Thread by @jcolinhill

Inspired by arxiv.org/abs/1907.10625 and several important observational updates in recent months, I put together an updated compilation plot of H0 measurements from indirect (cosmological-model-dependent) and direct methods.  References are in the thread below. All units km/s/Mpc

Planck 2018: arxiv.org/abs/1807.06209  H0 = 67.36 +/- 0.54  This is derived from the CMB TT+TE+EE and CMB lensing power spectra.  ("This value is our “best estimate” of H0 from Planck, assuming the base-LCDM cosmology." on their page 17)

ACT DR4 + WMAP9: arxiv.org/abs/2007.07288   H0 = 67.6 +/- 1.1 This is derived from the CMB TT+TE+EE power spectra, with a conservative prior on the optical depth tau.   @ACT_Pol verifies that Planck 2018 'low' H0 value is not due to any systematics in CMB data.

WMAP9: arxiv.org/abs/1212.5225  H0 = 70.0 +/- 2.2  This is derived from the CMB TT+TE+EE power spectra.  Included for historical completeness, and still impressive!

DES-Y1 + BAO + BBN: rb.gy/xwioxy (arxiv version is not up-to-date, hence MNRAS link)  H0 = 67.4 +1.1 -1.2 No CMB needed: @theDESurvey combined with BAO (mostly BOSS), BBN, and COBE-FIRAS T0 yields H0 from the sound horizon scale in agreement with Planck, assuming LCDM.

BOSS-EFT + BBN: arxiv.org/abs/2002.04035  H0 = 68.6 +/- 1.1 No CMB needed: using EFT to model the full shape of the BOSS galaxy power spectrum combined with BAO, BBN, and COBE-FIRAS T0 yields H0 (from the sound horizon scale and P(k) shape) in agreement with Planck, assuming LCDM.

BOSS-EFT + Pantheon SNIa + Planck CMB lensing: arxiv.org/abs/2008.08084  H0 = 70.6 +3.7 -5.0  No sound horizon needed: combining uncalibrated (relative) SNIa distances with BOSS-EFT and CMB lensing yields H0 from the matter-radiation equality scale, but with large error bars.

Now for direct measurements, starting with SH0ES: arxiv.org/abs/1903.07603  H0 = 74.03 +/- 1.42  Inference from SNIa distances calibrated with Cepheids, themselves calibrated by combining LMC detached eclipsing binaries, masers in NGC 4258, and Milky Way parallaxes.

CCHP: arxiv.org/abs/2002.01550  H0 = 69.6 +/- 0.8 (stat) +/- 1.7 (syst)  Inference from SNIa calibrated with tip-of-the-red-giant-branch (TRGB) distances, themselves calibrated with LMC detached eclipsing binaries (and other distance cross-checks, e.g., SMC DEBs).

TDCOSMO: arxiv.org/abs/2007.02941  H0 = 67.4 +4.1 -3.2  No distance ladder needed: Inference of H0 from strong gravitational lensing time delay distances.  Important update of earlier H0LiCOW result, now with more conservative marginalization over lens mass profiles.

Megamasers: arxiv.org/abs/2010.01119  H0 = 69.0 +2.9 -2.8  No distance ladder needed: Inference of H0 from geometric megamaser distances (see arxiv.org/abs/2001.09213), but with updated modeling/marginalization over peculiar velocity corrections using 2M++ galaxy redshift data.

Surface brightness fluctuations (SBF): arxiv.org/abs/2008.07754  H0 = 70.50 +/- 2.37 (stat) +/- 3.38 (syst)  Inference from SNIa calibrated with SBF-derived distances to 24 SN host galaxies, but with large error bars at present.

Mira variables: arxiv.org/abs/1908.10883  H0 = 73.3 +/- 4.0  Inference from SNIa calibrated with Mira variable distances to NGC 1559 and NGC 4258, along with megamaser and the LMC DEBs, but with fairly large error bars at present.

Comments/feedback welcome -- hopefully this is a useful guide to keep track of recent developments in this fast-moving subject.  Please feel free to use in talks or elsewhere (with attribution) #H0tension #cosmology #CMB #Hubble

(I don't plan to add any analysis or interpretation to this thread, but feel free to do so.)

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