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 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 An Optical and Infrared Analysis of Blue Compact Dwarf Galaxies written by Bethan Lesley James and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical and Near Infrared Studies of the Photometric Structure and Starburst Acticity of Blue Compact Dwarf Galaxies written by Kai Gerhard Noeske and published by . This book was released on 2003 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical and Near Infrared Studies of the Photometric Structure and Starburst Activity of Blue Compact Dwarf Galaxies written by Kai Gerhard Noeske and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Infrared Astronomy at Extremely Faint Light Levels in Support of the LAIRTS Program written by Trinh X. Thuan and published by . This book was released on 1987 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Near - infrared observations have been obtained for a large sample of dwarf irregular galaxies, dwarf elliptical and blue compact dwarf galaxies. Near infrared photometry was obtained for radio sources discovered in a deep VLA radio survey. Near infrared observations were also obtained for the first brightest galaxy in a sample of nearby clusters. A large redshift survey, using the 21-cm hydrogen line, of dwarf galaxies in the northern hemisphere has been completed. Work has been done to understand the stellar populations and star formation are presently occurring. Keywords: Astronomy.
Download or read book A Mid infrared Study of Local Luminous Infrared Galaxies written by Tanio Díaz Santos and published by . This book was released on 2009 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of the Neutral Hydrogen Content of Blue Compact Dwarf Galaxies written by Jeremy A MacHattie and published by . This book was released on 2013 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of a study of the neutral hydrogen (HI) content and distribution within a sample of 18 blue compact dwarf galaxies (BCDs) are presented. An investigation of the behaviour of the gas-to-dust ratio (GDR) as a function of metallicity (Z) is also presented. Observations of these BCDs was performed using the Very Large Array (VLA) in 2009, a year in which the array was undergoing a technological upgrade to the the Karl G. Jansky VLA (JVLA). The observations were reduced and images processed using the Astronomical Image Processing Software (AIPS), and data cubes for each galaxy were produced. The results include detections of eleven HI lines (two new detections) and ten background continuum sources (two new discoveries). All detections are at a higher resolution and/or sensitivity than previous measurements. These detections spanned a large range of line widths and HI masses; some masses comparable to those in normal galaxies. Of particular interest was the discovery of a compact absorption feature in the dwarf galaxy Haro 11. A paper submitted to the Monthly Notices of the Royal Astronomical Society (MNRAS) Letters on this discovery is presented. Another significant result was the discovery of a highly extended and massive HI region in the dwarf galaxy CGCG 297-017. For those galaxies with no detected HI line or radio continuum, an upper limit to the flux density was computed, which was used to derive upper limits to the HI mass or star-formation rate (SFR) respectively. Three HI flux density upper limits are new results, and seven continuum flux density upper limits are also new. The GDR-Z relation at low metallicities shows a potential power law or broken power law relation with a turning point at Z=7.96 or Z=8.05. To within error, these turning points and power law indices of the broken power law fits are consistent with other work.
