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 $\chi^2$ statistic has a well-defined minimum value at M/L=175 and $t_0 = 10.0$ Gyr, and $\chi^2$ 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 $\chi^2$ by about 10\% ($\sim 1 \sigma$). The value of the cosmological density parameter $\Omega_0$ is determined by the global mean mass-to-light ratio. Our preliminary analysis yields $\Omega_0= 0.17 \pm 0.10$ 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