摘要：Context. Lacking a paradigm for the onset of star formation, it is
important to derive basic physical properties of prestellar cores and filaments like
density and temperature structures.
Aims. We aim to disentangle the spatial variation in density and
temperature across the prestellar core L1689B, which is embedded in a filament. We want to
determine the range of possible central densities and temperatures that are consistent
with the continuum radiation data.
Methods. We apply a new synergetic radiative transfer method: the
derived 1D density profiles are both consistent with a cut through the Herschel
PACS/SPIRE and JCMT SCUBA-2 continuum maps of L1689B and with a derived local
interstellar radiation field. Choosing an appropriate cut along the filament major axis,
we minimize the impact of the filament emission on the modeling.
Results. For the bulk of the core (5000−20 000 au) an isothermal sphere model with
a temperature of around 10 K provides the best fits. We show that the power law index of
the density profile, as well as the constant temperature can be derived directly from the
radial surface brightness profiles. For the inner region (<5000 au), we find a range of densities
and temperatures that are consistent with the surface brightness profiles and the local
interstellar radiation field. Based on our core models, we find that pixel-by-pixel single
temperature spectral energy distribution fits are incapable of determining dense core
properties.
Conclusions. We conclude that, to derive physical core properties, it is
important to avoid azimuthally-averaging core and filament. Correspondingly, derived core
masses are too high since they include some mass of the filament, and might introduce
errors when determining core mass functions. The forward radiative transfer methods also
avoids the loss of information owing to smearing of all maps to the coarsest spatial
resolution. We find the central core region to be colder and denser than estimated in
recent inverse radiative transfer modeling, possibly indicating the start of star
formation in L1689B.
