Strong Gravitational Lens Modeling of the Cosmic Horseshoe and Photon Simulation of DECam Images

Jun Cheng, Purdue University

Abstract

In this dissertation, we extend the study how the light path is altered due to different effects. In the first part, we study the gravitational lensing effects by modeling the Cosmic Horseshoe system. The Cosmic Horseshoe gravitational lensing system is an extraordinary example of strong gravitational lensing both due to the nearly complete Einstein ring formed in this system and due to the star forming nature of the lensed z = 2.38 Lyman-break galaxy. In this part, we describe the development of a new lens modeling package and the first lens models produced using the Hubble Space Telescope imaging. Our new lens modeling package uses adaptive grid methods. The new lens modeling package introduces the K-means method to deal with multiple background sources. We utilize two parameterized models, the singular isothermal ellipsoid (SIE) and the Navarro Frenk & White (NFW) in order to optimize the Bayesian penalty function. Color-color diagrams show two distinct colors exist in the Einstein ring which suggests that the Cosmic Horseshoe is formed from two background galaxies or from a highly irregular galaxy. We find the best lens model includes two components and total mass within the Einstein ring of (5.43 ± 0.08) × 1012solar masses. The background sources reconstruction shows two peaks in the source plane and the most probable lens profile is consistent with the light profile of the foreground galaxy when comparing axis ratios and position angles. In the the second part, we study how the light path is affected by atmosphere, optical system, and camera CCDs. We implement a Dark Energy Survey Camera Simulator (DECamSIM) using Photon Simulator (PhoSim) and also make a series of comparisons between the simulated images and the real DES observations.

Degree

Ph.D.

Advisors

Peterson, Purdue University.

Subject Area

Physics|Astronomy

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