The Physical Properties in the Interstellar Medium of Low-metallicity Dwarf Galaxies

The Physical Properties in the Interstellar Medium of Low-metallicity Dwarf Galaxies PDF Author: Diane Cormier
Publisher:
ISBN:
Category :
Languages : en
Pages : 257

Get Book Here

Book Description
In the framework of galaxy evolution, local star-forming dwarf galaxies are ideal laboratories to study star formation processes at low metallicity and the role of metal enrichment on the physical conditions. My thesis has focused on the study of the gas properties of the dwarf galaxies from "The Herschel Dwarf Galaxy Survey", combining observations and modeling efforts. I have investigated the role of the most important tracers of the multi-phase the interstellar medium (ISM), in the mid-infrared to submillimeter range. Particular attention was paid to the ionized and neutral gas coolants observed with Herschel Space Observatory (e.g. [OIII] 88, [OI]63, [CII] 157 micron lines), and to the CO molecule, probing the molecular phase, with complementary ground-based observations. The data are interpreted in physical terms (density, radiation field, filling factors) with radiative transfer models. This work has helped elucidate the structure and conditions of the low-metallicity ISM. It highlights the porosity of the ISM of dwarf galaxies, with ultraviolet photons from the massive star-forming regions excitinig the gas out to large distances. This results in the presence of large volume filling factor diffuse ionized/neutral gas, clumpy photodissociation regions, and little observed molecular gas due to large-scale photodissociation.

The Physical Properties in the Interstellar Medium of Low-metallicity Dwarf Galaxies

The Physical Properties in the Interstellar Medium of Low-metallicity Dwarf Galaxies PDF Author: Diane Cormier
Publisher:
ISBN:
Category :
Languages : en
Pages : 257

Get Book Here

Book Description
In the framework of galaxy evolution, local star-forming dwarf galaxies are ideal laboratories to study star formation processes at low metallicity and the role of metal enrichment on the physical conditions. My thesis has focused on the study of the gas properties of the dwarf galaxies from "The Herschel Dwarf Galaxy Survey", combining observations and modeling efforts. I have investigated the role of the most important tracers of the multi-phase the interstellar medium (ISM), in the mid-infrared to submillimeter range. Particular attention was paid to the ionized and neutral gas coolants observed with Herschel Space Observatory (e.g. [OIII] 88, [OI]63, [CII] 157 micron lines), and to the CO molecule, probing the molecular phase, with complementary ground-based observations. The data are interpreted in physical terms (density, radiation field, filling factors) with radiative transfer models. This work has helped elucidate the structure and conditions of the low-metallicity ISM. It highlights the porosity of the ISM of dwarf galaxies, with ultraviolet photons from the massive star-forming regions excitinig the gas out to large distances. This results in the presence of large volume filling factor diffuse ionized/neutral gas, clumpy photodissociation regions, and little observed molecular gas due to large-scale photodissociation.

Properties of the Interstellar Medium of the Star-forming Galaxy, IC10, at Various Spatial Scales

Properties of the Interstellar Medium of the Star-forming Galaxy, IC10, at Various Spatial Scales PDF Author: Fiorella Lucia Polles
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Get Book Here

Book Description
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.

Constraining the Properties of the Metal-poor ISM with Interferometric CO Observations of Low Metallicity Dwarf Galaxies

Constraining the Properties of the Metal-poor ISM with Interferometric CO Observations of Low Metallicity Dwarf Galaxies PDF Author: Edward M. Molter
Publisher:
ISBN:
Category : Cobalt
Languages : en
Pages :

Get Book Here

Book Description
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.

Toward the Comprehension of the Infrared to Submillimeter View of the Interstellar Medium of Nearby Galaxies

Toward the Comprehension of the Infrared to Submillimeter View of the Interstellar Medium of Nearby Galaxies PDF Author: Maud Galametz
Publisher:
ISBN:
Category :
Languages : en
Pages : 200

Get Book Here

Book Description
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.

