The realspace correlation function measured from the APM Galaxy Survey
Abstract
We present a determination of the realspace galaxy correlation function, xi(r), for galaxies in the APM Survey with 17<=b_J<=20. We have followed two separate approaches, based upon a numerical inversion of Limber's equation. For Omega=1 and clustering that is fixed in comoving coordinates, the correlation function on scales <e1>r<=</e1>4 h^1 Mpc is well fitted by a power law xi(r)=(r/4.5)^1.7. There is a shoulder in xi(r) at 4<=<e1>r<=</e1>25 h^1 Mpc, with the correlation function rising above the quoted power law, before falling and becoming consistent with zero on scales r>=40 h^1 Mpc. The shape of the correlation function is unchanged if we assume that clustering evolves according to linear perturbation theory; the amplitude of xi(r) increases, however, with r_0=5.25 h^1 Mpc. We compare our results against an estimate of the realspace xi(r) made by Loveday et al. from the StromloAPM Survey, obtained using a crosscorrelation technique. We examine the scaling with depth of xi(r), in order to make a comparison with the shallower StromloAPM Survey and find that the changes in xi(r) are within the 1sigma errors. The estimate of xi(r) that we obtain is smooth on large scales, allowing us to estimate the distortion in the redshiftspace correlation function of the StromloAPM Survey caused by galaxy peculiar velocities on scales where linear perturbation theory is only approximately correct. We find that beta=Omega^0.6/b=0.61 with the 1sigma spread 0.38<=beta<=0.81, for Omega=1 and clustering that is fixed in comoving coordinates; b is the bias factor between fluctuations in the density and the light. For clustering that evolves according to linear perturbation theory, we recover beta=0.20 with 1sigma range 0.02<=beta<=0.39. We rule out beta=1 at the 2sigma level. This implies that if Omega=1, the bias parameter must have a value <e1>b<~</e1>1 on large scales, which disagrees with the higher order moments of counts measured in the APM Survey (Gaztanaga).
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 1996
 DOI:
 10.1093/mnras/280.1.267
 arXiv:
 arXiv:astroph/9512011
 Bibcode:
 1996MNRAS.280..267B
 Keywords:

 SURVEYS;
 GALAXIES: CLUSTERS: GENERAL;
 DARK MATTER;
 LARGESCALE STRUCTURE OF UNIVERSE;
 Astrophysics
 EPrint:
 Accepted for publication in MNRAS. 11 pages uuencoded posctscript, containing 9 figures