks with increasing S _sum. Our result highlights tidal interaction as an important environmental effect in producing the faint end of the star formation suppressed sequence in galaxy groups.