Dwarf Galaxies (IAU S344)

Dwarf Galaxies (IAU S344) PDF Author: Kristen B. W. McQuinn
Publisher: Cambridge University Press
ISBN: 9781108471619
Category : Science
Languages : en
Pages : 500

Get Book Here

Book Description
Dwarf galaxies are important tools for understanding structure formation and galaxy evolution across cosmic time. These low-mass systems allow us to gain a detailed understanding of stellar, chemical, and dynamical properties in the nearby universe; they also provide a unique window into the complex physics of the early universe. The Proceedings of IAU Symposium 344 present our current understanding of dwarf galaxies, with sections dedicated to: Local Group dwarf galaxies; the interstellar medium and star formation in dwarfs; metallicity, massive stars, and chemical evolution; the dwarf galaxy-environment connection; low-mass galaxies at high redshift; and dwarfs as cosmological probes. Broad overviews from leaders in the field, detailed presentation of cutting-edge results, and short summaries of a wide range of work are included for each of these topics, suitable for both experts and newcomers to the field.

Galaxies in the Local Volume

Galaxies in the Local Volume PDF Author: Bärbel Silvia Koribalski
Publisher: Springer Science & Business Media
ISBN: 1402069332
Category : Science
Languages : en
Pages : 375

Get Book Here

Book Description
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.

Evolution of Stars and Stellar Populations

Evolution of Stars and Stellar Populations PDF Author: Maurizio Salaris
Publisher: John Wiley & Sons
ISBN: 9780470092224
Category : Science
Languages : en
Pages : 386

Get Book Here

Book Description
Evolution of Stars and Stellar Populations is a comprehensive presentation of the theory of stellar evolution and its application to the study of stellar populations in galaxies. Taking a unique approach to the subject, this self-contained text introduces first the theory of stellar evolution in a clear and accessible manner, with particular emphasis placed on explaining the evolution with time of observable stellar properties, such as luminosities and surface chemical abundances. This is followed by a detailed presentation and discussion of a broad range of related techniques, that are widely applied by researchers in the field to investigate the formation and evolution of galaxies. This book will be invaluable for undergraduates and graduate students in astronomy and astrophysics, and will also be of interest to researchers working in the field of Galactic, extragalactic astronomy and cosmology. comprehensive presentation of stellar evolution theory introduces the concept of stellar population and describes "stellar population synthesis" methods to study ages and star formation histories of star clusters and galaxies presents stellar evolution as a tool for investigating the evolution of galaxies and of the universe in general

The Interstellar Medium in Galaxies

The Interstellar Medium in Galaxies PDF Author: J.M. van der Hulst
Publisher: Springer Science & Business Media
ISBN: 9401156204
Category : Science
Languages : en
Pages : 217

Get Book Here

Book Description
It has been more than five decades ago that Henk van de Hulst predicted the observability of the 21-cm line of neutral hydrogen (HI ). Since then use of the 21-cm line has greatly improved our knowledge in many fields and has been used for galactic structure studies, studies of the interstellar medium (ISM) in the Milky Way and other galaxies, studies of the mass distribution of the Milky Way and other galaxies, studies of spiral struc ture, studies of high velocity gas in the Milky Way and other galaxies, for measuring distances using the Tully-Fisher relation etc. Regarding studies of the ISM, there have been a number of instrumen tal developments over the past decade: large CCD's became available on optical telescopes, radio synthesis offered sensitive imaging capabilities, not only in the classical 21-cm HI line but also in the mm-transitions of CO and other molecules, and X-ray imaging capabilities became available to measure the hot component of the ISM. These developments meant that Milky Way was no longer the exclusive playground for ISM studies and that by reaching out to other galaxies astronomy had gained the advantage of having an "outside" view, though at the expense of giving up some linear resolution. Studies of the ISM in other galaxies are intimately connected to studies of the ISM in the Milky Way.

Properties and Kinematics of the Interstellar Medium in a Small Sample of Nearby Dwarf Galaxies

Properties and Kinematics of the Interstellar Medium in a Small Sample of Nearby Dwarf Galaxies PDF Author: Lisa Marie Young
Publisher:
ISBN:
Category :
Languages : en
Pages : 334

Get Book Here

Book Description


Highlights of Astronomy, Volume 11A

Highlights of Astronomy, Volume 11A PDF Author: Johannes Andersen
Publisher: Springer Science & Business Media
ISBN: 9780792353416
Category : Medical
Languages : en
Pages : 632

Get Book Here

Book Description
Since 1967, the main scientific events of the General Assemblies of the International Astronomical Union have been published in the separate series, Highlights of Astronomy. The present Volume 11 presents the major scientific presentations made at the XXIIIrd General Assembly, August 18-30, 1997, in Kyoto, Japan. The two volumes (11A + B) contain the text of the three Invited Discourses as well as the proceedings or extended summaries of the 21 Joint Discussions and two Special Sessions held during the General Assembly.