“ … York, D.G. et al. 2000, AJ.120,1579 Srihari Balaji (Union College), Prof. Rebecca A. Koopmann … ”
Abstract
The Undergraduate ALFALFA Team (UAT) Groups Project is investigating the influence of the environment on galaxies in group environments. Galaxies in clusters show evidence for a variety of environmental effects. The UAT team has chosen groups from the RASSCALS sample (groups defined using the Rosat X-ray satellite, Mahdavi et al. 2000). Galaxies within 2 degrees of group center and 3 sigma of the central velocity of the group were targeted for Hα observations. We cross-matched the 52 RASSCALS groups and clusters the UAT has observed to the Tempel et al. (2017) group catalog based on Sloan Digital Sky Survey observations, finding 26 that matched within 10 arcminutes of the RASSCALS group. Here we compare properties of these groups.
“ … Boyle, SrihariBalaji, and Manav Bilakhia at the Department of … ”
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.
“ … pressure system. Elise Liebow, Melanie Boyle, SrihariBalaji, and Manav Bilakhia at the Department of … ”
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.
