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Constraining The Properties Of The Metal Poor Ism With Interferometric Co Observations Of Low Metallicity Dwarf Galaxies
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Book Synopsis Constraining the Properties of the Metal-poor ISM with Interferometric CO Observations of Low Metallicity Dwarf Galaxies by : Edward M. Molter
Download or read book Constraining the Properties of the Metal-poor ISM with Interferometric CO Observations of Low Metallicity Dwarf Galaxies written by Edward M. Molter and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal deficient dwarf galaxies are critical test beds for theories about the structure of star forming clouds at low metallicity, the chemical evolution of the inerstellare medium, and the conditions in the early Universe. I present new high-resolution interferometric observations of the CO (J=1{right arrow] 0) emission line in five nearby metal poor dwarf irregular dwarf galaxies taken with the CARMA array. The first half of this work considers four galaxies with very extreme metaliicites (3-10% Solar), including Leo P, DDO 68, Sextans B. While CO was not detected in any of these systems, we are able to derive very sensitive upper limits to their global CO luminosities, calculate molecular hydrogen masses using various CO-to-H2 conversion factors, and compare these results to chemical evolution models. The second half of this work consists of a case study on the interstellar medium of NGC 6822, a famous Local Group dwarf irregular galaxy at ~30% of Solar metallicity. CARMA resolves ten individual clouds of dense CO emission at ~10 pc linear scales in a central region of the galaxy\. CO luminosities and derived H2 masses are presented for each cloud, and the cloud properties are compared to similar observations in the literature. I then leverage data at a myriuad of wavelenghts to draw spatial comparisons between the distributions of dense molecular gas, atomic gas, and dust at various temperatures.
Book Synopsis Properties of the Interstellar Medium of the Star-forming Galaxy, IC10, at Various Spatial Scales by : Fiorella Lucia Polles
Download or read book Properties of the Interstellar Medium of the Star-forming Galaxy, IC10, at Various Spatial Scales written by Fiorella Lucia Polles and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The properties of the Interstellar Medium (ISM) strongly influence the environment and processes that lead to star-formation, which in turn, drives the evolution of a galaxy. Dwarf galaxies in the Local Group are perfect laboratories to investigate how the metal-poor ISM affects the interplay between gas, dust and stars. In this thesis, I investigate the properties of the HII regions and the diffuse ionized gas of the nearby dwarf galaxy IC10, which has a metallicity of 1/3 solar. Its proximity (d=700 kpc) enables the analysis on different spatial scales: from the compact clumps (~25 pc) to the whole star-forming body of the galaxy (~650pc). In order to measure the physical properties of the ISM, I model the infrared emission lines observed with Spitzer and Herschel with photoionization and photodissociation models. I present an extensive exploration of different methods to determine the most reliable ISM properties, based on the available constraints. I determined the properties of the brightest star-forming clumps within the galaxy and show that the emission at large scales (~300 pc) is dominated by that of the compact, bright clumps that lie within the region. I further demonstrate the need for a multi-component model to fully reproduce the observations.
Book Synopsis Toward the Comprehension of the Infrared to Submillimeter View of the Interstellar Medium of Nearby Galaxies by : Maud Galametz
Download or read book Toward the Comprehension of the Infrared to Submillimeter View of the Interstellar Medium of Nearby Galaxies written by Maud Galametz and published by . This book was released on 2010 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis aims to study the interstellar medium (ISM) of low-metallicity galaxies to characterize the physical properties of the gas and dust and to study the influence of metal enrichment on the ISM properties of galaxies. We adopt a multi-wavelength (infrared/submillimeter) approach to model the spectral energy distributions (SEDs) of these galaxies and showed that their fraction of cool dust can be significant compared to their total dust mass. Some dust-to-gas mass ratios are incoherent compared to what is expected from current chemical évolution models, revealing possible reservoirs of gas not detected by current HI or CO observations. I enlarged the first sample to a wider range of metallicities and showed that submm measurements significantly affect the dust mass estimates of galaxies. We also obtained submm observations of a resolved star forming complex of the Large Magellanic Cloud and studied the spatial variations of the SEDs to get a handle on the temperature distribution. I finally present the first images of dwarf galaxies with Herschel. For one of them, we modeled the SEDs of some HII regions and less active regions. The SEDs of HII regions show warmer ranges of dust temperature. We also studied the influence of using amorphous carbon to describe carbon dust in the total dust mass estimates. Our results indicate that SED models including Herschel data may require different dust properties than commonly used.
