Strong Clustering of Faint Galaxies at Small Angular Scales

The 2-point angular correlation function of galaxies, \wt, has been computedon equatorial fields observed with the CTIO 4m prime focus, within a total areaof 2.31 deg$^2$. In the magnitude range $19\le m_R \le 21.5$, corresponding to$\approx 0.35$, we find an excess of power in \wt at scales $2''\le\theta\le6''$ over what would be expected from an extrapolation of \wt measured atlarger $\theta$. The significance of this excess is $\approx 5\sigma$. Atlarger scales, $6''< \theta \le 24''$, the amplitude of \wt is 1.6 timessmaller than the standard no evolutionary model. At these scales there isremarkable agreement between the present data and Infante \& Pritchet (1995). At large angular scales ($6''< \theta \le 24''$) the data is best describedby a model where clustering evolution in $\xi(r,z)$ has taken place. Strongluminosity evolution cannot be ruled out with the present data. At smallerscales, $2''\le \theta \le 6''$, our data are formally fit by models where$\epsilon=-2.4 (\Omega=0.2, r_o=5.1h^{-1}$Mpc) or $r_o = 7.3h^{-1}$Mpc$(\Omega=0.2, \epsilon=0)$. If the mean redshift of our sample is 0.35 then ourdata show a clear detection of the scale ($\approx 19h^{-1}kpc$) where theclustering evolution approaches a highly non linear regime, i.e., $\epsilon \le0$. The rate at which galaxies merge has been computed. If this rate isproportional to $(1+z)^m$, then $m=2.2 \pm 0.5$.Comment: 10 pages, LaTeX text, 2 Postscript figures, To appear in ApJ Let