THE MOTION OF THE LOCAL GROUP WITH RESPECT TO THE 15,000-KILOMETER-PER-SECOND ABELL CLUSTER INERTIAL FRAME

We have measured the velocity of the Local Group with respect to an in ertial frame defined by the 119 Abell and Abell, Corwin, & Olowin (ACO ) clusters contained within 15,000 km s(-1). The observations consist of a full-sky peculiar velocity survey with an effective depth ranging from 8000 to 11,000 km s(-1), depending on how the observations are w eighted with redshift. This is the deepest peculiar velocity survey ye t conducted. Clusters are selected by heliocentric redshift, and the s ample is volume-limited. We use the Hoessel (1980) relationship betwee n the metric luminosities of the brightest clusters galaxies (BCGs) an d the slope of their brightness profiles as the distance indicator. Th e Cousins R-band luminosity within a metric radius of 10 h(-1) kpc yie lds a typical distance error of 16% for a single BCG. We test for conv ergence of the local flow on scales within 10,000 km s(-1) (i.e., alig nment of the Local Group velocity vector with the cosmic microwave bac kground [CMB] dipole), but we find that our sample is not at rest with respect to the CMB. The velocity of the local Group relative to the A bell cluster sample is 561 +/- 284 km s(-1) toward l = 220 degrees, b = -28 degrees (+/-27 degrees), using optimal redshift weighting. This vector is inconsistent with the Local Group absolute space velocity in ferred from the CMB dipole anisotropy at 99.99% confidence. An extensi ve error analysis has been conducted to validate this result. The resu lt is extremely robust and is insensitive to Galactic extinction, velo city biases, sample composition, and geometry. If the CMB dipole is ki nematic in origin, then this result implies that the Abell cluster fra me itself is moving at 689 +/- 178 km s(-1) toward l = 343 degrees, b = +52 degrees (+/-23 degrees), and that the CMB dipole is generated la rgely by mass concentrations beyond 100 h(-1) Mpc.