Astrophysics and Astronomy Commons^™

Numerical Simulations Of Accretion Disks And Extrasolar Planets, Stefan Luketic

UNLV Theses, Dissertations, Professional Papers, and Capstones

We study mass outflows from astrophysical objects. Using numerical hydrodynamical simulations, we investigate outflows from accretion disks and exoplanets. In the first part of this dissertation, we present the results of Zeus 2D hydrodynamical simulations of the disk photosphere irradiated by strong X–rays that are produced in the innermost part of the disk of an accreting black hole. As expected, the irradiation heats the photosphere and drives a thermal wind. To apply our results to the well– studied X–ray transient source GRO J1655–40, we utilized the observed mass of its black hole and the observed properties of its X–ray radiation …

Oral Presentation: The Universe In A Box, Jason Jaacks

Festival of Communities: UG Symposium (Posters)

When and how galaxies formed throughout the history of the Universe is one of the most fundamental questions of astronomy and astrophysics. As technology improves, astronomers are able to push the frontier of galaxy observation to a period when the Universe was less than 1 billion years old. This is when the first galaxies are beginning to form. However, beyond the limits of observational technology lies data fundamental to our complete understanding of these processes. Using state-of-the-art cosmological hydrodynamic computer codes combined with access to the nation’s largest and fastest supercomputers, we are able to simulate the formation and evolution …

Serpentinite Weathering And Implications For Mars, Valerie Tu, Julie Baumeister, Rodney Metcalf, A. Olsen, Elisabeth Hausrath

Festival of Communities: UG Symposium (Posters)

In the search for life on Mars near-surface soil environments may be important habitats for life accessible to future missions. Serpentinite rocks have been documented on Mars, as well as other clay minerals including smectite and kaolinites. Previous studies of soils formed on serpentinites on Earth have documented the formation of extensive clays. Serpentinites are additionally of interest as habitats for life such as methanogens. Here we examine weathering of serpentinites from bedrock to soil surface, as a potential route for the formation of clay minerals on Mars from abundant ultramafic minerals. We additionally test for the presence of Fe-oxidizing …

Halo Occupation Of Lyman-Break Galaxies, Saju Varghese, Ken Nagamine, Jason Jaacks, Jun-Hwan Choi

Festival of Communities: UG Symposium (Posters)

Lyman-break galaxies (LBGs) are star-forming galaxies found at high redshift that provide large amounts of information on early star and galaxy formation. We use large-scale cosmological smoothed-particle hydrodynamical simulations to simulate the physical properties of LBGs, such as stellar mass, star-formation rate, and magnitude. In particular, we focus on the question of which dark matter (DM) halos host LBGs. Our simulation suggests that only 1.74% of all DM halos host LBGs, though among the massive DM halos with mass Mhalo >1011.5 Msun, the fraction is 51.93%. The occupation number of LBGs ranges from 1 to 17 per halo.

The Interaction Of Rock And Water During Shock Decompression: A Hybrid Model For Fluidized Ejecta Formation, Audrey Hughes Rager

UNLV Theses, Dissertations, Professional Papers, and Capstones

Crater and ejecta morphology provide insight into the composition and structure of the target material. Martian rampart craters, with their unusual single-layered (SLE), double-layered (DLE), and multi-layered ejecta (MLE), are the subject of particular interest among planetary geologists because these morphologies are thought to result from the presence of water in the target. Also of interest are radial lines extending from the crater rim to the distal rampart of DLE craters. Exactly how these layered ejecta morphologies and radial lines form is not known, but they are generally thought to result from interaction of the ejecta with the atmosphere, subsurface …

Potassium Chlorate Decomposition Under High Pressure, Harrison Ruiz, Michael G. Pravica, Martin Galley

Undergraduate Research Opportunities Program (UROP)

High pressure physics involves placing various substances under high pressure and observing changes in that substance. In this experiment this high amount of pressure is induced using a diamond anvil cell. A diamond anvil cell uses a metal gasket to hold the sample between two diamonds, which will press on the sample to reach high pressures. High pressures are reached with a moderate amount of force by exerting that force over a small area. Diamonds are used for the compression because of their hardness and ability to resist compression. The pressure being exerted on the sample using a diamond anvil …

Properties Of Z≥6 Galaxies In Cosmological Sph Simulations, Jason Jaacks

Undergraduate Research Opportunities Program (UROP)

Recent upgrades to the Hubble Space Telescope have given observers their deepest look into our Universe yet, seeing nearly 13 billion years into the past. This new observational data has presented those of us that use simulations to study the early Universe a benchmark opportunity to evaluate the ability of these codes to reproduce the photometric properties being observed. Establishing this agreement allows us to probe deeper into the physical properties such as mass, star formation histories and star formation rates of these early galaxies. This research lays the ground work for examining the contribution of primordial galaxies to the …

Velocity Distribution Of Dark Matter Halos: A Critical Test For The Λ Cold Dark Matter Model, Robert Jo Thompson

UNLV Theses, Dissertations, Professional Papers, and Capstones

The existence of a bullet cluster (such as 1E0657-56) poses a challenge to the concordance cold dark matter model. Here we investigate the velocity distribution of dark matter halo pairs in large N-body simulations with differing box sizes and resolutions. We examine various basic statistics such as halo masses, relative halo velocities, collisional angles, and separation distances in our simulations. We then compare the results to the observational properties of 1E0657-56. Our results suggest that it is very difficult to produce such a halo pair with such a high relative velocity at a redshift of z=0. The relative velocities increase …

