Astrophysics and Astronomy Commons^™

Exceptionally Bright Tev Flares From The Binary Ls I+61 Degrees 303, P. T. Reynolds, Et Al

Physical Sciences Publications

The TeV binary system LS I +61° 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (>300 GeV). In this article, VERITAS observations of LS I +61° 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. …

Upper Limits On The Rates Of Binary Neutron Star And Neutron Star–Black Hole Mergers From Advanced Ligo's First Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov

Physics & Astronomy Faculty Publications

We report here the non-detection of gravitational waves from the merger of binary–neutron star systems and neutron star–black hole systems during the first observing run of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). In particular, we searched for gravitational-wave signals from binary–neutron star systems with component masses ∈[1,3]M⊙ and component dimensionless spins <0.05. We also searched for neutron star–black hole systems with the same neutron star parameters, black hole mass ∈[2,99]M⊙, and no restriction on the black hole spin magnitude. We assess the sensitivity of the two LIGO detectors to these systems and find that they could have detected the merger of binary–neutron star systems with component mass distributions of 1.35 ± 0.13 M⊙ at a volume-weighted average distance of ∼70 Mpc, and for neutron star–black hole systems with neutron star masses of 1.4 M⊙ and black hole masses of at least 5 M⊙, a volume-weighted average distance of at least ∼110 Mpc. From this we constrain with …

The Jcmt Nearby Galaxies Legacy Survey – X. Environmental Effects On The Molecular Gas And Star Formation Properties Of Spiral Galaxies, Angus Mok, C. D. Wilson, J. Golding, B. E. Warren, F. P. Israel, S. Serjeant, J. H. Knapen, José R. Sánchez-Gallego, P. Barmby, G. J. Bendo, E. Rosolowsky, P. Van Der Werf

Physics and Astronomy Faculty Publications

We present a study of the molecular gas properties in a sample of 98 H I – flux selected spiral galaxies within ∼25 Mpc, using the CO J = 3 − 2 line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H₂ mass in the Virgo galaxies, despite their lower mean H I mass. This leads to a significantly higher H₂ to H I ratio for Virgo galaxies. Combining our data …

How Uncertainty In The Neutral Wind Limits The Accuracy Of Ionospheric Modeling And Forecasting, Michael David, Jan J. Sojka, Robert W. Schunk

Publications

One of the most important input fields for an ionospheric model is the horizontal neutral wind. The primary mechanism by which the neutral wind affects ionospheric densities is the inducement of an upward or downward ion drift along the magnetic field lines; this affects the rate at which ions are lost through recombination. The magnitude of this effect depends upon the dip angle of the magnetic field; for this reason, the impact of the neutral wind is somewhat less in polar regions than at mid-latitudes. It is unfortunate that observations of the neutral wind are relatively scarce, as compared for …

The Small Scatter Of The Baryonic Tully-Fisher Relation, Federico Lelli, Stacy S. Mcgaugh

Faculty Scholarship

In a Γ cold dark matter (ΓCDM) cosmology, the baryonic TullyFisher relation (BTFR) is expected to show significant intrinsic scatter resulting from the massconcentration relation of dark matter halos and the baryonic-tohalo mass ratio. We study the BTFR using a sample of 118 disk galaxies (spirals and irregulars) with data of the highest quality: extended H I rotation curves (tracing the outer velocity) and Spitzer photometry at 3.6 μm (tracing the stellar mass). Assuming that the stellar mass-to-light ratio (Υ∗) is nearly constant at 3.6 μm, we find that the scatter, slope, and normalization of the BTFR systematically vary with …

Factorized Runge-Kutta-Chebyshev Methods, Stephen O'Sullivan

Conference papers

The second-order extended stability Factorized Runge-Kutta-Chebyshev (FRKC2) class of explicit schemes for the integration of large systems of PDEs with diffusive terms is presented. FRKC2 schemes are straightforward to implement through ordered sequences of forward Euler steps with complex stepsizes, and easily parallelised for large scale problems on distributed architectures.

