Measuring dark energy equation of state parameter from the compound lens system DES0408-5354

This is the project of my Master’s thesis carried out during my master studies in astrophysics at EPFL.

Overview

Compound lenses — strong lenses with multiple Einstein rings or arcs from multiple sources at different redshifts — allow measuring the cosmological parameters such as the matter density parameter Omega_m and the dark energy equation of state parameter w. However, such systems are extremely rare, with only one system analyzed so far to constrain the aforementioned parameters. This project will analyze a new compound lens system, DES J0408-5354, and constrain the w parameter for the dark energy. To model this complex system, with multiple source components and one source quasar, we will use the state-of-the-art modeling software lenstronomy.

Gravitational lensing acts as a coordinate transformation that distorts the images of background objects (usually galaxies) near a foreground mass. A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer that is capable of bending the light from the source as the light travels toward the observer

Alt Text

RGB color composite of the lens systems DES J0408−5354. The three HST filters used to create the RGB image are F160W (red), F814W (green), and F475X (blue). The relative amplitudes between the three filters are adjusted in this figure for better visualization by achieving a higher contrast. We label different components of the lens system. G1 is the main deflector galaxy and G2 is its satellite galaxy. In addition to the lensed arcs from the extended quasar host galaxy, this lens system has extra source components S2 and S3. The source component S2 is doubly imaged and forms an extended arc inside the Einstein radius. S3 forms another fainter extended arc on the North-East outside the Einstein radius without a noticeable counterimage. Four nearby perturbers G3–G6 along the line of sight are marked with the dashed, white circles.

References

About this project

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