Precision Measurements of Higher-Order Angular Galaxy. Correlations Using 10 Million SDSS Galaxies
Abstract
We present estimates of the galaxy, N-point, area-averaged angular correlation functions, ωN(θ),; for N = 2,...,7 from the third data release (DR3) of the Sloan Digital Sky Survey. Our sample was constructed from galaxies with r magnitude between 18 and 21, and is currently the largest study of galaxy higher-order correlations. The calculated angular correlation functions are used to measure the projected, sN, and real space, SN, hierarchical amplitudes. Our measurements of the real space amplitudes are remarkably precise over the physical scales 0.2-10 h-1 Mpc, and are consistent with Gaussian primordial density fluctuations. Our measurements also suggest that higher-order galaxy bias is non-negligible. By defining b1 = 1, we find that c2 = -0.26 ± 0.10 and c3 = 1.0 ± 0.9. This is the first reported measurement of a marginally significant third-order bias, and it hints at the importance of even higher-order bias terms. We find early-type galaxies exhibit significantly different clustering than late-types at both small and large scales. At large scales (r > 1 h-1 Mpc), we find the SN for late-type galaxies are lower than for early-types, implying a difference between the higher-order bias of the respective samples. We find b1,early = 1.38 ± 0.10, c2,early = 0.29 ± 0.12, b1,late = 0.81 ± 0.03, and c2,late = -0.68 ± 0.09. This supports recent measurements of the higher-order correlations of infrared-selected galaxies, which found a positive c2, presumably due to the dominance of early-type galaxies in the 2MASS sample (Frith et al. 2005). We have extended our analysis to photometrically-selected quasars in the SDSS DR3, and are planning to leverage future SDSS data releases to make even tighter constraints on primordial non-Gaussianity and non-linear bias components. We acknowledge support from NASA grants NAG5-12578 and NAG5-12580, Microsoft Research, and the NSF PACI Project.
- Publication:
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American Astronomical Society Meeting Abstracts #208
- Pub Date:
- June 2006
- Bibcode:
- 2006AAS...208.1301R