The Dipole Anisotropies of the IRAS Galaxies and the Microwave
Background Radiation
- A.
Yahil
- Department of Earth and Space Sciences
- State University of New YorK at Stony Brook
- Stony Brook, NY 11794-2100
- U. S. A.
-
D. W. Walker
and M. Rowan-Robinson
- Theoretical Astronomy Unit
- Queen Mary College
- Mile End Road
- London E1 4NS
- U. K.
Abstract
IRAS 60 micron sources are used to map the local (less than approximately 200
h-1 Mpc) gravitational field, and to determine its dipole
component, on the assumption that the infrared radiation traces the matter.
The dipole moment is found to point in the direction l = 248 +/- 9 and
b = 40 +/- 8, 26 degrees +/- 10 degrees away from the direction of the velocity
of the Local Group relative to the microwave background radiation
(statistical sampling errors only). Comparison of the two anisotropies,
using the luminosity function of the IRAS galaxies and linear
perturbation theory, yields an estimate of the cosmological density parameter,
Omega0 = 0.85 +/- 0.16 (statistical IRAS error only), with
nonlinear effects increasing Omega0 by approximately 0.15%. These
values are in apparent disagreement with the values of Omega0 =
0.1-0.2 deduced from the Virgocentric infall and the cosmic virial theorem.
A. Yahil, D. W. Walker, and M. Rowan-Robinson,
The Dipole Anisotropies of the IRAS Galaxies and the Microwave Background
Radiation, Astrophysical Journal Letters, Vol. 301, L1-L5, 1986.