Terahertz ammonia absorption as a probe of infall in high-mass star forming clumps

TL;DR

This study introduces a new method using ammonia absorption to directly detect and measure infall in high-mass star-forming regions, providing clearer evidence of star formation processes.

Contribution

It presents a novel approach of using rotational ammonia absorption against dust emission to study infall in massive star-forming clumps, overcoming limitations of previous methods.

Findings

Redshifted ammonia absorption detected in all three regions.

Infall rates estimated between 3-10 x 10^-3 solar masses per year.

Method proves effective across different evolutionary stages.

Abstract

Cloud contraction and infall are the fundamental processes of star formation. While "blue-skewed" line profiles observed in high- mass star forming regions are commonly taken as evidence of infall by an ever increasing number of studies, their interpretation offers many pitfalls. Detecting infall via redshifted absorption in front of continuum sources is a much more direct and reliable method but so far mostly restricted toward absorption in the centimeter toward strong HII regions. Here we present a novel approach by probing absorption of rotational ammonia transitions in front of the strong dust emission of massive star-forming regions. A carefully selected sample of three regions with different stages of evolution is selected to study infall through the evolution of massive star-forming clumps. Redshifted absorption is detected toward all three sources and infall rates between 3-10x10-3 Msol yr-1 are derived.