Massive star formation around I05345+3157 -- I. The dense gas

TL;DR

This study investigates dense gas cores in a massive star-forming region using molecular line observations, identifying potential sites of ongoing or future massive star formation and analyzing their physical properties.

Contribution

The paper provides detailed characterization of dense gas cores in I05345+3157, revealing their masses, dynamics, and potential for massive star formation, using CS(2-1) molecular line data.

Findings

Seven dense gas cores identified, with two likely forming massive stars.

Core 3 shows signs of gas infall, indicating collapse.

Non-thermal motions suggest interactions with outflows or turbulence.

Abstract

We present observations of the intermediate to massive star-forming region I05345+3157 using the molecular line tracer CS(2-1) with CARMA to reveal the properties of the dense gas cores. Seven gas cores are identified in the integrated intensity map of CS(2-1). Among these, core 1 and core 3 have counterparts in the 2.7 millimeter continuum data. We suggest that core 1 and core 3 are star-forming cores that may already or will very soon harbor young massive protostars. The total masses of core 1 estimated from the LTE method and dust emission by assuming a gas-to-dust ratio are 5 +- 1 solar masses and 18 +- 6 solar masses, and that of core 3 are 15 +- 7 solar masses and 11 +- 3 solar masses. The spectrum of core 3 shows blue-skewed self-absorption, which suggests gas infall -- a collapsing core. The observed broad linewidths of the seven gas cores indicate non-thermal motions. These non-thermal motions can be interactions with nearby outflows or due to the initial turbulence; the former is observed, while the role of initial turbulence is less certain. Finally, the virial masses of the gas cores are larger than the LTE masses, which for a bound core implies a requirement on the external pressure of ~ 10^8 K/cm^3. The cores have the potential to further form massive stars.