Km. Strom et al., THE EVOLUTIONARY STATUS OF THE STELLAR POPULATION IN THE RHO-OPHIUCHICLOUD CORE, The Astrophysical journal, 438(2), 1995, pp. 813-829
This contribution reports the results of an infrared imaging survey ai
med at characterizing the stellar populations associated with the thre
e densest star-forming cores in the Ophiuchus molecular cloud complex.
The survey has sufficient sensitivity at J, H, and K (at 5 sigma limi
ts of 16.5, 15.4, and 14.2) to provide a complete census of embedded y
oung stellar objects (YSOs) with masses greater than the hydrogen-burn
ing limit, provided that their ages are less than 3 Myr and that they
are obscured by no more than similar to 18 mag of visual extinction. O
ur data suggest (1) a large fraction (> 70%) of the sources located wi
thin the cores are still surrounded by circumstellar disks and/or enve
lopes; and (2) the shape of the initial mass function for masses, M <
1 M., appears to be consistent with that derived from the solar neighb
orhood. We also report the results of a deeper imaging survey of centi
meter continuum sources (14 sources) in these star-forming cores and i
n the larger Ophiuchus complex (eight sources). A large fraction (11/1
4) of the radio sources associated with the cores appear to have infra
red excesses diagnostic of circumstellar accretion disks and/or infall
ing circumstellar envelopes. In these cases, the centimeter continuum
radiation most likely diagnoses the ionized component of energetic win
ds or jets which characterize YSOs during the disk accretion phase. By
contrast, of the eight radio sources located outside dense cores, onl
y two show infrared excesses. For the sources which lack infrared exce
sses, the centimeter continuum emission is probably produced by gyrosy
nchrotron radiation arising in the stellar magnetospheres of weak emis
sion T Tauri stars. There is some evidence that the frequency of binar
y companions among the sample of centimeter continuum sources in the m
olecular cores may be higher (by as much as a factor of 3-4) than that
among the older, distributed population of young stars in the larger
Ophiuchus cloud complex.