RUI: Observational Studies of Galactic and Extragalactic Supernova Remnants

点击翻译按钮获取中文摘要

Abstract Winkler Supernovae are the cataclysmic events in which massive stars (more than about 8 times the mass of our Sun) end their lives. They are the most energetic localized events which now occur in the universe: a typical supernova explosion releases in a few seconds an energy of about 10 to the 44th Joules, comparable to what the Sun will expend throughout the entire course of its 10 billion year lifetime. Not surprisingly, such a prodigious release of energy can have profound effects on the dynamics of galaxies in which supernovae occur. The shock waves from supernovae are believed to trigger episodes of star formation when they encounter dense interstellar clouds. Furthermore, supernovae are responsible for the production and distribution of most of the heavy elements in the universe. Virtually all the elements from helium to iron, on the periodic table, were created by nucleosynthesis in the cores of massive stars, and these elements have been distributed around the cosmos through the supernova explosions of the stars in which they were originally formed. By studying supernovae and the remnants they leave behind, we can gain insight into the processes of nucleosynthesis, the evolution of the universe's chemical composition, and the effects of such prodigious energy release on the host galaxies of supernovae. Extragalactic samples of supernova remnants (SNRs) offer two significant advantages over ones in our Galaxy: (I) the view toward other galaxies is far less impeded by interstellar absorption than in the Milky Way, where fewer than a third of all known remnants have been detected at all by optical means, and (2) all the remnants in another galaxy are at the same, known distance, making comparisons among them much more meaningful and reliable. Supernovae searches to be conducted in the Large and Small Magellanic Clouds, nearest neighbors to our Milky Way, and in M31, the largest galaxy in the Local Group, should increase the samples of SNRs in t hese galaxies several-fold. Wide-field digital imaging through the use of CCD cameras on small Schmidt telescopes at Kitt Peak and Cerro Tololo observatories will be used. A technique which has already led to the identification of over 100 SNR candidates. These supernovae candidates will be further studied through spectroscopy and high-resolution imaging to confirm whether they are, in fact, SNRs and then their properties will be observed. The expanded extragalactic SNR samples will be used to study the local environments of supernovae, to probe elemental abundances and abundance gradients in galaxies, to measure the energy of supernova events, and to study the effects of supernovae on galactic structure. Detailed attention will be focused on the handful of young SNRs where uncontaminated ejecta from the supernova can be identified. In older remnants, which are much more numerous, shocks driven through the interstellar medium can probe the density, structure, and abundances of the interstellar gas. Wide-field imaging techniques will be used to study individual SNRs in our Galaxy in unprecedented detail. The proposed optical investigations will be combined with new radio and X-ray data to study the interstellar environments of supernovae and the fundamental physics of shocks. These detailed studies of a few selected objects will complement the broader extragalactic surveys. Significant collaboration with undergraduate students is integral to carrying out the research.