Book Synopsis Dust at Low-metallicity by : Dale Clayton Jackson
Download or read book Dust at Low-metallicity written by Dale Clayton Jackson and published by . This book was released on 2007 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seper maʻaśeh šaʻašẇʻiym written by and published by . This book was released on 1868 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Local Group and Its Dwarf Galaxy Members in the Standard Model of Cosmology by : Azadeh Fattahi
Download or read book The Local Group and Its Dwarf Galaxy Members in the Standard Model of Cosmology written by Azadeh Fattahi and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: According to the current cosmological paradigm, ``Lambda Cold Dark Matter'' (LambdaCDM), only ~20% of the gravitating matter in the universe is made up of ordinary (i.e. baryonic) matter, while the rest consists of invisible dark matter (DM) particles, which existence can be inferred from their gravitational influence on baryonic matter and light. Despite the large success of the LambdaCDM model in explaining the large scale structure of the Universe and the conditions of the early Universe, there has been debate on whether this model can fully explain the observations of low mass (dwarf) galaxies. The Local Group (LG), which hosts most of the known dwarf galaxies, is a unique laboratory to test the predictions of the LambdaCDM model on small scales. I analyze the kinematics of LG members, including the Milky~Way-Andromeda (MW-M31) pair and dwarf galaxies, in order to constrain the mass of the LG. I construct samples of LG analogs from large cosmological N-body simulations, according to the following kinematics constraints: (a) the separation and relative velocity of the MW-M31 pair; (b) the receding velocity of dwarf galaxies in the outskirts of the LG. I find that these constraints yield a median total mass of 2*10^#x12; solar masses for the MW and M31, but with a large uncertainty. Based on the mass and the kinematics constraints, I select twelve LG candidates for the APOSTLE simulations project. The APOSTLE project consists of high-resolution cosmological hydrodynamical simulations of the LG candidates, using the EAGLE galaxy formation model. I show that dwarf satellites of MW and M31 analogs in APOSTLE are in good agreement with observations, in terms of number, luminosity and kinematics. There have been tensions between the observed masses of LG dwarf spheroidals and the predictions of N-body simulations within the LambdaCDM framework; simulations tend to over-predict the mass of dwarfs. This problem is known as the ``too-big-to-fail'' problem. I find that the enclosed mass within the half-light radii of Galactic classical dwarf spheroidals, is in excellent agreement with the simulated satellites in APOSTLE, and that there is no too-big-to-fail problem in APOSTLE simulations. A few factors contribute in solving the problem: (a) the mass of haloes in hydrodynamical simulations are lower compared to their N-body counterparts; (b) stellar mass-halo mass relation in APOSTLE is different than the ones used to argue for the too-big-to-fail problem; (c) number of massive satellites correlates with the virial mass of the host, i.e. MW analogs with virial masses above ~ 3*10^#x12; solar masses would have faced too-big-to-fail problems; (d) uncertainties in observations were underestimated in previous works. Stellar mass-halo mass relation in APOSTLE predicts that all isolated dwarf galaxies should live in haloes with maximum circular velocity (V_max) above 20 km/s. Satellite galaxies, however, can inhabit lower mass haloes due to tidal stripping which removes mass from the inner regions of satellites as they orbit their hosts. I examine all satellites of the MW and M31, and find that many of them live in haloes less massive than V_max=20 km/s. I additionally show that the low mass population is following a different trend in stellar mass-size relation compared to the rest of the satellites or field dwarfs. I use stellar mass-halo mass relation of APOSTLE field galaxies, along with tidal stripping trajectories derived in Penarrubia et al., in order to predict the properties of the progenitors of the LG satellites. According to this prediction, some satellites have lost a significant amount of dark matter as well as stellar mass. Cra~II, And~XIX, XXI, and XXV have lost 99 per-cent of their stellar mass in the past. I show that the mass discrepancy-acceleration relation of dwarf galaxies in the LG is at odds with MOdified Newtonian Dynamics (MOND) predictions, whereas tidal stripping can explain the observations very well. I compare observed velocity dispersion of LG satellites with the predicted values by MOND. The observations and MOND predictions are inconsistent, in particular in the regime of ultra faint dwarf galaxies.
