Astrophysics and Astronomy Commons^™

A Digital Calibration Source For 21 Cm Cosmology Telescopes, Kalyani Balkrishna Bhopi

Graduate Theses, Dissertations, and Problem Reports (ETD)

Precise calibration of radio telescope beams and gains is a central requirement for 21 cm intensity mapping experiments, which aim to measure large scale cosmological structure through the redshifted emission line of neutral hydrogen. Bright astrophysical foregrounds dominate the sky at these frequencies, and separating them from the cosmological signal demands precise control over instrumental systematics, particularly the telescope beam and its frequency-dependent response. Existing aerial calibration sources are incoherent broadband emitters, detectable only as total power. They provide no direct phase information and suffer from poor sensitivity in low signal-to-noise regimes.

We present the Precision Emitter for 21cm Array …

Large Telescope Mount For Long Exposure Photos, Payne M. Landis, Anna J. Gray

Williams Honors College, Honors Research Projects

When viewing the stars through a telescope, it is common that the object you are viewing drifts out of view. Many amateur astronomers seek to capture long exposure images of the stars, planets, and galaxies with commercially available sky tracking telescope mounts. The complication is that these telescope mounts are both incredibly expensive and have low weight limits. These issues limit accessibility to these products based on the telescope. For each person, telescope parameters determine the amount of light and magnification that can be viewed, which then determines exposures time for adequate photo results. The options on the market for …

An Application Of Molecular Dynamics To Hed Plasma Physics: Point And Group Defect Diffusion In Coulomb Crystals, Levi Webb

Theses and Dissertations

Molecular dynamics (MD) simulations are used to explore the microscopic behaviors of complex systems that cannot be easily studied experimentally. In particular, the microphysics of high energy density (HED) astrophysical plasma environments remain inaccessible by modern experiment---even in laser facilities, these plasmas exist only on short timescales that do not lend easily to investigation. The diffusion of point and group defects through crystallized plasmas in the cores of white dwarfs and neutron star crusts, called Coulomb crystals, has potentially macroscopic implications for the evolution of these bodies. Thus, I employ the widely-used MD code LAMMPS to simulate small Coulomb crystal …

Additional Information For Fully Anharmonic Ir Spectra Of Neutral Polycyclic Aromatic Hydrocarbons With Up To 38 Carbons, Nolan J. H. White, Vincent J. Esposito, Christiaan Boersma, Louis J. Allamandola, Jesse D. Bregman, Alexandros Maragkoudakis, Pasquale Temi, Ryan C. Fortenberry

Faculty and Student Publications

Interstellar aromatic infrared band (AIB) spectra are showing strong agreement with presently-computed, anharmonic spectra for various types of polycyclic aromatic hydrocarbons (PAH) determined using a novel semi-empirical quantum chemical method. Since the AIB spectrum is a blend of emission spectra from a vast number of different PAHs, likely with an array of different molecular structures, the spectra for a sample set of 31 PAHs ranging in size from naphthalene (C$_{10}$H$_8$) up to circumbiphenyl (C$_{38}$H$_{16}$) are combined giving consideration to almost all PAH structural motifs. The computed, numerical quartic force fields coupled to second-order vibrational perturbation theory clearly confirm that PAH …

Numerical Modeling Of Multi-Scale Jet Feedback In Seyfert Galaxies, Julianne Goddard

Theses and Dissertations--Physics and Astronomy

We present a suite of high-resolution cosmological zoom-in simulations investigating the impact of mechanical and thermal feedback from low-luminosity jets launched from supermassive black holes (SMBHs) on Seyfert galaxy evolution from early cosmic times to the present (z ≤ 10). Our models follow the formation of central galaxies within identical dark matter halos of logMhalo/M⊙ ∼ 11.8 at z = 0, seeded with ∼ 10^6M⊙ SMBHs at z ∼ 9.1 and z ∼ 3.7. Feedback from active galactic nuclei (AGN) is implemented in the form of bipolar jets launched along the SMBH spin axis, with jet powers spanning Ljet ∼ …

Quantum General Relativity V2, James Glimm, James Glimm

Department of Applied Mathematics & Statistics Faculty Publications

We construct a quantum general relativity theory.. The construction includes specification of a cosmological model. Based on type Ia supernova data, the model has zero dark energy and zero cosmological constant.

The analysis is at the level of theoretical physics, with some mathematical details omitted.

Mathematicly Rigorous Quantum General Relativity, I: Pure, James Glimm

Department of Applied Mathematics & Statistics Faculty Publications

A pure quantum general relativity field is one lacking in matter. Such a field has a Lorentzian space-time geometry. A renormalized perturbation expansion, truncated to all finite orders, establishes  the existence of pure quantum general relativity with full mathematical rigor

Dynamic Modeling Of The Earth's Trapped Proton Environment, Xiaojing Xu, Steve R. Blattnig, Francis F. Badavi, Martha S. Clowdsley, Edward J. Semones

Physics Faculty Publications

Context: Reliable prediction of space radiation exposure is critical for safeguarding spacecraft systems and ensuring astronaut health during missions. Accurate radiation risk assessment for space mission requires advanced models of the Earth’s trapped proton environment. These models must reflect temporal variations driven by geomagnetic field evolution and solar cycle modulation. Existing static models, such as AP8 and IRENE-AP9, are not designed to fully capture these evolving conditions. Aims: This paper presents a dynamic modeling method for the prediction of trapped proton fluxes, which incorporate time-dependent variations due to geomagnetic field evolution and solar cycle fluctuations. Methods: The …

Active Galactic Nuclei Across Scales: From Blazar Jets To Dark Matter Halos, Stephanie Ann Podjed

Dartmouth College Ph.D Dissertations

Within ΛCDM, galaxies form and evolve within dark matter halos, with both central and satellite galaxies contributing to the total stellar mass content. Virtually every massive galaxy harbors a supermassive black hole (SMBH) at its center, with a small fraction of the population growing by actively accreting material; we call this an active galactic nucleus (AGN). The processes giving rise to an AGN phase (i.e., growth of a SMBH) releases enormous amounts of energy in the form of radiation, outflows, and relativistic jets that are able to significantly affect the formation and evolution of galaxies. Blazars are an extreme class …

Laws Of Mechanics And Stationary Black Holes, Asma Iqbal

Master of Science in Mathematics

The aim of this thesis is to study laws of mechanics of Black Holes in the context of General Relativity. Important tools of General Relativity have been covered including concept of curvature and causal structure of spacetime. It then explore some characteristics of Schwarzschild and Kerr Black Holes and derived global quantities of them. These global quantities which are defined on Event Horizon of Black Hole makes analogy with the thermodynamics of physics. It then presents the Black Hole analogue of the zeroth, first, second and third laws of classical mecanics in General Relativity.