GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

TL;DR

This study uses NIKA2 on the IRAM 30-m telescope to map the Galactic plane, discovering new star-forming clumps and providing evidence that these clumps grow in mass, supporting clump-fed high-mass star formation models.

Contribution

First large-scale NIKA2 observations of the Galactic plane revealing new star-forming clumps and evidence for mass growth during star formation.

Findings

Discovered 321 new clumps, mostly starless and less massive.

Found evidence of mass growth in star-forming clumps.

Identified a population of 70 μm-quiet, potentially pre-stellar clumps.

Abstract

Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millim\'etrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping $\approx$2 deg$^2$ of the inner Galactic plane (GP), centred on $\ell$=23.9$^\circ$, $b$=0.05$^\circ$, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 $\mu$m-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction - an indicator of evolutionary stage - we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.