Book Synopsis Star Formation in Low Metallicity Dwarf Galaxies by : David Whitworth
Download or read book Star Formation in Low Metallicity Dwarf Galaxies written by David Whitworth and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dwarf Galaxies written by Jürgen Ott and published by . This book was released on 2002 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Exploring Stellar Metallicities in Dwarf Galaxies and Their Implications by : Teresa Lynn Ross
Download or read book Exploring Stellar Metallicities in Dwarf Galaxies and Their Implications written by Teresa Lynn Ross and published by . This book was released on 2015 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I discuss issues involving stellar metallicities in dwarf galaxies. Stars reflect the gas composition at the time they formed, thereby making the metallicity distribution function (MDF - the relative number of stars as a function of metallicity) a record of the chemical evolution within a galaxy. I measure photometric metallicities using Wide Field Camera 3 (WFC3) obervations aboard the Hubble Space Telescope. Advantages of photometric metallicities include measuring every star in the field down to fainter magnitudes than allowed by spectroscopy. I quantified and calibrated the metallicity and temperature sensitivities of colors derived from nine WFC3 filters using Dartmouth isochrones and Kurucz model atmospheres. The photometric metallicities were tested and calibrated with five well studied Galactic clusters spanning three orders of magnitude in metallicity M92, NGC 6752, NGC 104, NGC 5927, and NGC 6791. The greatest accuracy in assigning metallicity was found using the (F390M-F555W) color, with the main advantage being the increased color sensitivity at low metallicity. MDFs for a population, along with chemical evolution models provide evolutionary information about gas flows and enrichment within the galaxy. I measured photometric metallicities in Leo I, Leo II, IC 1613, and Phoenix, and analytical chemical evolution models were fit to their MDFs. The MDF shapes, chemicals evolution models and dynamic histories suggest that the galactic conditions during periods of star formation influenced the metallicities. I find that the narrower MDFs are indicative of interactions occurring in concert with star formation, while a broader MDF indicates a passive evolution. Additionally, I explore ways to combine chemical evolution models and star formation histories (SFH), to quantify the metallicity evolution with time. The SFHs of Weisz et al. (2014) are assessed for their potential to determine MDFs for 40 Local Group dwarf galaxies. The SFH-MDF connection is examined by comparing similar MDFs measured by Kirby et al. (2013) and the SFHs. Galaxies with comparable MDFs show similar characteristics in their SFHs. Overall, I find that the SFH, interaction history, and stellar mass are important contributors to the metallicity enrichment in dwarf galaxies.
