Analysis of the spiral structure in disk galaxies using the FFT transform

Identifier:  TDX:2794

Handle: https://hdl.handle.net/20.500.11797/TDX2794

Authors:  Barbera Escoi, Carlos

Abstract:
This thesis wants to provide mathematical methods to go deeper in the study of the spiral structure within disk spiral galaxies. Approximately two thirds of all galaxies are spiral galaxies, hence the interest to study them in depth. The first step for their study is to deproject them from the plane of the sky to the plane of sight. In the first part of this tesis we focus on providing methods allowing to deproject the galaxies objectively (or numerically). Our methods are based on the assumption that galactic disks are circular. We select information from the galactic disk and using Fourier techniques we bring it circular. HII regions clearly belong to the galactic disk, so our first deprojecting methods use those HII regions. The next step is working with galaxy images. Since galaxy images contain information from all the galaxy components, first we have to select the disk information before applying our methods. We finish this first part performing statistical studies to show the viability and robustness of our methods. Once, the galaxies are already deprojected, we start studying the spiral structure. Namely, we isolate the bar present in most of the spiral galaxies to proceed with their classification according to the bar strength. Our results are in good agreement with Hubble’s classification, therefore we have managed to perform a quantitative classification of spiral galaxies according their morphology.