Download or read book NASA Reference Publication written by and published by . This book was released on 1987 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book A mid infrared study of local luminous infrared galaxies written by Tanio Díaz Santos and published by . This book was released on 2009 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Catalog of Infrared Observations Appendixes written by Daniel Y. Gezari and published by . This book was released on 1987 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Starbursting Dwarf Galaxies at Z 1 written by and published by . This book was released on 2015 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dwarf Galaxies as Laboratories of Protogalaxy Physics written by Jacqueline Ann Monkiewicz and published by . This book was released on 2018 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the upcoming decade, powerful new astronomical facilities such as the James Webb Space Telescope (JWST), the Square Kilometer Array (SKA), and ground-based 30-meter telescopes will open up the epoch of reionization to direct astronomical observation. One of the primary tools used to understand the bulk astrophysical properties of the high-redshift universe are empirically-derived star-forming laws, which relate observed luminosity to fundamental astrophysical quantities such as star formation rate. The radio/infrared relation is one of the more mysterious of these relations: despite its somewhat uncertain astrophysical origins, this relation is extremely tight and linear, with 0.3 dex of scatter over five orders of magnitude in galaxy luminosity. The effects of primordial metallicities on canonical star-forming laws is an open question: a growing body of evidence suggests that the current empirical star forming laws may not be valid in the unenriched, metal-poor environment of the very early universe. In the modern universe, nearby dwarf galaxies with less than 1/10th the Solar metal abundance provide an opportunity to recalibrate our star formation laws and study the astrophysics of extremely metal-deficient (XMD) environments in detail. I assemble a sample of nearby dwarf galaxies, all within 100 megaparsecs, with nebular oxygen abundances between 1/5th and 1/50th Solar. I identify the subsample of these galaxies with space-based mid- and far-infrared data, and investigate the effects of extreme metallicities on the infrared-radio relationship. For ten of these galaxies, I have acquired 40 hours of observations with the Jansky Very Large Array (JVLA). C-band (4-8 GHz) radio continuum emission is detected from all 10 of these galaxies. These represent the first radio continuum detections from seven galaxies in this sample: Leo A, UGC 4704, HS 0822+3542, SBS 0940+544, and SBS 1129+476. The radio continuum in these galaxies is strongly associated with the presence of optical H-alpha emission, with spectral slopes suggesting a mix of thermal and non-thermal sources. I use the ratio of the radio and far-infrared emission to investigate behavior of the C-band (4-8 GHz) radio/infrared relation at metallicities below 1/10th Solar. I compare the low metallicity sample with the 4.8 GHz radio/infrared relationship from the KINGFISHER nearby galaxy sample Tabatabaei et al. 2017 and to the 1.4 GHz radio/infrared relationship from the blue compact dwarf galaxy sample of Wu et al. 2008. The infrared/radio ratio q of the low metallicity galaxies is below the average q of star forming galaxies in the modern universe. I compare these galaxies' infrared and radio luminosities to their corresponding Halpha luminosities, and find that both the infrared/Halpha and the radio/H-alpha ratios are reduced by nearly 1 dex in the low metallicity sample vs. higher metallicity galaxies; however the deficit is not straightforwardly interpreted as a metallicity effect.
Download or read book Catalog of Infrared Observations written by Daniel Y. Gezari and published by . This book was released on 1993 with total page 884 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Literature 1987 Part 2 written by U. Esser and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy and Astrophysics Abstracts aims to present a comprehensive documen tation of the literature concerning all aspects of astronomy, astrophysies, and their border fields. It is devoted to the recording, summarizing, and indexing of the relevant publications throughout the world. Astronomy and Astrophysics Abstracts is prepared by a special department of the Astronomisches Rechen-Institut under the auspices of the International Astronomical Union. Volume 44 records literature published in 1987 and received before February 15, 1988. Some older documents which we received late and which are not surveyed in earlier volumes are inc1uded too. We acknowledge with thanks contributions of our colleagues all over the world. We also express our gratitude to all organiza tions, observatories, and publishers which provide us with complimentary copies of their publications. Dr. Siegfried Böhme retired from his duties as co-editor of Astronomy and Astro physics Abstracts on December 31, 1987. Since 1950 he partieipated in the biblio graphie work of the institute. He served as a reviewer for the Astronomischer Jahresbericht and became one of the editors of Astronomy and Astrophysics Ab stracts in 1969. After his retirement in 1975 he took care of, particularly, the Russian literature on a voluntary basis for 12 years. It is a pleasure to thank Siegfried Böhme for his valuable contributions. Starting with Volume 33, all the recording, correction, and data processing work was done by means of computers. The recording was done by our technical staff members Ms. Helga Ballmann, Ms. Christiane Jehn, Ms. Monika Kohl, Ms.
Download or read book Galaxies in the Local Volume written by Bärbel Silvia Koribalski and published by Springer Science & Business Media. This book was released on 2009-04-29 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: This timely book presents an overview of the galaxies within the Local Volume, including the Local Group and our closest neighbours, the Andromeda Galaxy and the Magellanic Clouds. Presented here are the latest results from radio, infrared and optical surveys as well as detailed multi-wavelength studies of individual galaxies. The book aims to provide a vibrant forum for presentations and discussions across a broad range of astrophysical topics.
