カテゴリー: ALMA Jセミナー

2023.9.26-2023.10.1

September　26　Tue　 10:00-11:30 　　太陽系小天体セミナー　zoom

September　27　Wed　 14:30-15:30 　　 ALMA-J seminar  ALMA building #102 / Zoom (hybrid) 　　　　　　　　　　　　　　　

September 　29　Fri　 　　 16:00-17:00　　　　 　NAOJ Seminar 　　　　　　　　　　　Zoom / the large seminar room (hybrid)　　　　　　　　　　　　　　

詳細は下記からご覧ください。

=============== September　26　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：9月26日（火曜日）10時00分～11時30分
場所：zoom

世話人の連絡先
名前：渡部潤一
備考：テレビ会議またはスカイプによる参加も可

=============== September　27　Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: September 27, 2023 (Wed), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)
Speaker: Kana Morokuma-Matsui
Affiliation: Tsukuba University
Title: Star-formation quenching in galaxies in the Virgo, Fornax and Antlia clusters
Abstract:
Understanding how star formation (SF) is suppressed in galaxies is a crucial aspect of galaxy evolution research.
The cosmic SF rate (SFR) density has a peak around z~1-2, and the last half of the universe is the history of SF quenching in galaxies.
In this talk, we present our findings on how the galaxy-cluster environment affects SF activity in galaxies by observing molecular gas in cluster galaxies.
We investigate three nearby galaxy clusters, the Virgo, Fornax, and Antlia clusters. Our results show that SF activity is low in cluster galaxies due to the depletion of cold gas reservoirs rather than the decrease in star-formation efficiency.
We find that the molecular gas in Virgo galaxies is likely to be removed in a shorter timescale than the typical gas depletion timescale of ~1-3 Gyr.
We also discuss the similarities and differences between the three clusters.

Facilitator: Bunyo Hatsukade and Kouichiro Nakanishi

=============== September　29　Fri===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regularly Scheduled Date and time：2023 Sep 29, 16:00-17:00
Place： Zoom / Large Seminar Room (hybrid)

Speaker: Kazunori Kohri, Ph. D
Affiliation: Division of Science, NAOJ
Title: What is Dark Matter? From the Standpoint of Particle Cosmology
Abstract：
What is the nature of dark matter? Observations have determined that dark matter is approximately 25% of the total energy in the Universe today. However, its true nature is still unknown. Only when we uncover its true nature, we can call it a triumph of science. We do not have to say there is no argument that this is beyond the scope of astronomy. In particle physics, for example, the LHC experiment at CERN in Geneva, Switzerland, was expected to reveal a new particle, dark matter, but it did not. The energy of particle physics experiments cannot be dramatically increased in a short period of time. Therefore, there is a growing trend to use future astronomical/cosmological observations to uncover the true nature of dark matter. In this talk, I will introduce my lifeworks for candidates for dark matter, 1) WIMPs, 2) axions, 3) primordial black holes, 4) right-handed neutrinos and so on, and show how they can be constrained by using cosmology, particle physics, gravity, high-energy astrophysics or multi-messenger astronomy. I will also explain how they may be elucidated in the future.

Facilitator
-Name：Takuma Izumi

2023.9.11-2023.9.17

Sep　11　Mon　 　15:00-16:30　　Solar and Space Plasma Seminar
　　　　　　　　　　　　　　　　hybrid; Central Building (North) / 310 or Zoom

Sep　13　Wed　　　　14:30-15:30 　　 ALMA-J seminar 　
　　　　　　　　　　　　　　　　　　　ALMA building #102 / Zoom (hybrid)　　　　　　　　　　　　　　

詳細は下記からご覧ください。

=============== Sep　11　Mon===============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：Sep 11th (Sep), 15:00-16:30
Place： hybrid; Central Building (North) / 310 or Zoom
Speaker：Teodora Mihailescu
Affiliation：Mullard Space Science Laboratory, University College London
Title：Intriguing Plasma Composition Pattern in a Solar Active Region: a Result of Non-Resonant Alfvén Waves?

