A Modified Conveyor Belt Model: Implications for Surface Density Thresholds for Massive Star Formation

TL;DR

This study uses a modified conveyor belt model to simulate cluster formation, revealing that early-stage high-mass star-forming regions can be misclassified by standard surface density thresholds, emphasizing the importance of environmental observations.

Contribution

The paper introduces modifications to the conveyor belt model to better match observed properties of high-mass prestellar clumps and highlights the significance of environmental factors in classification.

Findings

High-mass clumps at early stages can be misclassified using standard thresholds.

The quantity of material entering star-forming regions is key to differentiating regions.

Environmental observations are crucial for accurate classification at early stages.

Abstract

Recent models and simulations of cluster formation within molecular clumps consider multi-scale, hierarchical accretion, which leads to clump mass growth over time. This mode of mass accumulation could have implications regarding the evolution of observable properties such as mass and radius, bringing into question the interpretation of commonly cited thresholds for high-mass star formation. In this paper, we use the conveyor belt model of cluster formation to create synthetic cores/clumps and derive physical and observational properties. We show that while this model successfully predicts many observed trends, modifications are required to match properties of high-mass prestellar clumps. When the model clumps are observationally classified as intermediate- or high-mass star-forming, the threshold delineating these two groups agrees with those found in the literature; however, results show that high-mass clumps at early evolutionary stages can be misclassified using standard surface density thresholds. Our logistic regression analysis reveals the quantity of material to ever enter a star-forming region is the most important factor in differentiating intermediate- and high-mass star-forming regions. This implies observations characterising the environment surrounding star-forming regions are crucial, especially at early evolutionary stages.