Star-gas decoupling and a non-rotating stellar core in He 2-10: Integral field spectroscopy with FLAMES/ARGUS

TL;DR

This study uses integral field spectroscopy to compare stellar and gas kinematics in He 2-10, revealing decoupled motions that suggest the galaxy is transforming into a dwarf elliptical.

Contribution

First detailed kinematic comparison of stars and gas in He 2-10 using integral field spectroscopy, highlighting decoupled motions and galaxy evolution insights.

Findings

Stellar kinematics governed by random motions.

Gas shows spatial velocity variations up to 60 km/s.

Evidence of decoupled star and gas motions indicating galaxy transformation.

Abstract

We study the two-dimensional distribution and kinematics of the stellar and gaseous components in the centre of the blue compact dwarf galaxy, He 2-10. The aim is to compare the kinematics of gas and stars in order to determine whether they are consistent with one another, or if stars and gas can be decoupled due to gravitational perturbations and feedback from star formation. We have used the integral field unit ARGUS, part of FLAMES on the European Southern Observatory's Very Large Telescope, to target the near-infrared Ca-triplet in the central 300 times 480 parsecs of He 2-10. The selected wavelength regime includes several prominent spectral features, including the Paschen series and an [SIII] emission-line, which we have used to derive the kinematics of the ionised interstellar medium. We find no systematic trend in the velocities of the stars over the observed field of view and conclude that the stellar kinematics is governed by random motions. This is in contrast to the motions the ionised interstellar medium, where we find spatial velocity variations up to 60 km/s. Our gas velocity field is consistent with previous studies of both the molecular gas and the feedback-driven outflow in He 2-10. We interpret the kinematic decoupling between the stars and the gas as He 2-10 being in the process of transformation to a dwarf elliptical galaxy.