eprintid: 20249
rev_number: 12
eprint_status: archive
userid: 2347
dir: disk0/00/02/02/49
datestamp: 2016-02-16 14:59:12
lastmod: 2016-04-27 11:47:48
status_changed: 2016-02-16 14:59:12
type: doctoralThesis
metadata_visibility: show
creators_name: Fabris, Agnese
title: Light and shadow on gravitational flexion measurements
subjects: 520
divisions: 714200
adv_faculty: af-13
cterms_swd: cosmology
cterms_swd: weak lensing
cterms_swd: dark matter
abstract: Is gravitational flexion reliably measurable in realistic observational conditions?
To address this question we undertook an exhaustive investigation into the problem of estimating flexion. By means of synthetic data, we tested the ability of different methods to recover the shape of faint background galaxies with the level of detail necessary to account for the spin-1 and spin-3 distortions caused by flexion. Three different methods for weak lensing measurements have been extended in order to measure the high-order moments of surface brightness necessary to quantify the flexion-induced deformations. We observed that, for the two methods which exploit a weight function to control the noise and afterwards correct for the impact of this procedure, a successful outcome depends upon numerous assumptions on the properties of the objects investigated, making these techniques less appealing for practical applications. The third method we tested employs a principal component analysis algorithm to de-noise the images. Even though, in the most strict observational conditions, we could not achieve a precise measurement of the high-order distortions, this method stood out as a promising technique for shape measurements in weak lensing applications. Our analysis shows that a deeper understanding of the impact of pixel noise on the flexion estimators is required before measurements of flexion in real data can be carried out and, finally, used to exploit the vast potential of gravitational flexion.
date: 2016
id_scheme: DOI
id_number: 10.11588/heidok.00020249
ppn_swb: 1656500671
own_urn: urn:nbn:de:bsz:16-heidok-202493
date_accepted: 2015-12-18
advisor: HASH(0x564e1c53bbc8)
language: eng
bibsort: FABRISAGNELIGHTANDSH2016
full_text_status: public
citation:   Fabris, Agnese  (2016) Light and shadow on gravitational flexion measurements.  [Dissertation]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/20249/1/thesis_fabris.pdf