UMBC Physics Department

Permanent URI for this collectionhttp://hdl.handle.net/11603/57

The mission of the Department of Physics at UMBC is based on three pillars: education, research and service to society. We strive to provide outstanding educational opportunities, through instruction and research, for undergraduate physics majors seeking preparation for graduate school or entry into the workforce. We also aim to train graduate students to be leaders in their field of research. Our research goal is to grow and sustain internationally recognized research groups in atmospheric physics, astrophysics, condensed matter physics and quantum optics and information science. Through our teaching of physics to non-science and non-physics majors and through our Physics for Secondary Education Teachers program, we provide professional service to the university community and the State.

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A Machine-Learning Approach to Mitigate Ground Clutter Effects in the GPM Combined Radar-Radiometer Algorithm (CORRA) Precipitation Estimates
(AMS, 2024-11-13) Grecu, Mircea; Heymsfield, Gerald M.; Nicholls, Stephen; Lang, Stephen; Olson, William S.
In this study, a machine-learning based methodology is developed to mitigate the effects of ground clutter on precipitation estimates from the Global Precipitation Mission Combined Radar-Radiometer Algorithm. Ground clutter can corrupt and obscure precipitation echo in radar observations, leading to inaccuracies in precipitation estimates. To improve upon previous work, this study introduces a general machine learning (ML) approach that enables a systematic investigation and a better understanding of uncertainties in clutter mitigation. To allow for a less restrictive exploration of conditional relations between precipitation above the lowest clutter-free bin and surface precipitation, reflectivity observations above the clutter are included in a fixed-size set of predictors along with the precipitation type, surface type, and freezing level to estimate surface precipitation rates, and several ML-based estimation methods are investigated. A Neural Network Model (NN) is ultimately identified as the best candidate for systematic evaluations, as it is computationally fast to apply while effective in applications. The NN provides unbiased estimates; however, it does not significantly outperform a simple bias correction approach in reducing random errors in the estimates. The similar performance of other ML approaches suggests that the NN’s limited improvement beyond bias removal is due to indeterminacies in the data rather than limitations in the ML approach itself.
Identifying Economic Factors Affecting Unemployment Rates in the United States
(2024-11-04) Green, Alrick; Nasim, Ayesha; Radadia, Jaydeep; Kallam, Devi Manaswi; Kalyanam, Viswas; Owenga, Samfred; Ashqar, Huthaifa
In this study, we seek to understand how macroeconomic factors such as GDP, inflation, Unemployment Insurance, and S&P 500 index; as well as microeconomic factors such as health, race, and educational attainment impacted the unemployment rate for about 20 years in the United States. Our research question is to identify which factor(s) contributed the most to the unemployment rate surge using linear regression. Results from our studies showed that GDP (negative), inflation (positive), Unemployment Insurance (contrary to popular opinion; negative), and S&P 500 index (negative) were all significant factors, with inflation being the most important one. As for health issue factors, our model produced resultant correlation scores for occurrences of Cardiovascular Disease, Neurological Disease, and Interpersonal Violence with unemployment. Race as a factor showed a huge discrepancies in the unemployment rate between Black Americans compared to their counterparts. Asians had the lowest unemployment rate throughout the years. As for education attainment, results showed that having a higher education attainment significantly reduced one chance of unemployment. People with higher degrees had the lowest unemployment rate. Results of this study will be beneficial for policymakers and researchers in understanding the unemployment rate during the pandemic.
