Speaker
Shingo Akama

Date/Place
11:00-, 27(Wed), May. @ES606

Title
Observational Predictions of General Bounce Cosmology

Abstract
Inflation is widely regarded as the most successful paradigm for the early universe. Nevertheless, alternative scenarios have also been studied, motivated in particular by the conceptual problems of inflation, such as the initial singularity problem and the trans-Planckian problem. In this talk, I will first introduce various aspects of bouncing cosmology as an alternative to inflation, including its successes and challenges. In the latter half, I will present a general framework of bouncing cosmology that admits a parameter space capable of explaining the observed CMB fluctuations, as inflation does. Finally, among its observational predictions, I will discuss the statistical properties of CMB B-mode polarization.

Speaker
Federica Tarsitano

Date/Place
11:00-, 20(Wed), May. @ES606

Title
Optical-to-near-infrared studies of AGN and dual AGN systems with Euclid and the HSC-Niji survey

Abstract
Supermassive black holes (SMBHs), almost ubiquitous in galaxies, are polyglot citizens of the Universe: we observe them igniting as Active Galactic Nuclei (AGN) across the electromagnetic spectrum, and potentially hear the ripples in spacetime, the gravitational waves (GW), they create in collisions. The upcoming Laser Interferometer Space Antenna (LISA) mission will be sensitive to the GW signals from SMBH coalescence, complementing Pulsar Timing Array (PTA) observatories. The ESA Euclid space mission, surveying billions of galaxies in the optical to near-infrared (NIR) with unmatched high-resolution imaging and wide field of view, will bring remarkable advances in the study of the co-evolutionary path of SMBHs and their host galaxies. A fundamental yet poorly explored stage of this evolution is represented by dual AGN systems, which trace the pathway to SMBH coalescence, and can be used to set empirical priors for LISA GW events. Despite their high scientific value, instrumental challenges have limited the number of dual AGN detections confirmed so far, as exquisite spatial and spectral resolution is needed to characterise the galaxy nuclear light, and most surveys lack the necessary statistical power. In this talk, I will discuss recent efforts to build up the first systematic census of dual AGN in Euclid, and to advance our understanding of AGN activity and feedback by exploiting unprecedented synergies with HSC-Niji, a new medium-band survey with the Subaru telescope. The latter will also enable the study of AGN-linked populations, such as Little Red Dots, as well as cosmology-focused analyses, including the multi-wavelength characterisation of galaxy shapes and more accurate galaxy SED reconstruction and photo-z estimates, all relevant for weak-lensing analyses in current and future Stage IV surveys.

Speaker
Shintaro Yoshiura

Date/Place
11:00-, 13(Wed), May. @ES606

Title
Probing the Early Universe with Low-Frequency 21-cm Signals: From Cosmic Reionization to the Dark Ages

Abstract
After the birth of the Universe, the universe went through three important epochs: the Dark Ages, when no astronomical objects had yet formed; the Cosmic Dawn, when the first stars were born; and the Epoch of Reionization, when ultraviolet radiation from young galaxies ionized hydrogen in intergalactic medium. Although these epochs are crucial for understanding the early history of galaxy formation and cosmology, many aspects remain observationally unexplored. One promising approach is to observe the 21-cm line, a radio signal emitted by neutral hydrogen atoms at a rest frequency of approximately 1420 MHz. By detecting the signal from hydrogen that filled the early Universe, we can probe the cosmology of the Dark Ages and the formation of the first cosmic structures. Due to the expansion of the Universe, this 21-cm signal is redshifted to lower frequencies and is observed as low-frequency radio signal below about 200 MHz. In particular, for the Dark Ages, the 21-cm line is almost the only available observational probe. To correctly extract physical information from 21-cm observations, researchers are developing cosmological models as well as instruments and analysis methods that can deal with foreground emission, such as radio emission from our Galaxy. In this seminar, I will first give a brief introduction to studies of the distant Universe using the 21-cm line. I will then explain how the latest observational experiments are working toward the detection of this signal.

Speaker
Daisuke Watanabe

Date/Place
11:00-, 22(Wed), April. @ES606

Title
Self introduction

Abstract
Self introduction

Speaker
Kauri Ueda

Date/Place
11:00-, 22(Wed), April. @ES606

Title
Self introduction

Abstract
Self introduction

Speaker
Masaya Inoue

Date/Place
11:00-, 22(Wed), April. @ES606

Title
Self introduction

Abstract
Self introduction

Speaker
Shohei Kanda

Date/Place
11:00-, 15(Wed), April. @ES606

Title
Self introduction

Abstract
Self introduction

Speaker
Tomoya Honke

Date/Place
11:00-, 15(Wed), April. @ES606

Title
Self introduction

Abstract
Self introduction

Speaker
Kiyotomo Ichiki

Date/Place
11:00-, 15(Wed), April. @ES606

Title
Policy speech

Abstract
Policy speech