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Astron. Astrophys. 332, 1025-1034 (1998)

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A study of the interstellar gas surrounding Carina OB2

J.R. Rizzo * 1 and E.M. Arnal ** 1, 2

1 Instituto Argentino de Radioastronomía, C. C. [FORMULA] 5, 1894 Villa Elisa, Argentina
2 Facultad de Ciencias Astronómicas y Geofísicas, Av. Paseo del Bosque s/n, 1900 La Plata, Argentina

Received 15 September 1997 / Accepted 8 December 1997


A huge HI cavity delimited by a large and ellipsoidal HI feature, has been found toward the stellar association Car OB2. Based on the good agreement found between the mean radial velocity of the HI feature ([FORMULA] km s-1) and the radial velocity of the OB association ([FORMULA] km s-1), and the coincidence in position between the barycentral position of the HI feature and the optical position of Car OB2, a physical link between the neutral gas and the stellar association is suggested. The interaction of the stellar winds of the most massive members of Car OB2 with its local ISM could have given rise to both the HI low emissivity region and the surrounding HI shell. The HI shell appears to be expanding at [FORMULA] 22 km s-1.

The HI feature has a counterpart in the CO emission. The size and kinematical parameters of the molecular gas almost mimic those of the atomic gas.

Based on the evidence presented in this paper, the anomalous behavior of the HI along [FORMULA], first noticed by Humphreys & Kerr (1974), would merely be a perturbation of the HI local to Car OB2, and would not represent a phenomenon on a galactic scale.

Key words: open clusters and associations: individual: Car OB2 – ISM: clouds – Hii regions – ISM: kinematics and dynamics – radio lines: ISM

* Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, Argentina
** Member of the Carrera del Investigador Científico of the CONICET

Send offprint requests to: José Ricardo Rizzo

© European Southern Observatory (ESO) 1998

Online publication: March 30, 1998