投稿者: YamashitaKazuyoshi

Ultraviolet Spectroscopy and Imaging in Solar System Science and Beyond

Speaker: Go Murakami

Abstract:

Ultraviolet spectroscopy technique is one of the most powerful tools for solar-terrestrial plasma physics, planetary science, and astronomy. For example, JAXA’s UV space telescope Hisaki performed long-term and continuous monitoring of Io plasma torus and revealed dynamic relations between Io’s volcanic activity and Jupiter’s magnetosphere. We also developed a UV spectrograph for planetary exploration probes such as BepiColombo, ESA-JAXA joint Mercury exploration mission. Now we are studying a concept and preliminary design of future UV spectroscopy mission LAPYUTA. Here I present overviews of our past UV observation heritages such as Kaguya, BepiColombo, and Hisaki, brief instrumentations, current developments, and future plans.

Chaotic Diffusion: Importance, approaches and consequences

Speaker: GUIMARÃES Gabriel

Abstract:

Regular motion in the dynamical systems might now be regarded as the odd phenomena instead of chaotic ones. That is because chaotic motion seems to take place more widely and commonly than periodic ones, and in Celestial Mechanics it could be no different.
Still, it is not uncommon to characterise orbits of asteroids and comets that are clearly stable as chaotic ones and vice versa. That is because of Chaotic Diffusion, which is responsible to drive dynamical systems from a regular state to a chaotic one.
Nonetheless, the onset of chaos — as well as the effective “chaoticity” of an orbit — might not be immediate nor evident, pronouncing themselves in distinct timescales, sometimes larger than the system’s own lifetime.
Such cases, those of “stable” or “weak” chaos, chaotic diffusion is thought to play a significant role in shaping and sculpting our Solar system and other extrasolar counterparts orbital architecture.
In this presentation, I will explain a bit about chaos, contextualize it within the realms of celestial mechanics and planet formation, present tools for quantification of chaotic diffusion and how to use them to estimate instability times that are comparable to observed/simulated ones without the need to intensive and extensively making use of computational resources nor sophisticated mathematical models.

The First Spatially-resolved Detection of 13CN in a Protoplanetary Disk and Evidence for Complex Carbon Isotope Fractionation

Speaker: Tomohiro Yoshida

Abstract:

Recent measurements of carbon isotope ratios in both protoplanetary disks and exoplanet atmospheres have suggested a possible transfer of significant carbon isotope fractionation from disks to planets. For a clearer understanding of the isotopic link between disks and planets, it is important to measure the carbon isotope ratios in various species. In this talk, we present a detection of the 13CN N = 2−1 hyperfine lines in the TW Hya disk with the Atacama Large Millimeter/submillimeter Array. This is the first spatially-resolved detection of 13CN in disks, which enables us to measure the spatially resolved 12CN/13CN ratio for the first time. We conducted non-local thermal equilibrium modeling of the 13CN lines in conjunction with previously observed 12CN lines to derive the kinetic temperature, H2 volume density, and column densities of 12CN and 13CN. The H2 volume density is found to range between (4 − 10) × 10^7 cm−3, suggesting that CN molecules mainly reside in the disk atmosphere. The 12CN/13CN ratio is measured to be ~70 at 30 < r < 80 au from the central star, which is similar to the 12C/13C ratio in the interstellar medium. However, this value differs from the previously reported values found for other carbon-bearing molecules (CO and HCN) in the TW Hya disk. This could be self-consistently explained by different emission layer heights for different molecules combined with preferential sequestration of 12C into the solid phase towards the disk midplane. This study reveals the complexity of the carbon isotope fractionation operating in disks.

MHD Simulation of The Inner Galaxy with Radiative Cooling and Heating

Speaker: Kensuke Kakiuchi

Abstract:

Magnetic field is supposed to play a key role in the interstellar gas of the Galactic Center region (inner Galactic Bulge region). Observations show that the strength of the magnetic field within the central few hundred parsecs of the Galaxy is stronger than in the Galactic disk region, and its magnetic energy is comparable poor even surpasses the thermal and kinetic energy of the interstellar gas. Therefore, it is essential to study the role of the magnetic field to understand the behavior of the interstellar gas in the Galactic center region.

