ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) II. Survey overview: a first look at 1.3 mm continuum maps and molecular outflows

Abstract

Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm (band 6) using three different configurations (resolutions ∼ 0. 35, 1. 0, and 7. 0) to statistically investigate their evolutionary stages and sub-structures. We have obtained images of the 1.3 mm continuum and molecular line emission ( 12 CO, and SiO) at an angular resolution of ∼ 0. 35 (∼ 140 au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust-mass ∼ 0.093 M and deconvolved size ∼ 0. 27. Dense substructures are clearly detected within the central 1000 au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class 0 to Class I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 (>50%) show high-velocity jets in SiO. The CO velocity-extents (∆Vs) span from 4 to 110 km/s with outflow cavity opening angle width at 400 au ranging from [Θ obs ] 400 ∼ 0. 6 to 3. 9, which corresponds to 33. • 4−125. • 7. For the majority of the outflow sources, the ∆Vs show a positive correlation with [Θ obs ] 400 , suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows.

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Detection of Extremely High-density Compact Structure of Prestellar Cores and Multiple Substructures Within

“…None of the five cores displays an outflow signature when observed in CO (J=2-1), its isotopologue lines and SiO (J=5-4) (Dutta et al 2020). Neither near-infrared nor midinfrared emission is present within these targets based on our archival search 1 .…”

“…The spectral set-up covers the continuum emission at 233.0 GHz and 216.6 GHz, and offers simultaneous coverage of the molecular lines CO (2-1), C 18 O (2-1), N 2 D + (3-2), SiO (5-4) and other hot corino tracers as well (see Hsu et al 2020). The remaining details of the observational parameters are presented in Dutta et al (2020).…”

“…Recently, we performed a survey (ALMA Survey of Orion Planck Galactic Cold Clumps or ALMASOP; Dutta et al 2020) with ALMA, in which we targeted 72 cores toward the Orion Molecular Clouds (distance ∼ 400 pc; Kounkel et al 2018). An overview of the ALMASOP is presented in Dutta et al (2020). Among the 72 targets in ALMASOP observations, 23 were previously classified as (candidate) starless cores.…”