Multiwavelength study of 1eRASS J085039.9-421151 with eROSITA NuSTAR and X-shooter
(2024-11-04) Zainab, Aafia; Avakyan, Artur; Doroshenko, Victor; Thalhammer, Philipp; Sokolova-Lapa, Ekaterina; Ballhausen, Ralf; Zalot, Nicolas; Stierhof, Jakob; Haemmerich, Steven; Diez, Camille M.; Weber, Philipp; Dauser, Thomas; Berger, Katrin; Kretschmar, Peter; Pottschmidt, Katja; Pradhan, Pragati; Islam, Nazma; Maitra, Chandreyee; Coley, Joel B.; Blay, Pere; Corbet, Robin; Rothschild, Richard E.; Wood, Kent; Santangelo, Andrea; Heber, Ulrich; Wilms, Joern
The eROSITA instrument on board Spectrum-Roentgen-Gamma has completed four scans of the X-ray sky, leading to the detection of almost one million X-ray sources in eRASS1 only, including multiple new X-ray binary candidates. We report on analysis of the X-ray binary 1eRASS J085039.9-421151, using a ~55\,ks long NuSTAR observation, following its detection in each eROSITA scan. Analysis of the eROSITA and NuSTAR X-ray spectra in combination with X-shooter data of the optical counterpart provide evidence of an X-ray binary with a red supergiant (RSG) companion, confirming previous results, although we determine a cooler spectral type of M2-3, owing to the presence of TiO bands in the optical and near infrared spectra. The X-ray spectrum is well-described by an absorbed power law with a high energy cutoff typically applied for accreting high mass X-ray binaries. In addition, we detect a strong fluorescent neutral iron line with an equivalent width of ~700\,eV and an absorption edge, the latter indicating strong absorption by a partial covering component. It is unclear if the partial absorber is ionised. There is no significant evidence of a cyclotron resonant scattering feature. We do not detect any pulsations in the NuSTAR lightcurves, possibly on account of a large spin period that goes undetected due to insufficient statistics at low frequencies or potentially large absorption that causes pulsations to be smeared out. Even so, the low persistent luminosity, the spectral parameters observed (photon index, photon index, Γ<1.0), and the minuscule likelihood of detection of RSG-black hole systems, suggest that the compact object is a neutron star.
The XRISM/Resolve view of the Fe K region of Cyg X-3
(2024-11-08) XRISM Collaboration; Boissay-Malaquin, Rozenn; Hamaguchi, Kenji; Hayashi, Takayuki; Mukai, Koji; Pottschmidt, Katja; Tamura, Keisuke; Yaqoob, Tahir
The X-ray binary system Cygnus X-3 (4U 2030+40, V1521 Cyg) is luminous but enigmatic owing to the high intervening absorption. High-resolution X-ray spectroscopy uniquely probes the dynamics of the photoionized gas in the system. In this paper we report on an observation of Cyg X-3 with the XRISM/Resolve spectrometer which provides unprecedented spectral resolution and sensitivity in the 2-10 keV band. We detect multiple kinematic and ionization components in absorption and emission, whose superposition leads to complex line profiles, including strong P-Cygni profiles on resonance lines. The prominent Fe XXV Heα and Fe XXVI Lyα emission complexes are clearly resolved into their characteristic fine structure transitions. Self-consistent photoionization modeling allows us to disentangle the absorption and emission components and measure the Doppler velocity of these components as a function of binary orbital phase. We find a significantly higher velocity amplitude for the emission lines than for the absorption lines. The absorption lines generally appear blueshifted by ∼−500-600km s⁻¹. We show that the wind decomposes naturally into a relatively smooth and large scale component, perhaps originating with the background wind itself, plus a turbulent more dense structure located close to the compact object in its orbit.
Evaluation of 10-m Wind Speed From ISD Meteorological Stations and the MERRA-2 Reanalysis: Impacts on Dust Emission in the Arabian Peninsula
(AGU, 2024-10-30) Faber, Emily; Rocha-Lima, Adriana; Colarco, P.; Baker, Barry
Mineral dust is one of the most important aerosols when studying the radiative balance and climate of the planet. There are different dust emission schemes utilized by the atmospheric modeling communities, many of which disagree on basic output quantities such as mass of dust emitted and distribution of mass among size bins. In this work, we examined mineral dust emission from a leading model scheme, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), as utilized in the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) Reanalysis and compared it to dust emissions calculated using wind measurements from ground based weather stations located in the Arabian Peninsula that are included in the National Oceanic and Atmospheric Administration’s (NOAA) integrated surface database (ISD). An intercomparison of 10-m wind speed is shown for the Arabian Peninsula region, differences of the observed and modeled wind field are quantified, and impacts of differences on dust emissions are calculated. This analysis shows 10-m winds in the ISD were generally lower than MERRA-2 winds, which propagated to dust emissions errors. Our estimate of one of the most significant mass impacts in dust emission is 0.178 Tg/year/grid box with a percent change of over 200% to the recalculated dust emissions from MERRA-2. These differences in wind speed propagated to a difference in dust mass emitted by the use of a static source function which aids in scaling the mass emitted by the availability of dust in each grid. Additionally, the magnitude of these differences varies seasonally.
Sensitivity of the Shallow-to-Deep Convective Transition to Moisture and Wind Shear in the Amazon
(2024-04-16) Viscardi, Leandro Alex Moreira; Torri, Giuseppe; Adams, David Kenton; Barbosa, H. M. J.
