Envelope Structure of Starless Core L694-2 Derived from a Near-Infrared Extinction Map
- Autor(en)
- Daniel W. A. Harvey, David J. Wilner, Charles J. Lada, Philip C. Myers, João F. Alves
- Abstrakt
We present a near-infrared extinction study of the dark globule L694-2,
a starless core that shows strong evidence for inward motions in the
profiles of molecular spectral lines. The J-, H-, and K-band data were
taken using the European Southern Observatory New Technology Telescope.
The best-fit simple spherical power-law model has index p=2.6+/-0.2,
over the ~0.036-0.1 pc range in radius sampled in extinction. This
power-law slope is steeper than the value of p=2 for a singular
isothermal sphere, the initial condition of the inside-out model for
protostellar collapse. Including an additional component of extinction
along the line of sight further steepens the inferred profile. A fit for
a Bonnor-Ebert sphere model results in a supercritical value of the
dimensionless radius ξmax=25+/-3. This unstable
configuration of material in the L694-2 core may be related to the
observed inward motions. The Bonnor-Ebert model matches the shape of the
observed density profile but significantly underestimates the amount of
extinction observed in the L694-2 core (by a factor of ~4). This
discrepancy in normalization has also been found for the nearby
protostellar core B335 (Harvey and coworkers). A cylindrical model with
scale height H=0.0164+/-0.002 pc (13.5"+/-5'') viewed at a
small inclination to the axis of the cylinder provides an equally good
radial profile as a power-law model, and it also reproduces the
asymmetry of the L694-2 core remarkably well. In addition, this model
provides a possible basis for understanding the discrepancy in the
normalization of the Bonnor-Ebert model, namely, that L694-2 has prolate
structure, with the full extent (mass) of the core being missed by
analysis that assumes symmetry between the profiles of the core in the
plane of the sky and along the line of sight. If the core is
sufficiently magnetized, then fragmentation may be avoided, and later
evolution might produce a protostar similar to B335.
- Organisation(en)
- Institut für Astrophysik
- Externe Organisation(en)
- Harvard-Smithsonian Center for Astrophysics
- Journal
- The Astrophysical Journal
- Band
- 598
- Seiten
- 1112-1126
- ISSN
- 0004-637X
- DOI
- https://doi.org/10.1086/378977
- Publikationsdatum
- 12-2003
- Peer-reviewed
- Ja
- Schlagwörter
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/5e3d3c72-5a6f-47e2-9148-5ce3d7933e96