WLM: Dynamics of an isolated Dwarf Irregular Galaxy Under Ram Pressure in the Local Group

TL;DR

This study investigates how ram pressure from the intergalactic medium influences the gas dynamics of the dwarf irregular galaxy WLM, revealing asymmetric rotation and the importance of modeling multiple dynamical components for accurate mass estimates.

Contribution

It demonstrates the impact of ram pressure on WLM's gas kinematics and decomposes its structure into components with different dynamical responses, highlighting the need for detailed modeling.

Findings

Ram pressure perturbs WLM's outer gas dynamics.

WLM decomposes into a bar-like core and an extended disk.

Mass estimates must consider asymmetric rotation and multiple components.

Abstract

WLM is an archetypal dwarf irregular galaxy that has not experienced interactions with major Local Group galaxies within the past 8 Gyr. It has recently been shown that WLM is losing its gas due to ram pressure forces exerted by the surrounding intergalactic medium (IGM). In this work, we explore how ram pressure may also affect the WLM gas kinematics, and we show that its dynamics is especially perturbed at its outskirts, explaining the asymmetric rotation between the approaching and receding sides. Moreover, we have been able to decompose WLM in two main components, a compact one with a solid-body rotation that resembles a bar-like structure, and a more extended one with a characteristic double-horn profile suggesting an edge-on disk. The former is relatively unaffected by ram pressure while the latter has its dynamics considerably affected by ram pressure. This study shows that mass estimates of a dwarf galaxy like WLM should account for a full modeling of its dynamical components, especially accounting for its asymmetric rotation curve.