Deep convection is the primary influence on weather and climate in tropical regions. However, understanding and simulating the shallow-to-deep (STD) convective transition has long been challenging. Here, we conduct high-resolution numerical simulations to assess the environmental controls on the evolution of isolated convection in the Amazon during the wet season. Observations and large-scale forcing derived through the constrained variational analysis approach for the GoAmazon2014/5 experiments are used in the simulations and model validation. The model consistently reproduces the GOAmazon observations for precipitation, moisture, and surface fluxes of radiation, latent and sensible heat. Through sensitivity experiments, we examine the relative importance of moisture and vertical wind shear in controlling the STD convective transition. Reducing the pre-convective humidity within the lower 1.5 km significantly suppresses vertical development and lowers the ice water path. Additionally, the maximum precipitation rate decreases almost quadratically with column water vapor. Conversely, a reduction of column water vapor above 1.5 km by a factor of two or more is necessary to produce a comparable decrease in ice water path or precipitation. Moderate low-level wind shear facilitates the STD transition, leading to an earlier peak of ice water compared to stronger wind shear or its absence. Although upper-level wind shear negatively influences high cloud formation, its role in controlling the STD transition is relatively smaller than that of low-level wind shear. Our results help quantify the role of moisture and wind shear on the STD transition, but also suggest that dynamic factors may exert a more pronounced influence.
Evaluation of easterly wave disturbances over the tropical South Atlantic in CMIP6 models
(2024-07-17) Cavalcante, Lucas; Gomes, Helber; Hodges, Kevin; Ray, Pallav; Herdies, Dirceu; Barbosa, H. M. J.; Gonçalves, Weber; Silva, Maria Cristina; Brito, José Ivaldo; Nobre, João Pedro; Lyra, Matheus; Baltaci, Hakki
This study assesses the performance of the latest phase of Coupled Model Intercomparison Project (CMIP6) models in simulating easterly wave disturbances (EWD) over the tropical South Atlantic (TSA) impacting northeast Brazil (NEB). Initially, we evaluate simulated precipitation from 17 historical CMIP, 16 AMIP, 7 hist-1950, and 10 highresSST-present models against the Global Precipitation Climatology Project (GPCP) dataset to identify models that accurately reproduce the spatial and temporal precipitation patterns in the study region. The ensemble's spatial analysis demonstrates their capability in reproducing annual and seasonal precipitation climatology. However, models underestimate precipitation intensity along NEB's coast while overestimating it in TSA and NEB's north. Model uncertainties tend to be greater with higher latitudes. The models represented the annual cycle in all subareas within the study region, particularly from July to October, albeit with a greater spread in the first half of the year, especially over the Intertropical Convergence Zone (ITCZ). Based on it, three top-performing models from each ensemble were selected for EWD evaluation. The automatic tracking algorithm for EWDs showed the model's ability to represent mean values of EWD lifetime(~ 6 days) and phase speed (~ 7 m s-1) as found in ERA5 reanalysis. However, they failed to capture EWD's interannual variability or climatological mean frequency. Despite CMIP6 model weaknesses, they accurately identified two primary EWD genesis regions: one over the TSA and another near the West African coast. Overall, CMIP6 models, particularly atmospheric and high-resolution models (HighResMIP), effectively captured precipitation climatology and EWD characteristics over NEB and the adjacent TSA.
Overlapping cusp ion dispersions formed by flux ropes on the day-side magnetopause
(frontiers, 2024-08-20) Petrinec, Steven; Connor, Hyunju K.; da Silva, Daniel; Ma, Xuanye; Dorelli, John C.; Porter, Azzan; Girma, Yohannes; Burkholder, Brandon
Introduction: Cusp ion dispersion signatures reflect properties of remote magnetic reconnection. Since the cusp is easier to observe in situ compared to the reconnection x-line, ion dispersions provide key insight on whether reconnection is variable in space and time. This study is motivated by a specific dispersion signature having two ion populations separated in energy but not space. These are known as overlapping dispersions because when observed by low-Earth orbiting satellites traversing the cusp, they appear as two dispersed ion populations overlapping in magnetic latitudes. Overlapping dispersion signatures have been observed for all interplanetary magnetic field (IMF) orientations and have been associated with multiple reconnection processes, but the three-dimensional magnetic reconnection topology and particle trajectories have not been examined.Methods: Forward particle tracing using the GAMERA-CHIMP global magnetohydrodynamic (MHD) with test particle framework is carried out to construct ion dispersion signatures throughout the cusp. Under idealized solar wind driving with steady purely southward IMF, both standard and overlapping dispersions are found.Results: Analysis of the test particle trajectories shows that the higher energy population of the overlapping dispersion travels along the axis of a flux rope before heading into the cusp, whereas the lower energy population goes directly into the cusp. Furthermore, the overlapping dispersions observed by the synthetic satellites compare well to Defense Meteorological Satellite Program (DMSP) F16 observations during strongly southward IMF.Discussion: It is thus concluded that during strongly southward IMF, cusp-entering particles interacting with a magnetopause flux rope (generated by secondary reconnection) is one way to produce an overlapping dispersion. This study lays the groundwork for the forthcoming NASA Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission, which will connect the cusp to the magnetosphere—discovering how spatial or temporal variations in magnetic reconnection drive cusp dynamics. The expected launch of TRACERS is in 2025.
