July 17 Wed 10:00-12:00
SOKENDAI Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom
July 17 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom
July 19 Fri 15:30-16:30
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom
詳細は下記からご覧ください。
=============== July 17 Wed===============
Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Scheduled
Date and time：July 17 10:00-12:00
Place：Large Seminar Room in Subaru Building and Zoom
Speaker：Tomokazu Kiyota
Affiliation：SOKENDAI 1st year (M1) (Supervisor:Masami Ouchi, Daisuke Iono, Masatoshi Imanishi)
Title：Exploring an Extremely Large Lya Source “Himiko” at z=6.6 with JWST
Speaker：Yui Takeda
Affiliation：SOKENDAI 1st year (M1) (Supervisor:Masami Ouchi, Miho Ishigaki, Ko Takahashi)
Title：JWST Exploration for the Properties and Origins of Nitrogen-Rich Galaxies
Speaker：Nana Matsuno
Affiliation：SOKENDAI 1st year (M1) (Supervisor:Mami Machida, Yuka Fuji, Nozomu Tominaga)
Title：MHD + thermal conduction simulations about the interaction of AGN jets and magnetic fields in a galaxy cluster
Facilitator
-Name：Yoshiaki Sato
Comment：Language: English
===============July 17 Wed==============
Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 July 17 (Wed.), 15:30-16:30 JST
Place: the large seminar room / Zoom (hybrid)
Speaker: Hiroshi Kobayashi
Affiliation: Nagoya University
Title: Collisional evolution from dust to planets
Abstract:
Planets were believed to form via the accretion of planetesimals
generated from dust grains in protoplanetary disks. However, the
growth of planets is much slower than their migration due to
disk-planet interaction. Comparably rapid growth via pebble
accretion was then proposed, which requires very massive
protoplanetary disks because most pebbles fall into the central
star. Although planetesimal formation, planetary migration, and
planetary growth have been studied with much effort, the full
evolution path from dust to planets was uncertain. We have
investigated full collisional evolution from dust to planets.
For collisional evolution, collisional outcomes are not simply
characterized as fragmentation, bouncing, etc. The impact
simulations for dust aggregates showed the detailed
outcomes. According to the outcome model, the growth of dust
grains are not prevent from collisional fragmentation. We thus
perform the full simulations (DTPSs) for collisional evolution
from dust to planet in whole protoplanetary disks. Dust growth
with high porosity allows the formation of icy planetesimals in
the inner disk (< 10 au), while pebbles formed in the outer
disk drift to the inner disk and there grow to planetesimals.
The growth of those pebbles to planetesimals suppresses their
radial drift and supplies small planetesimals sustainably in the
vicinity of cores. This enables rapid formation of sufficiently
massive planetary cores within 0.2-0.4 million years, prior to
the planetary migration. However, such porous pebbles are
unlikely to reproduce the polarized millimeter wavelength light
observed from protoplanetary disks. We thus investigate gas-giant
core formation with non-porous pebbles via DTPSs. Even non-porous
bodies can grow into planetesimals and massive cores to be gas
giants are also formed in several 100 thousand years. The rapid core
formation is mainly via the accretion of planetesimals produced
by collisional coagulation of pebbles drifting from the outer
disk. The formation mechanism is similar to the case with porous
pebbles, while core formation occurs in a wider
region (5-10 au) than that with porous pebbles. Although
pebble growth and core formation depends on the disk temperature,
core formation is likely to occur with disk temperatures in
typical optical thick disks around protostars.
Facilitator
-Name: Yuka Fujii
Comment: English
===============July 19 Fri==============
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：July 19, 2024 15:30-16:30
Place：Zoom/Large Seminar Room (hybrid)
Speaker：Dr. Seiji Fujimoto/ 藤本征史
Affiliation：University of Texas at Austin
Title： From Wide to Deep: The Quest for the Most Distant Universe with JWST and ALMA
Abstract: Finding and characterizing the earliest systems is crucial for answering fundamental cosmological questions such as the emergence of the first galaxies and black holes, as well as the cosmic reionization process. The advent of JWST has significantly advanced our capability to detect and analyze systems from the early universe, now identifying candidates out to z~17. Simultaneously, submm/mm observations have gained prominence, providing complementary insights into the characteristics of cold dust and gas. In this talk, I will overview my recent quest to explore the most distant universe. My strategy combines JWST, ALMA, and Gravitational Lensing for the most sensitive and comprehensive investigations of the earliest epochs. Our systematic JWST spectroscopic survey confirms the remarkably high abundance of z>9 luminous galaxies recently claimed from photometric measurements. By establishing the largest faint mm sample ever from the ALMA Lensing Cluster Survey, we also derive the infrared luminosity function and find a possible excess in the total (=unobscured + dust-obscured) cosmic star formation history estimate at z~4-8, compared to previously established measurements. A total of ~150 hours of our JWST and ALMA joint follow-up observations for a strongly lensed early galaxy resolve a single disk-like structure into at least 15 individual young massive star clusters with effective radii of 10-50pc, which dominate 70% of the galaxy’s total flux and are embedded in a smooth rotating disk (V/σ~3). This indicates that the feedback effect is significantly weak, providing a plausible physical explanation for the enhanced star-forming activities in the early universe, unveiled by our recent rest-UV and FIR studies above. At the end of my talk, I will also share some of my latest experiences with job applications in overseas countries.
Facilitator
-Name：Jun-Ichi Morino