The Onset of Massive Star Formation: The Evolution of Temperature and Density Structure in an Infrared Dark Cloud

Abstract

We present new NH3 (1,1), (2,2), and (4,4) observations from the Karl G. Jansky Very Large Array (VLA) compiled with work in the literature to explore the range of conditions observed in young, massive star-forming regions. To sample the effects of evolution independent from those of distance/resolution, abundance, and large-scale environment, we compare clumps in different evolutionary stages within a single Infrared Dark Cloud (IRDC), G32.02+0.06. We find that the early stages of clustered star formation are characterized by dense, parsec-scale filamentary structures interspersed with complexes of dense cores (<0.1 pc cores clustered in complexes separated by ~1 pc) with masses from about 10 to 100 Msun. The most quiescent core is the most extended while the star-forming cores are denser and more compact, showing very similar column density structure before and shortly after the onset of massive star formation, with peak surface densities >~ 1 g cm^-2. Quiescent cores and filaments show smoothly varying temperatures from 10-20 K, rising to over 40 K in star-forming cores. We calculate the virial parameters for 16 cores and find that the level of support provided by turbulence is generally insufficient to support them against gravitational collapse (alpha_vir ~ 0.6). The star-forming filaments show smooth velocity fields, punctuated by discontinuities at the sites of active star formation. We discuss the Massive Molecular Filament (MMF; M > 10^5 Msun, l > 60 pc) hosting the IRDC, hypothesizing that it may have been shaped by previous generations of massive stars.

Accepted in ApJ

References in corpus (15)

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Cited by in corpus (18)

• The Hi-GAL compact source catalogue -- II. The 360° catalogue of clump physical properties
• ALMA-IMF I -- Investigating the origin of stellar masses: Introduction to the Large Program and first results
• Investigating the structure and fragmentation of a highly filamentary IRDC
• Zooming in on Individual Star Formation: Low- and High-mass Stars
• The Role of Outflows, Radiation Pressure, and Magnetic Fields in Massive Star Formation
• CMZoom: Survey Overview and First Data Release
• The SQUALO project (Star formation in QUiescent And Luminous Objects) I: clump-fed accretion mechanism in high-mass star-forming objects
• The Lifetimes of Phases in High-Mass Star-Forming Regions
• A Massive Star is Born: How Feedback from Stellar Winds, Radiation Pressure, and Collimated Outflows Limits Accretion onto Massive Stars
• Environment and Protostellar Evolution
• The SOFIA Massive (SOMA) Star Formation Survey. IV. Isolated Protostars
• The Milky Way Project: What are Yellowballs?
• Large-scale Velocity-coherent Filaments in the SEDIGISM Survey: Association with Spiral Arms and Fraction of Dense Gas
• ALMA-IMF XVI: Mass-averaged temperature of cores and protostellar luminosities in the ALMA-IMF protoclusters
• Simulated observations of star formation regions: infrared evolution of globally collapsing clouds
• Sulphur-Bearing and Complex Organic Molecules in an Infrared Cold Core
• Star formation in IRDC G31.97+0.07
• Prospects for Detection of Synchrotron Emission from Secondary Electrons and Positrons in Starless Cores: Application to G0.216+0.016