The Extragalactic Distance Scale in Gaia Era

11 June - 6 July 2018

Lucas Macri, Rolf Kudritzki, Sherry Suyu, Wolfgang Gieren

Modern techniques applied to the Extragalactic Distance Scale have recently enabled a measurement of the local expansion rate of the Universe (H0) with a total uncertainty approaching 2%. In the current era of "precision cosmology", further improvements in the precision and accuracy this measurement are highly desirable. The comparison of local measurements of H0 with predictions based on observations of the Cosmic Microwave Background and Baryon Acoustic Oscillations serves as a stringent test of the assumed cosmological model. Furthermore, H0 provides needed additional constraints on the equation of state of dark energy and other cosmological parameters.

This programme will bring together experts on the theory and observation of “classical” distance indicators as well as those engaged in alternative routes to H0. Given the increasingly important role of astro-statistical techniques in our field (such as data mining, machine-learning classification, etc.), we will include experts on this area. Some of the topics that we propose to discuss are:

Primary distance indicators
  • Results from new observing techniques with Hubble and prospects for James Webb.
  • Results from Gaia and organisation of follow-up ground-based observations of newly-discovered Cepheids and RR Lyraes.
  • Further improvements on the distance to the Large Magellanic Cloud and other nearby galaxies that can provide absolute calibrations of distance indicators.
  • Improvements on the absolute calibration of RR Lyraes, red clump stars, blue supergiants, Miras and the tip of the red giant branch.
  • Current status and future prospects for pulsation & evolutionary models of Cepheids and RR Lyraes.
Secondary distance indicators
  • Type Ia supernovae.
  • Surface brightness fluctuations.
  • The luminosity-linewidth and fundamental plane relations.
  • Alternative routes to H0.
  • Megamasers in the Hubble flow.
  • Time-delay measurements in strong lensing systems.
  • Results from BAO, CMB and dark energy experiments (DES, Planck, SPT).
  • Cosmological implications.
  • Constraints on dark energy equation of state and cosmological model.
  • Prospects from future BAO, CMB and dark energy experiments (DESI, Euclid, LSST).