カテゴリー: 国立天文台談話会

国立天文台談話会

2024.2.12-2024.2.18

February 13 Tue 10:00-11:30
太陽系小天体セミナー
Zoom

February 13 Tue 11:00-12:00
SOKENDAI Doctoral Thesis Preliminary Evaluation
hybrid; Large Seminar Room in Subaru Building and Zoom

February 14 Wed 14:30-15:30
ALMA-J seminar
hybrid; Room 102 in the ALMA building and Zoom

February 14 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Lecture room and Zoom

February 16 Fri 16:00-17:00
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== February 13 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：2月13日（火曜日）10時00分～11時30分
場所：zoom
講演者：有松 亘
タイトル：中・大型太陽系外縁天体による恒星掩蔽キャンペーン観測の現状
Abstract：既知の太陽系外縁天体による恒星掩蔽イベントの観測は、外縁天体のサイズ・形状の決定、および衛星や環、表面大気への制約を得るうえで極めて有用である。本発表では現在国内の複数の観測装置を用いて実施している外縁天体恒星掩蔽キャンペーン観測の現状を報告する。

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

=============== February 13 Tue ===============

Campus：Mitaka
Seminar：SOKENDAI Doctoral Thesis Preliminary Evaluation
　　　　 総研大博士学位論文予備審査会
Regularly Scheduled/Sporadic：Sporadic
Date and time：February 13, 2024　11:00～12:00

Place : Large Seminar Room and Zoom

Speaker：Yuta Tashima
Title：Elucidation of galactic magnetic field structure by pseudo-observation focusing on depolarization

Facilitator
-Name：Nozomu Tominaga, Hideyuki Kobayashi, Natsuko Fujii (Graduate Student Affairs Unit)

=============== February 14 Wed===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: February 14 (Wed) 14:30-15:30
Place: hybrid (room 102 in the ALMA building and Zoom)

Speaker: Yulong GAO
Affiliation: School of Astronomy and Space Science, Nanjing University, Nanjing, China
Title: Unraveling the Low-Metallicity Merging Dwarf Galaxies: Insights into Starburst and Metal Dilution/Enrichment

Abstract:
Understanding the physical mechanisms driving starbursts within dwarf galaxies remains a challenge in astrophysics. Moreover, the impact of mergers on star formation activity in these galaxies remains unclear. In this talk, we employ observations from the VLT/MUSE and ALMA to investigate how the merger process influences star formation activities in metal-poor dwarf galaxies, focusing on galaxies of Haro 11 and NGC 4809/4810. Haro 11, situated in the late-stage merger phase, exhibits similar morphology and kinematics to the Antennae galaxy, offering valuable insights into the merger-induced starburst phenomenon. Conversely, the ongoing collision between NGC 4809 and NGC 4810 presents a unique opportunity to examine the effects of mergers on dwarf galaxies in real time, particularly within their overlapping regions. We find post-merger between low mass galaxies (e.g., Haro 11) can trigger global starburst, similar to ULIRGs. Notably, Haro 11 could be the analog of high-z dwarf starbursts and the potential progenitor of the nearby less massive elliptical galaxies. Furthermore, we find that NGC 4809/4810 interaction zone show enhanced SFR (sSFR), and deficient metallicity, indicating the capacity of dwarf galaxy mergers to instigate significant star formation activity even within metal-poor environments. Additionally, we detect clear evidence of metal enrichment resulting from the Type Ic SN 2011jm within NGC 4809, representing a pioneering detection of chemical pollution through stellar feedback beyond the Local Volume. These findings shed light on the underlying mechanisms driving starburst and stellar feedback processes within the dwarf galaxies.

=============== February 14 Wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 14 (Wed.), 15:30-16:30
Place: the lecture room / Zoom (hybrid)

Speaker: Ryota Kitamura
Affiliation: The University of Tokyo (M1)
Title: Review on Pan et al. (2022) “The terrestrial planet formation around M dwarfs: in situ, inward migration, or reversed migration”
Abstract of the paper:
Terrestrial planets are commonly observed to orbit M dwarfs with close-in trajectories. In this work, we extensively perform N-body simulations of planetesimal accretion with three models of in situ, inward migration, and reversed migration to explore terrestrial formation in tightly compact systems of M dwarfs. In the simulations, the solid discs are assumed to be 0.01 per cent of the masses of host stars and spread from 0.01 to 0.5 au with the surface density profile scaling with r−k according to the observations. Our results show that the in-situ scenario may produce 7.77+3.23 −3.77 terrestrial planets with an average mass of 1.23+4.01 −0.93 M⊕ around M dwarfs. The number of planets tends to increase as the disc slope is steeper or with a larger stellar mass. Moreover, we show that 2.55+1.45 −1.55 planets with a mass of 3.76+8.77 −3.46 M⊕ are formed in the systems via inward migration, while 2.85+1.15 −0.85 planets with 3.01+13.77 −2.71 M⊕ are yielded under reversed migration. Migration scenarios can also deliver plentiful water from the exterior of the ice line to the interior due to more efficient accretion. The simulation outcomes of the reversed migration model produce the best match with observations, being suggestive of a likely mechanism for planetary formation around M dwarfs

