Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 21 for “"HII Regions"”.
-
Open clusters and HII regions of our Galaxy
Open clusters are essential laboratories for understanding stellar evolution, as they allow constraints to be placed on stellar ages and luminosities. As distance indicators they are also important tracers of star formation in the Milky Way. One such cluster is Trumpler 27 that we identified for …
-
Untangling compact and diffuse ionized emission toward galactic hii regions
HII regions are clouds of ionized hydrogen gas surrounding B0- and O-type stars. The ionized hydrogen in these regions emits both radio recombination line (RRL) and also thermal radio continuum. Diffuse ionized hydrogen, known as the 'Warm Ionized Medium' (WIM) also exists in the Galaxy. The WIM …
-
Star formation in the HII regions RCW 38, RCW 36, and RCW 108
I present 1.2 mm observations of the HII regions RCW 38, RCW 36, and RCW 108 which reveal the distributions of dust associated with the three regions. The dust emission in RCW 38 exhibits a ring like structure centered around an O-star. A bright knot in the ring was determined to contain 15% of the …
-
Exploiting pulsar timing at low radio frequencies: applications to Pulsar Timing Arrays, Interstellar medium and HII regions
… attention is given to discrete ionised regions, such as HII regions, whose presence can shape both the amplitude and the spectral behaviour of DM fluctuations. This approach links the observed chromatic noise to the properties and location of intervening scattering screens. To assess how …
-
A molecular line and continuum study of water maser sources
… indicators of star formation, such as HII regions and near-infrared emission, but which do lie close to otherwise isolated H2O masers. This thesis describes a search, based on catalogues of known water maser positions, for new deeply embedded cores similar to those found in S106 and …
-
The environmental impact of high- and low-mass stars: from formation to main sequence
… measurements of 52 Galactic star-forming regions with their locations in the Galaxy. In particular, we find that there is no correlation between the average magnetic field direction of star-forming molecular clouds and the Galaxy, indicating that star formation may eventually become its …
-
The Scattering of H-alpha Emission Associated with the Rosette Nebula in the Monoceros Region Studied Using Polarimetry
Polarimetric CCD images of HII regions were obtained using a rotating polarizer device designed, built, and used in conjunction with the Spectral Line Imaging Camera (SLIC) at Virginia Tech's Martin Observatory in Giles County, Virginia. The SLIC uses a narrow bandpass interference filter coupled …
-
The formation of population III stars and their effect on cosmological structure in the early universe
… simulations which demonstrate the effects of the HII regions and metal enrichment from Population III stars. It appears that HII regions from these stars may hasten the formation of later generations of stars, and even the weakest supernova can spread material over large distances. Further …
-
The Galaxy and beyond with the Arcminute Microkelvin Imager
… unusual objects such as ultra- and hyper-compact HII regions. I describe my work on the survey strategy and its implementation and on some of the science I have extracted so far including the follow-up of candidate hyper-compact HII regions. The recently-released Planck satellite results include …
-
Massive Star Formation at High Spatial Resolution
… of this work are: 1) Two massive star-forming regions are observed in the infrared. The thermal emission from the ultra-compact HII regions is resolved and the spectral type of the ionizing stars is estimated. The hot cores are not detected thus implying line-of-sight extinction larger than 200 …
-
EoR in alternative cosmological scenarios
… for the evolution and the distribution of the HII regions, and for the global features of reionization, that can be constrained by future observations. Finally, we brie y discuss the possible future prospects of this Thesis work.
-
Simulations of cosmic reionization
… the speeds of ionization fronts of cosmological HII regions. This is accomplished by a much more thorough analysis of how to properly model the density field on the unstructured density field in SimpleX. The dependence of the ionizing emissivity of GALFORM galaxies on various parameters of the …
-
Understanding the Earliest Stages of High-mass Star Formation
… clumps in this field and their Ultracompact HII regions. We have found highly clustered environments, a range of evolutionary stages, and signatures of triggering within the parsec-scale clumps hosting OB stars. Our study of the W3 GMC comprises an analysis of the young stellar objects (YSO), …
-
CREATING TEST MECHANISMS FOR SILICON SUBSTRATE BASED (SSB) DEVICES FOR USE IN FAR-IR TO MILLIMETER ASTROPHYSICAL SPECTROSCOPY
… star formation. The [OIII] line traces gas in HII regions formed by OB stars, while the [CII] line arises from nearby neutral gas clouds heated by OB star radiation.
-
THE CEPHEIDS OF M33: DISTANCE AND METALLICITY EFFECTS THROUGH SLOAN FILTERS
… Shallower metallicity gradients derived from HII regions produce unreasonably large corrections, suggesting that the use of chemical abundances derived from such tracers as a proxy for Cepheid metallicity is unreliable. An independent distance determination to M33 was obtained with the tip of …
-
Environmental Influences On Dwarf Galaxy Evolution: The Group Environment
… but when constrained by the requirement of HII regions, we find only one such candidate in Leo I. The work presented here lays the groundwork for future HI-based group studies which will be made possible with rich ALFALFA dataset.
-
The Evolution of Massive Young Stellar Objects in the Large Magellanic Cloud
… and ionized their surroundings to form compact HII regions and photodissociation regions. We quantify the contributions of the various spectral features using the statistical method of principal component analysis. Using this analysis, we classify the YSO spectra into several distinct groups …
-
Molecular clouds and star formation in the Inner Galaxy
… that the shock fronts at the edges of expanding HII regions might trigger subsequent generations of star formation (e.g. Elmegreen & Lada, 1977; Bertoldi, 1989), and there are observational studies to support this (e.g. Thompson et al., 2012). It has also been proposed that large-scale effects …
-
Mapping the interstellar magnetic field: Observations of the Goldreich-Kylafis effect towards late-type evolved stars and star-forming regions
… in both late-type evolved stars and star-forming regions. Observations of linearly polarized molecular line transitions arising from the Goldreich-Kylafis (G-K) effect provide valuable insight into the magnetic field geometry in these sources. Through observing with CARMA, the VLA, and ALMA, this …
-
The AGN-host galaxy connection : new insights from the extended ionised gas
… separating the emission of AGN-ionised gas from HII regions, ionised solely by recently formed massive stars, we demonstrate that the specific star formation rates in several disc-dominated AGN hosts are consistent with those of normal star forming galaxies, while others display no detectable …
Page 1 of 2