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  1. Abstract We present Atacama Large Millimeter/submillimeter Array observations of the ∼10,000 au environment surrounding 21 protostars in the Orion A molecular cloud tracing outflows. Our sample is composed of Class 0 to flat-spectrum protostars, spanning the full ∼1 Myr lifetime. We derive the angular distribution of outflow momentum and energy profiles and obtain the first two-dimensional instantaneous mass, momentum, and energy ejection rate maps using our new approach: the pixel flux-tracing technique. Our results indicate that by the end of the protostellar phase, outflows will remove ∼2–4 M ⊙ from the surrounding ∼1 M ⊙ low-mass core. These high values indicate that outflows remove a significant amount of gas from their parent cores and continuous core accretion from larger scales is needed to replenish core material for star formation. This poses serious challenges to the concept of cores as well-defined mass reservoirs , and hence to the simplified core-to-star conversion prescriptions. Furthermore, we show that cavity opening angles, and momentum and energy distributions all increase with protostar evolutionary stage. This is clear evidence that even garden-variety protostellar outflows: (a) effectively inject energy and momentum into their environments on 10,000 au scales, and (b) significantly disrupt their natal cores, ejecting a large fraction of the mass that would have otherwise fed the nascent star. Our results support the conclusion that protostellar outflows have a direct impact on how stars get their mass, and that the natal sites of individual low-mass star formation are far more dynamic than commonly accepted theoretical paradigms. 
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  2. Abstract We present a comprehensive analysis of the evolution of envelopes surrounding protostellar systems in the Perseus molecular cloud using data from the MASSES survey. We focus our attention to the C 18 O(2–1) spectral line, and we characterize the shape, size, and orientation of 54 envelopes and measure their fluxes, velocity gradients, and line widths. To look for evolutionary trends, we compare these parameters to the bolometric temperature T bol , a tracer of protostellar age. We find evidence that the angular difference between the elongation angle of the C 18 O envelope and the outflow axis direction generally becomes increasingly perpendicular with increasing T bol , suggesting the envelope evolution is directly affected by the outflow evolution. We show that this angular difference changes at T bol = 53 ± 20 K, which includes the conventional delineation between Class 0 and I protostars of 70 K. We compare the C 18 O envelopes with larger gaseous structures in other molecular clouds and show that the velocity gradient increases with decreasing radius ( ∣  ∣ ∼ R − 0.72 ± 0.06 ). From the velocity gradients we show that the specific angular momentum follows a power-law fit J / M ∝ R 1.83±0.05 for scales from 1 pc down to ∼500 au, and we cannot rule out a possible flattening out at radii smaller than ∼1000 au. 
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  3. Abstract We use 3 mm continuum NOrthern Extended Millimeter Array and NH 3 Very Large Array observations toward the First Hydrostatic Core (FHSC) candidate CB 17 MMS in order to reveal the dust structure and gas properties to 600–1100 au scales and to constrain its evolutionary stage. We do not detect any compact source at the previously identified 1.3 mm point source, despite expecting a minimum signal-to-noise ratio of 9. The gas traced by NH 3 exhibits subsonic motions, with an average temperature of 10.4 K. A fit of the radial column density profile derived from the ammonia emission finds a flat inner region of radius ∼1800 au and a central density of ∼6 × 10 5 cm −3 . Virial and density structure analysis reveals the core is marginally bound ( α vir = 0.73). The region is entirely consistent with that of a young starless core, hence ruling out CB 17 MMS as an FHSC candidate. Additionally, the core exhibits a velocity gradient aligned with the major axis, showing an arc-like structure in the position–velocity diagram and an off-center region with high velocity dispersion, caused by two distinct velocity peaks. These features could be due to interactions with the nearby outflow, which appears to deflect due to the dense gas near the NH 3 column density peak. We investigate the specific angular momentum profile of the starless core, finding that it aligns closely with previous studies of similar radial profiles in Class 0 sources. This similarity to more evolved objects suggests that motions at 1000 au scales are determined by large-scale dense cloud motions, and may be preserved throughout the early stages of star formation. 
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  4. null (Ed.)
    ABSTRACT We present ALMA 3 mm molecular line and continuum observations with a resolution of ∼3.5 arcsec towards five first hydrostatic core (FHSC) candidates (L1451-mm, Per-bolo 58, Per-bolo 45, L1448-IRS2E, and Cha-MMS1). Our goal is to characterize their envelopes and identify the most promising sources that could be bona fide FHSCs. We identify two candidates that are consistent with an extremely young evolutionary state (L1451-mm and Cha-MMS1), with L1451-mm being the most promising FHSC candidate. Although our envelope observations cannot rule out Cha-MMS1 as an FHSC yet, the properties of its CO outflow and SED published in recent studies are in better agreement with the predictions for a young protostar. For the remaining three sources, our observations favour a pre-stellar nature for Per-bolo 45 and rule out the rest as FHSC candidates. Per-bolo 58 is fully consistent with being a Class 0, while L1448 IRS2E shows no emission of high-density tracers (NH2D and N2H+) at the location of the previously identified compact continuum source, which is also undetected in our observations. Thus, we argue that there is no embedded source at the presumptive location of the FHSC candidate L1448 IRS2E. We propose instead that what was thought to be emission from the presumed L1448 IRS2E outflow corresponds to outflow emission from a nearby Class 0 system, deflected by the dense ambient material. We compare the properties of the FHSC candidates studied in this work and the literature, which shows that L1451-mm appears as possibly the youngest source with a confirmed outflow. 
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  5. null (Ed.)