Speaker: Miho Tan
Affiliation: SOKENDAI (M1)
Title: Effect of stellar wind on SS433’s jet propagation
Abstract:
SS433 is an X-ray binary system consisting of a star and a compact star, and the compact star is known to emit spiral binaries. The jets propagate more than 100 pc; in Ohmura et al (2021) and other groups, uniform jets injected from 1 pc propagated 100 pc. But one of the important questions is how to travel to 1pc from the ejection region.
Therefore, in this study, we evaluate the propagation of the jet within 1pc including the effect of stellar winds. Since the orbital period of the binary is shorter than the jet propagation timescale, we assume the propagation area becomes turbulence formed by the stellar wind. We put turbulent velocity fields of 0.1% and 0.01% of the jet velocity in the ambient around the jet to see the effect of the turbulence on the jet propagation.

Facilitator
-Name: Doris Arzoumanian

Comment: English

=============== February 16 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：February 16, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Prof. Hideyuki Kobayashi
Affiliation：National Astronomical Observatory of Japan (NAOJ)
Title：Japanese VLBI development and research that I have been involved in

Abstract: Japanese VLBI development and research that I have been involved in, are reviewed. The VSOP programme, the world’s first space VLBI observation with the HALCA satellite launched in 1997, VERA which is specialized in astrometry and began construction in 2000, as well as the organisation of the East Asian VLBI observation network with the development of the domestic VLBI network are described. Expectations for the next generation of radio telescopes, the SKA, are also discussed.

Facilitator
-Name：Takashi Moriya

2024.2.5-2024.2.11

February 6 Tue 10:00-11:30
太陽系小天体セミナー
Zoom

February 7 Wed 14:00-15:00
ALMA-J seminar
hybrid; Small seminar room in the Subaru building and Zoom

February 7 Wed 15:30-16:30
NAOJ Science Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom

February 9 Fri 10:30-12:00
Solar and Space Plasma Seminar
Zoom

February 9 Fri 16:00-17:00
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom

詳細は下記からご覧ください。

=============== February 6 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：2月6日（火曜日）10時00分～11時30分
場所：zoom
講演者：和田 空大
所属：東京大学
タイトル：Tomo-e Gozen NEO 探査改善プロジェクトの現状共有と今後の展望
Abstract：東京大学木曽観測所では2019年から地球接近小惑星 (NEOs)
の探査を開始し、現在までで多数の小惑星の発見や物理量の測定を行ってきました。
探査を行うにつれ現在のプロセスの課題が浮き彫りになっており、私が主導して改善を試みている最中です。
今回の発表では、プロセス全体の中でも特に移動天体検出に使っている機械学習モデルについて、その改善の方針と現状共有をします。

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

=============== February 7 Wed ===============

Campus: Mitaka
Seminar: ALMA-J seminar
Date and time: February 7 (Wed) 14:00-15:00
Place: hybrid (Small seminar room in the Subaru building and Zoom)

Speaker: Yuhito Shibaike
Affiliation: NAOJ
Title: Constrains on the properties of forming planets from the dust continuum emission of the circumplanetary disks

Abstract:
Although there have been a lot of theoretical research on the formation of gas planets, observational supports have still been very rare. The young T Tauri star PDS 70 has two gas accreting planets sharing one large gap in a pre-transitional disk, which is a valuable system to obtain observational constraints. Recently, dust continuum emission from PDS 70 c has been detected by ALMA Band 7, considered as the evidence of a circumplanetary disk (CPD), a small gas (and dust) disk formed around the planet as a byproduct of the gas accretion. To obtain constraints on the planet properties, we introduce a model of dust evolution in the CPD and reproduce the detection of the dust continuum emission. We find positive correlations between the intensity of the dust emission and three important planet properties, the planet mass, gas accretion rate, and their product called MMdot. We then find that the MMdot of PDS 70 c must be larger than 0.4 MJ^2 /yr, corresponding to the lower limits of the planet mass and the gas accretion rate, 5 MJ and 0.02 MJ/yr. This is the first case to succeed in obtaining constraints on planet properties from the dust continuum emission of a CPD. We also find some loose constraints on the properties of PDS 70 b from the non-detection of its dust emission. We propose possible scenarios for the PDS 70 b and c explaining the non-detection respectively detection of the dust emission from their CPDs. I will also discuss my future plans to obtain constraints on other gas accreting planets if there is enough time.

