Each of the two searchable webpages has a link to the other, as well as to the source data. The webpages are self-contained with all the data included in the html file, which contains the javascript code for the searches and the CSS for styling.

The original purpose in doing this was because many of the submissions were not on the arXiv, and I wanted to see what else was available and also so the PDF file link were all on one page. In addition, though, the search feature has been very useful.

The webpages are coded with simple html and javascript (javascript must be enabled to view the data). The webpage search input box shows the syntax:

Use * for AND search, : keyword1*keyword2

Use | for OR search: keyword1|keyword2

For NOT, use — (2 hyphens) after 1st keyword: keyword1—keyword2

¹APC: Activity, Project, or State of the Profession Consideration

HashTags: #astrophysics #cosmology #physics

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

“This is significant for supernova cosmology because, along with photometric-calibration uncertainties, uncertain dust [extinction](https://en.wikipedia.org/wiki/Extinction_(astronomy) estimates and the intrinsic variability of SN Ia colors present challenging and important systematic problems for dark energy measurements. (pg2)”

“Recent work has demonstrated that SN Ia in the NIR are more nearly standard candles, even before correction for light curve (LC) shape or host galaxy dust reddening... Overall, a substantial body of evidence indicates that rest-frame LCs of SN Ia in NIR are both better standard candles than at optical wavelengths and less sensitive to the confounding effects of dust. When NIR data are combined with UBV RI photometry, this yields accurate and precise distance estimates. (pg2)”

This study analyzed 89 SNe Ia having both optical and NIR data avaiable. “While the current sample of optical SN Ia LCs exceeds 1000, and will be increased by orders of magnitude by ongoing and future surveys including the Dark Energy Survey, the Zwicky Transient Facility, and the Large Synoptic Survey Telescope, the number of normal SN Ia with published NIR LCs is still less than 250.” (abstract)

This growing NIR work is useful not only to help to standardize SNe Ia distance measurements, but also for Hubble constant estimates, “and eventually, cosmological parameter estimates, when the nearby and high-z samples² are combined as in the HST RAISIN⁴ program.” (pg3)

“We implement two different methods to derive the distance modulus for each supernova from the NIR LCs. We call them the template method and the Gaussian-process method (GP). The GP method requires data near the NIR maximum for all NIR bands being used, while the template method works for arbitrarily sampled data, even if the LC is sparse near maximum. For this reason, we have more objects in the template method Hubble diagrams...At the ∼2.5-3.1σ level, that NIR SN Ia LCs at NIR maximum, without LC shape or dust corrections, are already better standard candles than optical-only SN Ia LCs ... that apply such corrections. (pg12)” ... “For all NIR band subsets, the GP (NIR max) method produces the smallest scatter. (pg19)”

These NIR studies “could help to limit systematic galaxy distance errors that arise from the degeneracy between the intrinsic supernova colors and reddening of light by dust, that affects optical-only SN Ia cosmology...Studies combining NIR and optical SN Ia photometry have already shown that the addition of NIR data is an extremely promising way to break the degeneracy between intrinsic color and dust reddening, allowing distance estimates to become increasingly insensitive to the assumptions behind individual LC fitting models. (pg25)

“Upcoming missions that could exploit nearby NIR data as a low-z anchor include the Large Synoptic Survey Telescope, the NASA Wide-Field Infrared Survey Telescope, the European Space Agency’s EUCLID mission, as well as the NASA James Webb Space Telescope. (pg28)”

Another paper that might be of interest: Carnegie Supernova Project-II: The Near-infrared Spectroscopy Program ___

¹ “Systematic errors introduced by photometry, light curve fitters, and by dust extinction pose the limit of precision for today's large optical samples. Theory predicts and empirical evidence demonstrates that SN Ia are more nearly standard candles in infrared bands than in optical bands. Dust absorption is 3 times smaller in the near IR.” [Kirshner source]

² “This investigation is for a low-z sample, but we are working to extend this technique to cosmologically-interesting distances with the Hubble Space Telescope. (pg 1)”

³ Both Adam Riess and Brian Schmidt were Kirshner's PhD students. [source]

⁴ RAISIN: Tracers of cosmic expansion with SN IA in the IR (aside: what a convoluted acronym!)

Tags: #astrophysics #cosmology

Some infographics about the cosmic distance ladder:

[graphic source (credit: Matt Perko) from a UCSB article The Standard Siren] A graphic illustrating the technique of “building up a distance ladder using a number of different techniques for various ranges.”

The three rungs of the distance ladder, from a presentation by Stephen Feeney at the Gravitational Wave Probes of Fundamental Physics (11-13 November 2019) conference. The slides of this talk (keynote file format) are available here.

The graphic below is from page 49 of the paper A 2.4% Determination of the Local Value of the Hubble Constant [arxiv:1604.01424]

Some articles about the cosmic distance ladder: An IOP article on the cosmic distance ladder Cosmology is in crisis about how to measure the universe, by Sarah Scoles Why Cosmology’s Expanding Universe Controversy Is An Even Bigger Problem Than You Realize, by Ethan Siegel Cosmic Distance Ladder article

Other references: Slides from a talk by Stefano Casertano: Gaia DR2 and beyond: contributions to the local distance scale Additional materials from the Oct. 2018 KICP workshop: The Future of H₀: Crisis or Concordance

Tags: #astrophysics #cosmology