In this talk, we will present the results of 3D global magnetohydrodynamical simulations in the Galactic center region. A notable distinction from previous simulations is the inclusion of radiative cooling and heating effects. We found the formation of a mid-latitude low-plasma beta zone (dominated by magnetic field pressure), which would not have appeared in the model without radiative heating and cooling. While the thermal energy of the interstellar gas is lost because of radiative heating and cooling effects, the magnetic energy is independent of this direct effect and can contribute to the thickness that supports the interstellar gas clouds above the Galactic plane.In fact, it is difficult to explain the thickness of gas clouds in the Galactic center using only gas pressure scale heights, suggesting that the contribution of the magnetic field is important as an interpretation of this thickness.

Neutrino Mass Hierarchy from Supernova Nucleosynthesis of Light Elements and the Roles of Unstable Nuclei

Speaker: Xingqun Yao

Abstract:

The origin of neutrino mass and mass hierarchy is one of the biggest unanswered questions in physics. In this talk I propose an astrophysical method so that the supernova (SN) ν-process nucleosynthesis, which is consistent with the mass hierarchy constrained from various ν-oscillation experiments, should provide independent observational signals of nucleosynthetic products in the specific nuclei such as 138La, 19F, 7Li, 11B and others (so-called νnuclei) through the ν-flavor oscillation due to the MSW matter effect and the effect of collective oscillation [1].

Core-collapse SNe emits a huge number of neutrinos which bring valuable observational information on how the neutrinos propagate through the high-density matter and change their flavors and how explosive nucleosynthesis occurs. We found that the still unknown mass hierarchy is imprinted in the nucleosynthetic products of ν-nuclei [1,2]. In this talk, I will discuss the mechanism of SN ν-process nucleosynthesis and try to constrain the mass hierarchy by comparing our theoretical prediction of nuclear abundances and observed values in the meteorites and spectrascopy study. Among the calculated results, the abundance ratios of 11B/138La and 19F/16Oprovide exclusively sensitive probes to neutrino mass hierarchy [1]. These ratios are also influenced by the mass cut during the ejection phase of SN materials. These facts provide valuable quantitative tools to constrain the mass hierarchy through precise measurements of nuclear abundances of these ν-nuclei in SiC-X pre-solar grains and comprehensive studies of solar-system abundances.

Uncovering the Chemical Evolution of Galaxies from z=0–5 using the UniverseMachine

Speaker: Moka Nishigaki

Abstract:

Cosmic baryon cycling is pivotal to galaxy evolution, and the amount of metals present in galaxies’ ISMs provides a key window into the gas cycling process. Recent JWST metallicity measurements and constraints on galaxy ISM masses have made it possible to recover the chemical evolution history of galaxies. In this talk, I present a novel empirical model that infers the average metallicity evolution of galaxies from redshift z=5 to z=0. Anchored in the UniverseMachine (Behroozi+19) framework, our model converts observations of gas-phase metallicities across z=0—5 and galaxy ISM masses into constraints on the ISM return fraction, a key parameter quantifying the recycling of metals into the ISM versus expulsion into the CGM. I will show the initial results on how the ISM return fraction changes with mass and redshift.

Physical Structures Traced by Chemical Diagnostics in Disk-Forming Regions of Young Low-Mass Protostellar Sources

Speaker: Yoko Oya

Abstract:

To understand the origin of the Solar system, the physical/chemical evolution along the star/planet formation is a key issue. With the advent of ALMA, extensive observational studies have revealed that both the physical structure and the chemical composition drastically change during the disk formation around protostars. Furthermore, it has been found that molecular distributions are sensitive to changes in the physical conditions. Some kinds of molecular lines are therefore prospected to work as ‘molecular markers’ to selectively highlight particular structures of disk forming regions.
Specifically, sulfur-bearing species have empirically been good tracers; the kinematic structures of the circummultiple structure, the circumstellar disk, and the outflow lobes are traced by the OCS, H2CS, and SO emission, respectively, in a young low-mass protostellar source IRAS 16293-2422 Source A. The gas in its circummultiple structure was found to keep falling toward its periastron even beyond its centrifugal radius, which is often assumed to be the outer edge of a Keplerian disk. Angular momentum of the gas is the essential topic to understand the structure formation. The chemical diagnostics with the aid of the molecular markers can be a helpful tool to tackle with the redistribution of the angular momentum among the disk/envelope and outflow structures. Conversely, detailed physical characterization is essential to elucidating the chemical evolution occurring there.

