For refcode 2000ApJ...530..625T: Retrieve 10 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by American Astronomical Society.
Reproduced by permission
2000ApJ...530..625T
The Surface Brightness Fluctuation Survey of Galaxy Distances. II.
Local and LargeScale Flows
John L. Tonry
Institute for Astronomy, University of Hawaii, Honolulu, HI 96822;
jt@ifa.hawaii.edu, jt@ifa.hawaii.edu
John P. Blakeslee
Department of Astronomy, MS 10524, California Institute of Technology,
Pasadena, CA 91125; john@arneb.mit.edu
Edward A. Ajhar
Kitt Peak National Observatory, National Optical Astronomy
Observatories, P.O. Box 26732, Tucson, AZ 85726; ajhar@noao.edu
and
Alan Dressler
Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101;
dressler@omega.ociw.edu
Received 1999 July 2; accepted 1999 October 6
ABSTRACT
We present results from the Surface Brightness Fluctuation (SBF) Survey
for the distances to 300 earlytype galaxies, of which approximately half
are ellipticals. A modest change in the zero point of the SBF relation,
derived by using Cepheid distances to spirals with SBF measurements, yields
a Hubble constant H_0_ = 77 +/ 4 +/ 7 km s^1^ Mpc^1^, somewhat larger
than the HST Key Project result. We discuss how this difference arises from
a different choice of zero point, a larger sample of galaxies, and a
different model for largescale flows. Our result is 4% larger than found
in a recent comparison of the SBF Survey peculiar velocities with
predictions derived from the galaxy density field measured by redshift
surveys (Blakeslee et al. 1999b). The zero point of the SBF relation is the
largest source of uncertainty, and our value for H_0_ is subject to all the
systematic uncertainties of the Key Project zero point, including a 5%
decrease if a metallicity correction for the Cepheids is adopted. To
analyze local and largescale flowsdepartures from smooth Hubble flowwe
use a parametric model for the distribution function of mean velocity and
velocity dispersion at each point in space. These models include a uniform
thermal velocity dispersion and spherical attractors whose position,
amplitude, and radial shape are free to vary. Our modeling procedure
performs a maximum likelihood fit of the model to the observations. Our
models rule out a uniform Hubble flow as an acceptable fit to the data.
Inclusion of two attractors, one of which having a bestfit location
coincident with the Virgo cluster and the other having a fit location
slightly beyond the Centaurus clusters (which we refer to by convention as
the Great Attractor), reduces {chi}^2^/N from 2.1 to 1.1. The fits to these
attractors both have radial profiles such that v ~ r^1^ (i.e., isothermal)
over a range of overdensity between about 10 and 1, but fall off more
steeply at larger radius. The bestfit value for the smallscale, cosmic
thermal velocity is 180 +/ 14 km s^1^. The quality of the fit can be
further improved by the addition of a quadrupole correction to the Hubble
flow. The dipole velocity offset from the CMB frame for the volume we
survey (amplitude ~150 km s^1^) and the quadrupole may be genuine (though
weak) manifestations of more distant density fluctuations, but we find
evidence that they are more likely due to the inadequacy of spherical
models to describe the density profile of the attractors. The residual
dipole we find is comparable to the systematic error in these simple,
parametrized models; in other words, our survey volume of R < 3000 km s^1^
is, in a mass averaged sense, essentially at rest with respect to the CMB.
This contradicts claims of large amplitude flows in much larger volumes
that include our sample. Our bestfitting model, which uses attenuated
powerlaw mass distributions for the two attractors, has enclosed mass
overdensities at the Local Group of 7 x 10^14^ M_sun_ for the Virgo
Attractor and 9 W 1015 M_sun_ for the Great Attractor. Without recourse to
information about the overdensities of these attractors with respect to the
cosmic mean we cannot provide a good constraint on {OMEGA}M, but our data
do give us accurate measurements in terms of {delta}, the overdensities of
the enclosed masses with respect to the background: {delta} {OMEGA}_M_^2/3^
= 0.33 for the Virgo Attractor and {delta}{OMEGA}_M_^2/3^ = 0.27 for the
Great Attractor.
Subject headings: distance scalegalaxies: clusters: individual (Virgo,
Centaurus)galaxies: distances and redshiftslargescale structure of
universe
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