LINDITA HAMOLLI, ESMERALDA GULIQANI, MIMOZA HAFIZI
Abstract
Constraining the mass distribution of lensing galaxies in strongly lensed quasars is a fundamental challenge in gravitational lensing, as it directly affects the interpretation of key astrophysical and cosmological parameters. In this study, we assess the capability of the Roman Space Telescope (Roman) to distinguish between spherical and elliptical lens models in the case of double quasars. Using Monte Carlo simulations, we generate a synthetic population of quasar–galaxy lensing systems, incorporating their observed redshift distributions and the galaxy stellar mass function. Modeling the lensing galaxy as a Singular Isothermal Ellipsoid (SIE), we compute the positions of the lensed images by solving the lens equation. The simulation results confirm that double-image configurations dominate, representing over 80% of all strong lensing events. We adopt Roman’s expected angular resolution of 0.1 arcseconds as the detection threshold for image separation. Based on this criterion, we evaluate the geometric alignment of images with the lensing galaxy in double lensed quasars to determine whether the lens mass distribution can be reliably classified as spherical or elliptical. We find that in approximately 30% of double-image cases, the image configuration deviates sufficiently from perfect alignment to allow meaningful constraints on lens ellipticity. These results highlight both the potential and the observational limitations of the Roman Telescope in probing the internal structure of lensing galaxies.
Key words: quasar, galaxy, strong lensing.