Is the Short Distance Scale a Result of a Problem with the LMC Photometric Zero Point?
I present a promising route to harmonize distance measurements based on clump giants and RR Lyrae stars. This is achieved by comparing the brightness of these distance indicators in three environments: the solar neighborhood, Galactic bulge and Large Magellanic Cloud (LMC). As a result of harmonizing the distance scales in the solar neighborhood and Baade's Window, I derive the new absolute magnitude of RR Lyrae stars, M{sub v}(RR) at [Fe/H] = -1.6 (0.59 {+-} 0.05, 0.70 {+-} 0.05). Being somewhat brighter than the statistical parallax solution, but fainter than typical results of the main sequence fitting to Hipparcos data, these values of M{sub V}(RR) favor intermediate or old ages of globular clusters. Harmonizing the distance scales in the LMC and Baade's Window, I show that the most likely distance modulus to the LMC, {mu}{sub LMC} is in the range 18.24 - 18.44. The Hubble constant of about 70 km/s/Mpc reported by the HST Key Project is based on the assumption that the distance modulus to the LMC equals 18.50. The results presented here indicate that the Hubble Constant may be up to 12% higher. This in turn would call for a younger Universe and could result in some tension between the age of the Universe and the ages of globular clusters. I argue that the remaining uncertainty in the distance to the LMC is now a question of one, single photometric reference point rather than discrepancies between different standard candles.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15014055
- Report Number(s):
- UCRL-CONF-203267; TRN: US200803%%816
- Resource Relation:
- Conference: Presented at: Conference on Astrophysical Ages and Time Scales, Hilo, HI, United States, Feb 05 - Feb 09, 2001
- Country of Publication:
- United States
- Language:
- English
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