Measuring the Hubble Constant using Strongly Lensed Quasars

  • Oct. 9, 2019, 2:00 pm US/Central
  • Curia II
  • Anowar Shajib, UCLA

The recent tension between early- and late-Universe measurements of the Hubble constant highlights the necessity for independent and precise methods 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, H0. Due to a number of great advancements over the past decade in both the data quality and modeling techniques, the measurement of  H0 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 H0 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.