S. Bontemps 1, A.A. Kaas 1, G. Olofsson 1, L. Nordh 1, & P. André 1
1 Stockholm Observatory, Sweden
2 CEA/SAp, C.E. Saclay, France
The guaranteed time survey of star forming regions by Nordh, Olofsson et al. of the ISOCAM consortium consists of systematic mappings of the closest star forming regions into the 6.7 and 14.3 micron ISOCAM broad-band filters.
The Rho Ophiuchi cloud is one of the main targets of this program, and has been fully mapped to systematically survey for mid-IR sources. This star forming region is one of the corner-stones of the observational approach for star formation. It has been important in the past for our understanding of the process of the low-mass star formation by providing a closeby (125 pc), rich sample of Young Stellar Objects (YSOs) still deeply embedded in their parent cloud.
We will present the results of the ISOCAM survey in Rho Oph by reviewing the new ISOCAM census for the different Classes of YSOs, and by emphasizing the ability of the mid-IR photometry by ISOCAM at recognizing a large number of new YSOs. It appears that ISOCAM identifies a factor of 2 more Class II YSOs, and then emphasizes a rich sample of young T Tauri stars still deeply embedded in the cloud. This ISOCAM sample of 120 stars will then be used to discuss the recent star formation activity of Rho Ophiuchi, and to constrain the properties of the stars formed in this cloud. In particular, we will show a new luminosity function of the stars recently formed in Rho Oph, far more complete toward the low luminosities. This luminosity function appears to be consistent only with a rather young population of T Tauri stars of the order of 0.4 Myr. We will finally discuss the constrains on the Initial Mass Func- -tion in Rho Oph which can be extracted from this more complete luminosity function. We find that the underlying IMF should closely resemble the shape of the most recently derived galactic IMF obtained from nearby field stars down to, at least, 0.1 solar mass.