Density Structure of Centrally Concentrated Prestellar Cores from Multi-scale Observations

TL;DR

This study models the density profiles of dense prestellar cores using multi-scale submillimeter observations, revealing their potential instability and advanced evolutionary stage toward star formation.

Contribution

It provides a detailed modeling approach combining multi-scale data to characterize the density structure of prestellar cores, highlighting their instability and advanced evolution.

Findings

Cores have a flat inner density region and an r^-2 outer profile.

Modeled cores are likely unstable and prone to collapse.

Inner flat regions are as small as ~500 au, indicating advanced prestellar stages.

Abstract

Starless cores represent the initial stage of evolution toward (proto)star formation, and a subset of them, known as prestellar cores, with high density (~ 10^6 cm^-3 or higher) and being centrally concentrated are expected to be embryos of (proto)stars. Determining the density profile of prestellar cores, therefore provides an important opportunity to gauge the initial conditions of star formation. In this work, we perform rigorous modeling to estimate the density profiles of three nearly spherical prestellar cores among a sample of five highly dense cores detected by our recent observations. We employed multi-scale observational data of the (sub)millimeter dust continuum emission including those obtained by SCUBA-2 on the JCMT with a resolution of ~5600 au and by multiple ALMA observations with a resolution as high as ~480 au. We are able to consistently reproduce the observed multi-scale dust continuum images of the cores with a simple prescribed density profile, which bears an inner region of flat density and a r^-2 profile toward the outer region. By utilizing the peak density and the size of the inner flat region as a proxy for the dynamical stage of the cores, we find that the three modeled cores are most likely unstable and prone to collapse. The sizes of the inner flat regions, as compact as ~500 au, signify them being the highly evolved prestellar cores rarely found to date.