Tully-Fisher distances and motions in the northern sky

Details Tully-Fisher distances and motions in the northern sky Tully-Fisher distances and motions in the northern sky

Aug 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt.........5c&link_type=abstract

Ph.D. Thesis California Univ., Santa Cruz.

Physics

57

Galaxies, Northern Sky, Universe, Brightness, Distance, Galactic Rotation, Gravitational Collapse, Magnitude, Red Shift, Velocity Distribution

Scientific paper

The results of a study to test for large-scale velocity deviations in a uniformly expanding universe are presented. At the onset of this work, galaxy motions in the northern hemisphere, contrary to the impressive sky coverage in the south, were still very poorly mapped. To improve on this situation, we identified a well-defined sample of 380 northern Sb-Sc UGC spirals in the range of 2000-10000 km sec-1. Distances are estimated using the Tully-Fisher relation but with rotation velocities measured from long slit spectra in lieu of 21 cm delta V's. Surface brightness profiles and total magnitudes are extracted for 820 r-band images, and (H alpha + (NII)) rotation curves, fluxes, and rotation profiles are measured from 450 red spectra. The galaxy magnitudes are accurate internally to plus or minus 0m022 and the delta V's agree internally to plus or minus 12 km s-1. A tight linear correlation of optical versus radio velocity widths with a scatter of 25 km s-1 is also derived. We find evidence for large-scale motions near the concentration of Perseus-Pisces (PP), but identify a vast region of unperturbed, quiet Hubble flow (QHF) perpendicular to PP. The peculiar velocity (PV) data are corrected for uniform density Malmquist bias when they are analyzed in estimated distance space; an empirical correction for selection effects mainly due to magnitude cutoff is derived from the QHF region and applied to the PVs in redshift space. Both analyses are consistent in showing the PP Supercluster as streaming in bulk towards the Local Group at 392 plus or minus 79 km s-1 (with respect to the microwave background restframe). The cause for such motion remains undetermined. Gravitational collapse within PP is detected, but the statistical error is large. An emerging picture of large-scale velocity fields shows the main infall regions to be correlated with the observed clumpiness of luminous matter. Our data, combined with published PV surveys, provide strong support for the existence of low-amplitude perturbations in the universe on scales not yet probed by current samples (approxmately greater than 120h-1Mpc). The implications of cosmic bulk motions with such large coherence lengths pose a serious challenge for models of generation of structure in the universe.

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