Astrophysics and Astronomy Commons^™

What Is A Polygonal Impact Crater? A Proposed Framework Toward Quantifying Crater Shapes, Stuart J. Robbins, Jamie D. Riggs

College of Population Health Faculty Papers

Impact craters are used for a wide array of investigations of planetary surfaces. A crater form that is somewhat rare, forming only ∼10% of impact craters, is the polygonal impact crater (or PIC). These craters have been visually, manually identified as having at least two rim segments that are best represented as straight lines. Such straight lines or edges are most often used to infer details about the subsurface crust where faults control the structure of the crater cavity as it formed. The PIC literature is scant, but almost exclusively these craters are identified manually, and the potentially straight edges …

Noise Analysis Of The Indian Pulsar Timing Array Data Release I, Aman Srivastava, Shantanu Desai, Neel Kolhe, Mayuresh Surnis, Bhal Chandra Joshi, Abhimanyu Susobhanan, Aurélien Chalumeau, Shinnosuke Hisano, Nobleson K, Raghav Girgaonkar

Physics & Astronomy Faculty Publications

The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years of uGMRT observations. We present the results of single-pulsar noise analysis for each of these 14 pulsars using the InPTA DR1. For this purpose, we consider white noise, achromatic red noise, dispersion measure (DM) variations, and scattering variations in our analysis. We apply Bayesian model selection to obtain the preferred noise models among these for each pulsar. For PSR J1600−3053, we find no evidence of DM and scattering variations, while for PSR J1909−3744, we find …

Estimation Of The Kelvin–Helmholtz Unstable Boundary, Xuanye Ma

Publications

The Kelvin–Helmholtz (KH) instability is one of the most important mechanisms of the viscous like interaction between the solar wind and the magnetosphere (MSP), which transport the mass, energy, momentum, and magnetic flux. Thus, it is important to examine whether the magnetopause boundary is KH unstable or not. Based on the KH onset conditions, this report proposes to use a matrix to identify the most KH unstable direction based on the in-situ measurements of the density, velocity, and magnetic field in the MSP and magneto sheath. The range of the KH unstable direction can be easily estimated based on the …

Gama/Devils: Cosmic Star Formation And Agn Activity Over 12.5 Billion Years, Jordan C J D’Silva, Simon P. Driver, Claudia D P Lagos, Aaron S G Robotham, Sabine Bellstedt, Luke J M Davies, Jessica E. Thorne, Joss Bland-Hawthorn, Matias Bravo, Benne Holwerda, Steven Phillipps, Nick Seymour, Malgorzata Siudek, Rogier A. Windhorst

Faculty and Staff Scholarship

We use the Galaxy and Mass Assembly (GAMA) and the Deep Extragalactic Visible Legacy Survey (DEVILS) observational data sets to calculate the cosmic star formation rate (SFR) and active galactic nuclei (AGN) bolometric luminosity history (CSFH/CAGNH) over the last 12.5 billion years. SFRs and AGN bolometric luminosities were derived using the spectral energy distribution fitting code ProSpect, which includes an AGN prescription to self consistently model the contribution from both AGN and stellar emission to the observed rest-frame ultra-violet to far-infrared photometry. We find that both the CSFH and CAGNH evolve similarly, rising in the early Universe up to a …

Discovery Of Extraordinary X-Ray Emission From Magnetospheric Interaction In The Unique Binary Stellar System Ε Lupi, B. Das, V. Petit, Y. Nazé, M. F. Corcoran, David H. Cohen, A. Biswas, P. Chandra, A. David-Uraz, M. A. Leutenegger, C. Neiner, H. Pablo, E. Paunzen, M. E. Shultz, A. Ud-Doula, G. A. Wade

