For refcode 1994ApJ...426..473L: Retrieve 45 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by American Astronomical Society.
Reproduced by permission
1994ApJ...426..473L
MEASURING THE HUBBLE CONSTANT AND OUR VIRGOINFALL
VELOCITY INDEPENDENTLY
NANYAO Y. LU AND E. E. SALPETER
Center for Radiophysics and Space Research, Cornell University,
Ithaca, NY 14853;
lu@ipac.caltech.edu, hann@astrosun.tn.cornell.edu
AND
G. LYLE HOFFMAN
Department of Physics, Lafayette College, Easton, PA 18042;
hoffmang@astro.phys.lafayette.edu
Received 1993 June 16; accepted 1993 November 11
ABSTRACT
A sample of spiral galaxies with B_T_ < 14.5 located in two local
volumes, one in the direction of, but behind, the Virgo Cluster (behind
Virgo volume [BV]) and the other in the opposite direction (antiVirgo
volume [AV]), were used via a TullyFisher (TF) relation to derive the
following two parameters: H_AB_, the mean Hubble ratio between AV and BV,
and {DELTA}{nu}_parallel_, the peculiar velocity of the Local Group in
the direction of the Virgo Cluster (VC) with respect to a uniformly
expanding reference system defined by our AV and BV subsamples. The two
sampled volumes, separated by a velocity interval of 5600 km s^1^, form
an antipodal pair. This particular geometry not only allows us to derive
the two parameters independently but also reduces the dynamical effect of
the Local Supercluster on H_AB_ without increasing the Malmquist bias.
By limiting our sample to spiral galaxies having large velocity widths
W_R_, we effectively reduce the TF scatter and Malmquist bias in our
sample. The TF zero point and dispersion were then determined by further
correcting for the small residual Malmquist bias. An additional sample of
fainter galaxies was used to test for a nonGaussian tail to the TF
dispersion. We found no evidence for such a tail and formally give an
upper limit of about 18% for the fractional contribution of an unseen
tail. The average intrinsic TF dispersion for the dominant Gaussian
component is {sigma}_TF_^0^~0.33 mag for W_R_ ~> 180 km s^1^.
Our numerical results are {DELTA}{nu}_parallel_~ 414 +/ 82 km s^1^
and H_AB_ ~(84.0 +/ 2.4)(1 + {epsilon}) km s^1^ Mpc^1^, where (1 +
{epsilon}) accounts for any systematic error between the calibrators and
the sample galaxies. Various dynamical models were tested to explore the
effect on H_AB_ of the uncertainties in the local velocity field.
Constrained by our observed {DELTA}{nu}_parallel_ as well as other
observational quantities, we found that the rms deviation from unity of
H_AB_/H_0_ (where H_0_ is the Hubble constant for each model) is 5%,
making H_AB_ a good indicator for H_0_. Taking this variation as an
additional error, our formal estimate for the Hubble constant is
H_0_ ~ (84 +/ 5)(1 + {epsilon}) km s^1^ Mpc^1^.
Subject headings: cosmology: observations  distance scale  galaxies:
distances and redshifts  radio lines: galaxies
Retrieve 45 NED objects in this reference. Please click here for ADS abstract
