2020-04-09 Abstract
Title: Revealing dark sides of the Universe
Speaker: Tomotsugu Goto
Date: April 9 at 10:00
Location: R521, General Building II
Abstract:
Our Universe is filled with unknowns such as dark energy and dark age. In this talk, I will introduce our attempts to shed light on the dark sides of the Universe.
1. A new method to measure time variability of the Dark Energy
Nature of dark energy remains unknown. Especially, to constrain the time variability of the dark-energy, a new, standardizable candle that can reach more distant Universe has been awaited. We found an empirical positive correlation between the time-integrated luminosity and the rest-frame intrinsic duration of fast radio bursts (FRBs), which are a new emerging population of radio bursts that will be found in quantity at high-z in the fore coming future. This correlation can be used to measure time variability of Dark Energy, potentially revolutionizing our understanding of the Dark Energy.
2. Dark side of the cosmic star formation history.
Revealing cosmic star formation history is one of the major goals of astronomy. However, more than 90% of the star formation is hidden by dust, and thus, unreachable with ground-based telescopes. We have launched the AKARI space-infrared telescope, which can measure dust-hidden star-formation through infrared light. Combined with the new optical
data I obtained using 1.8 billion NTD Subaru Hyper-Suprime Cam, we reveal dust-hidden cosmic star-formation history with unprecedented accuracy.
3. One hundred super massive black holes are not enough.
Our team have achieved a milestone in discovering 100 super massive black holes (SMBHs) at z~6, where only ~10s were known previously, because in such distant Universe, black
holes are extremely faint. Due to the significance of the discovery, the results were reported in more than 8 newspapers and TVs internationally, including at least 12 medias in Taiwan. Using the 100 black holes, we have, for the first time, statistically ruled out that radiations from SMBHs are not the source of the cosmic re-ionization.
4. A discovery of the most distant proto-cluster at 13.0 billion years ago
Using the Subaru, Keck, and Gemini Telescopes, we discovered the most distant proto-cluster at 13.0 billion years ago. This is the earliest protocluster ever found. This discovery suggests that large structures such as protoclusters already existed when the Universe was only about 800 million years old, 6 percent of its present age. This result was also reported in at least in 220 media internationally.