Star formation in the Vela Molecular Clouds - III. Near IR images and mm photometry of D-cloud IRAS sources

We present the first results of a sensitive (K approximate to 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 coun terparts of the IRAS objects. Through near infrared and 1.3 mm photometry w e have determined the spectral energy distributions of 11 newly discovered Class I sources and possibly one Herbig Ae/Be star. Their bolometric lumino sities indicate that they are protostellar objects of intermediate masses ( less than or equal to 10 M.) with envelopes containing a not negligible fra ction of the central condensed matter. Many sources are associated to diffu se emission which hosts multiple systems of point-like objects. Although cl ustering 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 fie ld with J H K colours typical of Class I objects. These findings support th e fact that in VMR, as well, stars of different masses are sharing the same birthplace.