=============== February 7 Wed===============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Feb. 7 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)

Speaker: Yui Kawashima
Affiliation: ISAS/JAXA
Title: Subaru/IRD high-resolution spectroscopy of a T-type brown dwarf and investigation of its atmospheric properties with high-resolution spectrum model ExoJAX
Abstract:
While brown dwarf atmospheres share composition and temperature with those of extrasolar gas giant planets, in general, brown dwarfs are observable with a higher signal-to-noise ratio when compared to exoplanets. Thus, the observation of brown dwarf atmospheres helps us establish our understanding of various processes in the atmospheres of such temperature and composition, including chemistry, thermal structure, dynamics, and cloud formation. Also, their high-resolution spectra serve as excellent templates for the observational validation of the molecular line lists at such high temperatures. The accuracy of molecular line lists holds the key to detecting chemical species in exoplanet atmospheres, which are often observed with a lower signal-to-noise ratio.

Recently, we observed the high-resolution spectrum of a T6.5-type brown dwarf Gl 229B with the InfraRed Doppler (IRD) spectrograph mounted on the Subaru Telescope. We have constrained its atmospheric properties, such as the molecular abundances and thermal structure, using an inverse-problem approach with our high-resolution spectrum model ExoJAX (Kawahara, Kawashima et al. 2022). We have also investigated the possibility of inferring the object mass using the embedded information on collision-induced absorption uniquely accessible by high-resolution spectroscopy. Furthermore, we have revealed that in some wavelength regions, specific molecular line lists do not match the observed absorption features.

Facilitator
-Name: Kazumasa Ohno

Comment: English

=============== February 9 Fri==============

Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：9 February (Fri), 10:30-12:00
Place： Zoom

Speaker：Dr. Tetsu Anan
Affiliation：The National Solar Observatory
Title：Measurements of a reconnection electric field in the solar chromosphere

Abstract：The efficient release of magnetic energy in astrophysical plasmas can be achieved through magnetic-field diffusion, the rate of which is directly tied to the associated electric field. However, there have been only a
few attempts to measure electric fields in the solar atmosphere, because of the common assumption that electric fields must vanish quickly or only exist at unresolvable spatial scales. Using the newly commissioned National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), we observed NOAA active region 12995 on February 23rd, 2022, in three spectral bands 397 nm, 630 nm, and 854 nm using the Visible SpectroPolarimeter (ViSP). We successfully obtained Stokes spectra of an Ellerman bomb, which is brightening in the lower chromosphere and are thought to be associated with magnetic reconnection. At the Ellerman bomb, we discovered a broadband circular polarization in a Balmer line of the neutral hydrogen at 397 nm, H epsilon, that can only be explained by the presence of an electric field. Moreover, we found that the measured signal filled a region up to ~1000 km, which is three orders of
magnitude larger than that expected in theory. In this talk, we will present our findings and discuss why the diffusion region is so large, and what is the next step.

Facilitator
-Name：Akiko Tei

Comment：English

=============== February 9 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：February 9, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Dr. Eleonora Di Valentino
Affiliation：University of Sheffield

Title：Unresolved Anomalies and Tensions in the Standard Cosmological Model

Abstract: The standard Lambda Cold Dark Matter cosmological model has been incredibly successful in explaining a wide range of observational data, from the cosmic microwave background radiation to the large-scale structure of the universe. However, recent observations have revealed a number of inconsistencies among the model’s key cosmological parameters, which have different levels of statistical significance. These include discrepancies in measurements of the Hubble constant, the S8 tension, and the CMB tension. While some of these inconsistencies could be due to systematic errors, the persistence of such tensions across various probes suggests a potential failure of the canonical LCDM model. I will examine these inconsistencies and discuss possible explanations, including modifications to the standard model, that could potentially alleviate them. However, I will also discuss the limitations of these proposed solutions and note that none of them have successfully resolved the discrepancies.

Facilitator
-Name：Takashi Moriya

2024.1.8-2024.1.14

January 9 Tue 14:00-15:00 NAOJ Seminar
Face to face/ hybrid; Large Seminar Room in Subaru Building

If this NAOJ seminar is held also by hybrid form,
we will announce the Zoom URL with another email.

