Unveiling Lens Light Complexity with A Novel Multi-Gaussian Expansion Approach for Strong Gravitational Lensing
arxiv(2024)
摘要
In a strong gravitational lensing system, the distorted light from a source
is analysed to infer the properties of the lens. However, light emitted by the
lens itself can contaminate the image of the source, introducing systematic
errors in the analysis. We present a simple and efficient lens light model
based on the well-tested multi-Gaussian expansion (MGE) method for representing
galaxy surface brightness profiles, which we combine with a semi-linear
inversion scheme for pixelized source modelling. Testing it against realistic
mock lensing images, we show that our scheme can fit the lensed images to the
noise level, with relative differences between the true input and best-fit lens
light model remaining below 5
from the HST SLACS sample. We find that the new scheme provides a good fit for
the majority of the sample with only 3 exceptions – these show clear
asymmetric residuals in the lens light. We examine the radial dependence of the
ellipticity and position angles and confirm that it is common for a typical
lens galaxy to exhibit twisting, non-elliptical isophotes and boxy / disky
isophotes. Our MGE lens light model will be a valuable tool for understanding
the hidden complexity of the lens mass distribution.
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