|
We studied a sample of 21 Southern Bok globules, where 11 are classified
as starless and 10 have associated IRAS point sources. We used, for the first
time, the 2MASS catalog and applied the NICE method to map the extinction
distribution in Bok globules. This technique allowed us to identify embedded
cores with high visual extinctions (Av <= 25). In order to study the physical
conditions and the internal structure of the globules, we constructed radial
extinction profiles for the cores and modeled them with isothermal Bonnor-Ebert
spheres. By solving the Lane-Endem equation, we determined the stability parameter
Xi_max and the temperature T for each core. We found no remarkable differences
between the stability of starless globules and those with associated IRAS point
sources. The temperatures obtained from the model fitting show that unstable
globules have a mean temperature of 10 +- 3 K, while stable globules have 15 +- 6 K.
Finally, by means of millimetric observations of 13CO and C18O molecules, we found
a blue-asymmetric line profile in BHR 138, indicative of gravitational collapse
motions. Using a simple collapse model, it was possible to estimate an infall
velocity <= 0.25 km/s.
|
