The MUSE Atlas of Disks (MAD): Ionized gas kinematic maps and an application to Diffuse Ionized Gas

TL;DR

This study presents high-resolution ionized gas kinematic maps of 41 star-forming galaxies from the MAD survey, analyzing diffuse ionized gas dynamics and their relation to galaxy structure.

Contribution

It introduces a methodology for measuring ionized gas kinematics and applies it to study diffuse ionized gas, revealing its slower rotation and higher velocity dispersion compared to star-forming gas.

Findings

Diffuse ionized gas rotates slower than star-forming gas by 0-10 km/s.

Diffuse ionized gas has higher velocity dispersion than star-forming gas.

Most diffuse ionized gas kinematics are consistent with a thicker, lower scale height layer.

Abstract

We have obtained data for 41 star forming galaxies in the MUSE Atlas of Disks (MAD) survey with VLT/MUSE. These data allow us, at high resolution of a few 100 pc, to extract ionized gas kinematics ($V, \sigma$) of the centers of nearby star forming galaxies spanning 3 dex in stellar mass. This paper outlines the methodology for measuring the ionized gas kinematics, which we will use in subsequent papers of this survey. We also show how the maps can be used to study the kinematics of diffuse ionized gas for galaxies of various inclinations and masses. Using two different methods to identify the diffuse ionized gas, we measure rotation velocities of this gas for a subsample of 6 galaxies. We find that the diffuse ionized gas rotates on average slower than the star forming gas with lags of 0-10 km/s while also having higher velocity dispersion. The magnitude of these lags is on average 5 km/s lower than observed velocity lags between ionized and molecular gas. Using Jeans models to interpret the lags in rotation velocity and the increase in velocity dispersion we show that most of the diffuse ionized gas kinematics are consistent with its emission originating from a somewhat thicker layer than the star forming gas, with a scale height that is lower than that of the stellar disk.