IRDC G030.88+00.13: A Tale of Two Massive Clumps

TL;DR

This study investigates the fragmentation and core formation in the IRDC G030.88+00.13, revealing two distinct clumps with different evolutionary stages and proposing a model where protostellar cores grow in mass during star formation.

Contribution

It provides detailed observations of two molecular clumps in an IRDC, highlighting their different properties and evolutionary stages, and proposes a new model of simultaneous core and protostar mass growth.

Findings

C1 is likely precluster stage with no massive protostars.

C2 contains compact cores and water masers, indicating ongoing star formation.

Core masses increase over time, supporting a model of simultaneous mass growth.

Abstract

Massive stars (M $\gsim 10$ \msun) form from collapse of parsec-scale molecular clumps. How molecular clumps fragment to give rise to massive stars in a cluster with a distribution of masses is unclear. We search for cold cores that may lead to future formation of massive stars in a massive ($> 10^3$ \msun), low luminosity ($4.6 \times 10^2$ \lsun) infrared dark cloud (IRDC) G030.88+00.13. The \nh3 data from VLA and GBT reveal that the extinction feature seen in the infrared consists of two distinctive clumps along the same line of sight: The C1 clump at 97 \kms-1 coincides with the extinction in the Spitzer 8 and 24 $\mu$m. Therefore, it is responsible for the majority of the IRDC. The C2 clump at 107 \kms-1 is more compact and has a peak temperature of 45 K. Compact dust cores and \h2O masers revealed in the SMA and VLA observations are mostly associated with C2, and none is within the IRDC in C1. The luminosity indicates that neither the C1 nor C2 clump has yet to form massive protostars. But C1 might be at a precluster forming stage. The simulated observations rule out 0.1pc cold cores with masses above 8 \msun\ within the IRDC. The core masses in C1 and C2, and those in high-mass protostellar objects suggest an evolutionary trend that the mass of cold cores increases over time. Based on our findings, we propose an empirical picture of massive star formation that protostellar cores and the embedded protostars undergo simultaneous mass growth during the protostellar evolution.