Abstract
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 Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane (GP) 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 that is mapping ≈2 deg2 of the inner GP, centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, 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-μm-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.
Highlights
The stellar initial mass function (IMF) is an essential ingredient in cosmological simulations of galaxy formation and evolution, and its origin remains one of the most fundamental and important questions in the field of astronomy
We have identified a total of 1467 Galactic Star Formation with NIKA2 (GASTON) clumps, compared to 346 ATLASGAL compact sources (Urquhart et al 2018) and 164 from the BGPS (Ellsworth-Bowers et al 2015) within the same sky area
All of the ATLASGAL clumps lie within three convolved beam radii of a GASTON compact source, and they all fall within the boundaries of emission extracted by the dendrogram analysis in this work
Summary
The stellar initial mass function (IMF) is an essential ingredient in cosmological simulations of galaxy formation and evolution, and its origin remains one of the most fundamental and important questions in the field of astronomy. Systems with the so-called ‘hub-filament’ configuration (Myers 2009) are routinely found in high-spatial resolution observations of highmass clumps, with stellar protoclusters (Schneider et al 2012; Liu et al 2016), or the most massive dense cores found at the filament intersections (e.g. Peretto et al 2013, 2014) The filaments within these systems have been seen to exhibit longitudinal velocity gradients that could indicate large-scale gas flows (Kirk et al 2013; Peretto et al 2014; Lu et al 2018; Williams et al 2018; Chen 2019) that supply additional kinetic support at the hub centre, whilst funnelling sufficient mass to the high-mass cores on short time-scales. We describe the observations and present the first results from the GASTON GP project, in which we explore the potential for the NIKA2 observations to identify signatures of the core-fed or clump-fed scenarios of high-mass star formation.
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