2023 Departmental Poster Competition

When it launches, LISA (Laser Interferometer Space Antenna) will probe a lower frequency portion of the gravitational wave spectrum. White dwarf binaries will be the most numerous sources in its catalog, with around 30,000 directly resolvable binaries which will reveal information about the structure and history of the Milky Way. To investigate this, we used COSMIC (Compact Object Synthesis and Monte Carlo Investigation Code) to generate Milky-Way-like populations of double white dwarfs with user-specified galactic assumptions. COSMIC is a quick population synthesis code and functions by creating a small fixed population and then drawing from that population until it reaches a specified mass. By varying the galactic assumptions put into COSMIC, specifically the metallicity for this work, we investigated how the metallicity will impact the galactic double white dwarf population and the sources eventually observed by LISA. We used four metallicities: 0.011, 0.014, 0.017, and 0.02. These were the metallicities given to both the thin disks and bulges, while the thick disk metallicities were 15% of these values. Since the galaxies drawn from the fixed populations are random, we made 500 galaxies per metallicity and compared their medians to minimize random effects. For each catalog, we created histograms of the binaries’ orbital periods, chirp masses, and individual masses to compare between metallicities. These histograms showed points in the parameter space where the distribution of histograms completely separates meaning that the metallicity of the galaxy has a potentially observable effect on the distribution of resolvable LISA double white dwarf binaries in the Milky Way. Future improvements on this project include examining the catalogs with Bayesian analysis and expanding the grid to include more galactic parameters such as the scale height, total galactic mass, and star formation history.