Spatial and spectral comparisons of soft X-rays from galaxies of different morphological types
type: CreativeWork
description: Encounters between galaxies have long been recognised as having a possible influence over a galaxy's evolution. Nevertheless for years such encounters were regarded as rare events, with models incapable of producing the tidal tails, ripples and shells observed in classical mergers. Numerical simulations and advances in observational techniques have emphasised the significance of mergers as a delayed formation or evolution process for a sizable number of galaxies. Many of the initial worries over the theory of ellipticals being the remnants of merged disk systems have since been answered. X-ray analysis of normal galaxies demonstrated a dichotomy between the nature of X-ray emission associated with spirals and that of ellipticals. This thesis compares spectral and spatial information for normal galaxies to that of galaxies experiencing environmental encounters in order to clarify the evolutionary relationship between spirals, mergers and ellipticals. As a pilot study we present statistical analysis for luminosity data derived from Einstein observations. Our analysis shows that the properties of galaxies experiencing environmental encounters are intermediate between those of normal spiral and elliptical galaxies. We present spectral analysis of deep exposure ROSAT PSPC observations of 27 spirals, 35 ellipticals and 18 galaxies classified as peculiar. Single-temperature models (Raymond Smith, bremsstrahlung or power law) give unacceptable fits (x>1.5) for many cases in all morphological subsets, unless a free abundance of heavy elements was allowed for, in which case very sub-solar values were derived (<0.5 solar). Two-temperature models give substantially better fits, for all morphological types. Lower emission temperatures are measured for both spirals and ellipticals in comparison to Einstein results. We suggest this is a consequence of the complexity of the galaxy spectra and the softer energy band of ROSAT. In order to better characterise the soft X-ray emission f…
abstract: Encounters between galaxies have long been recognised as having a possible influence over a galaxy's evolution. Nevertheless for years such encounters were regarded as rare events, with models incapable of producing the tidal tails, ripples and shells observed in classical mergers. Numerical simulations and advances in observational techniques have emphasised the significance of mergers as a delayed formation or evolution process for a sizable number of galaxies. Many of the initial worries over the theory of ellipticals being the remnants of merged disk systems have since been answered. X-ray analysis of normal galaxies demonstrated a dichotomy between the nature of X-ray emission associated with spirals and that of ellipticals. This thesis compares spectral and spatial information for normal galaxies to that of galaxies experiencing environmental encounters in order to clarify the evolutionary relationship between spirals, mergers and ellipticals. As a pilot study we present statistical analysis for luminosity data derived from Einstein observations. Our analysis shows that the properties of galaxies experiencing environmental encounters are intermediate between those of normal spiral and elliptical galaxies. We present spectral analysis of deep exposure ROSAT PSPC observations of 27 spirals, 35 ellipticals and 18 galaxies classified as peculiar. Single-temperature models (Raymond Smith, bremsstrahlung or power law) give unacceptable fits (x>1.5) for many cases in all morphological subsets, unless a free abundance of heavy elements was allowed for, in which case very sub-solar values were derived (<0.5 solar). Two-temperature models give substantially better fits, for all morphological types. Lower emission temperatures are measured for both spirals and ellipticals in comparison to Einstein results. We suggest this is a consequence of the complexity of the galaxy spectra and the softer energy band of ROSAT. In order to better characterise the soft X-ray emission f…
author: Peace, Gregory Antony
language: en
keywords: F510 - Astrophysics
date published: 2000-01
date modified: 2026-07-24T01:36:06Z
provider: University of Central Lancashire
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Central Lancashire