Highly ionized plasma in the Large Magellanic Cloud: evidence for outflows and a possible galactic wind

Abstract

Based on an analysis of the interstellar highly ionized species C iv, Si iv, N v and O vi observed in the Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) E140M spectra of four hot stars in the Large Magellanic Cloud (LMC), we find evidence for a hot LMC halo fed by energetic outflows from the LMC disc and even possibly an LMC galactic wind. Signatures for such outflows are the intermediate- and high-velocity components relative to the LMC disc observed in the high- and low-ion absorption profiles. The stellar environments produce strong, narrow components of C iv and Si iv associated with the LMC disc; in particular they are likely signatures of H ii regions and expanding shells. Broad components are observed in the profiles of C iv, Si iv and O vi with their widths implying hot, collisionally ionized gas at temperatures of a few times 105 K. There is a striking similarity in the O vi/C iv ratios for the broad LMC and high-velocity components, suggesting much of the material at is associated with the LMC. The velocity of the high-velocity component is large enough to escape altogether the LMC, polluting the intergalactic space between the LMC and the Milky Way. The observed high-ion ratios of the broad LMC and high-velocity components are consistent with those produced in conductive interfaces; such models are also favoured by the apparent kinematically coupling between the high and the weakly ionized species. © 2007 The Authors. Journal compilation © 2007 RAS.