カテゴリー: 国立天文台談話会

July 31 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

Aug 2 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 31 Wed===============

Seminar: NAOJ Science Colloquium
Date and time: 2024 July 31 (Wed.), 15:30-16:30 JST
Place: the large seminar room / Zoom (hybrid)

Speaker: Jiaqing Bi
Affiliation: Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)/University of Toronto
Title: Where 3-dimensional analysis matters: dust distribution in protoplanetary disks under planet-disk interactions

Abstract:
Protoplanetary disks are the birthplaces of planets. However, these disks also
embed young planets, making them extremely difficult to detect. Substructures
within the disks, especially those observed in millimeter-wavelength dust thermal emissions, such as gaps and rings, have been used to suggest the presence of planets.
Nevertheless, planet-disk interactions are not the only mechanisms that can explain these features. Therefore, distinguishing substructures caused by planets from those of other origins is crucial for current planet-hunting efforts and understanding the planet formation process. In this talk, I will summarize our recent studies on dust dynamics under planet-disk interactions, utilizing three-dimensional numerical simulations.
Our findings show that incorporating the vertical dimension in planet-disk models reveals a wealth of dynamics, leading to possible characteristic features in observations.

Facilitator
-Name: Kazumasa Ono
-Comment: English

===============Aug 2 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：August 2, 2024 15:30-16:30
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr. Toshihiro Fujii
Affiliation：Osaka Metropolitan University

Title：The 100-year endeavor for observing the Universe’s most energetic particles

Abstract: Clarifying origins and acceleration mechanisms of the most energetic
particles in the universe has been over-100-year endeavor, being one of the
most intriguing mysteries in an interdisciplinary research among
astroparticle physics, high-energy physics and nuclear physics. Since
ultra-high energy cosmic rays (UHECRs) are deflected less strongly by the
Galactic and extra-galactic magnetic fields due to their enormous kinetic
energies, their arrival directions would be correlated with their origins. A
next-generation “astronomy” using UHECRs is hence a potentially viable
probe to disentangle mysteries of extremely energetic phenomena in the
nearby universe.
In my talk, I will give an introduction of cosmic-ray physics, detection
techniques, history over 100 years, the latest results of the Telescope
Array experiment and ongoing upgrades, including the detection of an
extremely high-energy cosmic ray, dubbed “Amaterasu” particle. I will share
a new interdisciplinary project for combining the Subaru telescope and
cosmic ray detectors to decipher details of extensive air showers, dubbed
Air-shower Lensing Observatory at High Altitude (ALOHA).

Facilitator
-Name：Jun-Ichi Morino

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

July 9 Tue 10:00-11:30
太陽系小天体セミナー (Solar System Minor Body Seminar)
Zoom

July 10 Wed 10:30-12:00
SOKENDAI Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

July 10 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

July 11 Thu 14:00-
Visitor’s Talk
hybrid; Insei Seminar Room in Subaru Building and Zoom

July 12 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 9 Tue===============

キャンパス：三鷹
セミナー名：太陽系小天体セミナー (Solar System Minor Body Seminar)
定例・臨時の別：定例
日時：　7月　9日（火曜日）10時00分～11時30分
場所：zoom
講演者：橘省吾 所属: 東京大学
タイトル: 小惑星リュウグウ・べヌーサンプルから考える太陽系の起源と進化
Abstract:
「はやぶさ2」が持ち帰ったC型小惑星リュウグウやOSIRIS-REx が 持ち帰ったB型小惑星ベヌーの分析結果を通して，見えてきた太陽系や 小惑星の起源や進化について，皆さんと議論できればと考えております．

世話人の連絡先
-名前：渡部潤一

備考：zoomでの参加

=============== July 10 Wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Scheduled
Date and time：July 10 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker：Kyosuke Sato
Affiliation：SOKENDAI 3rd year (D1) (Supervisor:Sakurako Okamoto, Masayuki Tanaka, Miho Ishigaki)
Title：Study of the Formation Mechanism of Ursa Minor Dwarf Spheroidal
Galaxy using Subaru/HSC Wide Field Data

