演講資訊

摘要：

In this talk, I will first discuss the science goals and methodology of the Megamaser Cosmology project and present our final measurement of the Hubble constant made using geometric distance measurements to six megamaser-hosting galaxies. It will be shown that our fit Hubble constant, independent of distance ladders and the cosmic microwave background as well as cosmological models, is H0 = 73.9+/-3.0 km/s/Mpc, well consistent with the values obtained with the Type 1a supernovae (the SH0ES project) and strong gravitational lensing systems (the H0LiCOW project). This Hubble constant will then be compared with the value derived from observations of cosmic microwave background conducted by the Planck collaboration, and we will discuss the possible causes of the tension between the early and late universe Hubble constant measurements. In the end of the talk, I will explain how we could resolve the Hubble tension problem by making a 1% H0 measurement using the megamaser technique and discuss the role of the next generation Very Large Array (ngVLA) in our efforts to achieve this goal.