Download or read book Abudance Analysis and Chemical Evolution of Blue Compact Dwarf Galaxies written by David Theodore Frayer and published by . This book was released on 1993 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Mid infrared Study of Blue Compact Dwarf Galaxies written by Yanling Wu and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Blue Compact Dwarf Galaxies (BCDs) are characterized by their blue optical colors, low luminosities and small sizes. Typically BCDs are found to have low, subsolar metallicities, and they are proposed to be local analogs to the primeval galaxies in the early universe. The unprecedented sensitivity of the Spitzer Space Telescope has enabled, for the first time, the detection of a large sample of these low luminosity systems. In this dissertation, I will present my work employing Spitzer data to study the dust properties and chemical evolution of blue compact dwarf galaxies. Using Spitzer/IRS low-resolution spectra ([lambda]/[delta][lambda] ~ 100), I investigated the presence/absence of the Polycyclic Aromatic Hydrocarbon (PAH) features in lowmetallicity galaxies. After exploring different physical parameters, I find that the strength of PAH emission is best correlated with a combination of formation and destruction effects. In addition, using the high-resolution spectroscopy ([lambda]/[delta][lambda] ~ 600), I study the elemental abundances of neon and sulfur in BCDs and compare with the optical studies. I find that the infrared derived elemental abundances generally agree with the optical results, though the neon abundances are slightly higher from our study. I also analyze the FIR/radio correlation in BCDs and expand the discussion to the mid-IR. I find that the infrared luminosities are well correlated with the radio luminosities even in these low luminosity systems. A study on the spectral energy distribution (SED) and star formation rates (SFRs) in low-luminosity star-forming galaxies is also included in this thesis. The SEDs appear to be warmer than normal star-forming galaxies, and their SFRs vary over an order of magnitude. Finally, I also present a case study on the famous BCD IZw18, showing the first mid-infrared spectrum for this galaxy.
Download or read book Constraints on Environmental and Secular Effects on the Chemodynamical Evolution of Dwarf Galaxies written by Ryan Leaman and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents observations and analysis relating to the understanding of processes that govern the formation and evolution of low mass galactic systems. In particular we have focused on separating out the contribution to the chemical and dynamical evolution of dwarf galaxies due to solely secular (internal) processes compared to external effects from the local environment a galaxy resides in. Our observational data focus on an extremely isolated dwarf galaxy, WLM, which we demonstrate has had a uniquely quiescent tidal history, thereby making it an excellent test case for such a study. With spectroscopic and photometric observations of the resolved stars and neutral gas in WLM we have been able to characterize the chemical, structural and kinematic properties of this gas rich dwarf galaxy. As WLM has not been subject to strong tidal or ram-pressure stripping of its stellar and gaseous populations, we have been able to compare the dynamical evolution and chemical history of WLM to theoretical models which are environment independent. A differential comparison of WLM to more environmentally processed dwarf galaxies in the Local Group has revealed that WLM's structural and dynamical state is far from the idealized picture of dIrrs as thin gas-rich rotating systems. The stellar component of WLM shows equal parts rotation and dispersion, and both the gaseous and stellar structural properties show an intrinsically thick axisymmetric configuration. The time evolution of the random (dispersion) component of the stellar orbital energy shows an increase with stellar age, which we show is consistent with secular processes alone - such as disk heating from giant molecular clouds and dark matter substructure. While the degree to which the thick structural and dynamically hot configuration for WLM is surprising, its chemical properties show remarkably consistent values with other galaxies of the same halo mass. Comparing the spatial chemical trends in WLM with other dwarf galaxies we identify a correlation between the strength of the radial abundance gradients and the angular momentum content of dwarf galaxies in the Local Group. Finally using a large sample of chemical abundance measurements in the literature for dwarf galaxies and star clusters, we demonstrate that their distributions of chemical elements all exhibit a binomial form, and use the statistical properties of the distributions to identify a new metric for differentiating low luminosity stellar systems. We further apply a simple binomial chemical evolution model to describe the self-enrichment and pre-enrichment in the two classes of objects, and suggest how this may be used to place constraints on the formation environments of globular clusters in particular.
