The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). VIII. Dynamics of Embedded Dense Cores

Abstract

We present the dynamical properties of 294 cores embedded in twelve IRDCs observed as part of the ASHES Survey. Protostellar cores have higher gas masses, surface densities, column densities, and volume densities than prestellar cores, indicating core mass growth from the prestellar to the protostellar phase. We find that ~80% of cores with virial parameter ($\alpha$) measurements are gravitationally bound ($\alpha$< 2). We also find an anti-correlation between the mass and the virial parameter of cores, with massive cores having on average lower virial parameters. Protostellar cores are more gravitationally bound than prestellar cores, with an average virial parameter of 1.2 and 1.5, respectively. The observed non-thermal velocity dispersion (from N${}_2$D${}^{+}$ or DCO${}^{+}$) is consistent with simulations in which turbulence is continuously injected, whereas the core-to-core velocity dispersion is neither in agreement with driven nor decaying turbulence simulations. We find no significant increment in the line velocity dispersion from prestellar to protostellar cores, suggesting that dense gas within the core traced by these deuterated molecules is not yet severely affected by turbulence injected from outflow activity at the early evolutionary stages traced in ASHES. The most massive cores are strongly self-gravitating and have greater surface density, Mach number, and velocity dispersion than cores with lower masses. Dense cores have not significant velocity shifts relative to their low-density envelopes, suggesting that dense cores are co-moving with their envelopes. We conclude that the observed core properties are more in line with predictions of ``clump-fed" scenarios rather than with ``core-fed" scenarios.

29 pages, 14 figures, 5 tables. Accepted for publication by ApJ. Tables 2 and 3 are available here: https://github.com/ShanghuoLi/70-um-dark-high-mass-clumps

References in corpus (26)

• Theory of Star Formation
• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• Cold Dark Clouds: The Initial Conditions for Star Formation
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• Structural Analysis of Molecular Clouds: Dendrograms
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• Star formation through gravitational collapse and competitive accretion
• The Mass Distribution and Lifetime of Prestellar Cores in Perseus, Serpens, and Ophiuchus
• The Large and Small Scale Structures of Dust in the Star-Forming Perseus Molecular Cloud
• Fragmentation of Molecular Clumps and Formation of Protocluster
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- I. Survey description and a first look at G9.62+0.19
• Driven and Decaying Turbulence Simulations of Low-Mass Star Formation: From Clumps to Cores to Protostars
• Gravity Driven Magnetic Field at ~1000 au Scales in High-mass Star Formation
• VLA observations of ammonia in high-mass star formation regions
• Dense core properties in the Infrared Dark cloud G14.225-0.506 revealed by ALMA
• Unveiling the Early-Stage Anatomy of a Protocluster Hub with ALMA
• The ALMA Survey of 70 $\mu \mathrm{m}$ Dark High-mass Clumps in Early Stages (ASHES). II: Molecular Outflows in the Extreme Early Stages of Protocluster Formation
• Massive 70 micron quiet clumps II: non-thermal motions driven by gravity in massive star formation?
• Massive and low-mass protostars in massive "starless" cores
• The Kinematics of Molecular Cloud Cores in the Presence of Driven and Decaying Turbulence: Comparisons with Observations
• Characterizing the properties of cluster precursors in the MALT90 survey
• ALMA-IRDC: Dense gas mass distribution from cloud to core scales
• Initial Fragmentation in the Infrared Dark Cloud G28.53-0.25
• The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). VI. The core-scale CO-depletion
• The ALMA Survey of 70 $\mu \mathrm{m}$ Dark High-mass Clumps in Early Stages (ASHES). VII: Chemistry of Embedded Dense Cores
• On the relative motions of dense cores and envelopes in star-forming molecular clouds