The local Tully-Fisher relation for dwarf galaxies

TL;DR

This study examines the baryonic Tully-Fisher relation for Local Volume dwarf galaxies, finding a consistent relation with observed scatter influenced mainly by measurement errors, and noting similar trends in Milky Way and M31 satellites.

Contribution

It provides a detailed analysis of the local Tully-Fisher relation for dwarf galaxies, including factors affecting scatter and comparison with satellite galaxies.

Findings

Established a baryonic Tully-Fisher relation with specific parameters.

Identified main sources of scatter as observational errors and inclination uncertainties.

Found Milky Way and M31 satellites follow a similar relation with slightly lower masses.

Abstract

We study different incarnations of the Tully-Fisher (TF) relation for the Local Volume (LV) galaxies taken from Updated Nearby Galaxy Catalog. The UNGC sample contains 656 galaxies with $W_{50}$ HI-line-width estimates, mostly belonging to low mass dwarfs. Of them, 296 objects have distances measured with accuracy better than 10%. For the sample of 331 LV galaxies having baryonic masses $\log M_{bar} > 5.8 \log M_\odot$ we obtain a relation $\log M_{bar}= 2.49 \log W_{50} + 3.97$ with observed scatter of 0.38 dex. The largest factors affecting the scatter are observational errors in $K$-band magnitudes and $W_{50}$ line widths for the tiny dwarfs, as well as uncertainty of their inclinations. We find that accounting for the surface brightness of the LV galaxies, or their gas fraction, or specific star formation rate, or the isolation index do not reduce essentially the observed scatter on the baryonic TF-diagram. We also notice that a sample of 71 dSph satellites of the Milky Way and M31 with known stellar velocity dispersion $\sigma^*$ tends to follow nearly the same bTF relation, having slightly lower masses than that of late-type dwarfs.