LITTLE THINGS in 3D: robust determination of the circular velocity of dwarf irregular galaxies

TL;DR

This paper presents a new method for accurately determining the circular velocity of dwarf irregular galaxies by fitting 3D models to HI data, providing valuable kinematic data for understanding low-mass galaxy dynamics.

Contribution

It introduces a novel 3D modeling approach using $^ ext{3D}$BAROLO to derive detailed kinematic parameters of dwarf irregular galaxies from HI datacubes, improving upon previous methods.

Findings

Dwarf irregular galaxies follow the baryonic Tully-Fisher relation.

The 3D modeling yields high-quality kinematic data for 17 galaxies.

Results are publicly available for further dynamical analysis.

Abstract

Dwarf Irregular galaxies (dIrrs) are the smallest stellar systems with extended HI discs. The study of the kinematics of such discs is a powerful tool to estimate the total matter distribution at these very small scales. In this work, we study the HI kinematics of 17 galaxies extracted from the `Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey' (LITTLE THINGS). Our approach differs significantly from previous studies in that we directly fit 3D models (two spatial dimensions plus one spectral dimension) using the software $^\text{3D}$BAROLO, fully exploiting the information in the HI datacubes. For each galaxy we derive the geometric parameters of the HI disc (inclination and position angle), the radial distribution of the surface density, the velocity-dispersion ($\sigma_v$) profile and the rotation curve. The circular velocity (V$_{\text{c}}$), which traces directly the galactic potential, is then obtained by correcting the rotation curve for the asymmetric drift. As an initial application, we show that these dIrrs lie on a baryonic Tully-Fisher relation in excellent agreement with that seen on larger scales. The final products of this work are high-quality, ready-to-use kinematic data ($\textrm{V}_\textrm{c}$ and $\sigma_v$) that we make publicly available. These can be used to perform dynamical studies and improve our understanding of these low-mass galaxies.