Search

Protostellar outflows and jets are almost ubiquitous characteristics during the mass accretion phase and encode the history of stellar accretion, complex organic molecule (COM) formation, and planet formation. Episodic jets are likely connected to episodic accretion through the disk. Despite the importance, studies on episodic accretion and ejection links have not been done yet in a systematic fashion using high-sensitivity and high-resolution observations. To explore episodic accretion mechanisms and the chronologies of episodic events, we investigated 39 fields containing protostars with Atacama Large Millimeter/submillimeter Array observations of CO, SiO, and 1.3 mm continuum emission. We detected SiO emission in 19 fields, where 17 sources are driving molecular jets. Jet velocities, mass-loss rates, mass accretion rates, and periods of accretion events appear to have some dependence on the driving forces of the jet (e.g., bolometric luminosity, envelope mass). Next, velocities and mass-loss rates appear to be somewhat correlated with the surrounding envelope mass, suggesting that the presence of high mass around protostars increases the ejection–accretion activity. We determine mean periods of ejection events of 20–175 yr for our sample, which could be associated with perturbation zones of ∼2−25 au extent around the protostars. In addition, mean ejection periods show an apparent anticorrelation with the envelope mass, where high accretion rates may trigger more frequent ejection events. The observed periods of outburst/ejection are much shorter than the freezeout timescale of the simplest COMs like CH _3 OH, suggesting that episodic events could affect the ice–gas balance inside and around the snowline.

The internal structure of the prestellar core G208.68-19.02-N2 (G208-N2) in the Orion Molecular Cloud 3 (OMC-3) region has been studied with the Atacama Large Millimeter/submillimeter Array. The dust continuum emission revealed a filamentary structure with a length of ∼5000 au and an average H _2 volume density of ∼6 × 10 ^7 cm ^−3 . At the tip of this filamentary structure, there is a compact object, which we call a nucleus , with a radius of ∼150–200 au and a mass of ∼0.1 M _⊙ . The nucleus has a central density of ∼2 × 10 ^9 cm ^−3 with a radial density profile of r ^−1.87±0.11 . The density scaling of the nucleus is ∼3.7 times higher than that of the singular isothermal sphere (SIS). This as well as the very low virial parameter of 0.39 suggests that the gravity is dominant over the pressure everywhere in the nucleus. However, there is no sign of CO outflow localized to this nucleus. The filamentary structure is traced by the N _2 D ^+ 3–2 emission, but not by the C ^18 O 2–1 emission, implying the significant CO depletion due to high density and cold temperature. Toward the nucleus, the N _2 D ^+ also shows the signature of depletion. This could imply either the depletion of the parent molecule, N _2 , or the presence of the embedded very-low luminosity central source that could sublimate the CO in the very small area. The nucleus in G208-N2 is considered to be a prestellar core on the verge of first hydrostatic core (FHSC) formation or a candidate for the FHSC.

One of the most poorly understood aspects of low-mass star formation is how multiple-star systems are formed. Here we present the results of Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations toward a forming quadruple protostellar system, G206.93-16.61E2, in the Orion B molecular cloud. ALMA 1.3 mm continuum emission reveals four compact objects, of which two are Class I young stellar objects and the other two are likely in prestellar phase. The 1.3 mm continuum emission also shows three asymmetric ribbon-like structures that are connected to the four objects, with lengths ranging from ∼500 to ∼2200 au. By comparing our data with magnetohydrodynamic simulations, we suggest that these ribbons trace accretion flows and also function as gas bridges connecting the member protostars. Additionally, ALMA CO J = 2−1 line emission reveals a complicated molecular outflow associated with G206.93-16.61E2, with arc-like structures suggestive of an outflow cavity viewed pole-on.

Hot corinos are of great interest due to their richness in interstellar complex organic molecules (COMs) and the consequent potential prebiotic connection to solar-like planetary systems. Recent surveys have reported an increasing number of detected hot corinos in Class 0/I protostars; however, the relationships between their physical properties and the hot-corino signatures remain elusive. In this study, our objective is to establish a general picture of the detectability of hot corinos by identifying the origins of the hot-corino signatures in the sample of young stellar objects (YSOs) obtained from the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps project. We apply spectral energy distribution modeling to our sample and identify the physical parameters of the modeled YSOs directly, linking the detection of hot-corino signatures to the envelope properties of the YSOs. Imaging simulations of the methanol emission further support this scenario. We therefore posit that the observed COM emission originates from the warm inner envelopes of the sample YSOs, based on both the warm region size and the envelope density profile. The former is governed by the source luminosity and is additionally affected by the disk and cavity properties, while the latter is related to the evolutionary stages. This scenario provides a framework for detecting hot-corino signatures toward luminous Class 0 YSOs, with fewer detections being observed toward similarly luminous Class I sources.

Starless cores represent the initial stage of evolution toward (proto)star formation, and a subset of them, known as prestellar cores, with high density (∼ 10 ^6 cm ^−3 or higher) and being centrally concentrated are expected to be embryos of (proto)stars. Determining the density profile of prestellar cores therefore provides an important opportunity to gauge the initial conditions of star formation. In this work, we perform rigorous modeling to estimate the density profiles of three nearly spherical prestellar cores among a sample of five highly dense cores detected by our recent observations. We employed multiscale observational data of the (sub)millimeter dust continuum emission, including those obtained by SCUBA-2 on the James Clerk Maxwell Telescope with a resolution of ∼ 5600 au and by multiple Atacama Large Millimeter/submillimeter Array observations with a resolution as high as ∼ 480 au. We are able to consistently reproduce the observed multiscale dust continuum images of the cores with a simple prescribed density profile, which bears an inner region of flat density and an r ^−2 profile toward the outer region. By utilizing the peak density and the size of the inner flat region as a proxy for the dynamical stage of the cores, we find that the three modeled cores are most likely unstable and prone to collapse. The sizes of the inner flat regions, as compact as ∼ 500 au, signify them as being the highly evolved prestellar cores rarely found to date.

This study examines how best to present information in an antidepressant print DTCA. The objectives of this study are to: (1) modify an antidepressant print advertisement to enhance consumers’ understanding of the presented information, (2) create a questionnaire to measure consumers’ recall of the information presented in an antidepressant print advertisement and (3) pilot test the study instruments by comparing consumers’ recall of the information in the antidepressant print advertisement between those who view the original advertisement and those who view the modified advertisement. Modifications of the advertisement were based on the Explanatory Structure Building Model, findings from previous studies, and literature pertaining to the enhancement of the readability and comprehension of written health information. Data collection was conducted in three stages using mixed methods. This study details potential techniques that can be used to enhance the presentation of information in print DTCA in order to improve consumers’ recall of the information. Furthermore, this study shows that strategies to improve the presentation of information in print DTCA exist and that the strategies are feasible to apply. Conflict of Interest This research study was supported by the University of Wisconsin-Madison Population Health Dissertation Grants sponsored by the Robert Wood Johnson Foundation and the Sonderegger Research Center Dissertation Research Grants. Type: Original Research