Physics & Astronomy Faculty Works

We report detailed X-ray observations of the unique binary system ϵ Lupi, the only known short-period binary consisting of two magnetic early-type stars. The components have comparably strong, but anti-aligned magnetic fields. The orbital and magnetic properties of the system imply that the magnetospheres overlap at all orbital phases, suggesting the possibility of variable inter-star magnetospheric interaction due to the non-negligible eccentricity of the orbit. To investigate this effect, we observed the X-ray emission from ϵ Lupi, both near and away from periastron passage, using the Neutron Star Interior Composition Explorer mission (NICER) X-ray Telescope. We find that the system …

Toi-2498 B: A Hot Bloated Super-Neptune Within The Neptune Desert, G. Frame, D. J. Armstrong, H. M. Cegla, J. Fernández Fernández, A. Osborn, V. Adibekyan, K. A. Collins, E. Delgado Mena, S. Giacalone, J. F. Kielkopf, N. C. Santos, S. G. Sousa, K. G. Stassun, C. Ziegler, D. R. Anderson, S. C. C. Barros, D. Bayliss, C. Briceño, D. M. Conti, C. D. Dressing, X. Dumusque, P. Figueira, W. Fong, S. Gill, F. Hawthorn, J. M. Jenkins, Eric L.N. Jensen, M. A. F. Keniger, D. W. Latham, N. Law, J. J. Lissauer, A. W. Mann, L. D. Nielsen, H. Osborn, M. Paegert, S. Seager, R. P. Schwarz, A. Shporer, G. Srdoc, P. A. Strøm, J. N. Winn, P. J. Wheatley

Physics & Astronomy Faculty Works

We present the discovery and confirmation of a transiting hot bloated super-Neptune using photometry from the Transiting Exoplanet Survey Satellite (TESS) and the Las Cumbres Observatory Global Telescope (LCOGT) and radial velocity measurements from the High Accuracy Radial velocity Planet Searcher (HARPS). The host star TOI-2498 is a V = 11.2, G-type (T_eff = 5905 ± 12 K) solar-like star with a mass of 1.12 ± 0.02 M_⊙ and a radius of 1.26 ± 0.04 R_⊙. The planet, TOI-2498 b, orbits the star with a period of 3.7 d, has a radius of …

The Jwst Early Release Science Program For Direct Observations Of Exoplanetary Systems I: High-Contrast Imaging Of The Exoplanet Hip 65426 B From 2 To 16 Μm, Aarynn L. Carter, Sasha Hinkley, Jens Kammerer, Andrew Skemer, Beth A. Biller, Jarron M. Leisenring, Maxwell A. Millar-Blanchaer, Simon Petrus, Jordan M. Stone, Kimberly Ward-Duong, Jason J. Wang, Julien H. Girard, Dean C. Hines, Marshall D. Perrin, Laurent Pueyo, William O. Balmer, Mariangela Bonavita, Mickael Bonnefoy, Gael Chauvin, Elodie Choquet, Valentin Christiaens, Camilla Danielski, Grant M. Kennedy, Elisabeth C. Matthews, Brittany E. Miles, Polychronis Patapis, Shrishmoy Ray, Emily Rickman, Steph Sallum, Karl R. Stapelfeldt, Niall Whiteford, Yifan Zhou

Astronomy: Faculty Publications

We present JWST Early Release Science coronagraphic observations of the super-Jupiter exoplanet, HIP 65426b, with the Near-Infrared Camera (NIRCam) from 2 to 5 μm, and with the Mid-Infrared Instrument (MIRI) from 11 to 16 μm. At a separation of ∼0.″82 (87 − 31 + 108 au), HIP 65426b is clearly detected in all seven of our observational filters, representing the first images of an exoplanet to be obtained by JWST, and the first-ever direct detection of an exoplanet beyond 5 μm. These observations demonstrate that JWST is exceeding its nominal predicted performance by up to a factor of 10, depending …