Dla-Lbg Cross-Correlation And Basic Properties Of Infrared Galaxies In Cosmological Simulations, Tae Song Lee

UNLV Theses, Dissertations, Professional Papers, and Capstones

PART I

We calculate the cross-correlation function (CCF) between damped Ly-alpha systems (DLAs) and Lyman break galaxies (LBGs) using cosmological hydrodynamic simulations at z = 3. We compute the CCF with two different methods. First, we assume that there is one DLA in each dark matter halo if its DLA cross section is non-zero. In our second approach we weight the pair-count by the DLA cross section of each halo, yielding a cross-section-weighted CCF. We also compute the angular CCF for direct comparison with observations. Finally, we calculate the auto-correlation functions of LBGs and DLAs, and their bias against the …

Solar Eclipse Monitoring For Solar Energy Applications Using The Solar And Moon Position Algorithms, Ibrahim Reda

Publications (E)

This report includes a procedure for implementing an algorithm (described by Jean Meeus [1]) to calculate the Moon’s zenith angle with uncertainty of ±0.001° and azimuth angle with uncertainty of ±0.003°. The step-by-step format presented here simplifies the complicated steps Meeus describes to calculate the Moon’s position, and focuses on the Moon instead of the planets and stars. It also introduces some changes to accommodate for solar radiation applications. These include changing the direction of measuring azimuth angles from north and eastward instead of from south and eastward, and the direction of measuring the observer’s geographical longitude to be measured …

Martian Life Detection With Xylose Enantiomers, Arturo White, Gaosun Zhang, Henry J. Sun

Undergraduate Research Opportunities Program (UROP)

Ability of Martian soil to degrade carbohydrates, shown by the Viking mission, has two interpretations. One possibility is that the soil harbors living microorganisms. Alternatively, the soil is sterile but chemically oxidizing, i.e. it is laden with photochemical oxidants. It was shown by REU research last summer that these two possibilities can be distinguished by the use of glucose enantiomers. Life is selective: Earth organisms use D-glucose, but ignore Lglucose. This stereo selectivity is absent in chemical reactions. The goal of this project is to test if xylose, a five carbon sugar, is also suitable for chiral life detection. Mixed …

Martian Life Detection With Amino Acid Enantiomers, Ali Jamil, Gaosen Zhang, Henry J. Sun

Undergraduate Research Opportunities Program (UROP)

The Viking mission showed that Martian soil can degrade a heterotrophic medium to carbon dioxide as if live microorganisms were present. The result is considered inconclusive, however, because abiotic oxidants, such as superoxides, may also exist on Mars and would explain the Viking result. One way to resolve this ambiguity is to repeat the Viking experiment with a isomerically pure medium. The consumption of one isomer, either D or L, would indicate biological activity. Indiscriminate destruction of both isomers would indicate abiotic redox processes. This idea was validated for glucose by REU research last summer (Sun et al. 2009). The …

College Of Engineering Senior Design Competition Spring 2009, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.

The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects …

Stereospecificity In Glucose Consumption: A New Approach To Martian Life Detection, Vienna R. Saccomanno, Henry J. Sun

Undergraduate Research Opportunities Program (UROP)

In 1976, the Viking mission made a remarkable discovery: Martian soil was capable of decomposing an organic nutrient broth to carbon dioxide as if it contained live microorganisms. However, a biological interpretation of this finding is in apparent contradiction with the gas chromatograph-mass spectrometer aboard the Viking landers, which showed Martian soil to be devoid of indigenous organics. To reconcile these findings, it has been hypothesized that unknown abiotic oxidants, such as peroxide and superoxide, are present on Mars and that they were responsible for its soil reactivity. The objective of this research is to develop a life detection method …

An Investigation Of The Origin The Bimodal Distribution Of Optical Afterglow Luminosities Of Gamma-Ray Bursts, Tesla Birnbaum, Bing Zhang

Undergraduate Research Opportunities Program (UROP)

The determination of which properties of gamma-ray bursts and the surrounding interstellar medium contribute to the observed bimodal distribution of optical afterglow luminosities will provide insight into the physical processes that give rise to the two families of optical afterglows. Making this determination will require a solid understanding of the standard afterglow model, as well as the use of a language such as C to create programs consisting of codes that perform calculations involving afterglow parameters and Monte Carlo simulations.

Gamma-ray bursts (GRBs): the brightest sources of electromagnetic radiation since the Big Bang; also the most violent explosions in the …

Integral Neutron Multiplicity Measurements From Cosmic Ray Interactions In Lead, Thomas E. Ward, Alexander A. Rimsky-Korsakov, Nikolai A. Kudryashev, Denis E. Beller

Transmutation Sciences Physics (TRP)

Sixty element ³He neutron multiplicity detector systems were designed, constructed and tested for use in cosmic ray experiments with a 30-cm cube lead target. A series of measurements were performed for the cosmic ray configuration at ground level (3 meters water equivalent, mwe), in the St. Petersburg metro tunnel (185 mwe), and in the Pyhäsalmi mine in Finland (583 and 1185 mwe). Anomalous coincidence events with charged cosmic ray particles at sea level produced events with 100-120 neutrons due possibly to the total disintegration of the Pb nucleus. These events were also detected at 185 mwe, but the particles …