The two-point correlation function and morphological segregation in the Optical Redshift Survey

Abstract

We study the clustering of galaxies in real and redshift space using the Optical Redshift Survey (ORS). We estimate the two point correlation function in redshift space, $ξ(s)$, for several subsamples of ORS, spanning nearly a factor of 30 in volume and detect significant variations in $ξ(s)$ among the subsamples covering small volumes. For volumes \gtsima $(75 h^{-1} {\rm Mpc})^{3}$ the ORS subsamples present very similar clustering patterns. Powerlaw fits to $ξ(s)$ give best-fit values in the range $1.5 \leq γ_{s} \leq 1.7 $ and $6.5 \leq s_{0} \leq 8.8 h^{-1}$ Mpc for several samples extending to redshifts of 8000 km s$^{-1}$. We find that $ξ(s)$ is larger for the magnitude-limited sample than for diameter-limited one within a radius of 4000 km s$^{-1}$. We interpret this as an indirect result of morphological segregation coupled with differences in morphological mix. We split ORS into morphological subsamples and confirm the existence of morphological segregation of galaxies out to scales of $s \sim 10 h^{-1}$ Mpc. Our results indicate that the relative bias factor between early type galaxies and late-types may be weakly dependent on scale. If real, this would suggest non-linear biasing. We also compute correlations as a function of radial and projected separations, $ξ(r_p, π)$ and derive the real space correlation function, $ξ(r)$. The results obtained in real space confirm those found using $ξ(s)$.