Search for: All records

Abstract Magnetic fields likely play an important role in the formation of young protostars. Multiscale and multiwavelength dust polarization observations can reveal the inferred magnetic field from scales of the cloud to core to protostar. We present continuum polarization observations of the young protostellar triple system IRAS 16293-2422 at 89μm using HAWC+ on SOFIA. The inferred magnetic field is very uniform with an average field angle of 89° ± 23° (E of N), which is different from the ∼170° field morphology seen at 850μm at larger scales (≳2000 au) with JCMT POL-2 and at 1.3 mm on smaller scales (≲300 au) with Atacama Large Millimeter/submillimeter Array. The HAWC+ magnetic field direction is aligned with the known E-W outflow. This alignment difference suggests that the shorter wavelength HAWC+ data is tracing the magnetic field associated with warmer dust likely from the outflow cavity, whereas the longer wavelength data are tracing the bulk magnetic field from cooler dust. Also, we show in this source the dust emission peak is strongly affected by the observing wavelength. The dust continuum peaks closer to source B (northern source) at shorter wavelengths and progressively moves toward the southern A source with increasing wavelength (from 22 to 850μm). 

[Background] Selecting an appropriate task is challenging for Open Source Software (OSS) project newcomers and a variety of strategies can help them in this process. [Aims] In this research, we compare the perspective of maintainers, newcomers, and existing contributors about the importance of strategies to support this process. Our goal is to identify possible gulfs of expectations between newcomers who are meant to be helped and contributors who have to put effort into these strategies, which can create friction and impede the usefulness of the strategies. [Method] We interviewed maintainers (n=17) and applied inductive qualitative analysis to derive a model of strategies meant to be adopted by newcomers and communities. Next, we sent a questionnaire (n=64) to maintainers, frequent contributors, and newcomers, asking them to rank these strategies based on their importance. We used the Schulze method to compare the different rankings from the different types of contributors. [Results] Maintainers and contributors diverged in their opinions about the relative importance of various strategies. The results suggest that newcomers want a better contribution process and more support to onboard, while maintainers expect to solve questions using the available communication channels. [Conclusions] The gaps in perspectives between newcomers and existing contributors create a gulf of expectation. OSS communities can leverage our results to prioritize the strategies considered the most important by newcomers. 

Open Source Software projects add labels to open issues to help contributors choose tasks. However, manually labeling issues is time-consuming and error-prone. Current automatic approaches for creating labels are mostly limited to classifying issues as a bug/non-bug. In this paper, we investigate the feasibility and relevance of labeling issues with the domain of the APIs required to complete the tasks. We leverage the issues' description and the project history to build prediction models, which resulted in precision up to 82% and recall up to 97.8%. We also ran a user study (n=74) to assess these labels' relevancy to potential contributors. The results show that the labels were useful to participants in choosing tasks, and the API-domain labels were selected more often than the existing architecture-based labels. Our results can inspire the creation of tools to automatically label issues, helping developers to find tasks that better match their skills. 

Abstract We present H -band (1.65 μ m) and SOFIA HAWC+ 154 μ m polarization observations of the low-mass core L483. Our H -band observations reveal a magnetic field that is overwhelmingly in the E–W direction, which is approximately parallel to the bipolar outflow that is observed in scattered IR light and in single-dish 12 CO observations. From our 154 μ m data, we infer a ∼45° twist in the magnetic field within the inner 5″ (1000 au) of L483. We compare these new observations with published single-dish 350 μ m polarimetry and find that the 10,000 au scale H -band data match the smaller-scale 350 μ m data, indicating that the collapse of L483 is magnetically regulated on these larger scales. We also present high-resolution 1.3 mm Atacama Large Millimeter/submillimeter Array data of L483 that reveals it is a close binary star with a separation of 34 au. The plane of the binary of L483 is observed to be approximately parallel to the twisted field in the inner 1000 au. Comparing this result to the ∼1000 au protostellar envelope, we find that the envelope is roughly perpendicular to the 1000 au HAWC+ field. Using the data presented, we speculate that L483 initially formed as a wide binary and the companion star migrated to its current position, causing an extreme shift in angular momentum thereby producing the twisted magnetic field morphology observed. More observations are needed to further test this scenario. 

Abstract The alignment of dust grains with the ambient magnetic field produces polarization of starlight as well as thermal dust emission. Using the archival SOFIA/HAWC+ polarimetric data observed toward the ρ Ophiuchus (Oph) A cloud hosted by a B star at 89 and 154 μ m, we find that the fractional polarization of thermal dust emission first increases with the grain temperature and then decreases once the grain temperature exceeds ≃25–32 K. The latter trend differs from the prediction of the popular RAdiative Torques (RATs) alignment theory, which implies a monotonic increase of the polarization fraction with the grain temperature. We perform numerical modeling of polarized dust emission for the ρ Oph-A cloud and calculate the degree of dust polarization by simultaneously considering the dust grain alignment and rotational disruption by RATs. Our modeling results could successfully reproduce both the rising and declining trends of the observational data. Moreover, we show that the alignment of only silicate grains or a mixture of silicate–carbon grains within a composite structure can reproduce the observational trends, assuming that all dust grains follow a power-law size distribution. Although there are a number of simplifications and limitations to our modeling, our results suggest grains in the ρ Oph-A cloud have a composite structure, and the grain size distribution has a steeper slope than the standard size distribution for the interstellar medium. Combination of SOFIA/HAWC+ data with JCMT observations 450 and 850  μ m would be useful to test the proposed scenario based on grain alignment and disruption by RATs.