next previous
Up: Abstract

A&A Supplement series, Vol. 123, May II 1997, 31-41

Received May 28; accepted September 6, 1996

Cold neutral gas associated with the Gum nebula

E.M. Reynosogif - G.M. Dubnergif

Send offprint request: E.M. Reynoso
Instituto de Astronomía y Física del Espacio, C.C.67, Suc. 28, 1428 Buenos Aires, Argentina.


Based on HI maps covering the 3 600 square degrees area delimited by tex2html_wrap_inline1196, we investigated the neutral hydrogen distribution in the Gum nebula and its environments. The main result is the appearence of a huge disk of neutral gas at a kinematical distance compatible with that of the nebula, and whose angular dimensions coincide with the optical image of the Gum nebula. The disk, roughly centered at tex2html_wrap_inline1198, is located at tex2html_wrap_inline1200 and has a radius of tex2html_wrap_inline1202. We propose that this HI disk is the neutral gas component of the optical nebula, hence becoming the first time in which a structure with the dimensions of the optical nebula is detected in other wavelengths. We analyze the fitting of observations with different theoretical models and conclude that the most plausible interpretation is that the Gum nebula is a supershell produced by the action of repeated SN explosions, where the explosions may have originated in the aged association Vela OB2. In this context, the thick HI shell shown by Dubner et al. (1992) near tex2html_wrap_inline1204 and the Vela SNR are the debris of two of the several outbursts which started in the region about tex2html_wrap_inline1206 years ago. The southern boundary is distorted due to the presence of a tex2html_wrap_inline1208 radius shell, which appears to be an interstellar bubble driven by the stellar winds of the O-type star HD 49798.

keywords: ISM: supernova remnants -- ISM: individual objects: Gum nebula -- ISM: bubbles -- radio lines: ISM

next previous
Up: Abstract

Copyright by the European Southern Observatory (ESO)