Letter to the Editor

Star-gas decoupling and a non-rotating stellar core in He 2-10^*

Integral field spectroscopy with FLAMES/ARGUS

¹ Department of Astronomy and Space Physics, Box 515, 75120 Uppsala, Sweden e-mail: thomas.marquart@astro.uu.se
² Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
³ Stockholm Observatory, AlbaNova University Center, 106 91 Stockholm, Sweden
⁴ Observatoire Astronomique Marseille-Provence, Laboratoire d'Astrophysique de Marseille UMR 6110, 2 place Le Verrier, 13248 Marseille Cedex 4, France

Received: 22 June 2007
Accepted: 31 August 2007

Abstract

Aims.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.

Methods.We have used the integral field unit ARGUS, part of FLAMES on the European Southern Observatory's Very Large Telescope, to target the Ca ii 8498,8542,8662 Å triplet in the central 300  480 parsecs of He 2-10. The selected wavelength regime includes several prominent spectral features, including the Paschen series and the [S iii] emission-line, which we have used to derive the kinematics of the ionised interstellar medium.

Results.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^-1. 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.