FIRST USE OF ADAPTIVE OPTICS IMAGING TO CONSTRAIN COSMOLOGY WITH GRAVITATIONAL LENS TIME DELAYS

• Main Authors: Chih-Fan Chen, 陳之藩
• Other Authors: Sherry Suyu
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/57366031632214707453

碩士 === 國立臺灣大學 === 物理研究所 === 103 === Accurate and precise measurements of the Hubble constant are critical for testing our current standard cosmological model and revealing possibly new physics. With Hubble Space Telescope (HST) imaging, each strong gravita- tional lens with time delays can allow one to determine the Hubble constant with an uncertainty of ~7%. However, since HST will not last forever, alter- native approaches for obtaining follow-up imagings of strong lenses are de- sirable. Adaptive-optics (AO) imaging can provide higher angular resolution than HST imaging but has an unknown point spread function (PSF) due to atmospheric distortion. To make AO imaging useful for time-delay-lens cos- mography, we develop a method to extract the unknown PSF directly from the imaging of the lensed quasar by iteratively reconstructing the PSF. In a blind test with two mock data sets with different PSFs, we are able to recover the important cosmological parameters (time-delay distance, external shear, mass profile slope, and total Einstein radius) within 1-� uncertainty. Our analysis of the Keck AO image of the strong lens system RXJ 1131�1231 shows that except for the highly degenerate Einstein radius of the main galaxy, other important parameters for cosmography agree with those based on HST imag- ing and modeling within 1-� uncertainty. Most importantly, the constraint on the model time-delay distance by using AO imaging with 0.0400 resolution is tighter by ~50% than the constraint of time-delay distance by using HST imaging with 0.0500 when a power-law mass distribution for the lens system is adopted.