0 Assigned ID: 254 ----- Attempting Submission 1 (Thu Mar 05 17:29:29 GMT 2020) ----- HST Phase I Proposal 254 successfully submitted. Receipt: # 254-1 ----- Attempting Submission 2 (Fri Mar 06 19:44:22 GMT 2020) ----- HST Phase I Proposal 254 successfully submitted. Receipt: # 254-2 ----- Attempting Submission 3 (Fri Mar 06 20:35:39 GMT 2020) ----- HST Phase I Proposal 254 successfully submitted. Receipt: # 254-3 ----- Attempting Submission 4 (Fri Mar 06 21:17:32 GMT 2020) ----- The tip of the red giant branch (TRGB) method is a powerful and precise extragalactic stellar distance indicator. Indeed, the TRGB Method has recently been used to measure a value of the Hubble constant of 69.8 km/s/Mpc, which falls squarely between the far-field value (67.4 km/s/Mpc), as inferred from the (cosmological) Planck mission observations of the CMB, and that of the other local (stellar) value measured by Cepheids (73.5 km/s/Mpc). Before suggestions of the possibility of new physics are accepted as necessary to reconcile the near and far values of the Hubble constant, understanding the differences in the local distance scale, and the level of systematic errors is crucial. There are now over 30 galaxies in the HST Archive that are known to be hosts to well-observed Type Ia SNe. These all have VI imaging of sufficient depth that the TRGB can be measured for those stars clearly detected and uncrowded in their dust-free halos. SNe Ia are known to have an intrinsic dispersion of 0.10 mag, derived from samples of over 100 SNe in the far field flow. SNIa in nearby galaxies, having TRGB distances, give a consistent and totally independently-determined scatter of 0.11 mag. With this proposal we will double the number of distances to TRGB-calibrated supernova host galaxies, and in doing so, bring the systematic error on the Hubble constant, attributable to the supernova calibration, down to 1.0%. This will be below the systematic floor currently set by the geometric distance to the LMC at 1.2%. This program will provide the most precise value of the near-field value of Hubble constant measured to date. All data will be made public upon publication. Professor Wendy L. Freedman (University of Chicago) and Dr. Barry F. Madore (Carnegie Observatories) share a long-standing mutual interest and applied expertise in determining the expansion rate of the Universe, having pioneered the use of Cepheid variables and the TRGB method, in the optical and in the near infrared. Both were founding members of the original HST Key Project on the Hubble constant and they have over 100 refereed papers on this topic. Each of the individuals listed below have been active participants in the Carnegie-Chicago Hubble Constant Program and have years of experience reducing, analyzing and using HST imaging data. Prof. Freedman is the PI and will oversee the program as a whole, hosting weekly telecons and working closely, on all aspects of the program, with each of the postdocs and students, especially those in Chicago. As Co-PI Dr. Madore will also be responsible for guiding the activities of the postdocs and graduate students in Pasadena. Dr. In-Sung Jang (Leibniz-Institut fur Astrophysik, Potsdam) is a postdoc who has published numerous papers on the TRGB and the Hubble constant using HST data. He will be relocating to Chicago in the fall of this year. Taylor Hoyt and Abigail Lee are graduate students at the University of Chicago, working on the extragalactic distance scale with Professor Freedman. Dr. Rachael Beaton is a postdoc at Princeton University, specializing in variable star photometry. Dr. Mark Seibert is a free-lance research associate in Pasdean. He and Beaton wrote the existing version of the HST Photometry pipeline Large Scale Structure of the Universe Galaxies 0 Regular false false false false false SUPPORTED