THE LINEARITY OF THE COSMIC EXPANSION FIELD FROM 300 TO 30,000 km s{sup -1} AND THE BULK MOTION OF THE LOCAL SUPERCLUSTER WITH RESPECT TO THE COSMIC MICROWAVE BACKGROUND

• Published in: The Astrophysical journal 2010-05, Vol.714 (2)
• Main Authors: Sandage, A., Reindl, B., Tammann, G. A.
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BACKGROUND RADIATION; BINARY STARS; COORDINATES; DIPOLES; ELECTROMAGNETIC RADIATION; ERUPTIVE VARIABLE STARS; EXPANSION; GALAXIES; INTEGRALS; MICROWAVE RADIATION; MULTIPOLES; RADIATIONS; RED SHIFT; RELICT RADIATION; STARS; SUPERNOVAE; VARIABLE STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/714/2/1441

The meaning of 'linear expansion' is explained. Particularly accurate relative distances are compiled and homogenized for (1) 246 Type Ia supernovae and 35 clusters with v < 30, 000 km s{sup -1}, and (2) relatively nearby galaxies with 176 tip of the red-giant branch and 30 Cepheid distances. The 487 objects define a tight Hubble diagram from 300-30, 000 km s{sup -1} implying individual distance errors of {approx_lt}7.5%. Here the velocities are corrected for Virgocentric steaming (locally 220 km s{sup -1}) and-if v{sub 220} > 3500 km s{sup -1}-for a 495 km s{sup -1} motion of the Local Supercluster toward the warm cosmic microwave background (CMB) pole at l = 275, b = 12; local peculiar motions are averaged out by large numbers. A test for linear expansion shows that the corrected velocities increase with distance as predicted by a standard model with q{sub 0} = -0.55 (corresponding to ({Omega}{sub M}, {Omega}{sub {Lambda}} = (0.3, 0.7)), but the same holds-due to the distance limitation of the present sample-for a range of models with q{sub 0} between {approx}0.00 and -1.00. For these models H{sub 0} does not vary systematically by more than {+-}2.3% over the entire range. Local, distance-dependent variations are equally limited to 2.3% on average. In particular, the proposed Hubble Bubble of Zehavi et al. and Jha et al. is rejected at the 4{sigma} level. Velocity residuals in function of the angle from the CMB pole yield a satisfactory apex velocity of 448 {+-} 73 km s{sup -1} and a coherence radius of the Local Supercluster of {approx}3500 km s{sup -1} ({approx}56 Mpc), beyond which galaxies are seen on average at rest in comoving coordinates with respect to the CMB. Since no obvious single accelerator of the Local Supercluster exists in the direction of the CMB dipole, its motion must be due to the integral gravitational force of all surrounding structures. Most of the gravitational dipole probably come from within 5000 km s{sup -1}.