Prestellar core modeling in the presence of a filament - The dense heart of L1689B

TL;DR

This study introduces a new radiative transfer method to model prestellar cores within filaments, accurately deriving density and temperature profiles from continuum maps, and highlights the importance of avoiding azimuthal averaging for precise core property estimation.

Contribution

The paper presents a novel synergetic radiative transfer approach that improves core modeling accuracy by considering filament influence and spatial resolution, advancing understanding of prestellar core structures.

Findings

Isothermal sphere model fits bulk core with ~10 K temperature

Radial surface brightness profiles reveal density and temperature gradients

Pixel-by-pixel SED fits are insufficient for core property determination

Abstract

Short version: 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. For the bulk of the core (5000-20000 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. We conclude that, to derive physical core properties, it is important to avoid an azimuthal average of 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.