A 3% SOLUTION: DETERMINATION OF THE HUBBLE CONSTANT WITH THE HUBBLE SPACE TELESCOPE AND WIDE FIELD CAMERA 3
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
- George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, 4242 TAMU, College Station, TX 77843-4242 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom)
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
- Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)
- Harvard/Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to determine the Hubble constant from optical and infrared observations of over 600 Cepheid variables in the host galaxies of eight recent Type Ia supernovae (SNe Ia), providing the calibration for a magnitude-redshift relation based on 253 SNe Ia. Increased precision over past measurements of the Hubble constant comes from five improvements: (1) more than doubling the number of infrared observations of Cepheids in the nearby SN hosts; (2) increasing the sample size of ideal SN Ia calibrators from six to eight; (3) increasing by 20% the number of Cepheids with infrared observations in the megamaser host NGC 4258; (4) reducing the difference in the mean metallicity of the Cepheid comparison samples between NGC 4258 and the SN hosts from {Delta}log [O/H] = 0.08 to 0.05; and (5) calibrating all optical Cepheid colors with a single camera, WFC3, to remove cross-instrument zero-point errors. The result is a reduction in the uncertainty in H{sub 0} due to steps beyond the first rung of the distance ladder from 3.5% to 2.3%. The measurement of H{sub 0} via the geometric distance to NGC 4258 is 74.8 {+-} 3.1 km s{sup -1} Mpc{sup -1}, a 4.1% measurement including systematic uncertainties. Better precision independent of the distance to NGC 4258 comes from the use of two alternative Cepheid absolute calibrations: (1) 13 Milky Way Cepheids with trigonometric parallaxes measured with HST/fine guidance sensor and Hipparcos and (2) 92 Cepheids in the Large Magellanic Cloud for which multiple accurate and precise eclipsing binary distances are available, yielding 74.4 {+-} 2.5 km s{sup -1} Mpc{sup -1}, a 3.4% uncertainty including systematics. Our best estimate uses all three calibrations but a larger uncertainty afforded from any two: H{sub 0} = 73.8 {+-} 2.4 km s{sup -1} Mpc{sup -1} including systematic errors, corresponding to a 3.3% uncertainty. The improved measurement of H{sub 0}, when combined with the Wilkinson Microwave Anisotropy Probe (WMAP) 7 year data, results in a tighter constraint on the equation-of-state parameter of dark energy of w = -1.08 {+-} 0.10. It also rules out the best-fitting gigaparsec-scale void models, posited as an alternative to dark energy. The combined H{sub 0} + WMAP results yield N{sub eff} = 4.2 {+-} 0.7 for the number of relativistic particle species in the early universe, a low-significance excess for the value expected from the three known neutrino flavors.
- OSTI ID:
- 21574618
- Journal Information:
- Astrophysical Journal, Vol. 730, Issue 2; Other Information: DOI: 10.1088/0004-637X/730/2/119; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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