カテゴリー: ALMA Jセミナー

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August　2　Wed　　　14:30-15:30 　　ALMA-J seminar　　　

　　　　　　　　　　　　　　　　Zoom / ALMA building #102 (hybrid)

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August　2　Wed　　　15:30-16:30 　　NAOJ Science Colloquium

　　　　　　　　　　　　　　　　Zoom / Large Seminar Room (hybrid)　　 　　　　　　　　　　　　　　　　

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詳細は下記からご覧ください。

=============== August　2　Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: August 2, 2023 (Wed), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)

Speaker: Keiichi Maeda
Affiliation: Kyoto University
Title: Millimeter view on supernovae: uncovering the nature of massive star evolution toward their demise
Abstract:
Thanks to recent inflating opportunities in transient surveys and rapid follow-up observations, a new, surprising picture has emerged on the nature of massive starts in their final phase; through observations of core-collapse supernovae (CCSNe) in the optical window, dense circumstellar matter confined in the vicinity of the progenitor, reflecting the stellar activity, has been inferred around massive stars just before their demise – the massive stars are much more dynamic in the last few years than widely accepted previously. To further constraining the nature of the CSM and thus the evolution of massive stars in the final centuries to even months toward the explosion, radio synchrotron emission, especially in the higher frequency, can provide unique and unbiased diagnostics. In this talk, I will present some results from our rapid follow-up observation of nearby CCSNe with the ALMA, starting within ~5 days since the explosion; this is a new window that has become possible thanks to the great point-source sensitivity provided by the ALMA. I will especially focus on the following topics; sub-year timescale activity just before the explosion that changes the classical view of the single massive star evolution, and a case showing a rapid change in the mass-loss rate ~1,000 years before the explosion that confirms an important role of binarity in shaping the massive star evolution.

Facilitator: Bunyo Hatsukade, Kouichiro Nakanishi

=============== August 　2　Wed==============

Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2023 Aug. 2, 15:30-16:30
Place：Zoom / the large seminar room (hybrid)

Speaker：Kousuke Ishihara
Affiliation：NAOJ (D2)
Title：Observational study of the fragmentation process in nearby
star-forming regions
Abstract：
Star formation is the process of forming protostars from diffuse
interstellar clouds by gravitational contraction, and it is known from
both observation and theory that hierarchical structures called clumps,
filaments, and cores are formed in this process. The collapse and
fragmentation of those structures is thought to contribute to the
determination of the spatial distribution and initial mass of stars. The
most fundamental mechanism controlling the fragmentation is the balance
between the self-gravity and the thermal pressure that supports the
structure against it (Jeans instability). Furthermore, non-thermal
pressures such as turbulence, and magnetic fields are thought to have an
inhibitory effect on fission. But the mechanism is not clear.
In this presentation, I introduce the results of the analysis applied
to 15 nearby regions of the Herschel Gould Belt Survey. Especially,
closer regions (d<200 pc) such as CoronaAustralis, Lupus, and Polaris
areas show distributions below the jeans parameter and cannot be
explained by the jeans fragmentation.

Speaker：Shunsuke Sasaki
Affiliation：NAOJ (D2)
Title：Phenomenological turbulent effects of core-collapse supernovae
Abstract：
It is not yet known how massive the star can explode as core collapse
supernova (CCSN), how much explosive energy, neutrinos and other
quantities will be observed when it explodes. Researches into
simulations of CCSN mechanism have succeeded in showing that such
explosions are possible even in three-dimensional (3D) simulations. It
was also revealed that turbulence associated with neutrino heating plays
an important role in the explosion. This has led to an active discussion
on the relationship between the quantity of progenitor before the
explosion and the physical quantity of CCSNe, which is called progenitor
dependence. In recent years, the development of phenomenological
one-dimensional simulations (1D+) introducing turbulence effects has
become an urgent issue in order to investigate the progenitor dependence
more realistically. We developed 1D+ and we got the result that our 1D+
can mimic the shock evolution in 3D. In this tolk, I will explain our
1D+ and preliminary results about progenitor dependence.

