Physical and kinematical properties of a newly discovered star cluster and its associated jet in the Vela Molecular Clouds ^*,**,***

¹ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio, Italy e-mail: [teresa;dloren;bruni;vitali]@mporzio.astro.it
² Università degli Studi di Roma “Tor Vergata" – Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Roma, Italy
³ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: fmassi@arcetri.astro.it

Corresponding author: A. Caratti o Garatti, caratti@mporzio.astro.it

Received: 12 January 2004
Accepted: 31 March 2004

Abstract

The star forming region associated with IRAS 08211-4158 and located in the Vela Molecular Ridge (VMR) has been investigated with low () and high resolution () near infrared spectroscopy (1-2.5 μm) together with narrow band ([] and H₂) and broad band (H, K, L, M) imaging. The photometric results allow us to identify for the first time a young cluster with the less evolved star lying toward its center. Our results confirm that the most massive stars found in the clusters of the VMR do not form before the low mass ones. In particular, the only bipolar jet detected across the investigated field is driven by the most massive object which lacks an optical counterpart. Such a jet is composed of individual knots showing several H₂ and [] emission lines indicative of a coexistence of different shocks responsible for their excitation. Physical parameters of the emitting gas such as electron density, extinction and temperature have been derived from the low resolution spectroscopy. Some knots are already thermalized, while other present a stratification of temperature up to values of 5000 K. Through high resolution spectroscopy the [] lines profile for the majority of the knots can be resolved in a double peaked structure which is consistent with bow shock model predictions. Moreover, the radial velocity component is determined for different knots. Finally, by comparing [] images taken in different epochs, we have been able to derive the proper motion for some knots, hence to evaluate their total velocity (~300 km s^-1), the dynamical age and the jet inclination with respect to the plane of the sky.