cosmophysics seminar

会場Kenkyu-Honkan 1F Meeting Room 1
講演タイトルCosmology beyond the B-mode spectrum from BICEP/Keck Array
講演者Toshiya Namikawa (Stanford univ.)


The BICEP/Keck Array (BK) is a cosmic microwave background (CMB) experiment at the south pole to measure large-scale B-mode polarization. The main target of this experiment is to detect B modes from the inflationary gravitational waves. In addition, despite their modest angular resolution, the excellent sensitivity of these maps also makes it possible to detect other cosmological signals. I will talk about direct reconstruction of the gravitational lensing signals using only information at larger angular scales. Gravitational lensing will be important in near future CMB experiments to detect the inflationary gravitational waves and to constrain neutrino masses. In the collaboration, I led the gravitational lensing analysis using the 150 GHz maps which include all data taken by the BICEP2 & Keck Array CMB experiments up to and including the 2014 observing season (BK14). From the auto-spectrum of the reconstructed potential we detect the lensing signals at 5.8 sigma, which is the highest significance achieved to date using an EB lensing estimator. The auto-spectrum is consistent with the cross-spectrum of the reconstructed signals with the Planck 2015 lensing map. These measurements are consistent with the Planck Lambda-CDM cosmology, and with that derived from the previously reported BK14 B-mode auto-spectrum. These results unambiguously demonstrate that the B-modes previously reported by BK collaboration at intermediate angular scales are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B-modes at these angular scales. If possible, I will also talk about my efforts on other cosmological analysis such as delensing and measurement of cosmic birefringence.