Kinematics and dynamics in large-scale structure

We study a sample of x-ray observed groups of galaxies to examine the relation between group velocity dispersions and x-ray luminosities. For the rich groups, {dollar}Lsb{lcub}x{rcub}propto sigmasp{lcub}4.0pm0.6{rcub},{dollar} but poorer systems follow a flatter relation. This {dollar}Lsb{lcub}x{rcub}- sigma{dollar} relation probably arises from a combination of extended gas and individual galaxy emission.; We then concentrate on six poor clusters of galaxies with higher-quality x-ray data, and we measure the virial mass, gas mass, and x-ray temperature. From the x-ray surface brightness distribution, we construct models of the mass distribution. We use a modified {dollar}V{dollar}/{dollar}Vsb{lcub}max{rcub}{dollar} test to test whether the galaxies trace the potential marked by the gas. The galaxy distribution is consistent with the density distribution inferred from the x-rays. The mass in galaxies is {dollar}{lcub}sim{rcub}3hsp{lcub}-1{rcub}%{dollar} of the total mass of the systems. Galaxies contribute significantly to the baryonic mass total: {dollar}Msb{lcub}gas{rcub}{dollar}/{dollar}Msb{lcub}gal{rcub}sim1.4hsp{lcub}-1/2{rcub},{dollar} similar to the value for rich clusters. The baryon fraction in rich groups is {dollar}{lcub}sim{rcub}0.08{dollar} (for {dollar}Hsb{lcub}o{rcub}=100),{dollar} about half that in rich clusters. This result has significant implications for the origin of large-scale structure.; In a study of structure on a larger scale, we use the Tully-Fisher (TF) relation to examine the kinematics of the Great Wall of Galaxies. First, we examine the relation between rotation profiles of galaxies and HI linewidths, and investigate the effects on the TF relation. The rotation curve profile shapes and magnitudes of galaxies are correlated, implying that a galaxy yields different distance estimates with a linewidth measured at a different fraction of peak emission. Indiscriminatingly combining data based on different measures of the "rotation velocity" into a single TF relation leads to systematic errors and biases in the velocity field. We evaluate these effects using optical rotation curves and HI linewidth data. The TF relation can be improved by adding shape parameters to characterize the HI profiles.; We construct the I-Band Tully-Fisher Relation (IRTF) for a sample of 172 galaxies in the redshift-vicinity of the Great Wall. We measure isophotal and total I-band magnitudes for the galaxies and HI 20% and 50% linewidths for the galaxies. We construct TF relations from these, with scatter {dollar}sigmasim0.30{dollar}-0.32 Magnitudes. We investigage the effects of extinction on the IRTF. The data are consistent with only a moderate internal extinction.; We analyze the peculiar velocity field mapped by the GW sample spirals. We calculate the best-fit large scale flow: {dollar}vsb{lcub}flow{rcub}sim725{dollar} km s{dollar}sp{lcub}-1{rcub}{dollar} towards {dollar}alpha=174spcirc, delta=37spcirc.{dollar} Because our {dollar}delta{dollar} constraints are weak, this detected flow is consistent with the CMB dipole and with the flow vector from type Ia supernovae. The data are also not inconsistent with the large-scale flow direction reported by Lauer & Postman (1994).; We also present a Monte-Carlo based method for removing sampling biases from a peculiar velociy sample. For the GW sample we consider, the velocity bias is relatively small {dollar}rm(sbsp{lcub}sim{rcub}{lcub}<{rcub}150 km ssp{lcub}-1{rcub}).{dollar} In addition to the peculiar velocity flows, we place constraints on the infall velocity into the Great Wall. The {dollar}2sigma{dollar} upper limit on the infall velocity is {dollar}rm{lcub}sim{rcub}900 km ssp{lcub}-1{rcub}.{dollar}...