BD Lensing

In this project (presented in arXiv:2412.00361), the students analyzed a sample of 15 strong lensing systems (pictured above), utilizing Hubble Space Telescope imaging data to model the deflector galaxies' mass and light distributions. Then, they investigated the relationship between the environment and the internal structure of the deflectors, which are massive elliptical galaxies. The students used the lenstronomy software package to perform lens modeling and constrained the mass and light profiles of the galaxies. They also adopted the local galaxy density as a metric for the environment and tested their results against several alternative definitions. 

The results of their analysis revealed that the centroid offset between the mass and light distributions was not correlated with the local galaxy density. This finding supports using centroid offsets as a probe of dark matter theories, as the environment's impact can be considered negligible. Additionally, the students found a strong correlation between the position angle offset and the standard definition of the local galaxy density, consistent with previous studies. However, this correlation weakened when alternative definitions of local galaxy density were used, suggesting that the position angle misalignment may not solely originate from interactions with the environment. Furthermore, the students discovered that the 'residual shear' magnitude in the lens model was uncorrelated with the local galaxy density, supporting the interpretation that the residual shear originates, in part, from the inadequacy in modeling the angular structure of the lensing galaxy rather than solely from structures present in the environment or along the line of sight. 

The lens modeling tutorial used for this project can be found here. The GitHub repo containing modeling notebooks for all the lens systems in our sample are accessible here.