TITLE:
Inferring the Structure of the Pre-Protostellar Core L1498
AUTHORS:
Sandra L. Doty, Steven D. Doty, Matthew J. Perkett
KEYWORDS:
Stars: Formation, ISM: Clouds, ISM: L1498, Submillmeter: Stars, ISM: Structure, Infrared: Stars
JOURNAL NAME:
International Journal of Astronomy and Astrophysics,
Vol.4 No.3,
September
11,
2014
ABSTRACT: We present a study of the
pre-protostellar core (PPC) L1498. A series of self-consistent, three-dimensional
continuum radiative transfer models are constructed. The outputs of these
models are convolved with appropriate telescope beam responses, including the
effect of beam chopping to simulate SCUBA observations. The simulated
observations are compared with existing observational data. An automated search
is conducted in the multi-dimensional parameter space to identify the best-fit
model. Grids of models are constructed in the vicinity of the best fit in order
to understand the sensitivity/uncertainty of the results. We find that the
source is well fit by a prolate spheroid of cutoff (and thus approximately
outer) radius rcut =
0.073 ± 0.005 pc, axis ratio q = 2.0 ± 0.2, a central luminosity L* -3 Lsun, and an optical depth
in the visible of τv = 20 ± 5. We find that the PPC is
illuminated by two external radiation fields: a uniform ISRF of strength sISRF=
0.5 ± 0.25 and a local plane-parallel radiation field sPPRF = 1.0 ± 0.5. Both of these radiation
fields are locally attenuated, with τISRF = 1.0 ± 0.25, and τPPRF = 1.25 ± 0.75, consistent with the
fact that L1498 is embedded in a larger cloud. Most interestingly, the density
fall-off at the outer edge is extremely steep, having a power law of m > 10.
This is effectively a “sharp edge” to the PPC, and together with the constant
density interior, is interpreted as potential signs of a pressure-confined
core.