Astron. Astrophys. Suppl. Ser. 136, 471-490

Star formation in the Vela Molecular Clouds

III. Near IR images and mm photometry of D-cloud IRAS sources

F. Massi^1,2 - T. Giannini^1,2,3 - D. Lorenzetti^2,3 - R. Liseau⁴ - A. Moneti⁵ - P. Andreani⁶

Send offprint request: F. Massi

1 - Istituto Astronomico, Università "La Sapienza'', Via Lancisi 29, I-00161 Rome, Italy
2 - Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio (Rome), Italy
3 - Istituto di Fisica dello Spazio Interplanetario - CNR, Casella Postale 27, I-00044 Frascati (Rome), Italy
4 - Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden
5 - ISO Science Operation Centre, Astrophysics Division of ESA, Box 50727, E-28080 Madrid, Spain
6 - Dipartimento di Astronomia - Università di Padova, V.lo dell'Osservatorio 5, I-35122 Padova, Italy

Received July 17, 1998; accepted January 28, 1999

Abstract:

We present the first results of a sensitive ($K \approx$ 17 mag) near IR (JHK) imaging survey of a complete IRAS selected sample of Young Stellar Objects (YSO's) belonging to a Giant Molecular Cloud (GMC) located in the Vela Molecular Ridge (VMR). We provide accurate position and photometry for more than 1300 sources, along with the identification of possible NIR counterparts of the IRAS objects. Through near infrared and 1.3 mm photometry we have determined the spectral energy distributions of 11 newly discovered Class I sources and possibly one Herbig Ae/Be star. Their bolometric luminosities indicate that they are protostellar objects of intermediate masses ($\leq$ 10 $M_{\odot}$) with envelopes containing a not negligible fraction of the central condensed matter. Many sources are associated to diffuse emission which hosts multiple systems of point-like objects. Although clustering is well evident, the NIR counterparts of the IRAS sources seem to be single objects and quite often there are more than one source in the field with JHK colours typical of Class I objects. These findings support the fact that in VMR, as well, stars of different masses are sharing the same birthplace.

Key words: stars: formation -- stars: pre-main sequence -- infrared: stars -- ISM: individual objects (Vela clouds)