Surface functionalization and atomic layer deposition of metal oxides on MoS₂ surfaces
(SPIE, 2024-10-02) Gougousi, Theodosia; Kropp, Jaron A.; Ataca, Can
Transition metal dichalcogenides (TMDs), such as MoS₂, have attracted considerable interest in the field of nanoelectronics due to their unique properties. These layered materials possess a hexagonal structure similar to graphene and exhibit semiconducting behavior, making them ideal candidates for channel materials in field-effect transistors (FETs). However, integrating these channel materials into devices requires the fabrication of a high-quality interface between the TMD and a deposited dielectric layer. The sulfur-terminated MoS₂ surface is hydrophobic, and typical films deposited via atomic layer deposition (ALD) often exhibit a high concentration of pinhole-type defects. To improve the compatibility of MoS₂ with ALD processes, we investigated the effect of seeding the surface with HAuCl₄ salts. These chloride-terminated complexes are expected to react with H₂O, resulting in a hydroxyl-terminated surface that is conducive to a well-behaved ALD process. Following surface treatment, ALD titania and alumina films were deposited using tetrakis (dimethylamino) titanium and trimethylaluminum as the metal-organic precursors, with H₂O serving as the oxidizer. Raman spectroscopy confirmed that the surface treatment did not compromise the structural integrity of MoS₂. X-ray photoelectron spectroscopy measurements verified the presence of gold and aluminum on the surface and the successful removal of chlorine during the process. Atomic force microscopy revealed that the HAuCl₄ treatment influenced the titania film nucleation and morphology; however, 6 nm titania films deposited at 100°C and 200°C still exhibited some pinholes.
Emissive Surface Traps Lead to Asymmetric Photoluminescence Line Shape in Spheroidal CsPbBr3 Quantum Dots
(2024-10-07) Kline, Jessica; Gallagher, Shaun; Hammel, Benjamin F.; Mathew, Reshma; Ladd, Dylan M.; Westbrook, Robert J. E.; Pryor, Jalen N.; Toney, Michael F.; Pelton, Matthew; Yazdi, Sadegh; Dukovic, Gordana; Ginger, David S.
The morphology of quantum dots plays an important role in governing their photophysics. Here, we explore the photoluminescence of spheroidal CsPbBr3 quantum dots synthesized via the room-temperature trioctlyphosphine oxide/PbBr2 method. Despite photoluminescence quantum yields nearing 100%, these spheroidal quantum dots exhibit an elongated red photoluminescence tail not observed in typical cubic quantum dots synthesized via hot injection. We explore this elongated red tail through structural and optical characterization including small-angle x-ray scattering, transmission electron microscopy and time-resolved, steady-state, and single quantum dot photoluminescence. From these measurements we conclude that the red tail originates from emissive surface traps. We hypothesize that these emissive surface traps are located on the (111) surfaces and show that the traps can be passivated by adding phenethyl ammonium bromide, resulting in a more symmetric line shape
A Multi-Wavelength Characterization of the Obscuring Medium at the Center of NGC 6300
(2024-10-03) Sengupta, D.; Torres-Albà, N.; Pizzetti, A.; López, I. E.; Marchesi, S.; Vignali, C.; Barchiesi, L.; Cox, I.; Gaspari, M.; Zhao, X.; Ajello, M.; Esposito, F.