Preserving 7 digits for accuracy at 16 digit precision, the schemes are theoretically capable of maintaining internal stability at acceleration factors in excess of 6000 with respect to standard explicit Runge-Kutta methods. The stability domains have approximately the same extents as those of RKC schemes, and are a third longer …

The Effect Of Morphology On Carrier Dynamics In Solution Processed Solar Cells, Alexander G. Dixon

Electronic Theses and Dissertations

This dissertation looks at the charge transport properties of solution processed solar cells and how these properties are effected by the microstructure and morphology of the material. It begins with an introduction and history of the field of solution processed solar cells, focusing on organic photovoltaics and perovskites. The physics and issues of charge transport in these materials are reviewed, and the transport probing techniques of photo-Charge Extraction via Linearly Increasing Voltage (photo-CELIV), Metal Insulator Semiconductor-CELIV (MIS-CELIV), and Resistance Photovoltage (RPV) are detailed.

The photo-CEILV technique is used to probe P3HT devices of varying molecular weights. This material is known …

Discovery Of The Candidate Off-Nuclear Ultrasoft Hyper-Luminous X-Ray Source 3xmm J141711.1+522541, Dacheng Lin, Eleazar Carrasco, Natalie Webb, Jimmy Irwin, Renato Dupke, Aaron Romanowsky, Enrico Ramirez-Ruiz, Jay Strader, Jeroen Homan, Didier Barret, Olivier Godet

Faculty Publications

No abstract provided.

An Overmassive Dark Halo Around An Ultra-Diffuse Galaxy In The Virgo Cluster, Michael Beasley, Aaron Romanowsky, Vincenzo Pota, Ignacio Navarro, David Martinez-Delgado, Fabian Neyer, Aaron Deich

Faculty Publications

No abstract provided.

New Spectroscopic Technique Based On Coaddition Of Surface Brightness Fluctuations: Ngc 4449 And Its Stellar Tidal Stream, Elisa Toloba, Puragra Guhathakurta, Aaron Romanowsky, Jean Brodie, David Martínez-Delgado, Jacob Arnold, Neel Ramachandran, Kuriakose Theakanath

Faculty Publications

No abstract provided.

Stellar Populations Across The Black Hole Mass–Velocity Dispersion Relation, Ignacio Martín-Navarro, Jean Brodie, Remco Van Den Bosch, Aaron Romanowsky, Duncan Forbes

Faculty Publications

Coevolution between supermassive black holes (BH) and their host galaxies is universally adopted in models for galaxy formation. In the absence of feedback from active galactic nuclei (AGNs), simulated massive galaxies keep forming stars in the local universe. From an observational point of view, however, such coevolution remains unclear. We present a stellar population analysis of galaxies with direct BH mass measurements and the BH mass–σ relation as a working framework. We find that over-massive BH galaxies, i.e., galaxies lying above the best-fitting BH mass–σ line, tend to be older and more α-element-enhanced than under-massive BH galaxies. The scatter in …

Star Clusters In M31. Vii. Global Kinematics And Metallicity Subpopulations Of The Globular Clusters, Nelson Caldwell, Aaron Romanowsky

Faculty Publications

We carry out a joint spatial–kinematical–metallicity analysis of globular clusters (GCs) around the Andromeda Galaxy (M31), using a homogeneous, high-quality spectroscopic data set. In particular, we remove the contaminating young clusters that have plagued many previous analyses. We find that the clusters can be divided into three major metallicity groups based on their radial distributions: (1) an inner metal-rich group ([Fe/H] > -0.4); (2) a group with intermediate metallicity (with median [Fe/H] = −1); and (3) a metal-poor group, with [Fe/H] < -1.5. The metal-rich group has kinematics and spatial properties like those of the disk of M31, while the two more metal-poor groups show mild prograde rotation overall, with larger dispersions—in contrast to previous claims of stronger rotation. The metal-poor GCs are the least concentrated group; such clusters occur five times less frequently in the central bulge than do clusters of higher metallicity. Despite some well-known differences between the M31 and Milky Way GC systems, our revised analysis points to remarkable similarities in their chemodynamical properties, which could help elucidate the different formation stages of galaxies and their GCs. In particular, the M31 results motivate further exploration of a metal-rich GC formation mode in situ, within high-redshift, clumpy galactic disks.

Erratum: “Ngc 3628-Ucd1: A Possible Ω Cen Analog Embedded In A Stellar Stream” (2015, Apjl, 812, L10), Zachary Jennings, Aaron Romanowsky, Jean Brodie, Joachim Janz, Mark Norris, Duncan Forbes, David Martinez-Delgado, Martina Fagioli, Samantha Penny

Faculty Publications

No abstract provided.

