Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21541420f&link_type=abstract
American Astronomical Society, AAS Meeting #215, #414.20; Bulletin of the American Astronomical Society, Vol. 42, p.257
Astronomy and Astrophysics
Astronomy
Scientific paper
Stars form out of the gravitational collapse of centrally condensed cores of dense molecular gas. Systematic observations of molecular emission lines which are excited at the high densities and cold temperatures found in star forming regions have revealed the physical and chemical structure of solar-mass size cores which have formed or may soon form a single star or stellar binary, and form the basis of theories of single-star formation. The initial conditions of star formation in this `isolated' mode have consequently become well-understood. Most stars, however, form in more clustered environments.
With the goal of characterizing the physical conditions of dense gas in cluster-forming environments, we present the results of systematic mapping of expected dense gas tracers (including NH3, N2H+, N2D+ and H2D+) towards the small cluster-forming Ophiuchus B Core. We find strong evidence that NH3 and N2H+ do not trace the coldest and densest locations of the core, including significant offsets between objects identified in continuum emission and in NH3 and N2H+ (in contrast with typical good correspondence found in isolated regions), relatively low fractional NH3 and N2H+ abundance at the positions of continuum objects, and a general trend of decreasing fractional abundance of both species with increasing H2 column density. Observations across Oph B2 of the deuterated species N2D+ and H2D+ show no abundance trends with column density, density or gas temperature. Also, though some similarity with the respective line emission with continuum is seen, the line emission is surprisingly weak towards embedded protostars in Oph B2. Destruction mechanisms for deuterated molecules require gas temperatures greater than previously determined for Oph B through NH3 emission.
Andre Pascal
Belloche Arnaud
Bourke Tyler
di Francesco James
Friesen Rachel
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