57 research outputs found
SFI++ I: A New I-band Tully-Fisher Template, the Cluster Peculiar Velocity Dispersion and H0
The SFI++ consists of ~5000 spiral galaxies which have measurements suitable
for the application of the I-band Tully-Fisher (TF) relation. This sample
builds on the SCI and SFI samples published in the 1990s but includes
significant amounts of new data as well as improved methods for parameter
determination. We derive a new I-band TF relation from a subset of this sample
which consists of 807 galaxies in the fields of 31 nearby clusters and groups.
This sample constitutes the largest ever available for the calibration of the
TF template and extends the range of line-widths over which the template is
reliably measured. Careful accounting is made of observational and sample
biases such as incompleteness, finite cluster size, galaxy morphology and
environment. We find evidence for a type-dependent TF slope which is shallower
for early type than for late type spirals. The line-of-sight cluster peculiar
velocity dispersion is measured for the sample of 31 clusters. This value is
directly related to the spectrum of initial density fluctuations and thus
provides an independent verification of the best fit WMAP cosmology and an
estimate of Omega^0.6 sigma_8 = 0.52+/-0.06. We also provide an independent
measure of the TF zeropoint using 17 galaxies in the SFI++ sample for which
Cepheid distances are available. In combination with the ``basket of clusters''
template relation these calibrator galaxies provide a measure of H0 = 74+/-2
(random) +/-6 (systematic) km/s/Mpc.Comment: Accepted by ApJ (scheduled for 20 Dec 2006, issue 653). 21 pages (2
column emulateapj) including 12 figures. Version 2 corrects typos and other
small errors noticed in proof
SFI++ II: A New I-band Tully-Fisher Catalog, Derivation of Peculiar Velocities and Dataset Properties
We present the SFI++ dataset, a homogeneously derived catalog of photometric
and rotational properties and the Tully-Fisher distances and peculiar
velocities derived from them. We make use of digital optical images, optical
long-slit spectra, and global HI line profiles to extract parameters of
relevance to disk scaling relations, incorporating several previously published
datasets as well as a new photometric sample of some 2000 objects. According to
the completeness of available redshift samples over the sky area, we exploit
both a modified percolation algorithm and the Voronoi-Delaunay method to assign
individual galaxies to groups as well as clusters, thereby reducing scatter
introduced by local orbital motions. We also provide corrections to the
peculiar velocities for both homogeneous and inhomogeneous Malmquist bias,
making use of the 2MASS Redshift Survey density field to approximate large
scale structure. We summarize the sample selection criteria, corrections made
to raw observational parameters, the grouping techniques, and our procedure for
deriving peculiar velocities. The final SFI++ peculiar velocity catalog of 4861
field and cluster galaxies is large enough to permit the study not just of the
global statistics of large scale flows but also of the {\it details} of the
local velocity field.Comment: 14 pages, 6 figures, 4 external online tables, accepted for
publication in ApJ
The Arecibo Legacy Fast ALFA Survey: X. The HI Mass Function and Omega_HI From the 40% ALFALFA Survey
The Arecibo Legacy Fast ALFA (ALFALFA) survey has completed source extraction
for 40% of its total sky area, resulting in the largest sample of HI-selected
galaxies to date. We measure the HI mass function from a sample of 10,119
galaxies with 6.2 < log (M_HI/M_Sun) < 11.0 and with well-described mass errors
that accurately reflect our knowledge of low-mass systems. We characterize the
survey sensitivity and its dependence on profile velocity width, the effect of
large-scale structure, and the impact of radio frequency interference in order
to calculate the HIMF with both the 1/Vmax and 2DSWML methods. We also assess a
flux-limited sample to test the robustness of the methods applied to the full
sample. These measurements are in excellent agreement with one another; the
derived Schechter function parameters are phi* = 4.8 (+/- 0.3) * 10^-3, log
(M*/M_Sun) + 2 log(h_70) = 9.96 (+/- 0.2), and alpha = -1.33 (+/- 0.02). We
find Omega_HI = 4.3 (+/- 0.3) * 10^-4, 16% larger than the 2005 HIPASS result,
and our Schechter function fit extrapolated to log (M_HI/M_Sun) = 11.0 predicts
an order of magnitude more galaxies than HIPASS. The larger values of Omega_HI
and of M* imply an upward adjustment for estimates of the detection rate of
future large-scale HI line surveys with, e.g., the Square Kilometer Array. A
comparison with simulated galaxies from the Millennium Run and a treatment of
photoheating as a method of baryon removal from HI-selected halos indicates
that the disagreement between dark matter mass functions and baryonic mass
functions may soon be resolved.Comment: 21 pages, 13 figures, submitted to Ap
A Digital Archive of HI 21 cm Line Spectra of Optically-targeted Galaxies
We present a homogeneous compilation of HI spectral parameters extracted from
global 21 cm line spectra for some 9000 galaxies in the local universe
(heliocentric velocity -200 < V_Sun < 28,000 km/s) obtained with a variety of
large single dish radio telescopes but reanalyzed using a single set of
parameter extraction algorithms. Corrections to the observed HI line flux for
source extent and pointing offsets and to the HI line widths for instrumental
broadening and smoothing are applied according to model estimates to produce a
homogenous catalog of derived properties with quantitative error estimates.
Where the redshift is available from optical studies, we also provide flux
measurements for an additional 156 galaxies classified as marginal HI
detections and rms noise limits for 494 galaxies classified as nondetections.
Given the diverse nature of the observing programs contributing to it, the
characteristics of the combined dataset are heterogeneous, and as such, the
compilation is neither integrated HI line flux nor peak flux limited. However,
because of the large statistical base and homogenous reprocessing, the spectra
and spectral parameters of galaxies in this optically targeted sample can be
used to complement data obtained at other wavelengths to characterize the
properties of galaxies in the local universe and to explore the large scale
structures in which they reside.Comment: 13 pages, 9 figures, 3 external online tables, accepted for
publication in ApJ
Are peculiar velocity surveys competitive as a cosmological probe?
Peculiar velocity surveys, which measure galaxy velocities directly from standard candles in addition to redshifts, can provide strong constraints on the growth rate of structure at low redshift. The improvement originates from the physical relationship between galaxy density and peculiar velocity, which substantially reduces cosmic variance. We use Fisher matrix forecasts to show that peculiar velocity data can improve the growth rate constraints by about a factor of 2 compared to density alone for surveys with galaxy number density of 10(-2) (h(-1) Mpc)(-3), if we can use all the information for wavenumber
- …