The Rotating Molecular Core and Precessing Outflow of the Young Stellar Object Barnard 1c

We investigate the structure of the core surrounding the recently identified deeply embedded young stellar object Barnard 1c. B1c lies within the Perseus molecular cloud at a distance of 250 pc. It is a deeply embedded core of 2.4 M☉ (Kirk et al.) and a luminosity of 4 ± 2 L☉. Observations (and resolutions) of 12CO J = 1-0 (9.″2 × 5.″9), 13CO J = 1-0, C18O J = 1-0 (14.″3 × 6.″7), HCO+ J = 1-0 (7.″6 × 5.″8), and N2H+ J = 1-0 (5.″9 × 4.″6) were obtained with the BIMA array, together with the continuum at 3.3 mm (6.″4 × 4.″9) and 2.7 mm (9.″5 × 6.″3). Single-dish measurements of N2H+ J = 1-0 and HCO+ J = 1-0 with FCRAO reveal the larger scale emission in these lines with ~60 resolution. The 12CO and HCO+ emission traces the outflow extending over the full field of view (2.′1), which coincides in detail with the S-shaped jet recently found in Spitzer IRAC imaging. The N2H+ emission, which anticorrelates spatially with the C18O emission, originates from a rotating envelope with effective radius ~2400 AU and mass 2.1-2.9 M☉, as derived from the 3.3 mm continuum emission. N2H+ emission is absent from a 600 AU diameter region around the young star, offset from the continuum peak. The remaining N2H+ emission may lie in a coherent torus of dense material. With its outflow and rotating envelope, B1c closely resembles the previously studied object L483 mm, and we conclude that it is a protostar in an early stage of evolution, i.e., Class 0 or in transition between Class 0 and Class I. We hypothesize that heating by the outflow and star has desorbed CO from grains, which has destroyed N2H+ in the inner region, and surmise that the presence of grains without ice mantles in this warm inner region can explain the unusual polarization signature observed from B1c.

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