H <scp>I</scp> -detected Dwarf Galaxies in the FASHI Survey: Insights from Single- and Double-peaked Emission-line Samples

Abstract We present a sample of low H i mass ( M H I &lt; 10 8 M ⊙ ) dwarf galaxies detected by The FAST All Sky H i Survey (FASHI) project. Due to the faint and irregular morphology of these galaxies, the default photometry is often inaccurate. Therefore, we utilized The Dark Energy Camera Legacy Survey data to perform careful photometric measurements, and find that the low H i mass galaxies have similar stellar mass densities to dwarf elliptical galaxies. Compared to other dwarf galaxy populations, the H i -selected dwarfs exhibit higher stellar mass densities than ultradiffuse galaxies, and similar densities to H i -selected low-surface-brightness galaxies, albeit with lower stellar masses, suggesting a possible evolutionary connection among these populations. By classifying the galaxies according to their H i spectral-line profiles, we show that the double-peaked sources conform closely to the Tully–Fisher relation, whereas the single-peaked sources follow the Faber–Jackson relation but with large scatter. This indicates that the single-peaked systems are likely dispersion dominated and that the relationship between stellar mass and halo mass in such systems may remain consistent across both low- and high-mass regimes. These findings suggest that H i -selected dwarf galaxies with single-peaked H I profiles may share a similar dynamical state with massive ellipticals, offering new insights into their structural evolution and the diversity of formation pathways for low-mass galaxies.