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SOFIA MID-INFRARED IMAGING AND CSO SUBMILLIMETER POLARIMETRY OBSERVATIONS OF G034.43+00.24 MM1
摘要： We present 11.1 to 37.1 μm imaging observations of the very dense molecular cloud core MM1 in G034.43+00.24 using FORCAST on SOFIA and submillimeter (submm) polarimetry using SHARP on the Caltech Submillimeter Observatory. We ?nd that at the spatial resolution of SOFIA, the point-spread function (PSF) of MM1 is consistent with being a single source, as expected based on millimeter (mm) and submm observations. The spectral energy distributions (SEDs) of MM1 and MM2 have a warm component at the shorter wavelengths not seen in mm and submm SEDs. Examination of H(1.65 μm) stellar polarimetry from the Galactic Plane Infrared Polarization Survey shows that G034 is embedded in an external magnetic ?eld aligned with the Galactic Plane. The SHARP polarimetry at 450 μm shows a magnetic ?eld geometry in the vicinity of MM1 that does not line up with either the Galactic Plane or the mean ?eld direction inferred from the CARMA interferometric polarization map of the central cloud core, but is perpendicular to the long ?lament in which G034 is embedded. The CARMA polarimetry does show evidence for grain alignment in the central region of the cloud core, and thus does trace the magnetic ?eld geometry near the embedded Class 0 YSO.
关键词： stars: formation,stars: pre-main sequence,ISM: magnetic ?elds
更新于2025-09-16 10:30:52
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Near-infrared imaging polarimetry toward M?17 SWex
摘要： We conducted near-infrared (JHK s) imaging polarimetry toward the infrared dark cloud (IRDC) M 17 SWex, including almost all of the IRDC ?laments as well as its outskirts, with the polarimeter SIRPOL on the IRSF 1.4 m telescope. We revealed the magnetic ?elds of M 17 SWex with our polarization-detected sources that were selected by some criteria based on their near-IR colors and the column densities toward them, which were derived from the Herschel data. The selected sources indicate not only that the ordered magnetic ?eld is perpendicular to the cloud elongation as a whole, but also that at both ends of the elongated cloud the magnetic ?eld appears to be bent toward its central part, i.e., a large-scale hourglass-shaped magnetic ?eld perpendicular to the cloud elongation. In addition to this general trend, the elongations of the ?lamentary subregions within the dense parts of the cloud appear to be mostly perpendicular to their local magnetic ?elds, while the magnetic ?elds of the outskirts appear to follow the thin ?laments that protrude from the dense parts. The magnetic strengths were estimated to be ～70–300 μG in the subregions, of which the lengths and average number densities are ～3–9 pc and ～2–7 × 103 cm?3, respectively, by the Davis–Chandrasekhar–Fermi method with the angular dispersion of our polarization data and the velocity dispersion derived from the C18O (J = 1–0) data obtained by the Nobeyama 45 m telescope. These ?eld con?gurations and our magnetic stability analysis of the subregions imply that the magnetic ?eld has controlled the formation/evolution of the M 17 SWex cloud.
关键词： ISM: magnetic ?elds,ISM: clouds,ISM: structure,polarization,stars: formation
更新于2025-09-11 14:15:04
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24.1: <i>Invited Paper:</i> Development of 55 inch 4K AMOLED TV by Inkjet Printing Process
摘要： We simulate the evolution of supernova remnants (SNRs) in a strong magnetic ?eld. Usually, supernovae explode in a normal interstellar medium with magnetic ?eld of no more than 50 μG, which has been well studied. However, the surrounding magnetic ?eld will be much stronger in some situations, such as in a galactic center. Therefore, we try to explore these situations. The simulations show that a strong magnetic ?eld of 1 mG will align the motion of ejecta in a way similar to a jet. The ejecta propagating perpendicularly to the magnetic ?eld will be re?ected and generate a strong reverse shock. When the reverse shock converges in the explosion center, it will more or less ?ow along the central magnetic ?eld. Finally, most of the ejecta will propagate parallel to the magnetic ?eld.
关键词： ISM: supernova remnants,magnetohydrodynamics,ISM: magnetic ?elds
更新于2025-09-11 14:15:04
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Magnetic fields in star-forming systems (I): idealized synthetic signatures of dust polarization and Zeeman splitting in filaments
摘要： We use the POLARIS radiative transfer code to generate predictions of the two main observables directly sensitive to the magnetic ?eld morphology and strength in ?laments: dust polarization and gas Zeeman line splitting. We simulate generic gas ?laments with power-law density pro- ?les assuming two density-?eld strength dependencies, six different ?lament inclinations, and nine distinct magnetic ?eld morphologies, including helical, toroidal, and warped magnetic ?eld geometries. We present idealized spatially resolved dust polarization and Zeeman-derived ?eld strengths and directions maps. Under the assumption that dust grains are aligned by radiative torques, dust polarization traces the projected plane-of-the-sky magnetic ?eld mor- phology. Zeeman line splitting delivers simultaneously the intensity-weighted line-of-sight ?eld strength and direction. We show that linear dust polarization alone is unable to uniquely constrain the 3D ?eld morphology. We demonstrate that these ambiguities are ameliorated or resolved with the addition of the Zeeman directional information. Thus, observations of both the dust polarization and Zeeman splitting together provide the most promising means for obtaining constraints of the 3D magnetic ?eld con?guration. We ?nd that the Zeeman-derived ?eld strengths are at least a factor of a few below the input ?eld strengths due to line-of-sight averaging through the ?lament density gradient. Future observations of both dust polarization and Zeeman splitting are essential for gaining insights into the role of magnetic ?elds in star- and cluster-forming ?laments.
关键词： techniques: polarimetric,stars: formation,ISM: structure,methods: numerical,ISM: magnetic ?elds,techniques: Zeeman
更新于2025-09-11 14:15:04