The molecular gas content of blue dwarf galaxies^*

A collapsing detached molecular system in He 2–10?

¹ Departamento de Ingeniera Electrica, Pontificia Universidad Catolica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile e-mail: lvanzi@ing.puc.cl
² European Southern Observatory, Alonso de Cordoba 3107, Vitacura, Santiago, Chile
³ Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
⁴ Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁵ Institut dAstrophysique de Paris, 98bis Bd Arago, 75014 Paris, France

Received: 10 June 2008
Accepted: 20 January 2009

Abstract

We present new observations of a sample of blue dwarf galaxies in the lines of CO(3–2) and HCN(4–3). The observations were obtained with the 12 m APEX telescope located at an altitude of 5100 m in Chajnantor (ALMA site). We detected CO(3–2) emission in seven of nine observed galaxies in our sample. In two galaxies, NGC 5253 and He 2–10, we mapped the central in the CO(3–2) emission line. In He 2–10, we detected an extended component of molecular gas to the north-east of the main body of the galaxy. Comparing our data with previous HI and CO observations, we speculate that the presence of this detached cloud of molecular gas is produced by the merger already known in He 2–10, and could lead to the formation of a small tidal dwarf galaxy. The HCN(4–3) line was observed in NGC 5253 and He 2–10 only, but not detected.