The LCO/Palomar 10,000 km/sec Cluster Survey. II. Constraints on Large-Scale Streaming

Abstract

The LCO/Palomar 10,000 km/sec (LP10K) Tully-Fisher (TF) data set is used to test for bulk streaming motions on a ~150 Mpc scale. The sample consists of 172 cluster galaxies in the original target range of the survey, 9000-13,000 km/sec, plus an additional 72 galaxies with cz < 30,000 km/sec. A maximum-likelihood analysis that is insensitive to Malmquist and selection bias effects is used to constrain the bulk velocity parameters, and realistic Monte-Carlo simulations are carried out to correct residual biases and determine statistical errors. When the analysis is restricted to the original target range, the bias-corrected bulk flow is v_B=720 +/- 280 km/sec toward l=266, b=19. When all objects out to z=0.1 are included the result is virtually unchanged, v_B=700 +/- 250 km/sec toward l=272, b=10. The hypothesis that the Hubble flow has converged to the CMB frame at distances less than ~ 100 Mpc is ruled out at the 97% confidence level. The data are inconsistent with the flow vector found by Lauer & Postman. However, the LP10K bulk flow is consistent with that obtained from the SMAC survey of elliptical galaxies recently described by Hudson et al. If correct, the LP10K results indicate that the convergence depth for the Hubble flow is >~ 150 Mpc.