The Jwst Pearls View Of The El Gordo Galaxy Cluster And Of The Structure It Magnifies, Brenda L. Frye, Massimo Pascale, Nicholas Foo, Reagen Leimbach, Nikhil Garuda, Paulina Soto Robles, Jake Summers, Carlos Diaz, Patrick Kamieneski, Lukas J. Furtak, Seth H. Cohen, Jose Diego, Benjamin Beauchesne, Rogier A. Windhorst, S. P. Willner, Anton M. Koekemoer, Adi Zitrin, Gabriel Caminha, Karina I. Caputi, Dan Coe, Christopher J. Conselice, Liang Dai, Hervé Dole, Simon P. Driver, Norman A. Grogin, Kevin Harrington, Rolf A. Jansen, Jean Paul Kneib, Matt Lehnert, James Lowenthal, Madeline A. Marshall, Felipe Menanteau

Astronomy: Faculty Publications

The massive galaxy cluster El Gordo (z = 0.87) imprints multitudes of gravitationally lensed arcs onto James Webb Space Telescope Near-Infrared Camera (NIRCam) images. Eight bands of NIRCam imaging were obtained in the “Prime Extragalactic Areas for Reionization and Lensing Science” (“PEARLS”) program. Point-spread function-matched photometry across Hubble Space Telescope and NIRCam filters supplies new photometric redshifts. A new light-traces-mass lens model based on 56 image multiplicities identifies the two mass peaks and yields a mass estimate within 500 kpc of (7.0 ± 0.30) × 1014 M ⊙. A search for substructure in the 140 cluster members with spectroscopic redshifts …

Development And Testing Of A New Method For Velocity-Selecting White Dwarfs From Gaia By Galactic Population, Joseph Hammill

Doctoral Dissertations and Master's Theses

The detailed processes by which spiral galaxies form remains an open question in modern cosmology. Observations of the current configuration of spiral galaxies including the Milky Way reveal thin and thick disk and halo populations which must all be accounted for in formation theories and likely have distinct ages. Using the Milky Way as an example to probe this question, we are studying the formation history of these structures.

This work details our approach to age-dating the galaxy, velocity-selecting targets from a sample of white dwarfs from the Gaia DR3 catalog that have also been age-analysed using BASE-9. BASE-9 uses …

Optimizing Convolutional Neural Networks For Transient Detection In Optical Astronomy With Augmented Datasets, Wendy Mendoza

Theses and Dissertations

We present a technique for optical transient detection using artificial neural networks, particularly a Convolutional Neural Network (CNN), a deep learning algorithm. This method analyzes images of the same area of the sky captured by several telescopes, with one image serving as a reference for a probable transient’s epoch and the other as an image from a previous epoch. We train the CNN on simulated sources and test it on actual image data samples using data from the Dr. Cristina V. Torres Memorial Astronomical Observatory and Sloan Digital Sky Survey. This autonomous detection method replaces the standard procedure, which involves …

Revisiting The Properties Of X-Ray Active Galactic Nuclei In The Ssa22 Protocluster: Normal Supermassive Black Hole And Host-Galaxy Growth For Agns In A Z=3.09 Overdensity, Erik B. Monson, Keith Doore, Rafael T. Eufrasio, Bret D. Lehmer, David M. Alexander, Chris M. Harrison, Mariko Kubo, Cristian Saez, Hideki Umehata

Physics Faculty Publications and Presentations

We analyze the physical properties of eight X-ray-selected active galactic nuclei (AGNs) and one candidate protoquasar system (ADF22A1) in the z = 3.09 SSA22 protocluster by fitting their X-ray-to-IR spectral energy distributions (SEDs) using our SED-fitting code, Lightning (https://www.github.com/rafaeleufrasio/lightning). We recover star formation histories (SFHs) for seven of these systems which are well fit by composite stellar population plus AGN models. We find indications that four out of nine of the SSA22 AGN systems we study have host galaxies below the main sequence, with SFR/SFRMS ≤ −0.4. The remaining SSA22 systems, including ADF22A1, are consistent with obscured supermassive black hole …

