MrMARTIAN: A Multi-resolution Mass Reconstruction Algorithm Combining Free-form and Analytic Components

Abstract: We present ${\tt MrMARTIAN}$ (Multi-resolution MAximum-entropy Reconstruction Technique Integrating Analytic Node), a new hybrid strong lensing (SL) modeling algorithm. By incorporating physically motivated analytic nodes into the free-form method ${\tt MARS}$, ${\tt MrMARTIAN}$ enables stable and flexible mass reconstructions while mitigating oversmoothing in the inner mass profile. Its multi-resolution framework increases the degrees of freedom in regions with denser strong lensing constraints, thereby enhancing computational efficiency for a fixed number of free parameters. We evaluate the performance of ${\tt MrMARTIAN}$ using publicly available simulated SL data and find that it consistently outperforms ${\tt MARS}$ in recovering both mass and magnification. In particular, it delivers significantly more stable reconstructions when multiple images are sparsely distributed. Finally, we apply ${\tt MrMARTIAN}$ to the galaxy cluster MACS J0416.1--2403, incorporating two analytic nodes centered on the northeastern and southwestern BCGs. Our mass model, constrained by 412 multiple images, achieves an image-plane rms scatter of ~0".11, the smallest to date for this dataset.