Abstract
ABSTRACT The intrinsic alignments of galaxies, i.e. the correlation between galaxy shapes and their environment, are a major source of contamination for weak gravitational lensing surveys. Most studies of intrinsic alignments have so far focused on measuring and modelling the correlations of luminous red galaxies with galaxy positions or the filaments of the cosmic web. In this work, we investigate alignments around cosmic voids. We measure the intrinsic alignments of luminous red galaxies detected by the Sloan Digital Sky Survey around a sample of voids constructed from those same tracers and with radii in the ranges: [20–30; 30–40; 40–50] h−1 Mpc and in the redshift range z = 0.4−0.8. We present fits to the measurements based on a linear model at large scales, and on a new model based on the void density profile inside the void and in its neighbourhood. We constrain the free scaling amplitude of our model at small scales, finding no significant alignment at 1σ for either sample. We observe a deviation from the null hypothesis, at large scales, of 2σ for voids with radii between 20 and 30 h−1 Mpc, and 1.5σ for voids with radii between 30 and 40 h−1 Mpc and constrain the amplitude of the model on these scales. We find no significant deviation at 1σ for larger voids. Our work is a first attempt at detecting intrinsic alignments of galaxy shapes around voids and provides a useful framework for their mitigation in future void lensing studies.
Highlights
Galaxies are known to align their shapes towards each other in the Universe (Brown et al 2002; Mandelbaum et al 2006; Hirata et al 2007a; Blazek et al 2011; Singh et al 2015; Johnston et al 2018; Samuroff et al 2020; Pedersen et al 2020; Singh et al 2021)
We measure the intrinsic alignments of luminous red galaxies detected by the Sloan Digital Sky Survey around a sample of voids constructed from those same tracers and with radii in the ranges: [20 − 30; 30 − 40; 40 − 50] h−1 Mpc and in the redshift range z = 0.4 − 0.8
We have studied intrinsic alignments of galaxies around cosmic voids, in SDSS-III BOSS CMASS galaxies
Summary
Galaxies are known to align their shapes towards each other in the Universe (Brown et al 2002; Mandelbaum et al 2006; Hirata et al 2007a; Blazek et al 2011; Singh et al 2015; Johnston et al 2018; Samuroff et al 2020; Pedersen et al 2020; Singh et al 2021) They show preferential alignments with respect to the “cosmic web”, the network of nodes and filaments that constitutes the structure of the Universe (Chen et al 2015; Georgiou et al 2019). Models for intrinsic alignments rely on a connection between a galaxy shape and the tidal field (Catelan et al 2001; Blazek et al 2011; Vlah et al 2020) at large scales. This connection is a linear dependency in the case of elliptical, pressure-supported, galaxies; and quadratic for spirals. At small scales, alignments are modelled
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