The fragmentation of molecular clouds in starburst environments

TL;DR

This study uses hydrodynamical simulations to explore how extreme environments with high radiation and cosmic rays influence the fragmentation of molecular clouds, revealing a shift towards more massive cores and richer stellar clusters.

Contribution

It provides the first comprehensive analysis of star formation in high ISRF and CRIR environments, highlighting altered fragmentation patterns and mass functions.

Findings

High ISRF/CRIR reduces core fragmentation, producing fewer, more massive cores.

Enhanced fragmentation of stellar systems leads to richer clusters.

Mass functions of stellar systems shift towards higher masses in extreme environments.

Abstract

A significant amount of star formation occurs and has occurred in environments unlike the solar neighbourhood. The majority of stars formed closer to the peak of the cosmic star formation rate (z > 1.3) and a great deal of star formation presently occurs in the central molecular zone (CMZ) of the Galaxy. These environments are unified by the presence of a high interstellar radiation field (ISRF) and a high cosmic ray ionisation rate (CRIR). Numerical studies of stellar birth typically neglect this fact, and those that do not have thus far been limited in scope. In this work we present the first comprehensive analysis of hydrodynamical simulations of star formation in extreme environments where we have increased the ISRF and CRIR to values typical of the CMZ and starburst galaxies. We note changes in the fragmentation behaviour on both the core and stellar system scale, leading to top-heavy core and stellar system mass functions in high ISRF/CRIR clouds. Clouds fragment less on the core scale, producing fewer but more massive cores. Conversely, the cores fragment more intensely and produce richer clusters of stellar systems. We present a picture where high ISRF/CRIR clouds fragment less on the scale of cores and clumps, but more on the scale of stellar systems. The change in fragmentation behaviour subsequently changes the mass function of the stellar systems that form through enhanced accretion rates.