Carnegie Hubble Program: A Mid-Infrared Calibration of the Hubble Constant

Abstract

Using a mid-infrared calibration of the Cepheid distance scale based on recent observations at 3.6 µm 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 µm data for ten high-metallicity, Milky Way Cepheids having independently-measured trigonometric parallaxes. We have adopted the slope of the PL relation using time-averaged 3.6 µm 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 0 , also taking into account new data over the past decade. In combination with the new Spitzer calibration, the systematic uncertainty in H 0 over that obtained by the Hubble Space Telescope (HST) 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 0 = 74.3 with a systematic uncertainty of ± 2.1 (systematic) km s −1 Mpc −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 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 yields w 0 = -1.08 ± 0.10 and a value of N ef f = 4.13 ± 0.67, mildly consistent with the existence of a fourth neutrino species.

Observational probes of cosmic acceleration

“…Suyu et al (2012a) infer H 0 from gravitational lens time delays for two well constrained systems, an approach that sidesteps the traditional distance ladder entirely (see §7.10 for further discussion). These four recent H 0 determinations (Riess et al 2011;Freedman et al 2012;Sorce et al 2012;Suyu et al 2012a) agree with each other to better than 2%. While the data used for the first three are only partly independent, this level of consistency is nonetheless an encouraging indicator of the maturity of the field.…”

“…Prominent examples include the supernova and weak lensing programs of the CFHT Legacy Survey (CFHTLS; Conley et al 2011;Semboloni et al 2006a;Heymans et al 2012b), the ESSENCE supernova survey (Wood-Vasey et al, 2007), BAO measurements from the Sloan Digital Sky Survey (SDSS; Eisenstein et al 2005;Percival et al 2010;Padmanabhan et al 2012), and the SDSS-II supernova survey . These have been complemented by extensive multi-wavelength studies of local and high-redshift supernovae such as the Carnegie Supernova Project (Hamuy et al, 2006;Freedman et al, 2009), by systematic searches for z > 1 supernovae with Hubble Space Telescope Suzuki et al, 2012), by dark energy constraints from the evolution of X-ray or optically selected clusters (Henry et al, 2009;Vikhlinin et al, 2009;Rozo et al, 2010), by improved measurements of the Hubble constant (Riess et al, , 2011Freedman et al, 2012), and by CMB data from the WMAP satellite (Bennett et al, 2003;Larson et al, 2011) and from ground-based experiments that probe smaller angular scales. 4 Most data remain consistent with a spatially flat universe and a cosmological constant with Ω Λ = 1 − Ω m ≈ 0.75, with an uncertainty in the equation-of-state parameter w that is roughly ±0.1 at the 1 − 2σ level.…”

“…A number of subsequent developments have allowed substantial improvements in the measurement of H 0 (see Riess et al 2009Riess et al , 2011Freedman and Madore 2010;Freedman et al 2012). The recent determination of H 0 = 73.8 ± 2.4 km s −1 Mpc −1 by Riess et al (2011) yields a 1σ uncertainty of only 3.3%, including all identified sources of systematic uncertainty and calibration error.…”

“…Monson et al (2012) calibrate the 3.6µm P − L zero-point against Galactic Cepheid samples, including the Benedict et al (2007) parallax sample, and thereby infer the distance modulus to the LMC as a test of the optical Cepheid P − L relation and its metallicity correction. Freedman et al (2012) use these Milky Way parallaxes to calibrate the optical Cepheid P − L relation and then recalibrate the Key Project data set to infer H 0 ; this determination still relies on optical, WFPC2 Cepheid data (and the associated metallicity corrections and flux and color zero-point uncertainties), and the Key Project SN Ia calibrator sample includes several SNe with photographic photometry or high extinction. Sorce et al (2012) use the Tully-Fisher (1977) relation in the Spitzer 3.6µm band, normalized to the Monson et al (2012) LMC distance, to recalibrate the SN Ia absolute magnitude scale and thereby infer H 0 .…”

Measurement of the cosmological distance scale using X-ray and Sunyaev–Zel'dovich effect observations of galaxy clusters

“…To avoid effects from cool cores in clusters, we repeated this analysis excluding the central 100 kpc from the X-ray data, and find H 0 = 77.6 +4.8 −4.3 +10.1 −8.2 km s −1 Mpc −1 . This measurement of the Hubble constant for a dark-energy-dominated concordance cosmology (e.g., Komatsu et al 2011) is in agreement with the Hubble Space Telescope Key project measurements (e.g., Freedman et al 2001Freedman et al , 2012. fig.…”