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1. An Episodic Wide-angle Outflow in HH 46/47

   https://doi.org/10.3847/1538-4357/ab3850  

   Zhang, Yichen; Arce, Héctor G.; Mardones, Diego; Cabrit, Sylvie; Dunham, Michael M.; Garay, Guido; Noriega-Crespo, Alberto; Offner, Stella S.; Raga, Alejandro C.; Corder, Stuartt A. (September 2019, The Astrophysical Journal)
2. Maximal Tori in HH 1 and the Fundamental Group

   https://doi.org/10.1093/imrn/rnac026  

   Briggs, Benjamin; Rubio y Degrassi, Lleonard (March 2023, International Mathematics Research Notices)

   Abstract We investigate maximal tori in the Hochschild cohomology Lie algebra $${\operatorname {HH}}^1(A)$$ of a finite dimensional algebra $$A$$, and their connection with the fundamental groups associated to presentations of $$A$$. We prove that every maximal torus in $${\operatorname {HH}}^1(A)$$ arises as the dual of some fundamental group of $$A$$, extending the work by Farkas, Green, and Marcos; de la Peña and Saorín; and Le Meur. Combining this with known invariance results for Hochschild cohomology, we deduce that (in rough terms) the largest rank of a fundamental group of $$A$$ is a derived invariant quantity, and among self-injective algebras, an invariant under stable equivalences of Morita type. Using this we prove that there are only finitely many monomial algebras in any derived equivalence class of finite dimensional algebras; hitherto this was known only for very restricted classes of monomial algebras. 

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3. The HH 24 Complex: Jets, Multiple Star Formation, and Orphaned Protostars

   https://doi.org/10.3847/1538-3881/acadd4  

   Reipurth, Bo; Bally, J.; Yen, Hsi-Wei; Arce, H. G.; Rodríguez, L. -F.; Raga, A. C.; Geballe, T. R.; Rao, R.; Comerón, F.; Mikkola, S.; et al (April 2023, The Astronomical Journal)

   Abstract The HH 24 complex harbors five collimated jets emanating from a small protostellar multiple system. We have carried out a multiwavelength study of the jets, their driving sources, and the cloud core hosting the embedded stellar system, based on data from the Hubble Space Telescope, Gemini, Subaru, Apache Point Observatory 3.5 m, Karl G. Jansky Very Large Array, and Atacama Large Millimeter/submillimeter Array (ALMA) telescopes. The data show that the multiple system, SSV 63, contains at least 7 sources, ranging in mass from the hydrogen-burning limit to proto-Herbig Ae stars. The stars are in an unstable nonhierarchical configuration, and one member, a borderline brown dwarf, is moving away from the protostellar system with 25 km s⁻¹, after being ejected ∼5800 yr ago as an orphaned protostar. Five of the embedded sources are surrounded by small, possibly truncated, disks resolved at 1.3 mm with ALMA. Proper motions and radial velocities imply jet speeds of 200–300 km s⁻¹. The two main HH 24 jets, E and C, form a bipolar jet system that traces the innermost portions of parsec-scale chains of Herbig–Haro and H₂shocks with a total extent of at least 3 pc. H₂CO and C¹⁸O observations show that the core has been churned and continuously fed by an infalling streamer.¹³CO and¹²CO trace compact, low-velocity, cavity walls carved by the jets and an ultracompact molecular outflow from the most embedded object. ChaoticN-body dynamics likely will eject several more of these objects. The ejection of stars from their feeding zones sets their masses. Dynamical decay of nonhierarchical systems can thus be a major contributor to establishing the initial mass function. 

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4. Polarization Substructure in the Spiral-dominated HH 111 Disk: Evidence for Grain Growth

   https://doi.org/10.3847/2041-8213/ad68e1  

   Lee, Chin-Fei; Li, Zhi-Yun; Ching, Tao-Chung; Yang, Haifeng; Lai, Shih-Ping; Lin, Zhe-Yu Daniel; Hu, Ying-Chi (August 2024, The Astrophysical Journal Letters)

   Abstract The HH 111 protostellar disk has recently been found to host a pair of spiral arms. Here we report the dust polarization results in the disk as well as the inner envelope around it, obtained with the Atacama Large Millimeter/submillimeter Array in continuum atλ∼ 870μm and ∼0.″05 resolution. In the inner envelope, polarization is detected with a polarization degree of ∼6% and an orientation almost everywhere parallel to the minor axis of the disk and thus likely to be due to the dust grains magnetically aligned mainly by toroidal fields. In the disk, the polarization orientation is roughly azimuthal on the far side and becomes parallel to the minor axis on the near side, with a polarization gap in between on the far side near the central protostar. The disk polarization degree is ∼2%. The polarized intensity is higher on the near side than the far side, showing a near–far side asymmetry. More importantly, the polarized intensity and thus polarization degree are lower in the spiral arms but higher in between the arms, showing an anticorrelation of the polarized intensity with the spiral arms. Our modeling results indicate that this anticorrelation is useful for constraining the polarization mechanism and is consistent with the dust self-scattering by the grains that have grown to a size of ∼150μm. The interarms are sandwiched and illuminated by two brighter spiral arms and thus have higher polarized intensity. Our dust self-scattering model can also reproduce the observed polarization orientation parallel to the minor axis on the near side and the observed azimuthal polarization orientation at the two disk edges in the major axis. Further modeling work is needed to study how to reproduce the observed near–far side asymmetry in the polarized intensity and the observed azimuthal polarization orientation on the far side. 

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5. First Abundance Measurement of Organic Molecules in the Atmosphere of HH 212 Protostellar Disk

   https://doi.org/10.3847/1538-4357/ab15db  

   Lee, Chin-Fei; Codella, Claudio; Li, Zhi-Yun; Liu, Sheng-Yuan (May 2019, The Astrophysical Journal)