Most of the super-massive black holes in the Universe accrete material in an obscured phase. While it is commonly accepted that the "dusty torus" is responsible for the nuclear obscuration, its geometrical, physical, and chemical properties are far from being properly understood. In this paper, we take advantage of the multiple X-ray observations taken between 2007 and 2020, as well as of optical to far infra-red (FIR) observations of NGC 6300, a nearby (z=0.0037) Seyfert 2 galaxy. The goal of this project is to study the nuclear emission and the properties of the obscuring medium, through a multi-wavelength study conducted from X-ray to IR. We perform a simultaneous X-ray spectral fitting and optical-FIR spectral energy distribution (SED) fitting to investigate the obscuring torus. For the X-ray spectral fitting, physically motivated torus models, such as borus02, UXClumpy and XClumpy are used. The SED fitting is done using XCIGALE. Through joint analysis, we constrain the physical parameters of the torus and the emission properties of the accreting supermassive black hole. Through X-ray observations taken in the last 13 years, we have not found any significant line-of-sight column density variability for this source, but observed the X-ray flux dropping ∼40−50% in 2020 with respect to previous observations. The UXClumpy model predicts the presence of an inner ring of Compton-thick gaseous medium, responsible for the reflection dominated spectra above 10 keV. Through multi-wavelength SED fitting, we measure an Eddington accretion rate λEdd∼2×10⁻³, which falls in the range of the radiatively inefficient accretion solutions.
Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow
(IOP, 2020-02-10) Ajello, M.; Arimoto, M.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Berretta, A.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bottacini, E.; Bregeon, J.; Bruel, P.; Buehler, R.; Burns, E.; Buson, S.; Cameron, R. A.; Caputo, R.; Caraveo, P. A.; Cavazzuti, E.; Chen, S.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Costantin, D.; Cutini, S.; D’Ammando, F.; DeKlotz, M.; Torre Luque, P. De La; Palma, F. De; Desai, A.; Lalla, N. Di; Venere, L. Di; Fana Dirirsa, F.; Fegan, S. J.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Gill, R.; Giordano, F.; Giroletti, M.; Granot, J.; Green, D.; Grenier, I. A.; Grondin, M.-H.; Guiriec, S.; Hays, E.; Horan, D.; Jóhannesson, G.; Kocevski, D.; Kovac’evic’, M.; Kuss, M.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Li, J.; Liodakis, I.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Maldera, S.; Malyshev, D.; Manfreda, A.; Martí-Devesa, G.; Mazziotta, M. N.; McEnery, J. E.; Mereu, I.; Meyer, M.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Omodei, N.; Orienti, M.; Orlando, E.; Palatiello, M.; Paliya, V. S.; Paneque, D.; Pei, Z.; Persic, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Poon, H.; Porter, T. A.; Principe, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Rani, Bindu; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ryde, F.; Saz Parkinson, P. M.; Serini, D.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Tajima, H.; Takagi, K.; Takahashi, M. N.; Tak, D.; Thayer, J. B.; Thompson, D. J.; Torres, D. F.; Troja, E.; Valverde, Janeth; Klaveren, B. Van; Wood, K.; Yassine, M.; Zaharijas, G.; Mailyan, B.; Bhat, P. N.; Briggs, M. S.; Cleveland, W.; Giles, M.; Goldstein, A.; Hui, M.; Malacaria, Christian; Preece, R.; Roberts, O. J.; Veres, P.; Wilson-Hodge, C.; Kienlin, A. Von; Cenko, S. B.; O’Brien, P.; Beardmore, A. P.; Lien, Amy; Osborne, J. P.; Tohuvavohu, A.; D’Elia, V.; D’Aì, A.; Perri, M.; Gropp, J.; Klingler, N.; Capalbi, M.; Tagliaferri, G.; Stamatikos, M.; De Pasquale, M.
We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by theFermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process.
A combined Quantum Monte Carlo and DFT study of the strain response and magnetic properties of two-dimensional (2D) 1T-VSe₂ with charge density wave
(2024-09-27) Wines, Daniel; Ibrahim, Akram; Gudibandla, Nishwanth; Adel, Tehseen; Abel, Frank M.; Jois, Sharadh; Saritas, Kayahan; Krogel, Jaron T.; Yin, Li; Berlijn, Tom; Hanbicki, Aubrey T.; Stephen, Gregory M.; Friedman, Adam L.; Krylyuk, Sergiy; Davydov, Albert; Donovan, Brian; Jamer, Michelle E.; Walker, Angela R. Hight; Choudhary, Kamal; Tavazza, Francesca; Ataca, Can
Two-dimensional (2D) 1T-VSe₂ has prompted significant interest due to the discrepancies regarding alleged ferromagnetism (FM) at room temperature, charge density wave (CDW) states and the interplay between the two. We employed a combined Diffusion Monte Carlo (DMC) and density functional theory (DFT) approach to accurately investigate the magnetic properties and response of strain of monolayer 1T-VSe₂. Our calculations show the delicate competition between various phases, revealing critical insights into the relationship between their energetic and structural properties. We went on to perform Classical Monte Carlo simulations informed by our DMC and DFT results, and found the magnetic transition temperature (Tc) of the undistorted (non-CDW) FM phase to be 228 K and the distorted (CDW) phase to be 68 K. Additionally, we studied the response of biaxial strain on the energetic stability and magnetic properties of various phases of 2D 1T-VSe₂ and found that small amounts of strain can enhance the Tc, suggesting a promising route for engineering and enhancing magnetic behavior. Finally, we synthesized 1T-VSe₂ and performed Raman spectroscopy measurements, which were in close agreement with our calculated results. Our work emphasizes the role of highly accurate DMC methods in advancing the understanding of monolayer 1T-VSe₂ and provides a robust framework for future studies of 2D magnetic materials.
