Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

TL;DR

This study investigates how envelope gas temperature relates to protostellar multiplicity using molecular tracers, finding similar temperatures across different systems and suggesting mass and density are more influential in fragmentation.

Contribution

It provides observational evidence that gas temperature may not be the primary factor in protostellar fragmentation, highlighting the importance of mass and density instead.

Findings

Similar envelope gas temperatures across single and multiple systems.

Wide multiples have more cold gas reservoirs than singles or close binaries.

Gas temperature shows limited influence on protostellar fragmentation.

Abstract

Context: Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature structure. Aims: We aim to study the relationship between envelope gas temperature and protostellar multiplicity. Methods: Single dish observations of various molecules that trace the cold, warm and UV-irradiated gas are used to probe the temperature structure of multiple and single protostellar systems on 7000 AU scales. Results: Single, close binary, and wide multiples present similar current envelope gas temperatures, as estimated from H$_2$CO and DCO$^+$ line ratios. The temperature of the outflow cavity, traced by c-C$_3$H$_2$, on the other hand, shows a relation with bolometric luminosity and an anti-correlation with envelope mass. Although the envelope gas temperatures are similar for all objects surveyed, wide multiples tend to exhibit a more massive reservoir of cold gas compared to close binary and single protostars. Conclusions: Although the sample of protostellar systems is small, the results suggest that gas temperature may not have a strong impact on fragmentation. We propose that mass, and density, may instead be key factors in fragmentation.