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Session 13 - Large Scale Structure & Cosmology.
Display session, Monday, January 13
This project is an investigation of the peculiar velocities of elliptical galaxies selected from the new APM South Equatorial Strip Catalog, which fills in the ``missing'' region between the UGC and ESO Catalogs. This strip represents a totally unmapped region in the peculiar velocity field.
The goal of this study is to obtain a clearer picture of the overall flow pattern. One of the keys is measuring velocities of galaxies in directions perpendicular to the direction of the proposed Great Attractor (GA). The sample includes about 300 elliptical galaxies in three pencil-beam-like regions extending out to beyond 15 000 km s^-1; the magnitude limit is b_J = 16.4 mag. One sample region is close to the direction of the bulk flow found by Lauer amp; Postman, and also near to the GA direction. The second region is perpendicular to the GA direction, and the third is on the opposite side of the sky. From motions in these three particularly interesting directions, a better understanding of large-scale flows will be possible.
R-band CCD images and high-resolution spectra (with S/N \sim 25) of the sample galaxies have been obtained. The photometric parameters were derived using a bulge-plus-disk decomposition technique which includes corrections for seeing effects. The spectroscopic data were analyzed to measure the redshift, central velocity dispersion, and line strengths for each galaxy.
The D_n -- \sigma relation and Fundamental Plane analysis are being used to determine distances, with the Coma cluster as distance calibrator. Careful consideration is being given to the various biases involved; the analysis includes corrections for selection effects and Malmquist bias.
The peculiar velocity field can be compared with the density field of galaxies as determined from redshift surveys, to constrain the value of the cosmological density parameter Ømega.
Program listing for Monday