Tightening weak lensing constraints on the ellipticity of galaxy-scale dark matter haloes

Abstract

Cosmological simulations predict that galaxies are embedded into triaxial dark matter haloes, which appear approximately elliptical in projection. Weak gravitational lensing allows us to constrain these halo shapes and thereby test the nature of dark matter. Weak lensing has already provided robust detections of the signature of halo flattening at the mass scales of groups and clusters, whereas results for galaxies have been somewhat inconclusive. Here we combine data from five surveys (NGVSLenS, KiDS/KV450, CFHTLenS, CS82, and RCSLenS) in order to tighten observational constraints on galaxy-scale halo ellipticity for photometrically selected lens samples. We constrain $f_\rm{h}$, the average ratio between the aligned component of the halo ellipticity and the ellipticity of the light distribution, finding $f_\rm{h}=0.303^{+0.080}_{-0.079}$ for red lenses and $f_\rm{h}=0.217^{+0.160}_{-0.159}$ for blue lenses when assuming elliptical NFW density profiles and a linear scaling between halo ellipticity and galaxy ellipticity. Our constraints for red galaxies constitute the currently most significant ($3.8\sigma$) systematics-corrected detection of the signature of halo flattening at the mass scale of galaxies. Our results are in good agreement with expectations from the Millennium Simulation that apply the same analysis scheme and incorporate models for galaxy-halo misalignment. Assuming these misalignment models and the analysis assumptions stated above are correct, our measurements imply an average dark matter halo ellipticity for the studied red galaxy samples of $\langle|ε_\rm{h}|\rangle=0.174\pm 0.046$, where $|{\epsilon }_h|=(1-q)/(1+q)$ relates to the ratio $q=b/a$ of the minor and major axes of the projected mass distribution. Similar measurements based on larger upcoming weak lensing data sets can help to calibrate models for intrinsic galaxy alignments. [abridged]

23 pages, 11 figures, 2 tables. Accepted for publication in A&A. In this version corrections from the A&A language editor have been applied. Comments welcome

References in corpus (24)

• EAZY: A Fast, Public Photometric Redshift Code
• Dark energy constraints from cosmic shear power spectra: impact of intrinsic alignments on photometric redshift requirements
• Galaxies in the Hubble Ultra Deep Field: I. Detection, Multiband Photometry, Photometric Redshifts, and Morphology
• The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses
• The fourth data release of the Kilo-Degree Survey: ugri imaging and nine-band optical-IR photometry over 1000 square degrees
• Bayesian Galaxy Shape Measurement for Weak Lensing Surveys -I. Methodology and a Fast Fitting Algorithm
• Lensing is Low: Cosmology, Galaxy Formation, or New Physics?
• Potential sources of contamination to weak lensing measurements: constraints from N-body simulations
• CARS: the CFHTLS-Archive-Research Survey; I. Five-band multi-colour data from 37 sq. deg. CFHTLS-Wide observations
• Means of confusion: how pixel noise affects shear estimates for weak gravitational lensing
• KiDS+VIKING-450 and DES-Y1 combined: Mitigating baryon feedback uncertainty with COSEBIs
• Bayesian Galaxy Shape Measurement for Weak Lensing Surveys -II. Application to Simulations
• Galaxy Shapes and Intrinsic Alignments in The MassiveBlack-II Simulation
• The Masses and Shapes of Dark Matter Halos from Galaxy-Galaxy Lensing in the CFHTLS
• Cosmological Constraints From Weak Lensing Peak Statistics With CFHT Stripe 82 Survey
• Some like it triaxial: the universality of dark matter halo shapes and their evolution along the cosmic time
• The mass dependence of dark matter halo alignments with large-scale structure
• The Next Generation Virgo Cluster Survey. XV. The photometric redshift estimation for background sources
• The Stripe 82 Massive Galaxy Project III: A Lack of Growth Among Massive Galaxies
• Three-point galaxy-galaxy lensing as a probe of dark matter halo shapes
• The galaxy-galaxy lensing contribution to the cosmic shear two point function
• The prolate dark matter halo of the Andromeda galaxy
• The Orthogonally Aligned Dark Halo of an Edge-on Lensing Galaxy in the Hubble Frontier Fields: A Challenge for Modified Gravity
• The case for two-dimensional galaxy-galaxy lensing

Cited by in corpus (8)

• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• The Weak Lensing Radial Acceleration Relation: Constraining Modified Gravity and Cold Dark Matter theories with KiDS-1000
• 3D hydrodynamic simulations for the formation of the Local Group satellite planes
• The dark matter halo masses of elliptical galaxies as a function of observationally robust quantities
• The shape of dark matter haloes: results from weak lensing in the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS)
• Intrinsic correlations of galaxy sizes in a hydrodynamical cosmological simulation
• Host group degeneracy in gravitational lensing time delay determination of $H_0$
• Ellipticities of Galaxy Cluster Halos from Halo-Shear-Shear Correlations