Measuring the Hubble constant from time-delays of strongly lensed quasars

Speaker: 
Anowar Shajib (UCLA)
Date: 
Friday, September 27, 2019 - 12:15pm to 1:00pm

The recent tension between early- and late-Universe measurements of the Hubble constant highlights the necessity for independent and precise probes such as the time-delay cosmography. The measured time-delays between the lensed images of a background quasar depend on the absolute physical scales in the lens configuration. Thus, the time-delays allow measurements of these scales to infer the Hubble constant, H_0. Due to a number of great advancements over the past decade in both the data quality and modeling techniques, the measurement of  H_0 from the time-delays has fulfilled its promise to be competitive with other traditional methods such as the cosmic distance ladder. This is evident from the recent 2.4% blind measurement of H_0 from only six lenses (Wong et al. 2019). Simulation shows that a sample of nine lenses shrinks the uncertainty on this measurement to 2% (Shajib et al. 2018). I will present the Hubble constant measured from a newly analyzed lens system taking the sample size to seven. In addition, I will present the future roadmap of time-delay cosmography to independently reach 1% precision within a few years.

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