224 research outputs found
From Spitzer Galaxy Photometry to Tully-Fisher Distances
This paper involves a data release of the observational campaign: Cosmicflows
with Spitzer (CFS). Surface photometry of the 1270 galaxies constituting the
survey is presented. An additional ~ 400 galaxies from various other Spitzer
surveys are also analyzed. CFS complements the Spitzer Survey of Stellar
Structure in Galaxies, that provides photometry for an additional 2352
galaxies, by extending observations to low galactic latitudes (|b|<30 degrees).
Among these galaxies are calibrators, selected in K band, of the Tully-Fisher
relation. The addition of new calibrators demonstrate the robustness of the
previously released calibration. Our estimate of the Hubble constant using
supernova host galaxies is unchanged, H0 = 75.2 +/- 3.3 km/s/Mpc.
Distance-derived radial peculiar velocities, for the 1935 galaxies with all the
available parameters, will be incorporated into a new data release of the
Cosmicflows project. The size of the previous catalog will be increased by 20%,
including spatial regions close to the Zone of Avoidance.Comment: Accepted for publication in MNRAS, 16 pages, 14 figures, 6 table
Action Principle Solutions For Galaxy Motions Within 3000 Km/s
The numerical action variational principle is used to find fully nonlinear
solutions for the orbits of the mass tracers given their present redshifts and
angular positions and the cosmological boundary condition that the peculiar
velocities are small at high redshift. A solution predicts the distances of the
mass tracers, and is tested by a comparison with measured distances. The
current numerical results use 289 luminosity-linewidth distance measurements
designed to be close to unbiased. A catalog of 1138 tracers approximates the
luminosity distribution of galaxies in the vicinity of the Local Supercluster,
at redshifts cz < 3000 km/s. These mass tracers include groups with crossing
times less than the Hubble time and isolated galaxies. The measure of merit of
a solution is the sum of the mean square differences between the predicted and
observed distance moduli. In the 3000 km/s sample, this reduced
statistic has a well-defined minimum value at M/L=175 and Gyr, and
at the minimum is about 1.29 times the value expected from just the
standard deviation of the distance measurements. We have tested for the effect
of the mass at greater distance by using the positions of Abell clusters as a
model for the large-scale mass distribution. This external mass model reduces
the minimum value of by about 10\% (). The value of the
cosmological density parameter is determined by the global mean
mass-to-light ratio. Our preliminary analysis yields
at one standard deviation. A tighter bound is expected to come out of a larger
sample of measured distances now available.Comment: Replaced with shorter record size for machines with limits set by
their maile
Associations of Dwarf Galaxies
Hubble Space Telescope Advanced Cameras for Surveys has been used to
determine accurate distances for 20 galaxies from measurements of the
luminosity of the brightest red giant branch stars. Five associations of dwarf
galaxies that had originally been identified based on strong correlations on
the plane of the sky and in velocity are shown to be equally well correlated in
distance. Two more associations with similar properties have been discovered.
Another association is identified that is suggested to be unbound through tidal
disruption. The associations have the spatial and kinematic properties expected
of bound structures with 1 - 10 x 10^11 solar mass. However, these entities
have little light with the consequence that mass-to-light ratios are in the
range 100 - 1000 in solar units. Within a well surveyed volume extending to 3
Mpc, all but one known galaxy lies within one of the groups or associations
that have been identified.Comment: 50 pages, 2 tables, 15 encapsulated figures, 1 (3 part) jpg figure.
Submitted to Astronomical Journa
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