Day five of ESO H0 2020 Meeting: The Future Telescopes and Surveys

ESO has organized an important online conference (22-26 June 2020) on the current significant tension in measuring the expansion rate of the Universe, i.e. the Hubble constant H0. The video of each day’s talks and the panel discussion is uploaded on YouTube by the organizers and is publicly available.

Here is a summary of day five of the meeting with links to specific parts of each speaker’s talk mainly for future personal reference, but hopefully useful for others as well. Check previous summaries here: day 1, day 2, day 3, and day4.

After Richard Anderson announced the start of the 5th and the last day of the meeting, the talks went on as follows:

Giuliana Fiorentino, The distance ladder in the ELT era

1. Intro:
   Intro to two ELT instruments:
   MICADO: high-resolution imager/long-slit spectrograph
   MAORY: multi adaptive optics (AO) array
   Two pixel sizes: 0.0015 and 0.004 arcsec and two FOV: 20 arcsec each side and 50 arcsec each side.
2. Adaptive Optics:
3. How ELT will help with improving the Cepheid distance ladder:
   ELT will improve Cepheid distance measurements of SNIa host galaxies out to 40 Mpc.
   Thanks to its very high resolution, ELT Would increase Cepheid detection out to the Coma cluster (~100 Mpc), therefore would enable direct measurement of H0 in the Hubble flow.
4. Comparing the resolutions of HST, JWST, and ELT
   ELT -> sub-parsec resolution at ~ 100 Mpc
5. ELT and the Cepheids in SNIa host galaxies:
   A better understanding of the crowding effect.
   Direct stellar metallicity estimation.
6. Comparing different methods for the analysis of the same Cepheid data:
   A comparison of Riess et al. (2011) and Fiorentino et al (2013), the latter giving a slightly higher value of H0.
7. Astro-photometric performance of an ELT camera
8. Cepheids out to 100 Mpc
   ELT will detect more Cepheids in the Coma cluster.
9. Conclusions

Stefano Casertano, JWST and the distance ladder

1. Intro:
   A summary of the H0 Tension: it is not due to a single measurement.
   JWST will sharpen and validate several local measurements of H0 “and most likely will provide something completely new.”
2. JWST capabilities at a glance
   Will cover a large wavelength range from 0.6 to 30 microns in both imaging and spectroscopy.
3. What makes a good distance scale indicator?
   Physics-based, deterministic, accurate, precise local calibration, and small well-understood correctable systematics.
4. JWST at 100 Mpc is equivalent to HST at 40 Mpc
   It can extend the reach of Cepheids well into the Hubble flow but may need to be combined with HST for optimal results.
5. More about crowding
   “Crowding is retired as a systematic” and JWST would reduce the scatter and improve the distance accuracy.
6. Extending the reach of TRGB
   TRGB method currently extends to ~ 30 Mpc, JWST can reach that in one hour.
   But the color-dependent effects can be large.
7. JWST can be transformative for Miras
8. Time-delay cosmography with JWST
9. Summary

Elisabeth Krause, Future probes of dark energy

1. Intro:
   A review of photometric dark energy (DE) surveys: e.g. CFHTLS, COSMOS, KiDS, DES, HSC and the future surveys; e.g. Euclid, Nancy G. Roman Space Telescope, and Vera Rubin observatory.
2. The power of combining probes
3. Dark Energy Survey (DES) year 1
   Weak lensing + LSS analysis
   660k galaxies with excellent photo-z & 26 million source galaxies with shape measurements split in 4 redshift bins.
   Measured angular clustering, galaxy-galaxy lensing, and cosmic shear.
4. Systematics
   e.g. photo-z uncertainties (for both lens and source galaxies) and intrinsic alignments.
5. DES year 1 results:
6. Effect of systematic assumptions on the constraints on sigma8
7. Survey optimization
   The number density of galaxies and survey area.
8. The Rubin Observatory DE collaboration
   Data products and Fisher matrices: arXiv:1809.01669
9. Euclid Cosmological Probes Forecasts
   Euclid preparation: VII arXiv:1910.09273
10. Roman Space Telescope
11. Conclusions

Raphael Flauger, The future of the CMB

1. Intro:
   Planck measurements of the CMB.
   “You might ask if there is any thing more that CMB can contribute?” -> “yes”.
   Regarding H0 and sigma8 tensions: “There are indications that LCDM is cracking.”
2. Current experiments:
   SPT, BICEP, SPIDER, ACTPol, CLASS, and POLARBEAR
3. Era of CMB polarization:
   Large scale polarization is a probe of any gravitational waves at recombination.
   Small scale polarization -> Hubble Parameter.
4. Future CMB experiments:
   South Pole Observatory, SIMONS Observatory, CMB-S4, LiteBIRD, PICO,
5. H0 from the CMB:
6. Forecasts for H0 uncertainties from future CMB experiments:
   In the context of LCDM:
   0.9 to 0.09 km/s.Mpc
7. Conclusions

The Discussion Session

L. Verde:
The problem is not in any specific data set or analysis.
We should look for model-independent quantities.
J. L. Bernal
On using BAO constraints for searching for models beyond LCDM.
S. Jha
On the age of the Universe.
T. Shanks
On the local under-density extending out to 150 Mpc causing an around 3% difference in H0.

End of the meeting.

The images showing the first slide of each talk are screenshots obtained from the public YouTube video published by ESO. The featured image at the top of the post is obtained via the Wikimedia Commons, credit: NASA.