Issue |
A&A
Volume 407, Number 3, September I 2003
|
|
---|---|---|
Page(s) | 941 - 955 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20030918 | |
Published online | 17 November 2003 |
Monte Carlo radiative transfer in embedded prestellar cores
Department of Physics & Astronomy, Cardiff University, PO Box 913, 5 The Parade, Cardiff CF24 3YB, Wales, UK e-mail: A.Whitworth@astro.cf.ac.uk
Corresponding author: D. Stamatellos, D.Stamatellos@astro.cf.ac.uk
Received:
31
March
2003
Accepted:
12
June
2003
We implement a Monte Carlo radiative transfer method, that uses a large
number of monochromatic luminosity packets to represent the radiation
transported through a system.
These packets are injected into the system
and interact stochastically with it. We test our code against various
benchmark calculations and determine the number
of packets required to obtain accurate results under different circumstances.
We then use this method to study cores that are directly exposed to the
interstellar radiation field (non-embedded cores).
Our code predicts temperature and
intensity profiles inside these cores which are
in good agreement with previous studies using different
radiative transfer methods.
We also explore a large number of models of cores that are embedded in
the centre of a molecular cloud. We study cores
with different density profiles
embedded in molecular clouds with various optical extinctions
and we calculate temperature profiles, SEDs and intensity profiles.
Our study indicates that the temperature profiles
in embedded cores are less steep than those in non-embedded cores.
Deeply embedded cores (ambient cloud with visual extinction larger
than 15–25) are almost isothermal at around 7–8 K. The temperature
inside cores surrounded by an ambient cloud of even moderate thickness
() is less than 12 K, which is lower than previous
studies have assumed. Thus, previous mass calculations of embedded cores
(for example in the ρ Ophiuchi protocluster), based
on mm continuum observations, may underestimate
core masses by up to a factor of 2.
Our study shows that the best wavelength region to observe embedded
cores is between 400 and 500
, where the core is quite distinct from the
background.
We also predict that very sensitive observations (~
MJy
)
at 170–200
can be used to estimate how deeply a core is
embedded in its parent molecular cloud. The upcoming Herschel
mission (ESA, 2007) will, in principle, be able to detect these features
and test our models.
Key words: stars: formation / ISM: clouds / ISM: dust, extinction / ISM: structure / methods: numerical / radiative transfer
© ESO, 2003
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