January 10 Wed 10:30-12:00 SOKENDAI Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)

January 10 Wed 15:30-16:30 NAOJ Science Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)

詳細は下記からご覧ください。

=============== January 9 Tue ===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Sporadic
Date and time：January 9, 2024 14:00-15:00
Place：Large Seminar Room
*If this NAOJ seminar is held also by hybrid form, we will announce the Zoom URL with another email.

Speaker：Prof. Fabio Favata
Affiliation：Italian National Astronomy Institute (INAF) & Thalatta Consulting Ltd.
Title：Space astronomy, past and future: a personal (Western) perspective

Abstract:
Space astronomy is a fairly recent discipline, with the first successful space telescope (OAO-2, a 30 cm UV telescope) launched by NASA in 1968. While the first space telescopes were hardly larger than today’s amateur instruments, we have gone a long way to reach the Webb observatory, the largest space telescope ever launched. We have surely lived, in the past few decades, through a “golden age” of space astronomy, that has enabled discoveries that have changed our understanding of physics and of the Universe (e.g., the existence of dark energy, or the accurate cosmological models enabled by the CMB maps).

This unprecedented success story has been made possible by a number of circumstances which may not extend into the future, at least in the US and in Europe. While many astronomers take further significant progress in the development of space facilities for granted, in fact reality is likely to be more complex. The development of new large facilities by both NASA and ESA has met a number of challenges, both politically and technically. In addition, the time elapsed from the initial scientific idea to its fruition through the results of an actual space mission has become rather long. It is not obvious that the same approach and vision that has served space astronomy so well in the past will be successful in the future, and the golden age risks to be followed by an era in which the pace of progress slows significantly.

In my talk I discuss how and why have we come to this point, what are the risks for the future, in particular for the younger generation of scientists, and I will discuss new opportunities and possible solutions. Key elements include the importance of a diverse ecosystem of scientific ideas and facilities, of the new space ecosystem, as well as the growing, critical role in this field played by space actors in Asia.

Facilitator
-Name： Hori Yasunori

=============== January 10 wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：January 10, 2024 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Kiyoaki Doi
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Akimasa Kataoka, Hideko Nomura, Misato Fukagawa)
Title: Multi-wavelength ALMA observations of the PDS 70 disk with planets

Speaker: Suzuka Nakano
Affiliation: SOKENDAI 55h year (D3) (Supervisor: Koichiro Nakanishi, Takashi Sekii, Takuma Izumi)
Title: TBA

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== January 10 wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Jan. 10 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)

Speaker: Go Murakami
Affiliation: JAXA
Title: Ultraviolet Spectroscopy and Imaging in Solar System Science and Beyond
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.

Facilitator
-Name: Yuka Fujii
Comment: English

2023.12.25-2024.1.7

December 26 Tue 16:00-17:00 NAOJ Seminar
Large Seminar Room in Subaru Building and Zoom(hybrid)

December 27 Wed 10:30-12:00 SOKENDAI Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)

詳細は下記からご覧ください。

=============== December 26 Tue ===============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Sporadic
Date and time：December 26, 2023 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Prof. Daniel Jontof-Hutter
Affiliation：University of the Pacific
Title：Three-body resonances in Multitransiting Exoplanetary Systems
Abstract:Planet formation models with convergent migration show that planet pairs are easily trapped in mean motion resonances. Yet in Kepler’s multi-planet systems, orbital period ratios near resonance are rare.
Furthermore, those pairs with commensurate orbital period ratios, the measurement uncertainties of orbital eccentricities make it difficult to show that any planet pair is in libration.
Three-body resonances, however, may be easier to identify. Several systems have been shown to be in 3-body libration. Using transit timing data, we explore dynamical simulations of Kepler systems that are potentially in three-body resonances.
We further search for three-body resonances among all triples within the Kepler dataset, in search of additional systems in libration. Finally, we estimate the fraction of planetary systems with three-body resonant chains.

