Higher-Order Angular Galaxy Correlations in the SDSS: Redshift and Color Dependence of non-Linear Bias

Abstract

We present estimates of the N-point galaxy, area-averaged, angular correlation functions $\barω_{N}$($θ$) for $N$ = 2,...,7 for galaxies from the fifth data release of the Sloan Digital Sky Survey. Our parent sample is selected from galaxies with $18 \leq r < 21$, and is the largest ever used to study higher-order correlations. We subdivide this parent sample into two volume limited samples using photometric redshifts, and these two samples are further subdivided by magnitude, redshift, and color (producing early- and late-type galaxy samples) to determine the dependence of $\barω_{N}$($θ$) on luminosity, redshift, and galaxy-type. We measure $\barω_{N}$($θ$) using oversampling techniques and use them to calculate the projected, $s_{N}$. Using models derived from theoretical power-spectra and perturbation theory, we measure the bias parameters $b_1$ and $c_2$, finding that the large differences in both bias parameters ($b_1$ and $c_2$) between early- and late-type galaxies are robust against changes in redshift, luminosity, and $σ_8$, and that both terms are consistently smaller for late-type galaxies. By directly comparing their higher-order correlation measurements, we find large differences in the clustering of late-type galaxies at redshifts lower than 0.3 and those at redshifts higher than 0.3, both at large scales ($c_2$ is larger by $\sim0.5$ at $z > 0.3$) and small scales (large amplitudes are measured at small scales only for $z > 0.3$, suggesting much more merger driven star formation at $z > 0.3$). Finally, our measurements of $c_2$ suggest both that $σ_8 < 0.8$ and $c_2$ is negative.