The “External” Shears In Strong Lens Models

Nightingale, James W.; Etherington, Amy; Massey, Richard

Abstract

The distribution of mass in galaxy-scale strong gravitational lenses is often modelled as an elliptical power law plus ‘external shear’, which notionally accounts for line-of-sight galaxies and cosmic shear. We argue that it does not, using three lines of evidence from the analysis of 54 galaxy-scale strong lenses: (i) strong lensing external shears do not correlate with weak lensing; (ii) the measured shear magnitudes in strong lenses (which are field galaxies) are too large (exceeding 0.05) for their environment and; (iii) the external shear position angle preferentially aligns or anti-aligns with the mass model position angle, indicating an internal origin. We argue the measured strong lensing shears are therefore systematically accounting for missing complexity in the canonical elliptical power-law mass model. If we can introduce this complexity into our lens models, this will further lensing studies of galaxy formation, dark matter and Cosmology.

Citation

Nightingale, J. W., Etherington, A., & Massey, R. (2022). The “External” Shears In Strong Lens Models. Proceedings of the International Astronomical Union, 18(S381), 13-16. https://doi.org/10.1017/s1743921323003691

• Journal Article Type: Article
• Acceptance Date: Feb 2, 2024
• Online Publication Date: Mar 4, 2024
• Publication Date: 2022-12
• Deposit Date: Mar 11, 2024
• Publicly Available Date: Mar 11, 2024
• Journal: Proceedings of the International Astronomical Union
• Print ISSN: 1743-9213
• Electronic ISSN: 1743-9221
• Publisher: Cambridge University Press
• Peer Reviewed: Peer Reviewed
• Volume: 18
• Issue: S381
• Pages: 13-16
• DOI: https://doi.org/10.1017/s1743921323003691
• Keywords: Astronomy and Astrophysics; Space and Planetary Science
• Public URL: https://durham-repository.worktribe.com/output/2325165