Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21114703b&link_type=abstract
American Astronomical Society, AAS Meeting #211, #147.03; Bulletin of the American Astronomical Society, Vol. 39, p.1000
Astronomy and Astrophysics
Astrophysics
Scientific paper
One of the fundamental questions in astrophysics is how do the initial conditions for star formation differ from isolated cores to cluster forming regions. Observations at high spectral and spatial resolution are needed, and only interferometers operating at millimeter and submillimeter wavelengths are able to provide the necessary data. The Oph A ridge is the densest gas condensation in the nearest cluster-forming region, where previous observations of dust continuum and N2H+ 1-0 emission with 10" resolution (1250 AU) have revealed half a dozen local maxima, but with only one dust and molecular line peak being coincident. The line widths are narrow and similar to those observed from isolated dense cores, but the resolution is insufficient to reveal the structure of individual cores.
With the Submillimeter Array we have observed the Oph A ridge in dust continuum and N2D+ 3-2 emission with a resolution of 3". Toward the core with the narrowest linewidths, N6, additional very high spectral resolution observations (0.06 km/s) were made, and the data combined with single-dish observations to recover the emission on all spatial scales. All of the N2H+ cores are detected in N2D+, and weak compact dust emission is also coincident with each maxima. This was not the case for the single dish continuum emission, and may be a temperature effect, where the weak emission from the cold dust associated with each core is undetectable against the bright background from the warm dust in the ridge. This result suggests that while the Oph A ridge resembles an elogated isolated core in its density structure in single dish maps, but with a larger peak density, when observed with an interferometer it breaks up into smaller clumps of mass < 0.1 Msun, suggesting fragmentation into smaller units than a typical isolated core.
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