Warm Extended Dense Gas Lurking At The Heart Of A Cold Collapsing Dense Core

TL;DR

This study detects unexpectedly warm, extended dense gas within a cold collapsing core, suggesting a new star formation stage called WICCS that bridges starless cores and early protostars.

Contribution

It introduces the concept of WICCS, a novel star formation stage characterized by warm dense gas within a cold core, based on submillimeter CO observations.

Findings

Detection of warm (~30-70 K), extended (~2400 AU) dense gas in a cold core.

Warm gas likely originates from shock regions due to internal collisions.

Proposes WICCS as a transitional stage in star formation.

Abstract

In order to investigate when and how the birth of a protostellar core occurs, we made survey observations of four well-studied dense cores in the Taurus molecular cloud using CO transitions in submillimeter bands. We report here the detection of unexpectedly warm (~ 30 - 70 K), extended (radius of ~ 2400 AU), dense (a few times 10^{5} cm^{-3}) gas at the heart of one of the dense cores, L1521F (MC27), within the cold dynamically collapsing components. We argue that the detected warm, extended, dense gas may originate from shock regions caused by collisions between the dynamically collapsing components and outflowing/rotating components within the dense core. We propose a new stage of star formation, "warm-in-cold core stage (WICCS)", i.e., the cold collapsing envelope encases the warm extended dense gas at the center due to the formation of a protostellar core. WICCS would constitutes a missing link in evolution between a cold quiescent starless core and a young protostar in class 0 stage that has a large-scale bipolar outflow.