Two-component modeling of Strong Gravitational Lenses

Abstract

Determination of the mass distribution of various astrophysical objects is of utmost importance in multiple studies in astrophysics and cosmology. Strong gravitational lensing is a valuable tool in the estimation of mass distributions of lensing objects. Generally, galaxy-scale strong lensing is analyzed assuming a single component for the lensing galaxy, such as a singular isothermal ellipsoid or a power-law ellipsoid. However, both stars and dark matter account for the mass of the lensing galaxy. This project explores two-component mass models of the lensing galaxy that consists of the stellar and dark matter components. Such accurate stellar and dark matter estimations are precious for testing the many models of structure formation and evolution. We perform both one and two-component modeling on two strong gravitationally lensed systems. We model the first target system, SDSSJ002927.38+254401.7, selected from the BELLS GALLERY sample for training and understanding parameter degeneracies and other possible biases. Our principal target system is the double source plane lens system, Eye of Horus. Using the two-component modeling, we constrain the dark matter distribution of the foreground lensing galaxy within the Einstein radius. We also study the foreground lensing galaxy’s density profile and initial mass function (IMF). From one-component modeling, we find that the lensing galaxy of the Eye of Horus follows a power-law radial density profile (ρ ∝ r^ γ ) with γ = 1.7559. The stellar mass for the foreground lens is found to be 12.98 x 10^11M☉ . After comparing this with the stellar mass (6.6 x 10^11M☉ ) inferred from stellar population synthesis fitting, we find that a Salpeter IMF provides a good description of the stellar population of the foreground lens of the Eye of Horus. After analyzing the two-component model of the Eye of Horus, the dark matter distribution is found to be more elongated than the stellar mass distribution. The next step towards getting a robust conclusion on the shape comparison of the two mass distributions is to analyze two-component mass models of more such strong gravitationally lensed systems.