Abstract：The plasma composition of the solar corona is different from that of the solar photosphere. Elements that have a low first ionisation potential (FIP) are preferentially transported to the corona and, therefore, show enhanced abundances in the corona compared to the photosphere. The level of enhancement is measured using the FIP bias parameter. The highest FIP bias values are typically observed in active regions, but they also vary at sub-active region level. In this work, we use data from the EUV Imaging Spectrometer (EIS) on Hinode to study the plasma composition in an active region following an episode of significant new flux emergence into the pre-existing magnetic environment of the active region. We use two FIP bias diagnostics: Si X 258.375 Å/S X 264.233 Å (formation temperature of 1.5 MK) and Ca XIV 193.874 Å /Ar XIV 194.396 Å (formation temperature of 4 MK). We observe different plasma composition patterns in the newly emerging loops and the preexisting loops (those that had been formed before the flux emergence). This result can be interpreted in the context of the ponderomotive force model, which proposes that the enhancement of low-FIP elements in the corona is generally driven by Alfvén waves. We suggest that the low-FIP elements enhancement pattern observed in the emerging loops could be driven by resonant waves originating in the active region core loops. Conversely, we suggest that the pattern observed in preexisting loops could be driven by non-resonant waves and we discuss potential sources of these waves. This different type of wave activity is what could explain the different patterns of low-FIP elements enhancement in these two sets of loops.

Facilitator
Name：Takayoshi oba
Comment：in English

=============== Sep 13　Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: September 13, 2023 (Wed), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)
Speaker: Kaho Morii
Affiliation: The University of Tokyo/NAOJ
Title: Unveiling Early Stages of High-Mass Star Formation: Insights from Infrared Dark Clouds

Abstract:
Physical properties in infrared dark clouds (IRDCs) provide insights into the initial conditions of high-mass star and stellar cluster formation. We have conducted the ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES) on thirty-nine high-mass clumps, which are the dense parts of IRDCs. These targets are dark at 24 µm and 70 µm and have low temperatures, high masses, and high density, best candidates to investigate the earliest stages of high-mass star formation. Our ALMA observations reveal their internal structure and have identified an unprecedented number of 839 cores from dust continuum emission.  We find that less than 1% (7/839) of the cores possess masses exceeding 27 Msun. All of these cores are gravitationally bound and associated with molecular outflows. No high-mass prestellar core has been observed. Furthermore, among our sample, 90%  (35 out of 39) only host low- to intermediate-mass cores, indicating the necessity of additional mass input for high-mass star formation. Observed core properties generally follow the thermal Jeans fragmentation of the clumps. In this talk, I will present the first results of the statistical study of the 839 cores as well as a summary of the pilot survey, and discuss the characteristics of the initial stages of high-mass star formation.

Facilitator: Bunyo Hatsukade and Kouichiro Nakanishi

2023.8.28-2023.9.3

August　30　Wed　 　13:30-15:00　　Solar and Space Plasma Seminar
　　　　　　　　　　　　　　　　　　　　 hybrid; Central Building (North)310 or Zoom

August　30　Wed　　　14:30-15:30 　　 ALMA-J seminar 　
　　　　　　　　　　　　　　　　　　　　 Zoom / ALMA building #102 (hybrid)　　　　　　　　　　　　　　　

詳細は下記からご覧ください。

=============== August　30　Wed===============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：Aug 30th (Wed), 13:30-15:00
Place： hybrid; Central Building (North) / 310 or Zoom
Speaker：Dr. Masahito Kubo
Affiliation：NAOJ
Title：Comparison of polar magnetic fields derived from MILOS and MERLIN inversions for Hinode/SOT-SP data


Abstract：The detailed investigation of the polar magnetic field and its time evolution is one of the major achievements of Hinode. Precise measurements of the polar magnetic field are essential for understanding the solar cycle, and they provide important constraints for identifying the source regions of the solar wind. The Spectropolarimeter (SP) of the Solar Optical Telescope (SOT) on board Hinode has been the instrument best suited to make such measurements. In this study, we compare SOT-SP data for the polar regions as processed using two representative Milne-Eddington inversion codes, MILOS and MERLIN. These codes are applied to the same level-1 SOT/SP data, and the same disambiguation algorithm is used on the maps that go through the two inversions. We find that the MERLIN inversion tends to give the radial magnetic flux density (the magnetic flux density with respect to the local vertical) that is about 20% larger than the MILOS inversion. The somewhat higher radial magnetic flux density from MERLIN appears to be common to the polar magnetic fields observed at different phases of the solar cycle. We attribute the difference in the radial magnetic flux density to different filling factors adopted by the two inversions, based on different assumptions of the scattered light profiles. The relationship between the radial magnetic flux density and the magnetic filling factor could be more complex in the polar (limb) observations due to the possible contributions of the transverse magnetic field component that may affect the estimated radial magnetic flux density.

