The 4th Toyama International Symposium on "Physics at the Cosmic Frontier" (PCF2022-2023)

30 Sept 2022, 17:00 → 31 Mar 2023, 18:00 Asia/Tokyo

Faculty of Science, University of Toyama

Mitsuru Kakizaki (University of Toyama)

Wednesday, 5 October

13:00 → 03:30 seminar 1: "First Identification of a CMB Lensing Signal Produced by 1.5 Million Galaxies at z∼4"

We report the first detection of the dark matter distribution around Lyman break galaxies (LBGs) at the redshift of z~4 through the cosmic microwave background (CMB) lensing measurements with the public Planck PR3 κ map. The LBG sample consists of 1473106 objects at z∼4 that are identified in a total area of 305  deg2 observed by the Subaru/Hyper Suprime-Cam survey. After careful investigations of systematic uncertainties, such as contamination from foreground galaxies and cosmic infrared background, we obtain the significant detection of the CMB lensing signal at 5.1sigma which is dominated by 2-halo term signals of the LBGs. Fitting a simple model consisting of the Navarro-Frenk-White profile and the linear-bias model, we obtain the typical halo mass of Mh=2.9×1011  h−1 Msun. Combining the CMB lensing and galaxy-galaxy clustering signals on the large scales, we demonstrate the first cosmological analysis at z∼4 that constrains (Omega_m0,sigma_8). We find that our constraint on sigma_8 is roughly consistent with the Planck cosmology, while this sigma_8 constraint is lower than the Planck cosmology over the 1sigma level. This study opens up a new window for constraining cosmological parameters at high redshift by the combination of CMB and high-z galaxies, as well as studying the interplay between galaxy evolution and large-scale structure at such high redshift. In this seminar, we will also discuss the future prospects with ongoing/upcoming observations by large ground-based/space telescopes such as James Webb Space Telescope (JWST).

Speaker: Dr Yuichi Harikane (ICRR)

Monday, 31 October

14:45 → 15:45 Seminar 2: "Searches for Dark Matter with Cherenkov telescopes: Latest results and a glimpse into the future"

The quest for Dark Matter is a since long unsolved puzzle of modern physics. Imaging Atmospheric Cherenkov telescopes, like MAGIC located at Roque de los Muchachos Observatory on La Palma, have so far searched almost 1000 hours of their data for gamma-ray signals from annihilating or decaying heavy (>GeV) Dark Matter particles. Also, the next-generation Cherenkov Telescope Array (CTA) is under construction, promising a moment of truth for TeV Dark Matter in the near future. In this seminar, I will introduce how to search for Dark Matter with Cherenkov telescopes. I will present the latest Dark Matter constraints obtained with the MAGIC telescopes, as well as what we can expect to learn with CTA.

Speaker: Dr Moritz Hütten