In this thesis we use multi-transitional millimeter/submillimeter-wave molecular spectroscopy of CO and CS to determine the state of the molecular gas in the central regions of three starbursts: M82, IC342, and M83. High angular resolution 60 and 100 μm IRAS images provide complementary information about the thermal dust emission in IC342 and M83. Our CO observations reveal the presence of a molecular ring and supernovae driven wind in M82. In IC342 and M83 there is evidence for molecular bars and central rotating cores. The CO and CS line ratio analyses suggest a multicomponenet medium with clouds externally heated by ultraviolet flux from young, massive stars. Excitation temperatures typically range from 20 to 40 K throughout the nuclear regions of the sample galaxies. In M82 the CO and CS optical depths are ∼ 1. Our analysis of ¹²CO indicates that this gas is optically thick toward the centers of IC342 and M83. The molecular gas mass in each galaxy is ∼ 5x10⁷ M(⊙). We derive an average cloud size between 0.1 and 1 pc in the nuclear region of M82 and M83. An average cloud size of 10 pc is found over a comparable region in IC342. From tidal arguments we find that the clouds must have densities greater than 100 to 1000 cm⁻³ to survive. If the clouds are virialized, then the expected individual cloud linewidths are 9, 40, 5 and 27 km/s for M82, IC342, M83 and the Milky Way, respectively. For the clouds to be pressure-bound, inter-cloud pressures > 10x the peak value in the Galactic Center are required. If the magnetic fields are frozen into the gas, an average field strength of 8.5 mG is needed to support the nuclear clouds in each galaxy from collapse. Enhanced IRAS images reveal bright, compact nuclear components in IC342 and M83. HII regions are seen along spiral arms in IC342 and a dusty bar is seen in M83. The similarity between radio continuum maps and the high resolution IRAS maps suggest that infrared emission arises from HII regions. Using an emissivity law of β ∼ 1.5, the derived dust temperatures in the nuclei of IC342 and M83 are essentially the same as the gas excitation temperatures. For this to occur, gas densities of > 10⁴ cm⁻³ are implied. We derive a star-formation efficiency, ∊, of 77, 60, 10 and 2% for M82, M83, IC342, and the Milky Way, respectively. We find evidence that the gas surface density toward the centers of these galaxies is α ∊. We estimate star-formation rates of 16, 6, 2.5, and .06 M(⊙)/yr for M82, M83, IC342 and the Milky Way. The gas depletion timescales are a few million years for M82 and M83 and a few times 10⁷ and 10⁸ years in IC342 and the Milky Way. We find a strong correlation between cloud diameter and star-formation efficiency, with smaller clouds found in galaxies with higher ∊. We conclude these smaller clouds are a by-product and not a causal factor of the starburst phenomenon.

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This report looks closer on the physics of black holes and their related phenomena. Particularly, this report studies a certain black hole called Gargantua that is portrayed in the movie Interstellar. By using this as a source of inspiration we look at Gargantua’s effect on time, planetary orbits and tidalforces. The following report showed that the physics studied here corresponded fully to the physics represented in Interstellar, making the movie very credible from a physics point of view. I show that the black hole portrayed in Interstellar needed to spin at a rate of 1.33*10^-14 percent less than its maximum possible to achieve a timedilation of 61320 at the distance where stable planetary orbits are found. At a spin this high, planets can have stable orbits as close as half the Schwarzschild radius which means they are located just outside the event horizon of a maximally rotating black hole. The enormous timedilation at planets orbiting near the event horizon is a result of the planets close proximity to the black hole, its orbital velocity and frame dragging. Frame dragging describes the effects on spacetime on account of the rotation of the black hole. Looking at the tidal forces on objects surrounding the black hole it was found that an increasing mass would actually decrease the tidal forces on objects outside the event horizon. For a sufficiently large mass on the black hole, a planet could avoid being ripped apart but this restricted its size to a radial extension of about 5500 km which corresponds to 0.86 earth radiuses.

This dissertation presents a study of shock-excited molecular hydrogen (H2) in the interstellar medium. The aims of this thesis are to understand the shock-excitation process and to understand the global role of shocks in the interstellar medium. These aims are quantified as the investigation of specific problems. To address the problems, a variety of observing techniques have been applied and several sources studied, with particular reference on supernova remnant IC 443. An analytical model for the cooling flow behind a shock has also been developed. The observations show that extensive regions of low surface brightness H2 line emission are common in shocked molecular sources. Models are presented for three sources; IC 443, CRL 616 and OMC-1. In IC 443 emission comes from a sinuous ridge, about 20 parsecs long ans less than a parsec wide, with over 20 bright emission peaks distributed along it. The total H2 line luminosity is ~1600L, making IC 443 one of the brightest galactic H2 emission line objects yet detected. The spatial distributions of accelerated line emissions from other molecules (CO, HCO+, HCN) and atomic gas (HI) are remarkably similar to that of shocked H2. There is evidence for partial dissociation of molecular gas by the shock, but there can be little ionised gas present. Important cooling mechanisms for the hot gas (and possibly the dominant mechanisms) are H2 line radiation and H2 dissociation, except possibly in the densest clumps where far-IR emission from collisionally heated grains may dominate. H" line profiles were obtained in several sources and show considerable variation between sources. In CRL 618 the line is ~250km/s wide, the largest yet measured for a galactic source, and is composed of several discrete components. the high-velocity line emission is interpreted as being due to the shocking of high-velocity, discrete molecular clumps, embedded in and shocked by a stellar wind. Line polarization measurements in OMC-1 show there are two distinct regions of H2 line emission. In the outflow region the line is dichroically polarized by a slab of alligned grains lying between us and the outflow, with polarization vectors parallel to the outflow axis. The alignment mechanism is possibly due to the agency of a magnetic field, and thus the polarization vectors may trace the magnetic field direction which is therefore aligned with the outflow axis. Outside the core region the polarization vectors show a centro-symmetric pattern characteristic of scattering, centred on the region of peak molecular hydrogen emission. This amounts to the discovery of a molecular hydrogen reflection nebula. Observations of five H2 lines, in four types of sources, show no major differences in relative line ratios between sources. This is dispite different pre-shock conditions being expected in each source. The shocked gas cannot be characterised by a single excitation temperature. An analytical model has been developed for the cooling flow behind a jump-shock into molecular gas, driven by an isobaric thermal pressure. The model predicts that, when the density is larger than the critical density needed to thermalise the level populations of the dominant coolant, and t the post-shock temperature is sufficiently large, then the line ratios only depend on the upper-state level energies of the lines and on the form of the cooling function. For the observed excitation temperatures, the dominant cooling mechanism, consistent with the data, is cooling through the vibrational/ rotational lines of the hydrogen molecule itself. This conclusion applies when the temperature is in the range ~500 - 4000 K and the gas density is >10(5)cm-3

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 187). / Also available by subscription via World Wide Web / xxiii, 187 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 33).

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 187).

Thesis (Ph.D.) - Rijksuniversiteit Groningen (Netherlands), 2009.