The Kretschmann Scalar, Charles G. Torre

How to... in 10 minutes or less

On a pseudo-Riemannian manifold with metric g, the "Kretschmann scalar" is a quadratic scalar invariant of the Riemann R tensor of g, defined by contracting all indices with g. In this worksheet we show how to calculate the Kretschmann scalar from a metric.

Atmospheric, Orbital, And Eclipse-Depth Analysis Of The Hot Jupiter Hat-P-30-Wasp-51ab, Andrew Sd Foster

Honors Undergraduate Theses

HAT-P-30-WASP-51b is a hot-Jupiter exoplanet that orbits an F star every 2.8106 days at a distance of 0.0419 AU. Using the Spitzer Space Telescope in 2012 (Spitzer Program Number 70084) we observed two secondary eclipses at 3.6 and 4.5 μm. We present eclipse-depth measurements of 0.177 ± 0.018 % and 0.247 ± 0.024 % and estimate the infrared brightness temperatures to be 1990 ± 110 K and 2080 ± 130 K for these two channels, respectively, from an analysis using our Photometry for Orbits, Eclipses, and Transits (POET) pipeline. These may be grazing eclipses. We also refine its orbit using …

Modeling Extrasolar Trojan Asteroids In Gravitational Potentials Of Migrating Jovian-Like Planets To Inform Future Observations, Austin Hinkel

Lewis Honors College Capstone Collection

In this paper, I construct a program to map the evolution of the potential in a planet-star system where a planet with a few Jupiter masses migrates inward. Given a trojan asteroid librating around the fourth or fifth Lagrange point, the asteroid follows the evolving equipotential lines of the slowly changing potential map. As the planet and its trojan asteroids migrate inward towards the host star, the trojan asteroid librations become tighter, providing a denser “cloud” of trojan asteroids. Such a change in the density of trojan asteroids is examined with the intent to deduce the likelihood of detection via …

The Sluggs Survey: A New Mask Design To Reconstruct The Stellar Populations And Kinematics Of Both Inner And Outer Galaxy Regions, Nicola Pastorello, Duncan Forbes, Adriano Poci, Aaron Romanowsky, Richard Mcdermid, Adebusola Alabi, Jean Brodie, Michele Cappellari, Vincenzo Pota, Caroline Foster

Faculty Publications

Integral field unit spectrographs allow the 2D exploration of the kinematics and stellar populations of galaxies, although they are generally restricted to small fields-of-view. Using the large field-of-view of the DEIMOS multislit spectrograph on Keck and our Stellar Kinematics using Multiple Slits technique, we are able to extract sky-subtracted stellar light spectra to large galactocentric radii. Here, we present a new DEIMOS mask design named SuperSKiMS that explores large spatial scales without sacrificing high spatial sampling. We simulate a set of observations with such a mask design on the nearby galaxy NGC 1023, measuring stellar kinematics and metallicities out to …

Planetary Nebula Associations With Star Clusters In The Andromeda Galaxy, Yasmine Kahvaz

Theses, Dissertations and Capstones

The objective of this research is to find planetary nebulae (PNe) and star cluster associations in the Andromeda galaxy (M31). To identify PNe in M31, a red-green-blue image is obtained using 3 emission line filters of H↵, 5007˚A [OIII], and 6717, 6731˚A [SII], using images from the Local Group Survey. By completing a visual search of the RGB images, 477 PN candidates are identified. In order to find star clusters associated with the PN candidates, an RGB image is made using the Panchromatic Hubble Andromeda Treasury survey. Filter F814W is used as red and filter F475W is used as both …

Grange Stone Circle (B):New Thoughts On An Old Monument, Frank Prendergast

Book/Book Chapter

No abstract provided.

Robert Gowdy On Ripples In Space-Time, Dan Gaitanis

AUCTUS: The Journal of Undergraduate Research and Creative Scholarship

In February, a team of scientists announced that they had detected the sound of two black holes, some billion light years away, and that it confirmed the last part of Albert Einstein’s “Theory of Relativity.” It was a very faint sound, picked up by two detectors in the United States.