The Large Deficit Of Hmxb Emission From Luminous Infrared Galaxies: The Case Of The Circumnuclear Starburst Ring In Ngc 7552, Lacey West, Kristen Garofali, Bret D. Lehmer, Andrea Prestwich, Rafael Eufrasio, Wasutep Luangtip, Timothy P. Roberts, Andreas Zezas

Physics Faculty Publications and Presentations

Luminous infrared galaxies (LIRGs), the most extreme star-forming galaxies in the nearby (D < 30 Mpc) universe, show a notable X-ray emission deficiency (up to a factor of ∼10) compared with predictions from scaling relations of galaxy-wide high-mass X-ray binary (HMXB) luminosity with star formation rate. In the nearby (≈20 Mpc) LIRG NGC 7552, the majority of the IR emission originates in a circumnuclear starburst ring, which has been resolved into several discrete knots of star formation. We present results from recent Chandra observations of NGC 7552, which reveal significant deficits in the 2–7 keV X-ray luminosities from two of the most powerful star-forming knots. We hypothesize that the expected luminous HMXB populations in these knots are either (1) obscured by very large column densities or (2) suppressed due to the knots having relatively high metallicity and/or very young ages (≲5 Myr). We distinguish between these possibilities using data from recent NuSTAR observations, whose sensitivity above 10 keV is capable of uncovering heavily obscured HMXB populations, since emission at these energies is more immune to absorption effects. We find no evidence of a heavily obscured HMXB population in the central region of NGC 7552, suggesting suppressed HMXB formation. We further show that metallicity-dependent scaling relations cannot fully account for the observed deficit from the most powerful star-forming knots or the central region as a whole. Thus, we suggest that recent bursts in local star formation activity likely drive the high L_IR within these regions on timescales ≲5 Myr, shorter than the timescale required for the formation of HMXBs.

Near-Ir Spectroscopic Analysis Of The Primary Volatile Composition Of Long And Short-Period Comets, Younas Khan

Dissertations

Comets are among the most well-preserved objects that formed in the protosolar nebula ∼4.5 Gyr ago. Hence, they are important for understanding various aspects of the formation, evolution, and habitability of the solar system. Multiple primary volatiles (molecules directly sublimating into the coma from the nucleus) emit via rovibrational transitions in the near-IR, providing opportunities to calculate their abundances. To date, only ∼50 comets have been characterized for their primary volatiles, with the short-period Jupiter-family comets (JFCs) being significantly underrepresented. In contrast, hundreds of comets have been sampled at optical/UV wavelengths, primarily for the composition of daughter species, leading to …

Observation Of Robust Zero Energy Extended States, Jannatul Ferdous, Cem Yuce, Andrea Alu, Hamidreza Ramezani

Physics & Astronomy Faculty Publications

Topological edge states arise at the interface of two topologically distinct structures and have two distinct features: they are localized and robust against symmetry protecting disorder. On the other hand, conventional transport in one dimension is associated with extended states, which typically do not have topological robustness. In this letter, using lossy coupled resonators in one dimension, we demonstrate both theoretically and experimentally the existence of robust states residing in the bulk. We show that they are unusually robust against disorders in coupling between adjacent sites and losses. Our work paves the way to a different form of robust transport …

Dyonic Taub-Nut-Ads Space Phase Structure, Mohamed Tharwat

Theses and Dissertations

The Taub-NUT spacetime remains to hold many mysteries more than half a century after its discovery. The metric's controversy owes largely to the nut charge and the existence of Misner strings. Traditionally the metric is treated in the euclidean signature, this treatment hides the Misner strings. We treat the Taub-NUT spacetime with the Misner strings visible, not enforcing the time periodicity condition. We examine the phase structure belonging to three different horizon geometries. We deal with the hyperbolic, flat and spherical cases. We consider the stable phases, the phase transitions that exist between them, and find the preferable phases in …