Download or read book An Optical and Infrared Analysis of Blue Compact Dwarf Galaxies written by B. L. James and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An understanding of Blue Compact Dwarf galaxies (BCDs) and the processes occurring within their chemically un-evolved environments is fundamental in our understanding of the early universe. This thesis presents an investigation into their physical conditions, kinematics, chemical abundances and dust compositions. An optical integral field spectroscopy investigation of two perturbed BCDs, UM420 and UM462, is presented. Emission line maps show that both galaxies display signs of ongoing perturbation and/or interaction. Electron temperatures, densities and chemical abundances are computed from spectra integrated over the whole galaxies and for each area of star formation. A similar yet more complicated analysis is undertaken of the BCD Mrk996, which displays multi-component emission lines. The high excitation energy [O III] \lambda4363 and [N II] \lambda5755 lines are detected only in the inner regions and purely in broad component form, implying unusual excitation conditions. A separate physical analysis of the broad and narrow emission line regions is undertaken, yielding a revised metallicity and N/O ratio typical for the galaxy's metallicity. The mid-IR properties of 19 BCDs are studied through Spitzer spectral and imaging data. The depeletion of PAH emission in BCDs is investigated and found to be due to formation and destruction effects. The [S III] flux ratio is used as a density diagnostic, showing typically low-densities. Maps of PAH emission and radiation field hardness are derived from IRS spectral mapping data. Blackbody fits to IR photometric SEDs typically reveal two dust components. The observed physical and chemical properties of Mrk 996 are successfully reproduced using the photoionisation code MOCASSIN. The best-fit model involved the inclusion of a filling factor and an amorphous carbon dust component with a two-zone dust distribution. A STARBURST99 input spectrum was used, yielding ages consistent with the known young WR stars and old super star clusters within Mrk 996.
Download or read book Early Chemical Evolution of the Galaxy written by Lamya A. Saleh and published by . This book was released on 2001 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Star forming Dwarf Galaxies and Related Objects written by D. Kunth and published by Atlantica Séguier Frontières. This book was released on 1985 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Two Studies of the Galactic Chemical Evolution written by Sofia Feltzing and published by Coronet Books. This book was released on 1995 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Observational Evidence of the Large scale Environmental Influence on Dwarf Galaxy Evolution written by Kelly Ann Douglass and published by . This book was released on 2017 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate how the cosmic environment affects galaxy evolution in the Universe by studying gas-phase chemical abundances and other galaxy properties as a function of the large-scale environment and local density of galaxies. Using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, we estimate the oxygen and nitrogen abundances of 993 star-forming void dwarf galaxies and 759 star-forming dwarf galaxies in denser regions. We use the Direct Te method for calculating the gas-phase chemical abundances in the dwarf galaxies because it is best suited for low metallicity, low mass galaxies. A substitute for the [OII] 3727 doublet is developed, permitting oxygen abundance estimates of SDSS dwarf galaxies at all redshifts with the Direct Te method. We find that star-forming void dwarf galaxies have slightly higher oxygen abundances than star-forming dwarf galaxies in denser environments, but we find that void dwarf galaxies have slightly lower nitrogen abundances and lower N/O ratios than galaxies in denser regions. At smaller scales, we find that only the presence of a neighboring galaxy within 0.05 Mpc/h or 0.1 r_virial, or the presence of a group within 0.05 Mpc/h, influences a dwarf galaxy's evolution. Dwarf galaxies within 0.05 Mpc/h or 0.1 r_virial of another galaxy tend to be bluer, have higher sSFRs, have higher oxygen abundances, and have lower N/O ratios than average. In contrast, galaxies within 0.05 Mpc/h of the center of the closest group have lower oxygen and nitrogen abundances than average. We also investigate how a galaxy transitions through the color-magnitude diagram, evolving from a blue, star-forming spiral or irregular galaxy in the blue sequence to a red elliptical galaxy in the red cloud through the green valley. We discover that combining a galaxy's color, color gradient, and inverse concentration index determines a galaxy's location on the color-magnitude diagram. The results indicate that, in the green valley, there is a lower fraction of void dwarf galaxies than dwarf galaxies in denser regions. From these analyses, we surmise that void dwarf galaxies experience delayed star formation as predicted by the Lambda CDM cosmology. We also conjecture that cosmic downsizing corresponds to a shift towards star formation in both lower mass objects and void regions closer to the present epoch. We present evidence that void dwarf galaxies may have a higher ratio of dark matter halo mass to stellar mass when compared to dwarf galaxies in denser environments.
