Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997aas...191.0711k&link_type=abstract
American Astronomical Society, 191st AAS Meeting, #07.11; Bulletin of the American Astronomical Society, Vol. 29, p.1220
Astronomy and Astrophysics
Astronomy
Scientific paper
Fourteen SBGs were observed in the (J=1-> 0) rotational lines of (12) CO, (13) CO, and C(18) O, using the 14 meter radio telescope of the Five College Radio Astronomy Observatory (FCRAO).Maps were made with the fifteen-element QUARRY 3mm array receiver and the 1024 channel FAAS autocorrelator spectrometer. A total of 120 to 360 positions per globule, sampled with half-beam spacing, was observed in the (13) CO, line, mostly over 2.5 by 3 arcmin grids, while 30 to 60 full-beam-sampled C(18) O and (12) CO positions per globule were observed. (13) CO and C(18) O, were observed with a velocity resolution of less than 0.007km s(-1) channel (-1) ; (12) CO was observed with 0.013km s(-1) channel(-1) resolution. The median SBG in the sample has an apparent volume density profile which falls off as ~ r(-2.6) , significantly steeper than found in Yun & Clemens' 1991 sample (of which the majority contained YSO candidates) whose mean dust density profile fell off as a much shallower ~ r(-1.6) . Overall, assuming a distance of 600 pc, the sample of SBGs is characterized as containing cores of size 0.3\pc. SBGs contain about 10 Msun of gas, have mean H_2 densities of a few x 10(3) cm (-3) , and kinetic temperatures of ~ 10K. Most SBGs are near virial equilibrium. Using energy balance arguments, half of the SBGs may be quasi-statically contracting, and all of these globules still possess envelopes. The strongest association with cloud contraction is the existence of a relatively large envelope. Rotation is in most cases the least significant source of support against gravitational contraction; in the majority of cases kinetic energy owing to turbulent motions is providing the most support against contraction.
Clemens Dan P.
Kane Brian D.
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