February 28 Wed 10:30-12:00
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom
February 28 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Lecture room and Zoom
詳細は下記からご覧ください。
=============== February 28 Wed ===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：28 February (Wed), 10:30-12:00
Place： Insei Seminar Room and Zoom
Speaker：Dr. Yusuke Kawabata
Affiliation：The National Solar Observatory
Title：Multiline Stokes Synthesis of Ellerman Bombs: Obtaining Seamless Information from Photosphere to Chromosphere
Abstract：
There are many kinds of explosive phenomena caused by magnetic reconnections in the solar atmosphere. Ellerman bombs (EBs) are magnetic reconnection events occurring in weakly ionized and moderate plasma β (~1) environments in the solar photosphere and chromosphere. Owing to the observability of the physical quantities around the reconnection site, EBs are one of interesting observation targets for studying magnetic reconnections. While measuring the magnetic field in the solar corona is still difficult, inferring magnetic field in the chromosphere with high spatial resolution and reasonable temporal cadence will be achieved soon.
One such opportunity is SUNRISE III, which is an international balloon-borne solar observatory employing a 1 m diameter telescope. SUNRISE III will achieve five days of stable observations in a seeing-less environment at altitudes around 37 km. We are developing the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) as a focal plane instrument for SUNRISE III. SCIP will perform multi-line spectropolarimetric observations, enabling us to seamlessly diagnose the physical quantities (magnetic field, velocity field, and temperature) from the photosphere to the chromosphere.
In this talk, I would like to introduce the capability of SCIP for performing observations of magnetic reconnection events. In addition, I will present our recent study: we used a realistic magnetohydrodynamic (MHD) simulation of EB to study how SCIP will have access to the physical phenomena. We synthesized the polarimetric signals by solving radiative transfer equation based on the physical quantities in the MHD simulation and compared the polarimetric signals with the physical quantities in the MHD results. We found that the multiline observations of SCIP can detect the bidirectional flow associated with the EBs and suggest the height of the reconnection site.
Facilitator
-Name：Akiko Tei
Comment：English
=============== February 28 Wed===============
Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 28 (Wed.), 15:30-16:30
Place: the lecture room / Zoom (hybrid)
Speaker: Kuria Watanabe
Affiliation: SOKENDAI (M2)
Title: The Chemical enrichment and origin of Nitrogen-Rich Galaxies at High Redshift
Abstract:
Chemical properties of young galaxies are important to understand the chemical evolution in galaxy formation. We investigate the origin of abundance ratios in JWST star-forming galaxies (z ~ 4-10) by comparing chemical evolution models.
The high N/O ratio in GN-z11, CEERS_01019, and GLASS_150008 observed with JWST cannot be explained by typical chemical evolution models including AGB stars. We focus on the three candidates of rich nitrogen, the Wolf-Rayet stars (WR), supermassive stars (SMS), and tidal disruption events (TDE). We develop the chemical evolution models of three candidates. Although the Ar/O values of the high N/O galaxies are not obtained, we find that the Ar/O values are the key to distinguishing between the three models. The three models can show the high N/O values as much as the N/O values in GN-z11, CEERS_01019, and GLASS_150008.
Because the time scale of high N/O is very short due to the CCSNe, the massive stars (>25 Msun) should directly collapse into black holes.
Speaker: Yuki Kambara
Affiliation: The University of Tokyo (M2)
Title: Planetesimal accretion in planetesimal rings
Abstract:
In the standard planet formation scenario, planetesimals have been assumed to be smoothly distributed in the radial direction except for the snowline. Recently, however, simulations of gas and dust evolution have shown that planetesimals form only in radially limited locations, such as gas pressure bumps and snowlines, and are concentrated in ring-like regions.
The evolution process of planetesimals distributed in a ring is crucial to understanding planet formation theory. However, the evolution of planetesimal rings has not been studied in detail. In this work, we investigate the evolution of planetesimal rings using N-body simulations. We systematically change the initial width and the total mass of planetesimal rings and investigate the dependence of protoplanet properties on the initial conditions. In all simulations, protoplanets undergo oligarchic growth while ring width expands due to scattering by protoplanets. In planetesimal rings, massive protoplanets tend to be formed around the ring center, while protoplanets far from the center of rings are less massive. Scaled orbital separation depends neither on the initial ring width nor the total mass and is consistent with the estimate in the oligarchic growth model. The width of the expanded planetesimal ring does not depend on the initial ring width but on the total ring mass. The maximum mass of protoplanets depends strongly on the total ring mass and weakly on the initial ring width.
Facilitator
-Name: Kazumasa Ohno
Comment: English