Download or read book The Evolution of Galaxies written by José M. Vilchez and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies have a history. This has become clear from recent sky surveys showing that distant galaxies, formed early in the life of the Universe, differ from the nearby ones. This book contains the proceedings of a 2000 conference addressing observational clues in this area.
Download or read book Chemical Evolution of Galaxies written by Francesca Matteucci and published by Springer Science & Business Media. This book was released on 2012-01-05 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of the chemical evolution of the Milky Way, spheroidal galaxies, irregular galaxies and of cosmic chemical evolution. The aim of this book is to provide an introduction to students as well as to amend our present ideas in research; the book also summarizes the efforts made by authors in the past several years in order to further future research in the field.
Download or read book Chemodynamical Properties of Simulated Late type Galaxies written by Kate Pilkington and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Evolution of The Milky Way written by F. Matteucci and published by Springer Science & Business Media. This book was released on 2000 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt: This review of the most up-to-date observational and theoretical information concerning the chemical evolution of the Milky Way compares the abundances derived from field stars and clusters, giving information on the abundances and dynamics of gas.
Download or read book The Chemical Evolution of Phosphorus written by Enrique Macia-Barber and published by CRC Press. This book was released on 2019-11-21 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here is a fascinating reader-friendly exploration of “the phosphorus enigma.” The volume attempts to answer the questions: How did phosphorus atoms, which are produced inside the inner cores of a handful of huge stars, become concentrated in relatively high proportions in the organisms composing Earth’s biosphere? And how did these phosphate derivatives manage to be included in such a great variety of organic molecules playing essential biochemical roles in all known life forms? Due to the interdisciplinary nature of the topic, the volume is arranged in three sections. The first section introduces the fundamental concepts and notions of physics, chemistry, and biology necessary for the proper understanding of the topics discussed within an astronomical framework. The author then focuses on the role of phosphorus and its compounds within the context of chemical evolution in galaxies, considering its relevance in most essential biochemical functions as well as its peculiar chemistry under different physicochemical conditions. The third section provides an overall perspective on the role of phosphorus and its compounds in current areas of research of solid state physics, materials engineering, nanotechnology or medicine.
Download or read book Chemical Evolution of Galaxies with Active Star Formation written by Takakubo, K. and published by . This book was released on 1987 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book FORMATION AND EVOLUTION OF BLUE COMPACT DWARF GALAXIES written by Luz Marina Cairós Barreto and published by . This book was released on 2001 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NGC 1705 and the Evolution of Blue Compact Dwarf Galaxies written by Hans-Gerhardt R. Meurer and published by . This book was released on 1989 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites written by S. Randich and published by Springer Science & Business Media. This book was released on 2006-09-25 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings covers topics from chemical abundances in the different components of the Milky Way and in local group galaxies, via observational and theoretical papers on mixing in stars to big bang nucleosynthesis and galaxy formation and evolution. Like all volumes in the series ESO Astrophysics Symposia, this one gives a comprehensive overview of the forefront of research in this subject. It is a valuable reference for both students and researchers.
