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Abstract The Galactic diffuse emission (GDE) is formed when cosmic rays leave the sources where they were accelerated, diffusively propagate in the Galactic magnetic field and interact with the interstellar medium and interstellar radiation field. GDE in γ-rays (GDE-γ) has been observed up to subpetaelectronvolt energies, although its origin may be explained by either cosmic-ray nuclei or electrons. Here we show that the γ-rays accompanying the high-energy neutrinos recently observed by the IceCube Observatory from the Galactic plane have a flux that is consistent with the GDE-γ observed by the Fermi-LAT and Tibet ASγ experiments around 1 TeV and 0.5 PeV, respectively. The consistency suggests that the diffuse γ-ray emission above ~1 TeV could be dominated by hadronuclear interactions, although a partial leptonic contribution cannot be excluded. Moreover, by comparing the fluxes of the Galactic and extragalactic diffuse emission backgrounds, we find that the neutrino luminosity of the Milky Way is one-to-two orders of magnitude lower than the average of distant galaxies. This finding implies that our Galaxy has not hosted the type of neutrino emitters that dominates the isotropic neutrino background at least in the past few tens of kiloyears. 

Abstract High-energy neutrinos are detected by the IceCube Observatory in the direction of NGC 1068, the archetypical type II Seyfert galaxy. The neutrino flux, surprisingly, is more than an order of magnitude higher than theγ-ray upper limits at measured TeV energy, posing tight constraints on the physical conditions of a neutrino production site. We report an analysis of the submillimeter, mid-infrared, and ultraviolet observations of the central 50 pc of NGC 1068 and suggest that the inner dusty torus and the region where the jet interacts with the surrounding interstellar medium (ISM) may be a potential neutrino production site. Based on radiation and magnetic field properties derived from observations, we calculate the electromagnetic cascade of theγ-rays accompanying the neutrinos. When injecting protons with a hard spectrum, our model may explain the observed neutrino flux above ∼10 TeV. It predicts a unique sub-TeVγ-ray component, which could be identified by a future observation. Jet–ISM interactions are commonly observed in the proximity of jets of both supermassive and stellar-mass black holes. Our results imply that such interaction regions could beγ-ray-obscured neutrino production sites, which are needed to explain the IceCube diffuse neutrino flux. 

The Magellanic Stream (MS), a tail of diffuse gas formed from tidal and ram pressure interactions between the Small and Large Magellanic Clouds (SMC and LMC) and the Halo of the Milky Way, is primarily composed of neutral atomic hydrogen (HI). The deficiency of dust and the diffuse nature of the present gas make molecular formation rare and difficult, but if present, could lead to regions potentially suitable for star formation, thereby allowing us to probe conditions of star formation similar to those at high redshifts. We search for HCO+ ,HCN,HNC,andC2H using the highest sensitivity observations of molecular absorption data from the Atacama Large Millimeter Array (ALMA) to trace these regions, comparing with HI archival data from the Galactic Arecibo L-Band Feed Array (GALFA) HI Survey and the Galactic All Sky Survey (GASS) to compare these environments in the MS to the HI column density threshold for molecular formation in the Milky Way. We also compare the line of sight locations with confirmed locations of stars, molecular hydrogen, and OI detections, though at higher sensitivities than the observations presented here. 

Abstract The diffuse flux of cosmic neutrinos has been measured by the IceCube Observatory from TeV to PeV energies. We show that an improved characterization of this flux at lower energies, TeV and sub-TeV, reveals important information on the nature of the astrophysical neutrino sources in a model-independent way. Most significantly, it could confirm the present indications that neutrinos originate in cosmic environments that are optically thick to GeV–TeV γ -rays. This conclusion will become inevitable if an uninterrupted or even steeper neutrino power law is observed in the TeV region. In such γ -ray-obscured sources, the γ -rays that inevitably accompany cosmic neutrinos will cascade down to MeV–GeV energies. The requirement that the cascaded γ -ray flux accompanying cosmic neutrinos should not exceed the observed diffuse γ -ray background puts constraints on the peak energy and density of the radiation fields in the sources. Our calculations inspired by the existing data suggest that a fraction of the observed diffuse MeV–GeV γ -ray background may be contributed by neutrino sources with intense radiation fields that obscure the high-energy γ -ray emission accompanying the neutrinos. 

Our work aims to support engineering and science faculty in adapting core concepts and best practices from writing studies and technical communication for their courses. We also study the effectiveness of varied supports, with an aim of improving the diffusion of effective pedagogies. Our Writing Across Engineering and Science (WAES) program includes a semester-long faculty learning community, followed by sustained mentoring, during which faculty and graduate students from our multidisciplinary team work with mentees to develop and implement new pedagogies and course materials. For graduate students, we developed an engineering course focused on engineering and science writing practices and pedagogies. This paper focuses on one key finding from our analysis: discussions about writing practices involving people from different disciplines often involve irregular and sporadic bumpiness through which foundational changes can emerge. We call this phenomenon discursive turbulence. In our experience, signs of discursive turbulence include affective intensity and co- existing contradictory beliefs. We share four examples to illustrate ways in which discursive turbulence appears, drawn from people with varying degrees and types of engagement with our transdisciplinary work: i) project team members, ii) a faculty mentee, iii) faculty who participated in a focus group on disciplinary writing goals, and iv) engineering graduate students who took our class on writing practice and pedagogy. Discursive turbulence now informs our mentoring approach. It can be generative as well as challenging. Importantly, it takes time to resolve, suggesting the utility of sustained mentoring during pedagogical change.