Clustering at High Redshift: Precise Constraints from a Deep, Wide‐Area Survey

Abstract

We present constraints on the evolution of large-scale structure from a catalog of 710,000 galaxies with I AB ≤ 24 derived from a KPNO 4m CCD imaging survey of a contiguous 4 • × 4 • region. The advantage of using large contiguous surveys for measuring clustering properties on even modest angular scales is substantial: the effects of cosmic scatter are strongly suppressed. We provide highly accurate measurements of the two-point angular correlation function, ω(θ), as a function of magnitude on scales up to 1.5 • . The amplitude of ω(θ) declines by a factor of ∼ 10 over the range 16 ≤ I ≤ 20 but only by a factor of 2 − 3 over the range 20 < I ≤ 23. For a redshift dependence of the spatial correlation function, ξ(r), parameterized as ξ(r, z) = ( r ro ) −γ (1 + z) −(3+ǫ) , we find r o = 5.2 ± 0.4h −1 Mpc, and ǫ > ∼ 0 for I ≤ 20. This is in good agreement with the results from local redshift surveys. At I > 20, our best fit values shift towards lower r o and more negative ǫ. A strong covariance between r o and ǫ prevent us from rejecting ǫ > 0 even at faint magnitudes but if ǫ > 1, we strongly reject r o < ∼ 4h −1 Mpc (co-moving). The above expression for ξ(r, z) and our data give a correlation length of r o (z = 0.5) ≈ 3.0± 0.4h −1 Mpc, about a factor of 2 larger than the correlation length at z = 0.5 derived from the Canada-France Redshift Survey (CFRS; Le Fevre et al. (1996)). The small volume sampled by the CFRS and other deep redshift probes, however, make these spatial surveys strongly susceptible to cosmic scatter and will tend to bias their derived correlation lengths low. Our results are consistent with redshift distributions in which ∼ 30 − 50% of the galaxies at I = 23 lie at z > 1. The best fit power law slope of the correlation function remains independent of I magnitude for I ≤ 22. At fainter limits, there is a suggestive trend towards flatter slopes that occurs at fluxes consistent with similar trends seen by Neuschaffer & Windhorst (1995) and Campos et al. (1995). The galaxy counts span 11 magnitudes and provide an accurate calibration of the galaxy surface density. We find evidence for mild galaxy evolution -about 1 mag of brightening or a doubling of the density by I = 23 relative to an Ω o = 1 no evolution model; about 0.5 mag of brightening or a factor of 1.5 increase in surface density relative to an open model. Our galaxy counts agree well with those from the HDF survey and, thus, argue against a significant inclusion of sub-galactic components in the latter census for I < 24.

The Evolution of Galaxies in X‐Ray–luminous Groups

“…We note, however, that within a radius of 375 h À1 70 kpc the average density of our groups is 17 galaxies h 2 70 Mpc À2 , and in the annulus between 375 and 700 h À1 70 kpc this density is 1 galaxy h 2 70 Mpc À2 . These numbers were derived to the same limiting magnitude used by other studies (M V ¼ À20:4 for H 0 ¼ 50 km s À1 Mpc À1 ; Dressler et al 1997) and using the background number counts from Postman et al (1998a). Considering instead the two lowest redshift groups, RX J0720+71 and RX J1256+25, for which we have nearly complete spectroscopy at all radii and utilizing the spectroscopically confirmed members, the average galaxy densities are similar at 14 galaxies h 2 70 Mpc À2 (R 375 h À1 70 kpc) and 3.7 galaxies h 2 70 Mpc À2 (375 h À1 70 kpc < R 700 h À1 70 kpc).…”

A Deep Wide-Field, Optical, and Near-Infrared Catalog of a Large Area around the Hubble Deep Field North

“…Postman et al (1998) have looked at the clustering of galaxies using the two-point correlation function of galaxies projected on the sky. This work covered 16 deg 2 in I band.…”

Observational Constraints on Higher Order Clustering up toz≃ 1

“…Several deep surveys have been used to study the evolution of loworder galaxy clustering (Lilly et al 1995 ;Le Fevre et al 1995 ;Neuscha †er & Windhorst 1995 ;Campos et al 1995 ;Connolly et al 1996 ;Lidman & Peterson 1996 ;Woods & Fahlman 1997 ;Connolly, Szalay, & Brunner 1998), but most su †er from insufficient contiguous area and are therefore barely large enough to measure the two-point correlation function. The Deeprange survey (Postman et al 1998 ; hereafter Paper I) was designed to study the evolution of clustering out z D 1. The resulting catalog contains D710,000 galaxies with derived from a Kitt Peak I AB ¹ 24 National Observatory (KPNO) 4 m CCD imaging survey of a contiguous 4¡ ] 4¡ region.…”