The peculiar acceleration of the Local Group as deduced from the optical and IRAS flux dipoles
Open Access
- 1 October 1988
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 234 (3) , 677-701
- https://doi.org/10.1093/mnras/234.3.677
Abstract
We study the relation between the peculiar acceleration of the Local Group and the surface brightness dipole moments of all-sky optical and IRAS samples. Our revised optical dipole lies within 7° of the direction of the Local Group's motion through the Microwave Background Radiation (MBR). The directions of the optical, IRAS and MBR dipoles are all consistent with each other. To analyse the optical dipole we have calculated diameter functions for the UGC and ESO galaxy catalogues from redshift surveys. Most of the optical dipole arises from the Centaurus–Virgo direction and from the ‘Local Void’ on the opposite side of the sky. The sources of the IRAS dipole are more evenly distributed around the sky. A simple ‘shell model’, fitted to the variation of the dipoles as a function of flux, suggests that the dipoles arise from galaxies whose recession velocities are smaller than 4000 km s−1. We find a high γ0 value for the IRAS sample and a low one for the optical sample. These results may be reconciled if the optical galaxy distribution is more biased relative to the matter distribution than the IRAS galaxy distribution.Keywords
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