The Black Hole Mass and Photometric Components of NGC 4826
(AAS, 2024-10) Gültekin, Kayhan; Gebhardt, Karl; Kormendy, John; Foord, Adi; Bender, Ralf; Lauer, Tod R.; Pinkney, Jason; Richstone, Douglas O.; Tremaine, Scott
We present infrared photometry and Hubble Space Telescope imaging and spectroscopy of the Sab galaxy NGC 4826. Schwarzschild dynamical modeling is used to measure its central black hole mass M. Photometric decomposition is used to enable a comparison of M to published scaling relations between black hole masses and properties of host bulges. This decomposition implies that NGC 4826 contains classical and pseudobulges of approximately equal mass. The classical bulge has best-fit Sérsic index n = 3.27. The pseudobulge is made up of three parts, an inner lens (n = 0.18 at r ≲ 4''), an outer lens (n = 0.17 at r ≲ 45''), and a n = 0.58 Sérsic component required to match the surface brightness between the lens components. The total V-band luminosity of the galaxy is Mᵥₜ = -21.07, the ratio of classical bulge to total light is B/T ≃ 0.12, and the ratio of pseudobulge to total light is PB/T ≃ 0.13. The outer disk is exponential (n = 1.07) and makes up D/T = 0.75 of the light of the galaxy. Our best-fit Schwarzschild model has a black hole mass with 1σ uncertainties of M = 8.4⁺¹.⁷₋₀.₆ X 10⁶ M☉ and a stellar population with a K-band mass-to-light ratio of ϒₖ = 0.46 ± 0.03 M☉ L☉⁻¹ at the assumed distance of 7.27 Mpc. Our modeling is marginally consistent with M = 0 at the 3σ limit. These best-fit parameters were calculated assuming the black hole is located where the velocity dispersion is largest; this is offset from the maximum surface brightness, probably because of dust absorption. The black hole mass—one of the smallest measured by modeling stellar dynamics—satisfies the well known correlations of M with the K-band luminosity, stellar mass, and velocity dispersion of the classical bulge only. In contrast, the black hole is undermassive with respect to the correlation of M with total (classical plus pseudo) bulge luminosity. Thus the composite (classical bulge plus pseudobulge) galaxy NGC 4826 is consistent with previous results on black hole scaling relations and helps to strengthen these results at low black hole masses.
Coastal-Urban-Rural Atmospheric Gradient Experiment (CoURAGE) Science Plan
(2024-08-01) Davis, Kenneth; Zaitchik, Benjamin; Asa-Awuku, Akua; Bou-Zeid, Elie; Baidar, Sunil; Boxe, Christopher; Brewer, W. Alan; Chiao, Sen; Damoah, Richard; DeCarlo, Peter; Demoz, Belay; Dickerson, Russ; Giometto, Marco; Gonzalez-Cruz, Jorge; Jensen, Michael; Kuang, Chongai; Lamer, Katia; Li, Xiaowen; Lombardo, Kelly; Miles, Natasha; Niyogi, Dev; Pan, Ying; Peters, John; Ramamurthy, Prathap; Peng, Wei; Richardson, Scott; Sakai, Ricardo; Waugh, Darryn; Zhang, Jie
Understanding the mechanisms governing the urban atmospheric environment is critical for informing urban populations regarding the impacts of climate change and associated mitigation and adaptation measures. Earth system (climate and weather) models have not yet been adapted to provide accurate predictions of climate and weather variability within cities, nor do they provide well-tested representations of the impacts of urban systems on the atmospheric environment. These limitations are largely due to limited field data available for testing and development of these models. We will deploy the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) user facility’s first Mobile Facility (AMF1) to the mid-Atlantic region surrounding the city of Baltimore for the Coast-Urban-Rural Atmospheric Gradient Experiment (CoURAGE). This deployment will create a four-node regional atmospheric observatory network including Baltimore and its three primary surrounding environments – rural, urban, and bay. CoURAGE investigators will study the interactions among the Earth’s surface, the atmospheric boundary layer, aerosols and atmospheric composition, clouds, radiation, and precipitation at each site, and examine how the spatial gradients across the region interact to create the climate conditions in Baltimore. This study will determine the degree to which Baltimore’s atmospheric environment depends on interactive feedbacks in the atmospheric system and the degree to which conditions in Baltimore depend on the surrounding environment. Some topics of interest include how urban land management exacerbates heat waves, the impact of regional mesoscale winds (nocturnal jet, bay breeze) on urban air pollution and cloud cover, and the impact of the urban heat island and aerosol production on heavy precipitation events. Understanding this integrated coast-urban-rural system quantitatively and