Comparison between the Blue and the Red Galaxy Alignments Detected in the Sloan Digital Sky Survey

Abstract

We measure the intrinsic alignments of the blue and the red galaxies separately by analyzing the spectroscopic data of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6). For both samples of the red and the blue galaxies with axial ratios of b/a <= 0.8, we detect a 3 sigma signal of the ellipticity correlation in the redshift range of 0 <= z <= 0.4 for r-band absolute (model) magnitude cut of M_r <= -19.2 (no K correction). We note a difference in the strength and the distance scale for the red and the blue galaxy correlation eta_{2D}(r): For the bright blue galaxies, it behaves as a quadratic scaling of the linear density correlation of xi(r) as eta_{2D}(r) proportional to xi^{2}(r) with strong signal detected only at small distance bin of r <= 3 Mpc/h. While for the bright red galaxies it follows a linear scaling as eta_{2D}(r) proportional to xi(r) with signals detected at larger distance out to r~6 Mpc/h. We also test whether the detected correlation signal is intrinsic or spurious by quantifying the systematic error and find that the effect of the systematic error on the ellipticity correlation is negligible. It is finally concluded that our results will be useful for the weak lensing measurements as well as the understanding of the large scale structure formation.

accepted by ApJL, revised version, 12 pages, 2 figures, 1 table, systematic error analyzed and beaten down, cross-correlations between the blue and red galaxies shown, clearer discussion on the different generation mechanism for the blue and red galaxy alignments added

References in corpus (2)

• The 2dF-SDSS LRG and QSO survey: Evolution of the Luminosity Function of Luminous Red Galaxies to z=0.6
• Probabilistic Cross-Identification of Astronomical Sources

Cited by in corpus (7)

• Clustering of dark matter tracers: generalizing bias for the coming era of precision LSS
• The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology
• Angular momentum-Large-scale structure alignments in LCDM models and the SDSS
• Measuring alignments between galaxies and the cosmic web at $z\sim 2-3$ using IGM tomography
• The Anisotropic Two-Point Correlation Functions of the Nonlinear Traceless Tidal Field in the Principal-Axis Frame
• Galaxy Alignments with Surrounding Structure in the Sloan Digital Sky Survey
• Living with Neighbors. V. Better-aligned Spiral+Spiral Galaxy Pairs Show Stronger Star Formation