7月15日（水）13：30～15：00 NAOJ Science Colloquium zoom
Jul 15 Wed
7月15日（水）15：00～16：00 ALMA-J seminar zoom
Jul 15 Wed
7月17日（金）10：00～12：00 Final Defense for the doctoral thesis of the Department of Astronomical Science, SOKENDAI
Jul 17 Fri zoom
7月17日（金）16：00～17：00 談話会 zoom
Jul 17 Fri NAOJ Seminar
詳細は以下をご覧下さい。
7月15日（水）
- Campus
- Mitaka
- Seminar
- Date
- 2020 July 15
- Time
- 13:30-15:00
- Place
- Zoom
- Speaker
- Takahiro Ueda
- Title
- Grain size an d turbulence strength in protoplanetary disks inferred from multi-wavelength polarimetric observations
- Abstract
-
Dust grains are building blocks of rocky planets an d cores of giant planets. The evolution of dust grains into larger bodies is governed by turbulent motion of disk gas because turbulence controls the kinematic motion of dust grains. The ALMA polarimetric observations have shown that many disks show the scattering-induced polarization pattern at sub-millimeter wavelength. It suggests that the dust-size evolution might be halted at ~100um. In contrast, the turbulence strength has been not well constrained directly by observations. We investigate the grain size an d turbulence strength in the disk around HL Tau.
First, we give a constrain on the grain size in the disk by analyzing the spectral energy distribution (SED). The SED shows that the intensity at the ALMA Band 4 is lower than that estimated from the black body radiation even though it is optically thick. It indicates that the disk contains mm-sized grains which has high scattering opacity at the ALMA Band 4.
This result seems to contradict to the size previously predicted by the polarimetric observations which show that ~100um-sized grain is dominant. However, there is a possibility that the polarimetric observations trace only the upper layer of the disk which is dominated by ~100um-sized grains an d mm-sized grains are hidden into the disk mid-plane.
By using radiative transfer simulation with the differential settling, we demonstrate that the very low turbulence (α This approach would be a useful way to constrain grain size and turbulence strength in protoplanaetary disks.
NAOJ Science Colloquium Home page
URL: https://sci.nao.ac.jp/seminars/colloquium/
Read more - Facilitator
- -Name：Akimasa Kataoka
NAOJ Science Colloquium
7月15日（水）
7月17日（金）
- Campus
- Mitaka
- Seminar
- Final Defense for the doctoral thesis of the Department of Astronomical Science, SOKENDAI
- Regularly Scheduled/Sporadic
- Sporadic
- Date and time
- 17 July, 10:00～12:00
- Place
- Zoom
- Speaker
- Ananya Sahoo
- Affiliation
- Department of Astronomical Science, The Graduate University for Advanced Studies, SOKENDAI
- Title
- Precision Photometric and Astrometric Calibration for Exoplanet Imaging
- Facilitator
- -Name：Graduate Student Affairs Unit, Research Promotion Group
7月17日（金）
- Campus
- Mitaka
- Seminar
- NAOJ Seminar (国立天文台談話会)
- Regularly Scheduled/Sporadic
- Regular
- Date and time
- 7/17 (Fri) 16:00-17:00
- Place
- Zoom
- Speaker
- 原田 ななせ (国立天文台 助教) Nanase Harada (Assistant Professor, NAOJ)
- Affiliation
- Division of Science, NAOJ
- Title
- Astrochemical richness in external galaxies
- Abstract
-
Astrochemistry has been used as a tool to study the properties of star-forming molecular gas. Although a large number of chemical species has been observed in Galactic star forming regions, only several species have been observed in external galaxies until recently. High-capability radio telescopes such as ALMA have changed this picture dramatically, enabling spatially-resolved astrochemical studies for an increased number of species.
Studying external galaxies with astrochemistry has the potential to reveal the properties of molecular gas under the influence of extreme activities of star formation or active galactic nuclei (AGNs). These properties of molecular gas can explain variation of star formation efficiency due to feedback, or hidden activities of AGNs or star formation in the embedded regions.
In this talk, I present the roadmap of extragalactic astrochemistry in this initial stage of unleashing its potential. After introducing a necessary benchmark to understand astrochemistry in the scale of giant molecular clouds, I will present results in starburst galaxies and AGN-containing galaxies. Among them are initial results from one of our largest efforts, ALCHEMI survey (ALma Comprehensive High-resolution Extragalactic Molecular Inventory), an ALMA large program. - Facilitator
- -Name：Akimasa Kataoka