Search for High-Mass Protostellar Objects in Cold IRAS Sources

TL;DR

This study maps dense molecular regions in cold IRAS sources, identifying 12 high-mass protostellar candidates and analyzing their physical properties and early evolutionary stages.

Contribution

It presents new CS J=2-1 mapping data and criteria for identifying high-mass protostellar objects in cold IRAS sources.

Findings

12 HMPO candidates identified based on multi-wavelength data.

HMPOs exhibit low FIR luminosity to virial mass ratios.

Turbulence in HMPOs may be driven by protostellar outflows or other mechanisms.

Abstract

We present the results of CS J=2-1 mapping observations towards 39 massive star-forming regions selected from the previous CO line survey of cold IRAS sources with high-velocity CO flows along the Galactic plane (Yang et al. 2002). All sources are detected in CS J=2-1 showing the existence of CS clumps around the IRAS sources. However, one-third of the sources are not deeply embedded in the dense clumps by comparison of the central powering IRAS sources and the morphologies of CS clumps. Physical parameters of the dense molecular clumps are presented. We have identified 12 high-mass protostellar object (HMPO) candidates by checking the association between the dense cores and the IRAS sources, the detection of water maser, and the radio properties towards the IRAS sources. We find that the HMPO sources are characterized by low FIR luminosity to virial mass ratios since they are in very early evolutionary stages when the massive protostars have not reached their full luminosities, which are typical for zero-age main sequence stars. Large turbulent motion in the HMPO sources may be largely due to the large kinetic energy ejected by the central protostars formed in the dense clumps. However, alternative means or undetected outflows may also be responsible for the turbulence in the clumps.