Mathematics – Logic
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt........39s&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF CALIFORNIA, BERKELEY, 1995.Source: Dissertation Abstracts International, Volume: 57-03, Section: B
Mathematics
Logic
16
Large Scale Structure
Scientific paper
The peculiar velocities of 140 IRAS-selected, spiral galaxies are presented using the Tully-Fisher (TF) relation between luminosity and rotation width. Luminosities were measured in the Johnson V and Kron-Cousins I bandpasses. Rotation widths were measured from the profile of the H alpha emission line. Every effort was made to minimize spatially-coherent systematic errors that can mimic spatially-coherent velocity flows. To minimize the effects of Galactic extinction, we present a new method of deriving this extinction from the COBE DIRBE infrared emission and APM galaxy number counts. Our final galaxy sample is volume-limited to 40h^{-1 }Mpc and extends to within 10^ circ of the Galactic plane. The velocities are compared on a point-by-point basis to those predicted from the density map of the IRAS 1.2 Jy galaxy survey. The comparison yields the constraint beta=Omega_sp{0}{0.6 }/b=0.38_sp{-0.15}{+0.29} (95% C.L.), where Omega_0 is the density parameter of the universe and b is the bias of IRAS galaxies relative to the underlying mass. For any cosmological model with Omega _0=1, this implies that the density fluctuations in IRAS galaxies are 2.6 times that of the underlying mass. If the galaxies trace the mass without bias (b = 1), then the universe is open with Omega=0.20_sp {-0.11}{+0.29}. Some features of our peculiar velocity field are in disagreement with the IRAS predictions. The most pronounced discrepancy appears in the Hydra-Centaurus region where we observe a more pronounced infall than that predicted by IRAS. Our results yield new insight into the nature of the Tully-Fisher relation. A third parameter has been used implicitly in all previous TF studies. This parameter is the isophotal radius at which the rotation velocity is measured. Fitting the rotation profiles beyond this isophotal radius only increases the scatter in the luminosity -line width relation. Finally, the TF scatter for IRAS -selected galaxies is larger than from most optically-selected samples. The dispersion is 0.50 in magnitude or 0.10 in the logarithm of the rotation width. This may represent the true scatter in the TF relation, as no correlation with other galaxy properties can be identified.
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