Facilitator
-Name：Meizhi Liu

-Comment: English 　　

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July 　4　 Tue　　　10:00-11:30 　　　　太陽系小天体セミナー 　 Zoom 　　　

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July 　5　Wed　 　 10:00-12:00　　　　SOKENDAI Colloquium 　　

Zoom / the large seminar room (hybrid)

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July 　5　Wed　　14:30-15:30 　　　　ALMA-J seminar 　 　　　

Zoom / ALMA building #102 (hybrid)

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July　5 　Wed　　15:30-16:30 　　　　NAOJ Science Colloquium 　

Zoom / the large seminar room (hybrid)

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詳細は下記からご覧ください。

=============== July 　 4　Tue===============

キャンパス：三鷹
セミナー名：太陽系小天体セミナー
定例・臨時の別：定例
日時：7月4日（火曜日）10時00分～11時30分
場所：zoom
講演者：匠あさみ

世話人の連絡先
　名前：渡部潤一
　

=============== July 　5　Wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：July 5, 2023 10:00-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Kazuki Watanabe
Affiliation: SOKENDAI 1st year (M1) (Supervisor: Yoshinori Uzawa, Takafumi Kojima, Tai Oshima)
Title: Development of a sub-THz MKID Camera for Deep Space Observation

Speaker : Shubham Bhardwaj
Affiliation: SOKENDAI 3rd year (D1) (Supervisor: Maria Dainotti, Nozomu Tominaga, Kazunari Iwasaki)
Title: GRB Optical and X-ray Plateau Properties Classifier Using Unsupervised Machine Learning

Speaker: Ryota Hatami
Affiliation: SOKENDAI 1st year (M1) (Supervisor: Nozomu Tominaga, Tomoya Takiwaki, Koh Takahashi)
Title: Synthesis of Sc, Ti, and V in supernova

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== July 　5　Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: July 5, 2023 (Wed), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)

Speaker: Satoshi Ohashi
Affiliation: NAOJ
Title: Dust enrichment and grain growth in a smooth disk around the DG Tau protostar revealed by ALMA triple bands frequency observations
Abstract: Characterizing the physical properties of dust grains in a protoplanetary disk is critical
to comprehending the planet formation process. Our study presents ALMA high-resolution observations
of the young protoplanetary disk around DG Tau at a 1.3 mm dust continuum. The observations,
with a spatial resolution of 0.04 arcsec, or 5 au, revealed a geometrically thin and smooth disk
without substantial substructures, suggesting that the disk retains the initial conditions of the planet formation.
To further analyze the distributions of dust surface density, temperature, and grain size,
we conducted a multi-band analysis with several dust models, incorporating ALMA archival data
of the 0.87 mm and 3.1 mm dust polarization. The results showed that the Toomre Q parameter is
<2 at a disk radius of 20 au, assuming a dust-to-gas mass ratio of 0.01, which means that a higher
dust-to-gas mass ratio is necessary to stabilize the disk. In addition, grain sizes depend on the dust models,
and were found to be less than 0.1 -1 mm in the inner region (r<20 au), while they exceeded larger than 1 mm
in the outer part. Radiative transfer calculations show that the dust scale height is lower than at least
one-third of the gas scale height. These distributions of dust enrichment, grain sizes, and weak turbulence
strength may have significant implications for the formation of planetesimals through mechanisms such as streaming instability.
We also discuss the CO snowline effect and collisional fragmentation in dust coagulation for the origin of the dust size distribution.

Facilitator: Bunyo Hatsukade, Kouichiro Nakanishi

=============== July 　5　Wed===============

Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2023 July 5, 15:30-16:30
Place：Zoom / the large seminar room (hybrid)

Speaker：Satoshi Okuzumi
Affiliation：Tokyo Institute of Technology
Title：Modeling the thermal evolution of planet-forming disks
Abstract：
The thermal structure of protoplanetary disks determines when and
where planets of different compositions form. However, the thermal
structure of these disks remains largely uncertain due to two main
factors: (1) the existence of strong internal heating sources deep
inside the disks is still unknown, and (2) the cooling rate of the disks
is influenced by micron-sized dust grains and varies as the grains grow
into larger solid bodies. Dust growth can even impact disk heating
induced by magnetic fields, as the grains regulate the disks’ electric
conductivity by capturing plasmas. All these factors indicate that the
temperature structure of the disks evolves as planet formation (dust
evolution) progresses. In this presentation, I will discuss our recent
efforts to model the coupled evolution of dust and the thermal structure
of protoplanetary disks. Specifically, I will highlight the roles played
by magnetic fields, disk shadows, and planet-induced spiral shocks in
shaping the disks’ temperature distribution.

Facilitator:

Name：Kazumasa Ohno
Comment：English