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Subaru Seminars are
usually held in Room 104 of the Hilo Base Facility, adjacent
to the main lobby. Everyone is welcome to attend. If you would like to
give a seminar, please contact Subaru seminar organizers
(Thayne Currie, Tae-Soo Pyo, Nagayoshi Ohashi)
by email : sseminar_at_subaru.naoj.org (please change"_at" to @).
October 13, Friday, 1pm in 104B
" Probing the dark side of the universe "
Geoff Chih-Fan Chen (UC-Davis)
Discovering the accelerating expansion of the universe in 1999 was a revolution in
physics. Although it brought a concordance universe consisting of dark matter, dark energy,
and ordinary matter, the derived current expansion rate (H0) based on the standard
cosmological model has tension with the direct measurements at the local universe. It is
important to emphasize that the value of H0 critically depends on the curvature of the
universe, dark energy equation of state, and neutrino physics, which are all fixed in the
standard cosmological model. If we start relaxing all the assumptions, the degeneracies in
the parameters of space appear. Thus, these assumptions must be tested empirically. If this
tension between the H0 derived from CMB and the local measurements is not caused by any
systematic effect, it might be a hint of new physics. Time-delay gravitational lens system
serves a powerful tool to measure H0. Recently, H0LiCOW group has shown that the new H0
measurement by using three HST lensing imaging agrees with the H0 measured by using
supernova data, but is mildly in tension with the derived H0 by using CMB from the Planck
team. Since adaptive optics imaging can provide higher angular resolution than HST imaging
but suffers from the unknown point spread function problem, in this talk, I will present a
new method, which overcomes this obstacle, to constrain H0 by using three AO imaging from the SHARP team.