Tracing Evolution in Massive Protostellar Objects (TEMPO) -- I: Fragmentation and emission properties of massive star-forming clumps in a luminosity limited ALMA sample

TL;DR

This study investigates the fragmentation and emission characteristics of massive star-forming regions using ALMA data, revealing non-thermal fragmentation scales and potential evolutionary trends related to luminosity and spectral line richness.

Contribution

Introduces a new ALMA-based sample of massive star-forming regions and develops methods for analyzing fragmentation, emission, and source classification in these regions.

Findings

Fragments per field range from 2 to 15.

Fragmentation scales are larger than thermal Jeans length.

Possible evolutionary trend between luminosity and spectral line richness.

Abstract

The role of massive ($\geq$ 8M$_{\odot}$) stars in defining the energy budget and chemical enrichment of the interstellar medium in their host galaxy is significant. In this first paper from the Tracing Evolution in Massive Protostellar Objects (TEMPO) project we introduce a colour-luminosity selected (L$_*$ $\sim$ 3$\times10^3$ to 1$\times10^5$ L$_{\odot}$) sample of 38 massive star forming regions observed with ALMA at 1.3mm and explore the fragmentation, clustering and flux density properties of the sample. The TEMPO sample fields are each found to contain multiple fragments (between 2-15 per field). The flux density budget is split evenly (53%-47%) between fields where emission is dominated by a single high flux density fragment and those in which the combined flux density of fainter objects dominates. The fragmentation scales observed in most fields are not comparable with the thermal Jeans length, $\lambda_J$, being larger in the majority of cases, suggestive of some non-thermal mechanism. A tentative evolutionary trend is seen between luminosity of the clump and the `spectral line richness' of the TEMPO fields; with 6.7GHz maser associated fields found to be lower luminosity and more line rich. This work also describes a method of line-free continuum channel selection within ALMA data and a generalised approach used to distinguishing sources which are potentially star-forming from those which are not, utilising interferometric visibility properties.