with good accuracy and precision is critical to informing climate adaptation and mitigation efforts in the city of Baltimore. The understanding gained should be applicable to many similar coastal, mid-latitude urban centers. Another important objective of CoURAGE is to improve the representation of the climate of coastal cities in Earth systems models (ESMs). CoURAGE investigators will use the observations to test current ESMs, identify weaknesses and work towards improved simulations of this complex environment. The ARM core facility will be deployed in the city of Baltimore, complementing the Baltimore Social-Environmental Collaborative (BSEC), a DOE urban integrated field laboratory (UIFL). Ancillary sites will be deployed to rural Maryland northwest of Baltimore, and to the southern end of Kent Island within Chesapeake Bay. The fourth node will be a long-term atmospheric observatory operated in Beltsville, Maryland by Howard University and the Maryland Department of the Environment. Measurements will be conducted for one year, starting in December of 2024. There will be two intensive operational periods (IOPs), one in summer and one in winter, when the ancillary sites will be enhanced with additional balloon launches, tethered balloon system (TBS) operation, and added atmospheric composition measurements.
Visualizing 3-Dimensional Ptychography Data
(2024-08) Stanford, V. Vianne; Bhatt, Lopa; Muller, David
Ruddlesden-Popper Phases (RP) are a method of growing materials to induce specific properties in the material. In nickelates, the proper RP domain gives superconducting properties to the material. Unfortunately, measuring the distribution of RP domains in a sample in a statistically significant area is tedious and time consuming. To aid in this endeavor, we modified a previously created RP-domain tracking code² ̓ ³ to allow for analysis of ptychography data and to add 3-dimensional visualization capabilities.
Introducing UNIQuE: The Unconventional Noiseless Intermediate Quantum Emulator
(2024-09-11) Robertson, Reece; Ventura, Dan
We implement the first open-source quantum computing emulator that includes arithmetic operations, the quantum Fourier transform, and quantum phase estimation. The emulator provides significant savings in both temporal and spatial resources compared to simulation, and these computational advantages are verified through comparison to the Intel Quantum Simulator. We also demonstrate how to use the emulator to implement Shor's algorithm and use it to solve a nontrivial factoring problem. This demonstrates that emulation can make quantum computing more accessible than simulation or noisy hardware by allowing researchers to study the behavior of algorithms on large problems in a noiseless environment.
Chandra Discovery of a Candidate Hyper-Luminous X-ray Source in MCG+11-11-032
(2024-09-05) Foord, Adi; Civano, Francesca; Comerford, Julia M.; Elvis, Martin; Fabbiano, Giuseppina; Liu, Tingting; Lusso, Elisabeta; Marchesi, Stefano; Mezcua, Mar; Muller-Sanchez, Francisco; Nevin, Rebecca; Nyland, Kristina
We present a multi-wavelength analysis of MCG+11-11-032, a nearby AGN with the unique classification of both a binary and a dual AGN candidate. With new Chandra observations we aim to resolve any dual AGN system via imaging data, and search for signs of a binary AGN via analysis of the X-ray spectrum. Analyzing the Chandra spectrum, we find no evidence of previously suggested double-peaked Fe Kα lines; the spectrum is instead best fit by an absorbed powerlaw with a single Fe Kα line, as well as an additional line centered at ≈7.5 keV. The Chandra observation reveals faint, soft, and extended X-ray emission, possibly linked to low-level nuclear outflows. Further analysis shows evidence for a compact, hard source -- MCG+11-11-032 X2 -- located 3.27'' from the primary AGN. Modeling MCG+11-11-032 X2 as a compact source, we find that it is relatively luminous (L₂₋₁₀ ₖₑᴠ=1.52+0.96−0.48×10⁴¹ erg s⁻¹), and the location is coincident with an compact and off-nuclear source resolved in Hubble Space Telescope infrared (F105W) and ultraviolet (F621M, F547M) bands. Pairing our X-ray results with a 144 MHz radio detection at the host galaxy location, we observe X-ray and radio properties similar to those of ESO 243-49 HLX-1, suggesting that MCG+11-11-032 X2 may be a hyper-luminous X-ray source. This detection with Chandra highlights the importance of a high-resolution X-ray imager, and how previous binary AGN candidates detected with large-aperture instruments benefit from high-resolution follow-up. Future spatially resolved optical spectra, and deeper X-ray observations, can better constrain the origin of MCG+11-11-032 X2.
