Mathematics – Logic
Scientific paper
Nov 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990mnras.247....1r&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Vol. 247, NO. 1/NOV1, P. 1, 1990
Mathematics
Logic
179
Scientific paper
We have carried out a sparse-sampled redshift survey of IRAS Point Source Catalog 60-micron sources, at a sampling rate of one in six. For a sample of 2163 sources with S>=0.6 Jy at |b|>10^deg^, we have redshifts for 2093, or 97 per cent. Of the sources, which were selected from the IRAS 60-micron Galaxy Catalogue of Rowan-Robinson et al., 1.2 per cent turned out to be galactic and 0.4 per cent are blank fields. Our survey reaches significantly deeper than the all-sky IRAS galaxy redshift survey of Strauss & Davis, which is complete to 1.94 Jy. We have used these data to investigate the convergence of the IRAS dipole. We find that the peculiar acceleration acting on the Local Group, as measured with IRAS galaxies, is generated within 100h^-1^ Mpc. For d<50h^-1^ Mpc, our estimate of the acceleration generated agrees with that of Strauss & Davis. However, we find that a non-negligible acceleration is generated between 50 and 100h^-1^ Mpc. The direction of the acceleration is consistent, within the uncertainties, with that of the microwave background dipole. The amplitude implies a value for the cosmological density parameter {OMEGA}_0_ = 0.7 (+0.3,-0.2) if the IRAS galaxy distribution traces that of the total mass. If {OMEGA}_0_ = 1, a bias parameter b = 1.23+/-0.23 is inferred. The convergence properties of the dipole are similar to those obtained from random locations in N-body simulations of a cold dark matter universe. Assuming that the IRAS galaxies trace the mass distribution, we predict a peculiar velocity for each galaxy in the survey, by calculating the dipole at each galaxy position, initially assuming distances based on velocities. We then construct a simple analytical model for this flow field, involving 12 massive clusters (including the prominent superclusters within 150h^-1^Mpc) correcting galaxy distances and peculiar velocities in an iterative procedure. The model clusters have large haloes in which the density is proportional to r^-1.6^, extending to at least 30h^-1^Mpc. The model gives an excellent fit for the peculiar velocity of the Local Group inferred from the microwave background dipole and does not require the existence of a hypothetical 'Great Attractor' hidden behind the galactic plane, additional to the Hydra, Centaurus and Pave clusters, and their haloes. The haloes of the prominent nearby clusters merge with each other, so that Virgo, Eridanus-Fornax, Centaurus, Hydra, Pavo and Perseus-Pisces form a single large over-density, which plays a major role in explaining both our motion with respect to the microwave background and the IRAS north-south source-count anisotropy.
Allington-Smith Jeremy
Crawford J. J.
Efstathiou George
Ellis Richard
Frenk Carlos S.
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