This study consists of a quantitative optical emission-line analysis of spectra from five blue compact galaxies (Zw 0855, Mrk 1267, II Zw 33, Tol 2 & Tol 3), as well as a qualitative analysis of spectra from two galactic H II regions (NGC 3603 & NGC 3576). It serves a two-fold purpose: first, to understand the CCD reduction, spectra extraction and different nebular analysis methods, together with their applications and limitations, preparatory to studies using the Southern African Large Telescope (SALT) and second, to extend current star formation related research to include extragalactic starburst galaxies. The observations were carried out using the 1.9m telescope (equipped with a grating spectroscope and CCD detector) of the South African Astronomical Observatory (SAAO), during the period 1 to 7 March 2005. The necessary CCD data reduction, spectra extraction, wavelength and flux calibration, Doppler shift as well as reddening correction procedures were performed before the emission lines were identified and measured. A full nebular analysis, including temperature, density, metallicity (oxygen abundance) and other chemical abundance determinations, was performed on the blue compact galaxies (BCGs). Two different nebular analysis packages viz. IRAF's nebular and SNAPwere used, with all the results well within the range of values expected for metal poor BCGs. Recommendations on the different methods and their applications are made. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.

Blue compact galaxies (BCGs) are gas-rich star-forming low redshift galaxies with low metallicities. In some cases the relative strength of the starburst can be so high that it completely dominates the light output of the galaxy, an obstacle which has been countered by deeper optical imaging data and observations in the near infra-red (NIR) regime. This has revealed an older population referred to as the "host". In an effort to study the hosts of BCGs we have analyzed new and extremely deep UBVRIHKs imaging data for 46 high and low luminosity BCGs. For several BCGs the data reveal previously undetected extended low surface brightness components beyond the μB~26 mag arcsec-2 isophote. These are predominantly the luminous BCGs in the sample, and they show tails, plumes, optical bridges between companion galaxies, and other signs of merging or strong tidal interactions. The low luminosity BCGs, on the other hand, are well represented by an exponential disk profile down to the reliability limit of the data at a surface brightness level of μB~28 mag arcsec-2. The burst and host populations are examined separately. The integrated colors of both are compared to predictions from spectral evolutionary models, giving an indication of their respective ages and metallicities. Our analysis suggests that for the luminous BCGs a strong contribution by nebular emission is present almost down to the Holmberg radius, invalidating the host structural parameters obtained from brighter isophotes. Possible evolutionary links to quiescent galaxies like dEs, dIs, and LSBGs are explored by examining the structural parameters derived from two radial ranges typically assumed to be dominated by the underlying host galaxy. In this parameter space the luminous BCGs in our sample deviate from their low luminosity counterparts and from BCG data in the literature. They are instead consistent with the structural properties of giant low surface brightness galaxies with central surface brightnesses μB≥23 mag arcsec-2. We further examine the asymmetry and concentration parameters for the sample and study the correlation between the minimum asymmetry distribution in the optical and NIR vs morphological class, concentration and integrated colors to identify mergers/tidally interacting galaxies. A shift in the asymmetry distribution occurs for low luminosity BCGs from the optical to the NIR. In contrast, we find that the flocculent asymmetry component (due to star formation) completely dominates the composite asymmetry of high luminosity BCGs. We introduce an alternative asymmetry measure which successfully traces the dynamical asymmetry component (due to merging/tidal interaction) of the host. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>

This study consists of a quantitative optical emission-line analysis of spectra from five blue compact galaxies (Zw 0855, Mrk 1267, II Zw 33, Tol 2 & Tol 3), as well as a qualitative analysis of spectra from two galactic H II regions (NGC 3603 & NGC 3576). It serves a two-fold purpose: first, to understand the CCD reduction, spectra extraction and different nebular analysis methods, together with their applications and limitations, preparatory to studies using the Southern African Large Telescope (SALT) and second, to extend current star formation related research to include extragalactic starburst galaxies. The observations were carried out using the 1.9m telescope (equipped with a grating spectroscope and CCD detector) of the South African Astronomical Observatory (SAAO), during the period 1 to 7 March 2005. The necessary CCD data reduction, spectra extraction, wavelength and flux calibration, Doppler shift as well as reddening correction procedures were performed before the emission lines were identified and measured. A full nebular analysis, including temperature, density, metallicity (oxygen abundance) and other chemical abundance determinations, was performed on the blue compact galaxies (BCGs). Two different nebular analysis packages viz. IRAF's nebular and SNAPwere used, with all the results well within the range of values expected for metal poor BCGs. Recommendations on the different methods and their applications are made. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.

The study of dwarf galaxies is important in order to better understand the physics of the young universe and how larger galaxies form and evolve. In this work we focus on Blue Compact Galaxies (BCGs) which havemuch enhanced star formation (starbursts), causing blue colours and strong emission line spectra. Investigating of the inner motions of BCGs provides a means for determining masses and understanding what triggered the current starburst. We have used the Very Large Telescope to perform challenging observations of the stellar motions in several BCGs, as seen in the near-infrared Ca-triplet absorption lines. By comparing these to the kinematics of the ionized interstellar medium, we were able to look into the role of feeback from stellar winds and supernova explosions, as well as further strengthen the notion that the merging of galaxies plays an important role. Spatially resolved spectroscopy can yield information about the 3D-structure of galaxies. We have used a Fabry-Perot interferometer to study the kinematics of the interstellar medium in two samples of galaxies, each containing about twenty objects. We find strong indications for ongoing galaxy mergers that correlate well with the strength of the star-formation activity. Furthermore, by estimating dynamical masses, BCGs are shown to be on average not dynamically supported by rotation. In addition, we have used data from the Sloan Digital Sky Survey to study the frequency of starbursts in the local universe and the connection to their descendants. We selected starbursts by the strength of emission in H-alpha, the first Balmer recombination line, and post-starbursts by the strength of absorption in H-delta. These are indicators of currently ongoing and recent, on the order of 100 Myr, star-formation, respectively. By modelling the stellar populations we derive ages and masses and can establish a link between starbursts and postbursts in a time sequence. We find that starbursts are active on a 100 Myr timescale but are rare objects in the local universe.

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