Protostellar Outflow Heating in a Growing Massive Protocluster

TL;DR

This study uses EVLA observations to map heated gas and outflows in a young massive protocluster, revealing complex temperature structures and interactions that influence core formation.

Contribution

It provides detailed spatial and spectral analysis of protostellar heating and outflow interactions in a massive protocluster, highlighting the role of outflows in heating and fragmentation.

Findings

Heated gas is widely spread and offset from protostars.

Outflows are closely associated with hot spots of NH3 emission.

A new NH3 (3,3) maser was discovered at outflow interfaces.

Abstract

The dense molecular clump P1 in the infrared dark cloud (IRDC) complex G28.34+0.06 harbors a massive protostellar cluster at its extreme youth. Our previous Submillimeter Array (SMA) observations revealed several jet-like CO outflows emanating from the protostars, indicative of intense accretion and potential interaction with ambient natal materials. Here we present the Expanded Very Large Array (EVLA) spectral line observations toward P1 in the NH3 (J,K) = (1,1), (2,2), (3,3) lines, as well as H2O and class I CH3OH masers. Multiple NH3 transitions reveal the heated gas widely spread in the 1 pc clump. The temperature distribution is highly structured; the heated gas is offset from the protostars, and morphologically matches the outflows very well. Hot spots of spatially compact, spectrally broad NH3 (3,3) emission are also found coincident with the outflows. A weak NH3 (3,3) maser is discovered at the interface between an outflow jet and the ambient gas. These findings suggest that protostellar heating may not be effective in suppressing fragmentation during the formation of massive cores.