“ … in each annulus measured to complete the photometry SamanthaRosenfeld, Advisor Rebecca A. Koopmann, Undergraduate ALFALFA … ”
Abstract
Galaxies from the groups SRGb016, SRGb046, and WBL105 were examined through broadband R (stellar) and Hα (star formation) wavelengths to discover patterns within their areas of active star formation. The galaxy images were obtained from the Kitt Peak National Observatory WIYN 0.9m telescope. Radial profiles of R and Hα light were derived through surface photometry. There were 18 out of 23 galaxies from SRGb016 (78%), 9 out of 25 galaxies from SRGb046 (36%), and 4 out of 5 galaxies from WBL105 (80%) that were detected in Hα.
“ … Regions on DM Variations for PSRs J1614-2230 & J1643-1224 Samantha L. Rosenfeld 1, Shami Chatterjee2,3, James M. … [7] Ocker, S. K., Cordes, J. M., & Chatterjee, S. (2020). Samantha Rosenfeld participated in … ”
Abstract
Pulsar dispersion measure (DM) quantifies the integrated electron column density along the line of sight. Electron density fluctuations produce DM variations that induce errors in high precision pulsar timing used by the Nanohertz Observatory for Gravitational Waves (NANOGrav). We analyze DM variations of two pulsars observed by NANOGrav, PSRs J1614-2230 and J1643-1224, to determine if the HII regions along their LOS enhance their DM variations. Both pulsars exhibit linear changes in DM that are due to the transverse motions of the LOS through density gradients in the interstellar medium (ISM). We calculate the motion of the pulsars' LOS through the HII regions and determine that the observed DM variations could trace density fluctuations on scales of astronomical units (AU) or less within the HII regions. J1614-2230 exhibits DM variations dominated by the solar wind, but both pulsars show additional periodic DM variations that are out of phase with the expected solar wind-induced fluctuations. These periodic DM variations are too large to be explained by the LOS motion through the HII regions, but could be induced by another local plasma structure that obstructs the LOS to both pulsars. Funded by the Summer 2020 Astronomy REU program at Cornell University under NSF award NST/AST-1950324. The NANOGrav Physics Frontiers Center is supported by NSF award number 1430284.
“ … Computational Modeling of Europa’s Ice Shell INTRODUCTION Samantha L. Rosenfeld, Prof. Heather Watson In the search for life beyond … ”
Abstract
Planetary science is the study of different physical, atmospheric, and geological properties of planetary bodies in our Solar System. We are specifically interested in studying Jupiter's moon Europa, because of its large quantity of ice and water. This surplus of H2O is an essential piece in the search for life beyond Earth, which means in order to understand how life could exist outside of Earth, we must first enhance our intuition about the conditions on this icy moon. In this project, we use computational analysis methods and a program called SeaFreeze to model and calculate the thermodynamic properties of water and ice to learn more about how different pressure and temperature conditions influence their molecular behavior and phase changes. Through this analysis, we find relationships for the thermodynamic properties across phase boundaries and for each type of ice. We apply this analysis to create a model for the interior of the ice layer on Europa, plotting properties such as density, p-wave velocity, and s-wave velocity as functions of depth. We find a semi-linear relationship for these properties, and require future analyses to study the effects of salt in order to gain a full picture of the interior of Europa.
“ … through Pure-Water Modeling and Saltwater Experiments Samantha L. Rosenfeld 1, Heather C. Watson1 1Union College, … ”
Abstract
We explore the properties of the hydrosphere on Europa involving both a modeling technique and experimental methods. We perform a computational analysis of the thermodynamic properties for an ideal, pure-water Europan ice shell using a Python programming framework called SeaFreeze. We create four models assuming surface temperatures of either 50 K or 140 K and ice shell thicknesses of either 3 km or 30 km. We observe mostly linear trends for the density and seismic wave velocities with respect to depth, and find that surface temperatures have the greatest effect on the models. Simultaneously, we experimentally investigate the phase diagram of different saltwater concentrations in an attempt to further constrain the ice shell properties. We determine the freezing-melting points of 5%, 10%, and 20% by-weight NaCl-water solutions under constant pressures from 0 MPa to 70 MPa. We find that increasing the salt concentration, the pressure, or both decreases the freezing point temperature with a freezing point temperature depression of about -20 ¬?C from that of pure water at zero pressure. Based on our experimental results, we expect that adding NaCl to the pure-water computational models would cause them to have lower temperatures at the ice-water boundary, assuming saltwater has similar density and seismic wave velocity trends as pure-water. Areas of future development include continuing to explore the phase diagrams of different saltwater concentrations, including MgSO4, KCl, and varying combinations of all three salts, extending the pure-water SeaFreeze models to analyze Europa's subsurface ocean layer, implementing various new techniques to make our experiments more precise, and finally applying our results to the other icy moons, such as Ganymede or Callisto.
“ … through Pure-Water Modeling and Saltwater Experiments By Samantha L. Rosenfeld ********* Submitted in partial … Physics and Astronomy UNION COLLEGE June, 2022 … ABSTRACT Rosenfeld,SAMANTHA L. Investigating the Thermodynamics and Seismic … ”
Abstract
We explore the properties of the hydrosphere on Europa involving both a modeling technique and experimental methods. We perform a computational analysis of the thermodynamic properties for an ideal, pure-water Europan ice shell using a Python programming framework called SeaFreeze. We create four models assuming surface temperatures of either 50 K or 140 K and ice shell thicknesses of either 3 km or 30 km. We observe mostly linear trends for the density and seismic wave velocities with respect to depth and find that surface temperature has the greatest effect on the models. Simultaneously, we experimentally investigate the phase diagram of different saltwater concentrations in an attempt to further constrain the ice shell properties. We determine the freezing temperatures of 5%, 10%, and 20% by-weight NaCl-water solutions under constant pressures from 0 MPa to 70 MPa. We find increasing the salt concentration, the pressure, or both decreases the freezing point temperature with a depression at our most extreme conditions of about -20 °C from that of pure water at zero pressure. Based on our experimental results, we expect that adding NaCl to the pure-water models would lower their ice-water boundary temperatures. Areas of future development include continuing to explore the phase diagrams of different saltwater concentrations, including MgSO<sub>4</sub>, KCl, and varying combinations of all three salts, extending the pure-water SeaFreeze models to analyze Europa's subsurface ocean layer, implementing various new techniques to make our experiments more precise, and finally applying our results to the other icy moons, such as Ganymede or Callisto.