Facilitator
-Name：Shinobu Ozaki

=============== December 27 wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：December 27, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Ryota Ikeda
Affiliation: SOKENDAI 3rd year (D1) (Supervisor: Daisuke Iono, Masayuki Tanaka, Takuma Izumi)
Title: Study of spatial extent and haloes of [CII] line emission in star-forming galaxies at z=4-6

Speaker: Itsuki Ogami
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Wako Aoki, Hisanori Furusawa, Miho N. Ishigaki)
Title: Probing the stellar halo in M33 using Subaru/HSC

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

2023.12.4-2023.12.10

December　5 Tue 10:00-11:30 太陽系小天体セミナー
Zoom

December 　6 Wed 10:30-12:00 SOKENDAI Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)

December 　6 Wed 11:00-12:00 Tea Talk
Zoom

December 　6 Wed 15:30-16:30 NAOJ Science Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)

December 　8 Fri 16:00-17:00 NAOJ Seminar
Large Seminar Room in Subaru Building and Zoom (hybrid)

詳細は下記からご覧ください。

=============== December 　5 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：12月5日（火曜日）10時00分～11時30分
場所：zoom
講演者：渡部潤一

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

=============== December 　6 wed===============

Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：December 6, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom

Speaker: Abdurrahman Naufal
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Yusei Koyama, Masayuki Tanaka, Yuichi Matsuda)
Title: Searching for quiescent galaxies in the Spiderweb protocluster with HST grism observation

Speaker: Takaho Masai
Affiliation: SOKENDAI 55h year (D3) (Supervisor: Alvaro Gonzalez, Yoshinori Uzawa, Takafumi Kojima)
Title: The Design of Frequency Independent Optics for (Sub)Millimeter Wave Multibeam Receivers

Facilitator
-Name：Matsuda, Graduate Student Affairs Unit

=============== December 　6 wed==============

キャンパス：三鷹　野辺山 水沢 岡山 ハワイ
セミナー名：Tea Talk
定例・臨時の別：臨時
日時：12/6（水）11：00～12：00
場所：Zoom
Speaker: Séamus Duffy, Research Student, SOKENDAI
Title: Science Outreach in Ireland: Science Education at Birr Castle with I-LOFAR
Abstract: This tea-talk will talk a little bit about Ireland, and also about outreach there, broaching topics such as: who we target, how we target them, what activities and projects do we run, and adapting to Covid and a post-Covid world.

Bio: Séamus Duffy is a current research student at NAOJ working with the SCExAO team, focusing on applications of machine learning and AI to astronomy.
He originally came to Japan in 2017 and worked as an English teacher in Tokyo, where he stayed for four years before returning to Ireland in 2020. In Ireland he worked with the Technological University of the Shannon, Trinity College Dublin, and Dublin Institute for Advanced Studies as the education and engagement manager for the I-LOFAR project at Birr Castle, home of the Leviathan telescope. I-LOFAR is the Irish installation in the low frequency array, a radio telescope network which cover most of the European continent. He has a huge passion for teaching, outreach and inspiring younger minds to get involved with astronomy. During his time in outreach he worked to educate about I-LOFAR and the science being conducted at the telescope to the local population of Birr, local schools, businesses, and government officials. He was particularly interested in conducting outreach in a post-covid environment and utilising online and digital spaces for outreach programmes.

世話人の連絡先：
-名前：藤田登起子

=============== December 　6 wed==============

Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Dec. 6 (Wed.), 15:30-16:30
Place: the large seminar room / Zoom (hybrid)

Speaker: Moka Nishigaki
Affiliation: NAOJ (D1)
Title: Uncovering the Chemical Evolution of Galaxies from z=0–5 using the UniverseMachine
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.

Speaker: Xingqun Yao
Affiliation: Beihang University
Title: Neutrino Mass Hierarchy from Supernova Nucleosynthesis of Light Elements and the Roles of Unstable Nuclei
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 ν nuclei) 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.

Facilitator
-Name: Haruka Kusakabe
Comment: English

=============== December 　8 Fri==============

Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：December 8, 2023 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)

Speaker：Prof. Cecilia Lunardini
Affiliation：Arizona State University

Title：Neutrinos and gravity: multimessenger scenarios
Abstract:Multimessenger astronomy is developing rapidly, and neutrinos are major players in its vast landscape. It is hoped that, in the near future, experimental and theoretical developments will lead to the detection of neutrinos and gravitational waves from the same class of source. I discuss possible scenarios, involving neutrinos and gravitational waves from core collapse supernovae, and from binary mergers of matter-rich compact objects (for example, two neutron stars). I will also discuss tidal disruption events, where a star is torn apart and eventually accreted by a supermassive black hole. These events, which produce flares at infrared, optical and X-ray wavelengths, are sources of sub-Hz gravitational waves, and could emit very high energy neutrinos and cosmic rays. Emphasis will be placed on the feasibility and physics potential of future observations of neutrinos and other messengers from these diverse classes of emitters.

Facilitator
-Name：Shinobu Ozaki