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

Abstract

We present 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 (α) measurements are gravitationally bound (α < 2). We also find an anticorrelation 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 nonthermal velocity dispersion (from N2D+ 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 a not significant increment in the line velocity dispersion from prestellar to protostellar cores, suggesting that the 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 do not have significant velocity shifts relative to their low-density envelopes, suggesting that dense cores are comoving with their envelopes. We conclude that the observed core properties are more in line with the predictions of clump-fed scenarios rather than with those of core-fed scenarios.

Direct Observational Evidence of the Multi-scale, Dynamical Mass Accretion Toward a High-mass Star-forming Hub-filament System

“…HFSs have been the focus of several statistical studies (Kumar et al 2020;Zhou et al 2022;Liu et al 2023). In particular, Liu et al (2023) studied a sample of 17 HFSs composed of two distinct evolutionary stages using high-angular resolution (∼1″-2″) Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm (Li et al 2023;Morii et al 2023) and 3 mm continuum data (Liu et al 2020b;Sanhueza et al 2019). Liu et al (2023) discuss the observed trend on multi-scales (i.e., clumps and cores) of increasing mass and mass surface density with the evolution from IR-dark to IR-bright stage, the mass-segregated cluster of young stellar objects, and the potentially preferential escape directions of outflow feedback.…”

The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). IX. Physical Properties and Spatial Distribution of Cores in IRDCs

“…In a pilot survey, we mosaicked twelve candidate massive prestellar clumps with ALMA in dust continuum and molecular line emission at ∼224 GHz (Sanhueza et al 2019). We investigated fragmentation process (Sanhueza et al 2019), outflows (Li et al 2020), chemistry (Li et al 2022;Sabatini et al 2022), and dynamical properties (Li et al2023). We also conducted some case studies about a peculiar outflow (Tafoya et al 2021), active star formation signatures (Morii et al 2021), and deuterated chemistry (Sakai et al 2022).…”

The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE): Core Growth, Cluster Contraction, and Primordial Mass Segregation

“…The y value is normalized by the ratio to the value of IRDCs. (Kong et al 2021), the Orion Molecular Cloud (OMC; Takemura et al 2023), the ASHES IRDC sample (Li et al 2023), and the ALMA-initial mass function protoclusters (Nony et al 2023;Pouteau et al 2023) also suggest that the protostellar cores are considerably more massive than the starless cores, suggesting that cores grow with time. If the missing flux in the ASSEMBLE sample were recovered, the effect would be to increase the core mass and surface density, strengthening the arguments above.…”