HI-detected Dwarf Galaxies in the FASHI Survey: Insights from Single- and Double-Peaked Emission-Line Samples

TL;DR

This study analyzes low HI mass dwarf galaxies detected by the FASHI survey, revealing their photometric properties, dynamical states, and potential evolutionary links with other dwarf galaxy types, based on spectral profile classifications.

Contribution

It introduces a detailed photometric and dynamical analysis of HI-selected dwarf galaxies, highlighting differences based on spectral line profiles and proposing evolutionary connections.

Findings

Double-peaked sources follow the Tully-Fisher relation.

Single-peaked sources follow the Faber-Jackson relation with large scatter.

HI-selected dwarfs have similar stellar mass densities to dwarf ellipticals.

Abstract

We present a sample of low HI mass dwarf galaxies ($M_{\rm HI} < 10^8 M_\odot$) detected by The FAST All Sky HI 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 (DECaLS) data to perform careful photometric measurements, and find that the low HI mass galaxies have similar stellar mass densities to dwarf elliptical (dE) galaxies. Compared to other dwarf galaxy populations, the HI-selected dwarfs exhibit higher stellar mass densities than ultradiffuse galaxies, and similar densities to HI-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 HI 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 HI-selected dwarf galaxies with single-peaked HI 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.