CosmoPhys

New developments since this post was originally created: videos of presentations at the KITP-UCSB conference Tensions between the Early and the Late Universe in mid-July 2019: (1) Tomasso Treu presentation: Time delay cosmography and the Hubble constant tension, and (2) Anowar J. Shajib presentation: Towards a 1% Hubble constant measurement with time delay cosmography. ___

Subject paper: [1907.04869] H0LiCOW XIII. A 2.4% measurement of $H_0$ from lensed quasars: 5.3σ tension between early and late-Universe probes

This full report by the H0LiCOW collaboration¹ follows after their recent 5th (1905.09338) and 6th (1907.02533)² measurements based on a time-delay strong lensing technique. The 4th measurement was reported in September 2018 (1809.01274) and was the subject of a cosmology subreddit thread at that time.

From this paper's Summary section: “Our constraint on H_0 in flat ΛCDM is completely independent of and complementary to the latest results from the SH0ES collaboration, so these two measurements can be combined into a late-Universe constraint on H_0. Together, these are in tension with the best early-Universe (i.e., CMB) determination of H_0 from Planck at a significance of 5.3σ.”

Here are some examples of the enthusiastic reaction within the SH0ES team to these new results: Ex 1 and Ex 2.

For a summary overview of this technique, besides what's in the papers, see 'H_0 via standard clocks', Section 3, in 1903.05035. There's also an astrobites article on using strong gravitational lensing to measure H_0.

At a 3-day KITP-UCSB conference starting July 15, 2019, one of the topics presented was Tensions between the Early and the Late Universe by H0LiCOW team member Tommaso Treu: 'Time delay cosmography and the Hubble constant tension' [video of talk]. Also, the lead author of the 6th paper, Geoff Chi-Fan Chen ³ attended. Conference attendees tweeted highlights and visuals under the KITP_H0tTakes hashtag.

Here is a link to Figure 12 from this paper.

A list of papers on the arXiv with H0LiCOW in the title or abstract.

___ Footnotes: ¹ They have a web site here but at this time it hasn't been updated for these latest results. ² Also see this Astrobites article about the 6th measurement paper [1907.02533]. This is the one where they used adaptive-optics imaging from Keck and compared it with data from HST. ³ Geoff Chi-Fan Chen's personal website about his research work

Note: This note is based on my cosmology subreddit post on this paper.

Tags: #astrophysics #cosmology #H0