Extreme Horizontal Wind Perturbations In The Mesosphere And Lower Thermosphere Over South America Associated With The 2022 Hunga Eruption, Facundo L. Poblet, Jorge L. Chau, J. Federico Conte, Juha Vierinen, Jose Suclupe, Alan Liu, Rodolfo R. Rodriguez

Publications

On 15 January 2022, the Hunga volcano produced a massive explosion that generated perturbations in the entire atmosphere. Nonetheless, signatures in the mesosphere and lower thermosphere (MLT) have been challenging to identify. We report MLT horizontal wind perturbations using three multistatic specular meteor radars on the west side of South America (spanning more than 3,000 km). The most notorious signal is an exceptional solitary wave with a large vertical wavelength observed around 18 UT at all three sites, with an amplitude of ∼50 m/s mainly in the westward direction. Using a customized analysis, the wave is characterized as traveling at …

Bayesian Inference For The White Dwarf Initial-Final Mass Relation, Nathan Stein, Ted Von Hippel, David Van Dyk, Steven Degennaro, Elizabeth Jeffery, Bill Jefferys

Publications

Stars lose mass as they age, and understanding mass loss is important for understanding stellar evolution. The initial-final mass relation (IFMR) is the relationship between a white dwarf’s initial mass on the main sequence and its final mass. We have developed a new method for fitting the IFMR based on a Bayesian analysis of photometric observations, combining deterministic models of stellar evolution in an internally coherent way. No mass data are used. Our method yields precise inferences (with uncertainties) for a parameterized linear IFMR. Our method can also return posterior distributions of white dwarf initial and final masses.

Databases And Inter-Connectivity In Ground-Based Astronomy, Ted Von Hippel, C. M. Mountain

Publications

Optical and infrared ground-based astronomy is undergoing a renaissance. Advances in material technology, system modeling, and the ability to correct atmospheric distortions in real time have produced a new generation of powerful, large telescopes. An equally profound revolution stems from the availability of large observational databases that span the electromagnetic spectrum. The increased use of such databases as well as the need to operate the new telescopes efficiently requires the development of a National or International Virtual Observatory to set standards for astronomical database formats, data quality assurance, and access protocols, and also to provide all-inclusive centers for data products.

Cosmological Vector Fields And Constraining The Neutrino Masses, Avery J. Tishue

Dartmouth College Ph.D Dissertations

In this thesis I explore two main topics: the role and consequences of cosmological vector fields, and new ideas for constraining fundamental physics with state-of-the-art experiments. These topics are disparate in content and technique but unified in their attempt to leverage novel approaches to better understand longstanding questions in cosmology. These questions, such as ``What is causing the universe to accelerate today?'' and ``What are the neutrino masses?'', underpin the modern cosmological paradigm. They play a key role in our understanding of cosmic history, the formation of structure, and the fate of our universe. Answers to or hints about these …

Galaxy And Mass Assembly (Gama): Comparing Visually And Spectroscopically Identified Galaxy Merger Samples, Alice Desmons, Sarah Brough, Cristina Martínez-Lombilla, Roberto De Propris, Benne Holwerda, Ángel R. López-Sánchez

Faculty and Staff Scholarship

We conduct a comparison of the merging galaxy populations detected by a sample of visual identification of tidal features around galaxies as well as spectroscopically detected close pairs of galaxies to determine whether our method of selecting merging galaxies biases our understanding of galaxy interactions. Our volume-limited parent sample consists of 852 galaxies from the Galaxy And Mass Assembly (GAMA) survey in the redshift range 0.04 ≤ z ≤ 0.20 and stellar mass range 9.50 ≤ log 10(M⋆/M⊙)≤ 11.0" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant: inherit; font-stretch: inherit; line-height: normal; font-family: inherit; font-optical-sizing: inherit; font-kerning: inherit; …