A Candidate Detection of the First Hydrostatic Core

TL;DR

This paper reports the identification of a strong candidate for the first hydrostatic core in star formation, using observational data and radiative transfer modeling to distinguish it from very low luminosity protostars.

Contribution

It presents the first observational candidate for the FHSC phase and uses modeling to differentiate it from protostars, advancing understanding of early star formation stages.

Findings

Per-Bolo 58 is consistent with an FHSC based on spectral energy distribution.

The source may have a low-opacity envelope or cavity allowing 24 micron emission.

If a protostar, it would be among the lowest luminosity observed.

Abstract

The first hydrostatic core (FHSC) represents a very early phase in the low-mass star formation process, after collapse of the parent core has begun but before a true protostar has formed. This large (few AU), cool (100 K), pressure supported core of molecular hydrogen is expected from theory, but has yet to be observationally verified. Here we present observations of an excellent candidate for the FHSC phase: Per-Bolo 58, a dense core in Perseus that was previously believed to be starless. The 70 micron flux of 65 mJy, from new deep Spitzer MIPS observations, is consistent with that expected for the FHSC. A low signal-to-noise detection at 24 micron leaves open the possibility that Per-Bolo 58 could be a very low luminosity protostar, however. We utilize radiative transfer models to determine the best-fitting FHSC and protostar models to the spectral energy distribution and 2.9 mm visibilities of Per-Bolo 58. The source is consistent with a FHSC with some source of lower opacity through the envelope allowing 24 micron emission to escape; a small outflow cavity or a cavity in the envelope are both possible. While we are unable to rule out the presence of a protostar, if present it would be one of the lowest luminosity protostellar objects yet observed, with an internal luminosity of approximately 0.01 Lsun.