The infrared surface brightness fluctuation Hubble constant

We measured infrared surface brightness fluctuation (SBF) distances to an i sotropically distributed sample of 16 distant galaxies with redshifts reach ing 10,000 km s(-1) using the near-IR camera and multi-object spectrometer (NICMOS) on the Hubble Space Telescope (HST). The excellent spatial resolut ion, very low background, and brightness of the IR fluctuations yielded the most distant SBF measurements to date. Twelve nearby galaxies were also ob served and used to calibrate the F160W (1.6 mum) SBF distance scale. Of the se, three have Cepheid variable star distances measured with HST and eleven have optical I-band SBF distance measurements. A distance modulus of 18.5 mag to the Large Magellanic Cloud was adopted for this calibration. We pres ent the F160W SBF Hubble diagram and find a Hubble constant H-0 = 76 +/- 1. 3 (1 sigma statistical) +/- 6 (systematic) km s(-1) Mpc(-1). This result is insensitive to the velocity model used to correct for local bulk motions. Restricting the fit to the six most distant galaxies yields the smallest va lue of H-0 = 72 +/- 2.3 km s(-1) Mpc(-1) that is consistent with the data. This 6% decrease in the Hubble constant is consistent with the hypothesis t hat the Local Group inhabits an underdense region of the universe, but is a lso consistent with the best-fit value of H-0 = 76 km s(-1) Mpc(-1) at the 1.5 sigma level.