Facilitator
-Name：Takayoshi oba
-Comment：in English

=============== August 　30　Wed==============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: August 30, 2023 (Wed), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)
Speaker: Jan-Willem Steeb
Affiliation: National Radio Astronomy Observatory
Title: AstroHACK: Holography Antenna Commissioning Kit

Abstract: Correcting the surface of a dish antenna by adjusting the panels can significantly improve the dish’s performance. For instance, the VLA panel adjustments completed in 2000 more than doubled the high-frequency sensitivity of the VLA dishes. The software presently utilized by ALMA and VLA is written in Fortran and is becoming challenging to maintain. Consequently, the CASA team is developing AstroHACK, which generates antenna aperture images and calculates antenna panel adjustment corrections from calibrated holography measurement sets. AstroHACK is the first non-prototype software package developed using the Python-based VIPER (Visibility and Image Parallel Execution Reduction) Framework, previously known as the CASA Next Generation Infrastructure Software Framework. This framework was designed to meet the requirements of the ngVLA and the ALMA Wideband Sensitivity upgrade. In this seminar, I will provide an overview of the VIPER Framework and the functionalities of AstroHACK, followed by a live demonstration.

2023.8.21-2023.8.27

August　21　Mon　 　　　14:30-15:30 　　ALMA-J seminar 　　 Zoom / ALMA building #102 (hybrid)

August　23　Wed　　　　　 14:30-15:30 　　ALMA-J seminar 　　 Zoom 　　　　　　　　　　　　　　　　

詳細は下記からご覧ください。

=============== August　21　Mon===============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Sporadic
Date and time: August 21, 2023 (Mon), 14:30-15:30
Place: ALMA building #102 / Zoom (hybrid)

Speaker: Martin Bureau
Affiliation: University of Oxford
Title: WISDOM: Molecular cloud properties and star-formation quenching
Abstract: Molecular gas is the fuel for star formation in galaxies. Using observations from the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM), that spatially resolve (1-30 pc) individual molecular clouds across the Hubble sequence, I will reveal a clear dependence of the nature of the molecular interstellar medium of galaxies on Hubble type, and present a simple diagnostic of cloud formation. In particular, I will highlight the shortcomings of the usual virial approach to clouds as self-gravitating objects, and stress the importance of the external galactic potential and in-plane shear to regulate the dynamical states of clouds. I also introduce a simple but powerful cloud-cloud collision formalism that accounts for the cloud properties of several nearby as well as high-redshift systems. Finally, I note the peculiar properties of clouds within the bars of spiral galaxies, and I discuss the impact of these different mechanisms on the star formation efficiency of clouds and thus the quenching of star formation, particularly in galaxy nuclei and spheroids (morphological quenching).

Facilitator: Bunyo Hatsukade, Kouichiro Nakanishi

=============== August　23　Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and time: August 23, 2023 (Wed), 14:30-15:30
Place: Zoom

Speaker: Takashi Shimonishi
Affiliation: Niigata University
Title: The Role of Metallicity in the Chemical Evolution of Star-forming Regions
Abstract:
Understanding the chemistry of the interstellar medium at low metallicity is crucial to unveil physical and chemical processes in the past Galactic environment or those in high-redshift galaxies, where the metallicity was significantly lower compared to the present-day solar neighborhood. In the last decade, there has been a great progress in astrochemical studies of interstellar molecules in low-metallicity star-forming regions. Nearby low-metallicity laboratories, such as the Large and Small Magellanic Clouds, Local Group dwarf galaxies, and the outskirts of our Galaxy, play an important role in such studies. Single-dish radio observations have detected various dense gas tracers in those regions, which revealed the molecular-cloud-scale (<1-10 pc) chemistry at low metallicity. With ALMA, emission from dense and high-temperature molecular gas associated with embedded protostars (i.e., hot molecular cores) are detected in the LMC, SMC, and outer Galaxy, which revealed the chemical complexity of star-forming cores (<0.1 pc) at low metallicity. Besides gas-phase species, infrared observations have revealed chemical compositions of ices around deeply embedded protostars in the LMC and SMC. Do molecular abundances simply scale with the metallicity? If not, which processes govern the chemistry in the low-metallicity interstellar medium? In this presentation, I will discuss the role of metallicity in the chemical evolution of star-forming regions based on recent observations of interstellar molecules in low-metallicity environments.

Facilitator: Bunyo Hatsukade, Kouichiro Nakanishi

2023.7.31-2023.8.6

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

　　　　　　　　　　　　　　　　Zoom / ALMA building #102 (hybrid)

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

　　　　　　　　　　　　　　　　Zoom / Large Seminar Room (hybrid)　　 　　　　　　　　　　　　　　　　

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