The Core Population and Kinematics of a Massive Clump at Early Stages: An Atacama Large Millimeter/submillimeter Array View

Abstract

High-mass star formation theories make distinct predictions on the properties of the prestellar seeds of high-mass stars. Observations of the early stages of high-mass star formation can provide crucial constraints, but they are challenging and scarce. We investigate the properties of the prestellar core population embedded in the high-mass clump AGAL014.492-00.139, and we study the kinematics at the clump and clump-to-core scales. We have analyzed an extensive data set acquired with the Atacama Large Millimeter/submillimeter Array interferometer. Applying a dendrogram analysis to the Band 7 o‐H2D+ data, we identified 22 cores. We fitted their average spectra in local thermodinamic equilibrium conditions, and we analyzed their continuum emission at 0.8 mm. The cores have transonic to mildly supersonic turbulence levels and appear to be mostly low-mass, with M core < 30 M ⊙ . Furthermore, we have analyzed Band 3 observations of the N2H+ (1–0) transition, which traces the large-scale gas kinematics. Using a friend-of-friend algorithm, we identify four main velocity coherent structures, all of which are associated with prestellar and protostellar cores. One of them presents a filament-like structure, and our observations could be consistent with mass accretion toward one of the protostars. In this case, we estimate a mass accretion rate of M ̇ acc ≈ 2 × 10 − 4 M ⊙ yr − 1 . Our results support a clump-fed accretion scenario in the target source. The cores in the prestellar stage are essentially low-mass, and they appear to be subvirial and gravitationally bound, unless further support is available, for instance, due to magnetic fields.

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

“…The C 18 O emission, along the line of sight, presents asymmetric profiles toward some of cores. These line features in our sample can be attributed mostly to multiple velocity components because the C 18 O is virtually always optically thin in this sample (see Sabatini et al 2022), and these multiple velocity components match those of N 2 H + (J = 1-0) and ortho-H 2 D + (1 1,0 −1 1,1 ) toward G14.49 (the latter two lines are from Redaelli et al 2022). In order to fit the C 18 O emission associated to the cores, the central velocity derived from the other dense gas tracers (i.e., DCO + , N 2 D + , CH 3 OH, or H 2 CO) was used to guide the Gaussian fit of the C 18 O line.…”

“…In addition, the filamentary structures connected to cores can also transport material from the parental clump onto cores and thus further increase their masses. For example, the mass flow rate along a filamentary structure feeding a protostellar core in one of the ASHES targets, G14.49, is about 2.2 × 10 −4 M e yr −1 (Redaelli et al 2022). Such accretion rates along filamentary structures are not unusual in high-mass star-forming regions (e.g., Sanhueza et al 2021).…”

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 spite of infall rate estimations being so far rare in IRDCs, the few examples available (Contreras et al 2018;Chen et al 2019;Redaelli et al 2022) suggest that cores with masses as those found in ASHES cores can grow significantly in mass in a core freefall time (as discussed in two ASHES clumps; Contreras et al 2018;Redaelli et al 2022). Some ASHES cores have the conditions to become massive as hot cores and form high-mass stars.…”

The Effelsberg survey of FU Orionis and EX Lupi objects

“…Higher-angular resolution NH 3 observations could potentially probe whether there is a connection and/or ongoing accretion from cloud and/or filament down to core scales (e.g. Redaelli et al 2022), since NH 3 can be used to identify the presence of dense gas.…”