The expansion field: the value of H 0

摘要: Any calibration of the present value Hubble constant (H 0) requires recession velocities and distances galaxies. While conversion observed into true has only a small effect on result, derivation unbiased which rest solid zero point cover useful range about 4–30 Mpc is crucial. A list 279 such galaxy within v < 2,000 km s−1 given are derived from tip red-giant branch (TRGB), Cepheids, and/or supernovae type Ia (SNe Ia). Their random errors not more than 0.15 mag as shown by intercomparison. They trace linear expansion field narrow margins, supported also external evidence, v = 250 to at least 2,000 km s−1. Additional 62 distant SNe Ia confirm linearity 20,000 km The dispersion line dominated peculiar velocities, amounting locally <100 km but increasing outwards. Due H 0 can be found any distance >4.5 Mpc. RR Lyr star-calibrated TRGB 78 galaxies above this limit give 0 = 63.0 ± 1.6 an effective 6 Mpc. compensate motions their large number. Support for result comes 28 independently calibrated Cepheids that 0 = 63.4 ± 1.7 15 Mpc. This agrees with large-scale 0 = 61.2 ± 0.5 distant, Cepheid-calibrated SNe Ia. mean 0 = 62.3 ± 1.3 adopted. Because depends two independent points scale its systematic error estimated 6%. Other determinations discussed. either conform quoted (e.g. width data spirals or D n −σ method E galaxies) judged inconclusive. Typical come use universal, yet unjustified P–L relation neglect selection bias in magnitude-limited samples, they inherent adopted models.