Article

# Young starless cores embedded in the magnetically dominated Pipe Nebula. II. Extended dataset

07/2012;
Source: arXiv

ABSTRACT The Pipe nebula is a massive, nearby, filamentary dark molecular cloud with a
low star-formation efficiency threaded by a uniform magnetic field
perpendicular to its main axis. It harbors more than a hundred, mostly
quiescent, very chemically young starless cores. The cloud is, therefore, a
good laboratory to study the earliest stages of the star-formation process. We
aim to investigate the primordial conditions and the relation among physical,
chemical, and magnetic properties in the evolution of low-mass starless cores.
We used the IRAM 30-m telescope to map the 1.2 mm dust continuum emission of
five new starless cores, which are in good agreement with previous visual
extinction maps. For the sample of nine cores, which includes the four cores
studied in a previous work, we derived a Av to NH2 factor of
(1.27$\pm$0.12)$\times10^{-21}$ mag cm$^{2}$ and a background visual extinction
of ~6.7 mag possibly arising from the cloud material. We derived an average
core diameter of ~0.08 pc, density of ~10$^5$ cm$^{-3}$, and mass of ~1.7 Msun.
Several trends seem to exist related to increasing core density: (i) diameter
seems to shrink, (ii) mass seems to increase, and (iii) chemistry tends to be
richer. No correlation is found between the direction of the surrounding
diffuse medium magnetic field and the projected orientation of the cores,
suggesting that large scale magnetic fields seem to play a secondary role in
shaping the cores. The full abstract is available in the pdf.

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