#author("2022-05-12T04:34:12+00:00","default:wwwadm","wwwadm")
#author("2022-06-13T04:07:06+00:00","default:wwwadm","wwwadm")
[[IoA_Seminar]]

#contents

　
* 講演リスト [#occ7a02f]

** No. 382: [#wb7884f1]

*** Speaker: 堀内 貴史（東京大学天文学教育研究センター） [#o0772b98]

*** Title: Evaluation of magnitudes of the Starlink satellites by simultaneous multicolor observations [#s05bd89d]

Language: English

Abstract:
The U.S. company, SpaceX plans to launch 42,000 Starlink satellites by the
mid-2020s. However, these satellites orbit at relatively low altitudes
(e.g. 550 km), and there are concerns that the light pollution from
sunlight reflection likely affects observations. In January 2020, SpaceX
launched a test satellite, Darksat with a black coating on its surface to
reduce the reflection flux. In order to verify the effect of its black
coating, we observed Darksat and unpainted Starlink satellites by
simultaneous multicolor observations (g’: green, Rc: red, and Ic:
near-infrared) with the 105 cm Murikabushi telescope/MITSuME. While the
magnitude of Darksat is about 7, being difficult to see with the naked
eyes, this brightness is sufficient to affect any observations. In June
2020, SpaceX launched Visorsat, which is a satellite with a sun visor to
reduce the reflected sunlight. At the present stage, there is no sufficient
verification on whether the sun visor is effective at various wavelengths.
In this study, we are therefore conducting the simultaneous multicolor
observations of Visorsat and the ordinary Starlink satellites through the
OISTER campaign. The preliminary observations of Visorsat with the
Murikabushi telescope have already shown that the apparent magnitude of
Visorsat is not fainter than that of Darksat, ranging from 6.5 mag (g'
band) to 5.7 mag (Ic band). Since most of the satellites to be launched by
SpaceX in the future will be visor satellites, it is very important to
investigate the effects of the Starlink satellites as soon as possible to
reduce the light pollution in astronomical observations.



** No. 381: 10 May 2022 (Tue) 16:15 - 17:15 [#q621959c]

*** Speaker: 西村優里（東京大学天文学教室） ／ Yuri Nishimura (University of Tokyo, Department of Astronomy) [#ic3c24b1]

*** Title: Molecular spectroscopy in local and high-redshift galaxies: What do "dense gas tracers" mean? [#o0879c29]
Language: Japanese

Abstract:
Thanks to the technical advancement of (sub)millimeter observing
facilities, a great number of molecular lines are now routinely observed
with high sensitivity and high angular resolution. These molecular lines
and line ratios are useful tools for studying physical, kinematic, and
chemical properties of extragalactic systems. To fully exploit line
diagnostics, it is important to relate different size scale observations:
detailed understanding of nearby systems by spatially-resolved observations
is essential to better interpretation of more distant objects which cannot
be observed at the same physical resolution.
In this talk, I will present (1) 10 pc-scale multiline mapping toward a
Galactic star-forming region W3(OH); (2) spatially- and spectrally-resolved
HCN and HCO+ observations of local (ultra)luminous infrared galaxies from
the CONquest sample (for more detail on CONquest, see Falstad+2021); and
(3) ALMA Band 3 (rest-frame ~350 GHz) line survey toward the Cloverleaf, a
gravitationally-lensed quasar at z=2.56. I will first discuss which
molecular emission arises from which part of the molecular cloud, and then
focus on how galactic-scale dynamics, such as outflows, can alter line
ratios.
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