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)
=============== September 26 Tue===============
=============== September 27 Wed===============
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
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===============
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
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.