Book Synopsis NGC 1569 - the ISM of a Dwarf Galaxy in the Aftermath of a Starburst by : Stefanie Mühle
Download or read book NGC 1569 - the ISM of a Dwarf Galaxy in the Aftermath of a Starburst written by Stefanie Mühle and published by Cuvillier Verlag. This book was released on 2003 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Iron and Alpha Element Distributions in Milky Way Dwarf Satellite Galaxies from Medium-resolution Spectroscopy by : Evan N. Kirby
Download or read book Iron and Alpha Element Distributions in Milky Way Dwarf Satellite Galaxies from Medium-resolution Spectroscopy written by Evan N. Kirby and published by . This book was released on 2009 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dwarf Galaxies in a Cosmological Context by :
Download or read book Dwarf Galaxies in a Cosmological Context written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of this new model on our simulated dwarf galaxy is significant, as it produces stronger galactic winds that suppress and regulate star formation and more efficiently eject metals from star forming gas. The resulting system at z = 0 has an order of magnitude lower luminosity and an average stellar metallicity consistent with observed dwarfs. The distribution of stellar metallicity is too narrowly peaked, however, indicating the need for further refinement of our model and perhaps the inclusion other sources of stellar feedback such as Type Ia supernovae or stellar winds. We conclude that the observed chemical abundance patterns in local dwarf galaxies provide a unique testbench for refining models of stellar feedback in galaxy simulations at high resolution.
Book Synopsis Constraining Dwarf Galaxy Properties Using Tidal Streams by : Siddhartha Shelton
Download or read book Constraining Dwarf Galaxy Properties Using Tidal Streams written by Siddhartha Shelton and published by . This book was released on 2018 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Photometric Calibrations of Metallicity and Temperature For M Dwarfs by : Neda Hejazi
Download or read book Photometric Calibrations of Metallicity and Temperature For M Dwarfs written by Neda Hejazi and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book TASPO-Wissen written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Exploring Data Tables, Trends, and Shapes by : David C. Hoaglin
Download or read book Exploring Data Tables, Trends, and Shapes written by David C. Hoaglin and published by John Wiley & Sons. This book was released on 2011-09-28 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: WILEY-INTERSCIENCE PAPERBACK SERIES The Wiley-Interscience Paperback Series consists of selected books that have been made more accessible to consumers in an effort to increase global appeal and general circulation. With these new unabridged softcover volumes, Wiley hopes to extend the lives of these works by making them available to future generations of statisticians, mathematicians, and scientists. "Exploring Data Tables, Trends, and Shapes (EDTTS) was written as a companion volume to the same editors' book, Understanding Robust and Exploratory Data Analysis (UREDA). Whereas UREDA is a collection of exploratory and resistant methods of estimation and display, EDTTS goes a step further, describing multivariate and more complicated techniques . . . I feel that the authors have made a very significant contribution in the area of multivariate nonparametric methods. This book [is] a valuable source of reference to researchers in the area." —Technometrics "This edited volume . . . provides an important theoretical and philosophical extension to the currently popular statistical area of Exploratory Data Analysis, which seeks to reveal structure, or simple descriptions, in data . . . It is . . . an important reference volume which any statistical library should consider seriously." —The Statistician This newly available and affordably priced paperback version of Exploring Data Tables, Trends, and Shapes presents major advances in exploratory data analysis and robust regression methods and explains the techniques, relating them to classical methods. The book addresses the role of exploratory and robust techniques in the overall data-analytic enterprise, and it also presents new methods such as fitting by organized comparisons using the square combining table and identifying extreme cells in a sizable contingency table with probabilistic and exploratory approaches. The book features a chapter on using robust regression in less technical language than available elsewhere. Conceptual support for each technique is also provided.
Book Synopsis The Interstellar Medium by : James Lequeux
Download or read book The Interstellar Medium written by James Lequeux and published by Springer Science & Business Media. This book was released on 2005-08-29 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describing interstellar matter in our galaxy in all of its various forms, this book also considers the physical and chemical processes that are occurring within this matter. The first seven chapters present the various components making up the interstellar matter and detail the ways that we are able to study them. The following seven chapters are devoted to the physical, chemical and dynamical processes that control the behaviour of interstellar matter. These include the instabilities and cloud collapse processes that lead to the formation of stars. The last chapter summarizes the transformations that can occur between the different phases of the interstellar medium. Emphasizing methods over results, The Interstellar Medium is written for graduate students, for young astronomers, and also for any researchers who have developed an interest in the interstellar medium.
