Stars, Interstellar Medium and the Galaxy Commons^™

A Multi-Wavelength Determination Of The Total Luminosity And Star Formation Rate Of The Milky Way, Joshua L. Mascoop

Graduate Theses, Dissertations, and Problem Reports

The star formation rate (SFR) of the Milky Way is poorly understood in comparison to the SFR of other galaxies. In order to better find the Galaxy's place in the universe, it is imperative to understand the star formation activity occurring within it. We characterize the Galactic \hii\ region luminosity function (LF) at multiple infrared and radio wavelengths using a sample of 797 first Galactic quadrant \hii regions compiled from the WISE Catalog of Galactic \hii Regions. This sample is statistically complete for all regions powered by single stars of type O9.5V and earlier.

We find that neither a single …

Star Formation In Dwarf Galaxies, Simeon L. Bolds

FIU Electronic Theses and Dissertations

A catalog of neutral hydrogen (HI) of nearby dwarf galaxies obtained from the LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey) project along with ancillary data are used to examine the relative importance of star-induced star formation associated with the HI holes in 31 dwarf galaxies. HI shells/rings surrounding the HI holes are defined and the fractional amounts of HI and star formation in the rings relative to the global galactic amounts are calculated. These are then compared to look for correlations between the amount of star formation and neutral hydrogen in the rings. Two …

Mid-Infrared Studies Of Galactic Sources: Probing The Relationship Between Polycyclic Aromatic Hydrocarbons And Their Physical Environment, Collin Matthew Knight

Electronic Thesis and Dissertation Repository

Over the past 50 years, prominent mid-infrared (MIR) emission features from 3--20 $\mu$m have been observed ubiquitously in the interstellar medium (ISM) of Galactic and extragalactic sources. These emission features arise from the vibrational relaxation of polycyclic aromatic hydrocarbons (PAHs) after the absorption of a far-ultraviolet (FUV) photon. PAHs are astronomically significant in that they contain up to 15\% of the cosmic carbon inventory and play an important role in the physical and chemical processes of the ISM such as, for example, the gas heating and the ionization balance. Variations in the relative strengths of the major PAH bands can …

The Impact Of Hii Regions On The Interstellar Medium Of Our Galaxy, Matteo Luisi

Graduate Theses, Dissertations, and Problem Reports

The interstellar medium (ISM) of our Galaxy contains low-density diffuse ionized gas known as the warm ionized medium (WIM). O- and B-type stars emit large amounts of ionizing radiation and it is believed that a fraction of this radiation escapes from their fully ionized HII regions and into the ISM where it is responsible for maintaining the ionization of the WIM. Here we aim to better understand how the radiation produced by OB stars is able to leak from the HII regions, how the radiation field changes during this process, and how the radiation affects the ambient ISM. Using Green …

Dicke’S Superradiance In Astrophysics, Fereshteh Rajabi

Electronic Thesis and Dissertation Repository

It is generally assumed that in the interstellar medium much of the emission emanating from atomic and molecular transitions within a radiating gas happen independently for each atom or molecule, but as was pointed out by R. H. Dicke in a seminal paper several decades ago this assumption does not apply in all conditions. As will be discussed in this thesis, and following Dicke’s original analysis, closely packed atoms/molecules can interact with their common electromagnetic field and radiate coherently through an effect he named superradiance. Superradiance is a cooperative quantum mechanical phenomenon characterized by high intensity, spatially compact, burst-like features …

Zeeman Effect Studies Of Magnetic Fields In The Milky Way, Kristen Lynn Thompson

Theses and Dissertations--Physics and Astronomy

The interstellar medium (ISM) of our Galaxy, and of others, is pervaded by ultra low-density gas and dust, as well as magnetic fields. Embedded magnetic fields have been known to play an important role in the structure and dynamics of the ISM. However, the ability to accurately quantify these fields has plagued astronomers for many decades. Unfortunately, the experimental techniques for measuring the strength and direction of magnetic fields are few, and they are observationally challenging. The only direct method of measuring the magnetic field is through the Zeeman effect.

The goal of this dissertation is to expand upon the …

H2s (22,0-21,1) Observations Toward The Sgr B2 Region, Young C. Minh, William M. Irvine, S J. Kim

William M. Irvine

The H2S 22,0-21,1 line emission is observed to be strongly localized toward Sgr B2(M), and emissions from other positions in the more extended SgrB2 region are almost negligible. H2S is thought to form effectively by the passage of the C-type shocks but to be quickly transformed to SO2 or other sulfur species (Pineau des Forêts et al. 1993). Such a shock may have enhanced the H2S abundance in Sgr B2(M), where massive star formation is taking place. But the negligible emission of H2S from other observed positions may indicate that these positions have not been affected by shocks enough to …