Developing Small Satellite Ground Support Software for Orbit Tracking and Target Acquisition of the HARP Cubesat
(Frontiers, 2024-10-10) Sienkiewicz, Noah; Martins, J. Vanderlei; Xu, Xiaoguang; McBride, Brent; Remer, Lorraine
Small satellites are efficient at performing Earth science from space due to their limited cost and size. Small satellites (cubesats) achieve much with limited power production/storage, heat dissipation, data storage, and ground contact points/bandwidth. As such it is beneficial to offload as much as possible to ground support systems. Consider the HyperAngular Rainbow Polarimeter (HARP) Cubesat. Its goals were to serve as a technical demonstration prior to the development of HARP2 aboard the NASA Plankton Aerosol Cloud and ocean Ecosystem (PACE) mission and to serve as an Earth viewing remote sensing platform which measured the characteristics of clouds and aerosols. HARP cubesat was limited to taking 5-minute capture sequences once every 24 h. It took approximately 10 such captures before it needed to perform data downlink and have its memory cleared for continued use. A ground station at NASA Wallops supported HARP with approximately three points of contact each day. To maximize the value of each capture, ground support software was developed leveraging public data to inform the schedule of each capture. In this paper, we review the algorithms and data sources that allowed us to: 1; predict the HARP orbital track a week in advance, 2; predict also the location of other remote sensing satellites and ground stations relative to HARP, 3; predict the ground view geometry of the instrument along its orbital track, 4; compare global climatological data products of clouds and aerosols along the predicted orbital tracks, and 5; identify and integrate important ground target locations based on remote sensing literature and ongoing natural phenomena. This HARP Orbital Prediction System (HOPS) made HARP into a successful technical demonstration which also offered significant science value. The HOPS system presents a valuable methodology for small satellites to operate efficiently despite their limited capabilities. HOPS is also a useful testbed for studying the sensitivity of scene geometry. Using HOPS, we show that for a wide field-of-view (FOV) instrument, like HARP, latitude/longitude geolocation varies by approximately 0.1° at a height of 8–10 km. Scattering angles vary less than 0.01° at similar heights, with the worst performance near direct backscatter (180°).
Effect of Dust Morphology on Aerosol Optics in the GEOS-Chem Chemical Transport Model, on UV-Vis Trace Gas Retrievals, and on Surface Area Available for Reactive Uptake
(AGU, 2024-09-26) Singh, Inderjeet; Martin, Randall V.; Bindle, Liam; Chatterjee, Deepangsu; Li, Chi; Oxford, Christopher; Xu, Xiaoguang; Wang, Jun
Many chemical transport models treat mineral dust as spherical. Solar backscatter retrievals of trace gases (e.g., OMI and TROPOMI) implicitly treat mineral dust as spherical. The impact of the morphology of mineral dust particles is studied to assess its implications for global chemical transport model (GEOS-Chem) simulations and solar backscatter trace gas retrievals at ultraviolet and visible (UV-Vis) wavelengths. We investigate how the morphology of mineral dust particles affects the simulated dust aerosol optical depth; surface area, reaction, and diffusion parameters for heterogeneous chemistry; phase function, and scattering weights for air mass factor (AMF) calculations used in solar backscatter retrievals. We use a mixture of various aspect ratios of spheroids to model the dust optical properties and a combination of shape and porosity to model the surface area, reaction, and diffusion parameters. We find that assuming spherical particles can introduce size-dependent and wavelength-dependent errors of up to 14% in simulated dust extinction efficiency with corresponding error in simulated dust optical depth typically within 5%. We find that use of spheroids rather than spheres increases forward scattered radiance and decreases backward scattering that in turn decrease the sensitivity of solar backscatter retrievals of NO₂ to aerosols by factors of 2.0–2.5. We develop and apply a theoretical framework based on porosity and surface fractal dimension with corresponding increase in the reactive uptake coefficient driven by increased surface area and species reactivity. Differences are large enough to warrant consideration of dust non-sphericity for chemical transport models and UV-Vis trace gas retrievals.

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