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Systematic Errors Induced by the Elliptical Power-law model in Galaxy–Galaxy Strong Lens Modeling

Cao, Xiaoyue; Li, Ran; Nightingale, J.W.; Massey, Richard; Robertson, Andrew; Frenk, Carlos S.; Amvrosiadis, Aristeidis; Amorisco, Nicola C.; He, Qiuhan; Etherington, Amy; Cole, Shaun; Zhu, Kai

Systematic Errors Induced by the Elliptical Power-law model in Galaxy–Galaxy Strong Lens Modeling Thumbnail


Authors

Xiaoyue Cao

Ran Li

Nicola C. Amorisco

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Dr Qiuhan He qiuhan.he@durham.ac.uk
Post Doctoral Research Associate

Shaun Cole

Kai Zhu



Abstract

The elliptical power-law (EPL) model of the mass in a galaxy is widely used in strong gravitational lensing analyses. However, the distribution of mass in real galaxies is more complex. We quantify the biases due to this model mismatch by simulating and then analysing mock Hubble Space Telescope imaging of lenses with mass distributions inferred from SDSS-MaNGA stellar dynamics data. We find accurate recovery of source galaxy morphology, except for a slight tendency to infer sources to be more compact than their true size. The Einstein radius of the lens is also robustly recovered with 0.1% accuracy, as is the global density slope, with 2.5% relative systematic error, compared to the 3.4% intrinsic dispersion. However, asymmetry in real lenses also leads to a spurious fitted ‘external shear’ with typical strength, γext = 0.015. Furthermore, time delays inferred from lens modelling without measurements of stellar dynamics are typically underestimated by ∼5%. Using such measurements from a sub-sample of 37 lenses would bias measurements of the Hubble constant H0 by ∼9%. Although this work is based on a particular set of MaNGA galaxies, and the specific value of the detected biases may change for another set of strong lenses, our results strongly suggest the next generation cosmography needs to use more complex lens mass models.

Citation

Cao, X., Li, R., Nightingale, J., Massey, R., Robertson, A., Frenk, C. S., …Zhu, K. (2022). Systematic Errors Induced by the Elliptical Power-law model in Galaxy–Galaxy Strong Lens Modeling. Research in Astronomy and Astrophysics, 22(2), https://doi.org/10.1088/1674-4527/ac3f2b

Journal Article Type Article
Acceptance Date Oct 27, 2021
Online Publication Date Feb 2, 2022
Publication Date 2022-02
Deposit Date Jun 14, 2022
Publicly Available Date Oct 27, 2022
Journal Research in Astronomy and Astrophysics
Print ISSN 1674-4527
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 22
Issue 2
DOI https://doi.org/10.1088/1674-4527/ac3f2b

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Copyright Statement
This is the Accepted Manuscript version of an article accepted for publication in Research in Astronomy and Astrophysics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1674-4527/ac3f2b





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