Speaker：Shun Ishigami
Affiliation：SOKENDAI 4th year (D2) (Supervisor:Hirohisa Hara, Yukio Katsukawa, Masahito Kubo)
Title：Review of “Solar coronal heating from small-scale magnetic braids (Chitta et al. 2022)”

Facilitator
-Name：Yoshiaki Sato

Comment：Language: English

===============July 10 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 July 10 (Wed.), 15:30-16:30 JST
Place: the large seminar room / Zoom (hybrid)

Speaker: Hajime Fukushima
Affiliation: University of Tsukuba
Title: Radiation hydrodynamics simulations of massive star cluster formation

Abstract:
Globular clusters (GCs) are believed to form in early galaxies, but the formation mechanism of GCs are still debated. In the star cluster formation, radiative feedback hampers star formation and increase of stellar density. Hence, the stellar feedback is a key factor in determination of star cluster properties. In this talk, I will review the star cluster formation and star formation quenching mechanisms, and introduce our recent simulations of massive star cluster formation and metal enrichment in the GC formation.

Facilitator
-Name: Nanase Harada

Comment: English

===============July 11 Thu==============

Campus：Mitaka
Seminar：Visitor’s Talk
Regularly Scheduled/Sporadic：Sporadic
Date and time：July 11th (Thu) 14:00
On-site venue: Graduate student seminar room (院生セミナー室) in the Subaru building, NAOJ Mitaka
Speaker：Dr. Prasanta Gorai
Affiliation：University of Oslo
Title：Insights into Chemical Complexity and Diversity in Young Stellar Object
Abstract：Over 300 molecular species have been identified in the interstellar medium and circumstellar shells, revealing a diverse landscape of chemical complexity. Young Stellar Objects (YSOs) exhibit a wide variety of both simple and complex organic molecules (COMs), intricately linked to their physical properties and evolutionary stages. These objects play a pivotal role in shaping their surroundings, acting as potent sources of radiative and mechanical feedback that significantly influence the formation of interstellar molecules. Analyzing the millimeter and submillimeter spectra of YSOs offers crucial clues to the formation of numerous COMs, enhancing our understanding of the chemical complexity within these stellar nurseries. In this talk, I will discuss observational results from a large sample of YSOs and elaborate on how chemical diversity depends on the physical properties of the sources. I will also present astrochemical modeling results to describe the chemical evolution of several species and discuss how these models can be used to infer chemical origin and the physical properties of YSOs. By summarizing the current state of observational studies and astrochemical models, this presentation aims to elucidate the processes through which chemical complexity is attained in diverse YSOs.

Facilitator
-Name：Kotomi Taniguchi

Comment：(optional) English. You are also welcome to join us via zoom.
Zoom info: https://us02web.zoom.us/j/85668400316
Meeting ID: 856 6840 0316
Passcode: Please ask facilitator about zoom passcode

===============July 12 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：July 12, 2024 15:30-16:30
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr. Maryam Saberi
Affiliation：University of Oslo

Title：Tracing the impact of Evolved Stars on the Galactic Chemical enrichment (ESGC)

Abstract:
In this presentation, I will discuss ESGC project, which is awarded funding from the Research Council of Norway.
The primary focus of the project is on evolved stars and their impact on enriching the chemical composition of interstellar mediums and galaxies.
I will begin by providing an introduction to evolved stars and the chemistry active in their outflow.
Solar-type stars eject a substantial amount of heavy elements and dust particles to the interstellar medium through strong stellar winds at late phases of stellar evolution, known as the asymptotic giant branch (AGB) phase, and therefore significantly influence the chemical composition of galaxies.In ESGC project, we aim to target two main gaps in our knowledge that can be significantly advanced with current observational facilities, new laboratory molecular data, and upgraded chemical models. These gaps concern the role of AGB stars in the production of fluorine in our Galaxy, which is an essential element for the maintenance of solidity in our bones and teeth, and the impact of a chromospheric UV radiation field on the chemistry and dust-formation process around AGB stars. Through this project, we aim to create a more realistic picture of the recycled materials and stardust from evolved stars by considering the impact of internal UV radiation in the chemical models. Finally, I will outline the observational and simulation approaches we are planning to use to achieve the main objectives of the project and highlighting the unique opportunities associated with each approach.

Facilitator
-Name：Jun-Ichi Morino