#author("2021-05-21T01:52:26+00:00","default:wwwadm","wwwadm")
#author("2021-05-31T02:28:22+00:00","default:wwwadm","wwwadm")
[[IoA_Seminar]]

#contents

** No. 367: 13 April 2021 (Tue) 16:15 - 17:15 [#y9ef4ed5]
*** Speaker: 平野 信吾（東京大学理学系研究科天文学教室）／Shingo Hirano (Department of Astronomy, the University of Tokyo) [#u0d6faa7]
*** Title: The Effect of Misalignment between the Rotation Axis and Magnetic Field on the Circumstellar Disk [#h7fb3446]
Language: English

Abstract: 

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.

(This talk will be given online. Details will be announced via e-mail.)


** No. 368: 27 April 2021 (Tue) 16:15 - 17:15 [#mab58407]
*** Speaker: 西村 淳（東京大学理学系研究科天文学教育研究センター）／Atsushi Nishimura (Institute of Astronomy, the University of Tokyo) [#f54ae4b2]
*** Title: Observational study on high-mass star formation through development of own instruments [#t7485038]
Language: English

Abstract: 

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.

(This talk will be given online. Details will be announced via e-mail.)


** No. 369: 11 May 2021 (Tue) 16:15 - 17:15 [#h41102ef]
*** Speaker: 山岸 光義 （東京大学理学系研究科天文学教育研究センター）／Mitsuyoshi Yamagishi (Institute of Astronomy, the University of Tokyo) [#c9eff11d]
*** Title: Observational studies of neutral carbon in our Galaxy [#r7163fa5]
Language: Japanese (with English slide)

Abstract: Carbon is one of the major atoms in the Universe. It is valuable to examine carbon atoms and carbon-bearing molecules in the various interstellar environment to gain a deep understanding of interstellar chemistry. Emission lines from a neutral carbon atom ([CI]) are observed in the high-frequency ranges (492, 809 GHz). Since excellent atmospheric conditions are required in high-frequency observations, intensive studies of [CI] have been difficult before the ALMA era. In this talk, I will talk about two recent studies of [CI] with ALMA and ASTE in the different interstellar environments in our Galaxy (rho Oph A PDR and gamma-ray SNR W51C). Based on the results, I will discuss the origins of the [CI] emission in a star-forming region and the effects of cosmic-ray on interstellar chemistry. 

(This talk will be given online. Details will be announced via e-mail.)


** No. 370: 25 May 2021 (Tue) 16:15 - 17:15 [#u6187824]
*** Speaker: Jerome de Leon （東京大学理学系研究科天文学教室）／Jerome de Leon (Department of Astronomy, the University of Tokyo) [#x6aef741]
*** Title: Challenges and opportunities in young planet discoveries from Kepler to TESS [#f3abdd2b]
Language: English

Abstract: Studying young exoplanets is important because they inhabit a very important part of the exoplanet evolutionary timescale where several yet unknown processes are expected to shape their final outcome. However, finding and characterizing transiting exoplanets orbiting young stars is notoriously difficult. This is due to intrinsic high stellar activity in young stars that induces photometric variations and radial velocity jitter often a few orders of magnitude larger than the planet signal. This problem is compounded by the fact that most of the young stars usually reside in star clusters or moving groups where the false positive rate is high due to the crowded field. Despite the small sample of young planets discovered from the K2 mission however, there is tentative evidence that the planetʼs size depends with the host starʼs age. To confidently corroborate or refute such trends and to have a complete understanding on how exoplanets form and evolve from birth to maturity, the community needs a statistically significant sample of transiting planets orbiting bright young stars. As the TESS mission continues to survey the sky until 2022, new transiting planets around young stars will be discovered. The brightness of the host star would facilitate precise measurements of the fundamental parameters of the host stars and planets which in turn lead to better models to constrain their bulk density and atmospheric composition. 

(This talk will be given online. Details will be announced via e-mail.)
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