Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21360408s&link_type=abstract
American Astronomical Society, AAS Meeting #213, #604.08
Astronomy and Astrophysics
Astronomy
Scientific paper
We present a fully-sampled high spatial resolution J = 3→2 13CO map of the isolated, starless Bok globule CB4, obtained with the 10m antenna of the Caltech Submillimeter Observatory (HPBW 20 arcseconds). Complementary data in the common 12CO isotopic species was also obtained, along with a high quality spectrum of C18O near the cloud center. These observations were acquired in order to explore whether the extreme structural and dynamical simplicity of this cloud as a pressure-bounded equilibrium object, proposed by Dickman and Clemens on the basis of molecular line observations made at 45 arcsecond HPBW, is borne out by observations capable of resolving the globule's predicted density and thermal structure.
The distribution of the J = 3→2 13CO integrated intensity in the globule is found to reflect the essentially simple elliptical geometry of the cloud suggested by optical photographs of the cloud. Likewise, the extremely narrow (FWHM 0.13 km s-1) central C18O spectrum affirms the extremely quiescent nature of the gas motions within CB4 inferred by the earlier work and constrains the adiabatic Mach number in the cloud core to be no larger than 0.5. However, we find that the velocity field traced by the centroids of the 13CO spectra exhibits a large-scale variation of 0.05 km s-1 arcmin-1 across the cloud. This large-scale component is not especially well-described by a simple solid-body rotation model. We discuss the implications of this result.
Dickman Ronald
Lis Darek
Savello Alexander
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