CARNEGIE HUBBLE PROGRAM: A MID-INFRARED CALIBRATION OF THE HUBBLE CONSTANT

Journal Article · Wed Oct 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/758/1/24· OSTI ID:22092105

Freedman, Wendy L.; Madore, Barry F.; Scowcroft, Victoria; Burns, Chris; Monson, Andy; Persson, S. Eric; Seibert, Mark ^[1]; Rigby, Jane ^[2]

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1. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 (United States)
2. Observational Cosmology Lab, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

Using a mid-infrared calibration of the Cepheid distance scale based on recent observations at 3.6 {mu}m with the Spitzer Space Telescope, we have obtained a new, high-accuracy calibration of the Hubble constant. We have established the mid-IR zero point of the Leavitt law (the Cepheid period-luminosity relation) using time-averaged 3.6 {mu}m data for 10 high-metallicity, Milky Way Cepheids having independently measured trigonometric parallaxes. We have adopted the slope of the PL relation using time-averaged 3.6 {mu}m data for 80 long-period Large Magellanic Cloud (LMC) Cepheids falling in the period range 0.8 < log(P) < 1.8. We find a new reddening-corrected distance to the LMC of 18.477 {+-} 0.033 (systematic) mag. We re-examine the systematic uncertainties in H{sub 0}, also taking into account new data over the past decade. In combination with the new Spitzer calibration, the systematic uncertainty in H{sub 0} over that obtained by the Hubble Space Telescope Key Project has decreased by over a factor of three. Applying the Spitzer calibration to the Key Project sample, we find a value of H{sub 0} = 74.3 with a systematic uncertainty of {+-}2.1 (systematic) km s{sup -1} Mpc{sup -1}, corresponding to a 2.8% systematic uncertainty in the Hubble constant. This result, in combination with WMAP7 measurements of the cosmic microwave background anisotropies and assuming a flat universe, yields a value of the equation of state for dark energy, w{sub 0} = -1.09 {+-} 0.10. Alternatively, relaxing the constraints on flatness and the numbers of relativistic species, and combining our results with those of WMAP7, Type Ia supernovae and baryon acoustic oscillations yield w{sub 0} = -1.08 {+-} 0.10 and a value of N{sub eff} = 4.13 {+-} 0.67, mildly consistent with the existence of a fourth neutrino species.

• OSTI ID: 22092105
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 758; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
ASTRONOMY
ASTROPHYSICS
BARYONS
CEPHEIDS
COSMOLOGY
EQUATIONS OF STATE
LUMINOSITY
MAGELLANIC CLOUDS
MILKY WAY
NEUTRINOS
NONLUMINOUS MATTER
OSCILLATIONS
RED SHIFT
RELATIVISTIC RANGE
RELICT RADIATION
SUPERNOVAE
TELESCOPES
UNIVERSE