1999ApJ...527..513K -
Astrophys. J., 527, 513-524 (1999/December-3)
A determination of H0 with the CLASS gravitational lens B1608+656. II. Mass models and the Hubble constant from lensing.
KOOPMANS L.V.E. and FASSNACHT C.D.
Abstract (from CDS):
We present mass models of the four-image gravitational lens system B1608+656, based on information obtained through VLBA imaging, VLA monitoring, and Hubble Space Telescope (HST) WFPC2 and NICMOS imaging. We have determined a mass model for the lens galaxies that reproduces (1) all image positions within the observational errors, (2) two out of three flux-density ratios within about 10% from the observed ratios, and (3) the model time delays within 1% from their observed values, given our best estimate of the Hubble parameter. Using the time delays determined in a companion paper, we also find that the best isothermal mass model gives H0=59+7–6 km.s–1.Mpc–1 for Ωm=1 and ΩΛ=0.0, or H0=(65-63)+7–6 km.s–1.Mpc–1 for Ωm=0.3 and ΩΛ=0.0-0.7. The statistical errors indicate the 95.4% (2 σ) confidence interval. A systematic error of ±15 km.s–1.Mpc–1 is estimated from a 20% (1 σ) uncertainty in the steepness of radial mass profile. This cosmological determination of H0 agrees well with determinations from three other gravitational lens systems (i.e., B0218+357, Q0957+561, and PKS 1830-211), Type Ia supernovae, the Sunyaev-Zeldovich effect and local determinations. The current agreement on H0–within the 1 σ statistical errors–from four of five gravitational lens systems (1) emphasizes the reliability of its determination from isolated gravitational lens systems and (2) suggests that a close-to-isothermal mass profile can describe disk galaxies (e.g., B0218+357 and possibly PKS 1830-211), ellipticals (e.g., B1608+656), and central cluster ellipticals (e.g., Q0957+561). The average of H0 from B0218+357, Q0957+561, B1608+656, and PKS 1830-211, gives HGL0=69±7 km.s–1.Mpc–1 for a flat universe with Ωm=1 or HGL0=74±8 km.s–1.Mpc–1 for Ωm=0.3 and ΩΛ=0.0-0.7. When including PG 1115+080, these values decrease to 64±11 km.s–1.Mpc–1 and 68±13 km s–1.Mpc–1, respectively. The errors are the estimated 2 σ errors on the average. The Hubble parameter from gravitational lenses seems to agree best with local determinations of H0 for a low-density universe, under the assumption that all lenses are nearly isothermal.
Abstract Copyright:
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Journal keyword(s):
Cosmology: Dark Matter - Cosmology: Distance Scale - galaxies: individual (B1608+656) - Cosmology: Gravitational Lensing
Nomenclature:
[KF99] 1608+656 GN (Nos G1-G2).
CDS comments:
Components A to D = [MFD95] 1608+656 A to D.
Simbad objects:
13
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