The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Correlations between the intrinsic shapes of galaxy pairs, and between theintrinsic shapes of galaxies and the large-scale density field, may be inducedby tidal fields. These correlations, which have been detected at low redshiftsz<0.35 for bright red galaxies in the Sloan Digital Sky Survey SDSS, andfor which upper limits exist for blue galaxies at z~0.1, provide a window intogalaxy formation and evolution, and are also an important contaminant forcurrent and future weak lensing surveys. Measurements of these alignments atintermediate redshifts z~0.6 that are more relevant for cosmic shearobservations are very important for understanding the origin and redshiftevolution of these alignments, and for minimising their impact on weak lensingmeasurements. We present the first such intermediate-redshift measurement forblue galaxies, using galaxy shape measurements from SDSS and spectroscopicredshifts from the WiggleZ Dark Energy Survey. Our null detection allows us toplace upper limits on the contamination of weak lensing measurements by bluegalaxy intrinsic alignments that, for the first time, do not requiresignificant model-dependent extrapolation from the z~0.1 SDSS observations.Also, combining the SDSS and WiggleZ constraints gives us a long redshiftbaseline with which to constrain intrinsic alignment models and contaminationof the cosmic shear power spectrum. Assuming that the alignments can beexplained by linear alignment with the smoothed local density field, we findthat a measurement of \sigma 8 in a blue-galaxy dominated, CFHTLS-like surveywould be contaminated by at most +-0.02 95% confidence level, SDSS andWiggleZ or +-0.03 WiggleZ alone due to intrinsic alignments. Abridged



Author: Rachel Mandelbaum, Chris Blake, Sarah Bridle, Filipe B. Abdalla, Sarah Brough, Matthew Colless, Warrick Couch, Scott Croom, Tamar

Source: https://arxiv.org/







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