Motion of the Galaxy and the local group determined from the velocity anisotropy of distant SC I galaxies. II - The analysis for the motion

For an all-sky sample of 96 Sc I-Sc II galaxies, 3500 <V < 6500 km sec `,for which radial velocities and magnitudes have been obtained, the quantity HM=log V -0.2m =log H -0.2M0-5 varies across the sky. The form of the variation is consistent with a motion of the Sun of V0 =600+125 km sec - toward a=32'+20', &= +53'+ 11', (1 = 135', b = -8'), corresponding to a mdtion of the Galaxy and the Local Group of galaxies of VoM=454+125 km sec toward 1=163', b -11'. The mean error arises from the scatter of the data and does not take possible systematic errors into account. The Galaxy is moving almost edge-on; the leading edge is in the anticenter direction. Alternative explanations which might account for the observed anisotropy are examined: (1) that apex galaxies are intrinsically fainter than antapex galaxies; (2) that apex (anticenter) galaxies are more obscured; (3) that the Hubble constant varies by 20% across the sky. Each of these explanations is shown to be less likely than a motion of the observer. It is also demonstrated that a Malmquist bias does not produce the observed anisotropy. Additionally, undetected systematic errors in the magnitude system are probably no larger than 0". 1, so can account for no more than one-fourth of the observed effect. Moreover, 22 nearer galaxies, 1600< V < 3500 km exhibit a more pronounced anisotropy in HM than the sample 3500< V <6500 km . Of the explanations considered above, only a motion of our Galaxy is consistent with the variation in HM observed at both distances. Support for this explanation comes also from a sample of E and 50 galaxies, 3500< V <6500 km (Sandage 1975). After correction for the motion of the observer, the random motions of these Sc galaxies are small, cr(AV) ,,di,I<2O0 km , and the Hubble flow is uniform, cr(AH IH)<0.04.