Weak-Lensing Surveys and the Intrinsic Correlation of Galaxy Ellipticities

By R. Croft, C. Metzler. 2000

226 citations recorded by the source corpus.

We explore the possibility that an intrinsic correlation between galaxy ellipticities arising during the galaxy formation process may account for part of the shear signal recently reported by several groups engaged in weak gravitational lensing surveys. Using high-resolution N-body simulations, we measure the projected ellipticities of dark matter halos and their correlations as a function of pair separation. With this simplifying, but not necessarily realistic, assumption (halo shapes as a proxy for galaxy shapes), we find a positive detection of correlations up to scales of at least 20 h-1 Mpc (limited by the box size). The signal is not strongly affected by variations in the halo-finding technique, or by the resolution of the simulations (over the range tested). We translate our three-dimensional results into angular measurements of ellipticity correlation functions and shear variance, which can be directly compared to observational results. We also make simulated angular surveys by projecting our simulation boxes onto the plane of the sky and applying a radial selection function. Measurements from these catalogs are consistent with the analytic projection of the statistics. Interestingly, the shear variance we measure is a small, but not entirely negligible, fraction (from ~10%-20%, depending on the angular scale) of that seen by the observational groups, and the ellipticity correlation functions approximately mimic the functional form expected to be caused by weak lensing. The amplitude of these projected quantities depends strongly on the width in redshift of the galaxy distribution. If in the future photometric redshifts are used to pick out a screen of background galaxies with a small redshift width, then the intrinsic correlation may become comparable to the weak-lensing signal. Although we are dealing with simulated dark matter halos, we might expect there to be a similar sort of signal when real galaxies are used. This could be checked fruitfully using a nearby sample with known redshifts.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/743887969eb59f307d71a71978a558378af5c394

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Electrical and Electronic Engineering

In Instrumentation

Citations in the corpus

Simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy number density correlations (2009, background): “Detailed investigations have been performed on the alignment between haloes (Croft & Metzler 2000; Heavens et al. 1 Panoramic Survey Telescope & Rapid Response System, http://pan-starrs.ifa.hawaii.edu 2 Dark Energy Survey,https://www.darkenergysurvey.org 3 Large Synoptic Survey…”
The Angular Momentum of Gas in Protogalaxies. I. Implications for the Formation of Disk Galaxies (2002, methodology): “In the past, both tidal torque theory (Crittenden et al. 2001; Heavens, Refegier, & Heymans 2000; Natarajan et al. 2001) and pureN-body simulations (Croft & Metzler 2000) have been used to calculate the possibility of intrinsic alignments of galaxy shapes, which may be responsible for part of the…”
Internal and External Alignment of the Shapes and Angular Momenta of ΛCDM Halos (2004, background): “It is smaller than the ellipticities found by Croft & Metzler (2000) (note that they quantify ellipticity as e = (1−q2)/(1+q2), in which units our mean ellipticity is e = 0.27).”
Weak Gravitational Lensing by Large-Scale Structure (2003, methodology): “Theoretical estimation of the size of this effect has been performed using numerical simulations (Croft & Metzler 2000; Heavens, Refregier & Heymans 2000; Jing 2002) and analytical methods (Catalan, Kamionkowski & Blandford 2001; Crittenden et al. 2001a,b; Lee & Pen 2001; Mackey, White &…”
3D weak lensing (2003, background): “…ellipticities are uncorrelated, and this may not be true in detail, due to tidal effects during the galaxy formation process (Heavens, Refregier & Heymans 2000; Croft & Metzler 2000; Crittenden et al. 2001; Catelan, Kamionkowski & Blandford 2001; Mackey, White & Kamionkowski 2002; Jing 2002).”
Spin-induced Galaxy Alignments and Their Implications for Weak-Lensing Measurements (2000, methodology): “Croft & Metzler (2000) measure the projected ellipticities of dark matter halos and the correlation of pairs as a function of separation.”
CFHTLenS tomographic weak lensing cosmological parameter constraints: Mitigating the impact of intrinsic galaxy alignments (2013, background): “The broad agreement in results between the first estimates from numerical simulations (Heavens et al. 2000; Croft & Metzler 2000), analytical studies (Catelan et al. 2001; Crittenden et al. 2001; Lee & Pen 2001), and the first low redshift observational constraints (Pen et al. 2000; Brown et al.…”
Galaxy Alignments: Observations and Impact on Cosmology (2015, methodology): “13 at 3σ. Their analysis only differed in that it was updated to the larger and more homogeneous DR6 and used an absolute magnitude limit4 of Mr = −20.23 + 5 log h as the threshold for void detection. The larger area and higher filling factor for galaxies inside the survey volume resulted in a signi”
Gravitational lensing (2010, background): “In shallow surveys, however, intrinsic source alignments may substantially contaminate any weak-shear signal [70, 92, 93, 176].”
Testing tidal-torque theory: I. spin amplitude and direction (2001, background): “However, a series of observations (Brown et al. 2000; Pen, Lee & Seljak 2000) and numerical simulations (Croft & Metzler 2000; Heavens, Refregier & Heymans 2000; Dekel et al. 2000) evidenced that both the intrinsic galaxy shapes and their spins are spatially correlated.”
The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology (2014, methodology): “Following Croft and Metzler (2000), many large-scale intrinsic alignment measurements have been made in dark matter only simulations.”
Testing tidal-torque theory – II. Alignment of inertia and shear and the characteristics of protohaloes (2001, background): “…where the intrinsic distribution and alignment of galaxy shapes, which may be derived from TTT, play an important role in interpreting the signal (Croft & Metzler 2000; Heavens, Refregier & Heymans 2000; Catelan, Kamionkowski & Blandford 2001; Catelan & Porciani 2001; Crittenden et al. 2001).”
Constraints on intrinsic alignment contamination of weak lensing surveys using the MegaZ-LRG sample (2010, methodology): “Models for II correlations have been developed analytically or via fits to simulations (Croft & Metzler 2000; Heavens et al. 2000; Catelan et al. 2001; Crittenden etal.”