C. Alves de Oliveira, E. Moraux, J. Bouvier, H. Bouy
To investigate the universality hypothesis of the initial mass function in
the substellar regime, the population of the rho Ophiuchi molecular cloud is
analysed by including a new sample of low-mass spectroscopically confirmed
members. We have conducted a large spectroscopic follow-up of young substellar
candidates uncovered in our previous photometric survey. It is shown that the
study of the substellar population of the rho Ophiuchi molecular cloud is
hampered only by the high extinction in the cluster ruling out an apparent
paucity of brown dwarfs. The spectral types and extinction are derived for a
newly found population of substellar objects, and its masses estimated by
comparison to evolutionary models. A thoroughly literature search is conducted
to provide an up-to-date census of the cluster, which is then used to derive
the luminosity and mass functions, as well as the ratio of brown dwarfs to
stars in the cluster. These results are compared to other young clusters. The
discovery of 16 new members of rho Ophiuchi, 13 of them in the substellar
regime, reveals the low mass end of its population and shows the success of our
photometric candidate selection with the WIRCam survey. The study of the brown
dwarf population of the cluster reveals a high disk fraction of 76 (+5-8)%.
Taking into account the characteristic peak mass of the derived mass function
and the ratio of brown dwarfs to stars, we conclude that the mass function of
rho Ophiuchi is similar to other nearby young clusters.
View original:
http://arxiv.org/abs/1201.1912
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