CO observations in the direction of southern HII regions ^*,**

¹ Laboratoire d'Astronomie de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 04, France
² Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
³ Observatoire de Bordeaux, 2 rue de l'Observatoire, 33270 Floirac, France

Corresponding author: D. Russeil, delphine.russeil@oamp.fr

Received: 4 August 2000
Accepted: 2 December 2003

Abstract

We present ¹²CO(1–0), ¹²CO(2–1) and/or ¹³CO(1–0) observations, obtained with the 15 m SEST telescope, in the direction of 252 southern HII regions located within 2° of the galactic plane and in the interval 280. The data presented here are an important contribution to the study of the large scale structure of our Galaxy (not discussed here) as molecular information is part of the multi-wavelength study of the galactic plane. We used kinematical criteria to distinguish between lines associated with HII regions and non-associated ones. We find that HII regions are associated with molecular lines exhibiting a line-width larger than 2.5 km s^-1. From a kinematical point of view we find that the velocity difference (Vco-VHII) peaks at 0 km s^-1. Non-associated CO lines with the same kinematics as diffuse Hα emission (the Warm Interstellar Medium) are used to extract some statistical properties encountered in this more diffuse medium. We can determine the velocity of the three diffuse ionised gas layers detected in Hα: -3.6, -26.5 and -45.5 km .