The distribution of magnetic field strengths in star-forming regions

Speaker: Jihye Hwang

Abstract:

“What is the role of magnetic fields for regulating star-forming processes?” It is a long- standing issue in star formation studies. To judge the exact role of magnetic fields in star-forming regions, it is necessary to estimate the magnetic field strengths of those regions. However, previous studies have estimated a mean magnetic field strength in a whole star-forming region. I suggest a new application to estimate the distribution of magnetic field strengths in a star-forming region. I applied this towards three star-forming regions, the OMC-1 region, Mon R2 and G28.34 using POL-2/SCUBA-2 on the James Clerk Maxwell Telescope. In this talk, I will show the magnetic field strengths in those regions and discuss the relative importance between magnetic field, turbulence and gravity.

Impact of Magma Redox States on Super-Earth Atmospheres: Unveiling the Connection with Atmospheric Composition

Speaker: Chanoul Seo

Abstract:

Most exoplanets with radii larger than ~1.6Earth mass are more inflated than bare-rock planets with the same mass, indicating a substantial amount of volatile. While it is hard to constrain the origin of the volatiles or the planet’s bulk composition only from the mass-radius relation, the spectral characterization of their atmospheres is expected to solve this degeneracy. Previous models pointed out that the interaction between the accreted volatile and the likely molten rock (i.e., magma) beneath the atmosphere would affect the atmospheric composition significantly. However, existing models do not clarify the dependence of the atmospheric compositions with major spectral fingerprints on the observable planetary parameters. In this work, we explore the possible range of H, O, and C in the atmosphere of exoplanets as a function of observable planetary parameters (mass, radius, equilibrium temperature) using a simple chemical equilibrium model. Consistent with the previous work, we show that the water fraction in contact with magma ocean is the order of 10^-2~10^-1 if the dry planetary core accretes the nebula gas. Due to the difference in solubility of H-bearing and C-bearing species in molten rock, C/H shows an increase of ×3~10^2. The low values correspond to H2-rich atmospheres while the high values (the order of magnitude difference) correspond to the thin atmosphere with pressure <10^3 bar. Therefore, the C/O remains relatively low in most of the parameter range considered, below one-tenth of the nebula gas value if the atmospheric H2O fraction is over five percent. These trends provide a clue to verify or falsify the formation scenario of super-Earth/sub-Neptune from atmospheric compositions.

An Optical Gamma-Ray Burst catalogue with Measured Redshift: Data Release of 533 Gamma-Ray Bursts and colour evolution

Speaker: Biagio De Simone

Abstract:

Gamma-Ray Bursts (GRBs) are incredibly energetic cosmic phenomena observed across a wide range of wavelengths, including gamma-ray and optical frequencies, and occasionally even in radio waves. They allow extending the Hubble diagram and the cosmological analysis up to redshift z=9.4, much further than Supernovae Ia (z=2.26).
We therefore present a compilation of 533 optical lightcurves (LCs) of all GRBs with measured redshifts, detected mainly by Swift and 418 ground-based telescopes from February 28, 1997, to April 14, 2023. This catalogue is the largest optical repository of GRB LCs with redshifts to date, with 64615 photometric data points, including upper limits. Our user-friendly web tool, grbLC, allows the acquisition of GRB LCs, including information on the position, redshift, and a Gamma-ray Coordinates Network (GCN) crawler that can be used to collect data by gathering magnitudes from the GCNs. The web tool also includes a package for uniformly investigating colour evolution. We have crafted a procedure to distinguish between GRBs in our sample, which undergo colour evolution, and GRBs for which no colour evolution is present. We compared our results with the literature. This web-based archive is the first step towards unifying several community efforts to gather optical LCs by providing a unified format and repository for the optical catalogue. This catalogue will enable population studies by providing LCs with better coverage since we have gathered data from different ground-based locations, resulting in fewer gaps in the LCs and representing crucial support for the LC reconstructions analysis.