天文学教室・天文学教育研究センター合同談話会(2021年度)

last-update:2021/05/02

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  第1716回 天文学教室談話会/第367回 天文学教育研究センター談話会

2021年4月13日(火) 16:15-17:15

Title: The Effect of Misalignment between the Rotation Axis and Magnetic Field on the Circumstellar Disk

Speaker: 平野 信吾(天文学教室)/Shingo Hirano (Department of Astronomy)

Language: English

The formation of circumstellar disks is investigated using three-dimensional resistive magnetohydrodynamic simulations in which the initial prestellar cloud has a misaligned rotation axis with respect to the magnetic field. We examine the effects of (i) the initial angle difference between the global magnetic field and the cloud rotation axis and (ii) the ratio of the thermal to gravitational energy. We study 16 models in total and calculate the cloud evolution until ∼5000 yr after protostar formation. Our simulation results indicate that an initial nonzero promotes disk formation but tends to suppress outflow driving for models that are moderately gravitationally unstable. In these models, a large-sized rotationally supported disk forms and a weak outflow appears, in contrast to a smaller disk and strong outflow in the aligned case.

 

  第1717回 天文学教室談話会/第368回 天文学教育研究センター談話会

2021年4月27日(火) 16:15-17:15

Title: Observational study on high-mass star formation through development of own instruments

Speaker: 西村 淳(天文学教育研究センター)/Atsushi Nishimura (Institute of Astronomy)

Language: English

Finding new aspects of the universe through observations using own developed instruments is the most exciting experience for observational astronomers. Although the telescopes of big projects like ALMA provide opportunities to tackle excellent sciences, there is some room to flourish as well for smaller projects such as single dish telescopes in radio astronomy because they have advantages especially on their wider field of view. In this seminar, I introduce two projects in which I have been involved. One is the 1.85-m mm-submm telescope developed by Osaka Prefecture University aiming to observe CO(2-1) at 230 GHz (1.3 mm). Thus far, more than 1800 deg2 are mapped including the Galactic plane and nearby molecular clouds, and the project provides a good reference of the ratio between CO(1-0) and CO(2-1) toward the giant molecular clouds. The other is the FUGIN project which is a CO(1-0) survey toward the Galactic plane using the FOREST receiver (4-beam) installed on Nobeyama 45-m telescope. By grace of its high dynamic range (wide area with high resolution) data, we find that most of the giant molecular clouds associated with the high mass star formation region experienced cloud-cloud collision. Finally, I briefly introduce the latest activities on developments of future multi-beam receivers.