Abstract
ABSTRACT The physical processes behind the transfer of mass from parsec-scale clumps to massive star-forming cores remain elusive. We investigate the relation between the clump morphology and the mass fraction that ends up in its most massive core (MMC) as a function of infrared brightness, i.e. a clump evolutionary tracer. Using Atacama Large Millimeter/submillimeter Array (ALMA) 12 m and Atacama Compact Array, we surveyed six infrared dark hubs in 2.9 mm continuum at ∼3 arcsec resolution. To put our sample into context, we also re-analysed published ALMA data from a sample of 29 high-mass surface density ATLASGAL sources. We characterize the size, mass, morphology, and infrared brightness of the clumps using Herschel and Spitzer data. Within the six newly observed hubs, we identify 67 cores, and find that the MMCs have masses between 15 and 911 M⊙ within a radius of 0.018–0.156 pc. The MMC of each hub contains 3–24 per cent of the clump mass (fMMC), becoming 5–36 per cent once core masses are normalized to the median core radius. Across the 35 clumps, we find no significant difference in the median fMMC values of hub and non-hub systems, likely the consequence of a sample bias. However, we find that fMMC is ∼7.9 times larger for infrared dark clumps compared to infrared bright ones. This factor increases up to ∼14.5 when comparing our sample of six infrared dark hubs to infrared bright clumps. We speculate that hub-filament systems efficiently concentrate mass within their MMC early on during its evolution. As clumps evolve, they grow in mass, but such growth does not lead to the formation of more massive MMCs.
Highlights
Understanding what physical processes determine the mass of stars is an active area of astrophysics research
4.1 Broader sample of clumps and cores In order to get a sense of how fMMC values from our hub sample compare to those from a less biased Galactic plane population of clumps, we use the Csengeri et al (2017) sample of highmass ATLASGAL sources observed with Atacama Large Millimeter/submillimeter Array (ALMA) (Project ID: 2013.1.00960.S; PI: Csengeri)
We use two distinct clump classification schemes, one that qualitatively identifies the amount of star formation activity within it, and another that determines whether or not an most massive core (MMC) is at the centre of a hub filament system
Summary
Understanding what physical processes determine the mass of stars is an active area of astrophysics research. The most massive prestellar cores identified in the far-infrared and submillimetre surveys of Gould Belt regions are typically about 10 M (Konyves et al 2015, 2020), implying a stellar mass of about 3 M when accounting for the core to star formation efficiency derived by the same authors. Urquhart et al (2014) argued that clumps with signposts of active massive star formation are more spherical than those which do not have such associated tracers, while Rigby et al (2018) suggested that more spherical clumps are more efficient at concentrating their mass within their MMC. Liu et al 2012; Kirk et al 2013; Peretto et al 2013, 2014; Trevino-Morales et al 2019) They are found in all types of region, from low-mass star-forming clouds
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