Global and Local Infall in the ASHES Sample (GLASHES). III. Physical Parameters of Contracting Motion onto Dense Cores in 70 $μ$m Dark Massive Clumps

Abstract

Core growth is a key process in high-mass star formation. As part of the GLASHES (Global and Local Infall in the ASHES Sample) survey, we present infall velocities and mass infall rates derived from blue-asymmetric line profiles toward cores embedded in massive 70 \textmu m-dark clumps. Robust Hill5 model fits were obtained for 70 of the 135 cores exhibiting blue-asymmetric profiles, yielding infall velocities of 0.11--1.60 km s$^{-1}$ and mass infall rates ranging from $\sim$10$^{-5}$ to $5\times10^{-3}\,M_\odot\,{\rm yr}^{-1}$. Both quantities increase systematically from prestellar candidates to warm cores and outflow-associated cores. The inferred infall velocities are close to the cores' free-fall velocities (mean $v_{\rm in}/v_{\rm ff}\sim0.75$) and $t_{\rm in}=R/v_{\rm in}$ is comparable to the free-fall time, indicating dynamical fast contraction. Hill5 infall velocity correlates moderately with the non-thermal velocity dispersion and Mach number measured from optically thin tracers, indicating that organized infall contributes to the observed line widths. The mass infall rate follows a power-law relation with core mass, $\dot{M}=1.3\times10^{-4}\,(M/M_\odot)^{0.83\pm 0.06}\,M_\odot\,{\rm yr}^{-1}$, across $0.1\,M_\odot \lesssim M \lesssim 30\,M_\odot$. The power-law index increases from $\sim$0.65 for prestellar cores to $\sim$1.10 for outflow-associated cores, likely tracing an evolution in the dominant physical process. The Hill5 infall velocities and mass infall rates for the GLASHES cores are larger than those of cores in nearby low-mass star forming regions but smaller than those of larger scale high-mass clumps. These results provide the first statistical constraints on core-scale mass accumulation during the earliest stages of high-mass star formation.