2月24日（水）13：30～15：00 NAOJ Science Colloquium zoom
Feb 24 Wed
2月24日（水）15：00～16：00 ALMA-J Seminar zoom
Feb 24 Wed
2月26日（金）16：00～17：00 談話会 zoom
Feb 26 Fri NAOJ Seminar
詳細は以下をご覧下さい。
2月24日（水）
- Campus
- Mitaka
- Seminar
- NAOJ Science Colloquium
- Regularly Scheduled/Sporadic
- Every Wednesday
- Date
- 2021 February 24
- Time
- 13:30-15:00
- Place
- Zoom
- Speaker
- Takashi Shimonishi (Niigata University)
- Title
- Chemistry of star-forming regions at low metallicity
- Abstract
- Understanding chemistry of interstellar medium at low metallicity is crucial to unveil chemical processes in high-redshift galaxies and the past Galactic environment, where the metallicity was significantly lower compared to the present-day solar neighborhood. In this decade, there have been great progress in astrochemical studies of star-forming regions at low metallicity. A variety of interstellar molecules, including complex species, are detected towards molecular clouds, dense cores, embedded protostars, and hot molecular cores in nearby low-metallicity galaxies, the Large and Small Magellanic Cloud. In general, molecular abundances are lower in low-metallicity star-forming regions. However, current observations suggest that molecular abundances do not always simply scale with the elemental abundances, and indirect effects caused by the decreased metallicity, such as enhanced photochemistry or grain surface chemistry on warmer dust, are also important for understanding the chemical processes of the interstellar medium at low metallicity. In this presentation, I will summarize the current status of astrochemical studies of low-metallicity star-forming regions. Furthermore, I will show the initial results of our ongoing hot core survey towards the Magellanic Clouds with ALMA.
- Facilitator
- -Name：Akimasa Kataoka
2月24日（水）
- Campus
- Mitaka
- Seminar
- ALMA-J seminar
- Regularly Scheduled/Sporadic
- Every Wednesday
- Date and time
- 2021 Feb. 24 15:00-16:00
- Place
- Zoom
- Speaker
- Hiroshi Nagai (NAOJ)
- Title
- Diffuse Radio Continuum Emission Associated with the Starburst in the Circumnuclear Disk of NGC 1275
- Abstract
-
Recent ALMA observations found a positive correlation between the mass of dense molecular gas in the circumnuclear disk (CND) and AGN luminosity. Although the starburst-driven turbulence is one of the key mechanisms for the angular-momentum transfer and resultant mass accretion from the CND scale to accretion disk scale, the observational evidence has been lacking.
Using VLBA data at 330MHz, we found that the diffuse synchrotron emission on several tens-kpc scale spatially coincides with the molecular gas disk recently discovered by ALMA observations in NGC 1275. The synchrotron emission is most likely resulted from the relativistic electrons produced by the supernova remnants. This is an ambiguous evidence of the star formation activity in the CND. The derived star formation rate is about ~3 solar mass per year.
This star formation rate is comparable or smaller than the gas accretion rate in the CND estimated using alpha-viscosity model. Therefore, the CND gas is not entirely consumed by the star formation and a significant amount of gas must be accreted to the further inner region.
The diffuse low-frequency radio emission discovered by this observation could be ubiquitous in the CND of other AGNs but overlooked in the past. Future study using VLBA archival data would be useful to better understand the AGN-starburst connection in nearby Seyfert galaxies. - Facilitator
- Hiroshi Nagai, Xing Lu
2月26日(金）
- Campus
- Mitaka
- Seminar
- NAOJセミナー
- Regularly Scheduled/Sporadic
- Regular
- Date and time
- 26 February (Fri), 16:00-17:00
- Place
- zoom
- Speaker
- 末松 芳法 / Suematsu, Yoshinori
- Affiliation
- 太陽観測科学プロジェクト / Solar Science Observatory
- Title
- Solar-B, C and Beyond
- Abstract
-
Needless to say, high-resolution observations are important in astronomical
observations, but especially in solar observations, the high resolution is
critical because many phenomena occur in association with magnetic fields,
and the magnetic fields exist in the form of magnetic flux tubes with a width
of sub-arcsecond (a few hundred kilometers in the Sun’s surface). Therefore,
observations that can resolve these flux tubes and precisely track the
temporal changes that occur in a short time are essentially important.
It is necessary to obtain the magnetic field information at the same
(or higher) resolution, and a telescope with a large aperture is required
to collect as many photons as possible in order to improve the accuracy of
polarization information for deriving the magnetic field as well as the
resolution. Personally, I am interested in the origin of the chromospheric
jet phenomenon in magnetic flux tubes, and I have spent much of my time at
NAOJ developing and realizing space solar telescopes to solve the problem.
Despite the fact that chromospheric jets are an important ingredient
connecting the photosphere, which is the source of energy and mass, with
the corona, which is the ejector of energy and mass (the so-called solar
chromosphere is considered to consist of a collection of jet phenomena),
the formation mechanism of chromospheric jets is still a big mystery,
although their characteristics have been more clarified recently.
I would like to introduce various aspects of the development of
the Solar-B (Hinode) and Solar-C (EUVST) high-resolution space solar
telescopes through the science of the chromosphere jet phenomenon, and
entrust the realization of the next-generation large-aperture space-borne
solar telescopes to young generation researchers. - Facilitator
- -Name：浜名 崇 / Hamana,Takashi