Collaborative Research: The Hierarchical Mergers of Low Mass Galaxies

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Astronomical observations show that collisions between large galaxies are violent events. During collisions galaxies form many stars, and the galaxies change shape. Sometimes small galaxies, called dwarf galaxies, merge with larger galaxies during collisions. Other times the collisions produce long trains of stars thrown out into the space between galaxies. The investigators have numerically simulated the mergers of dwarf galaxies and studied the remnants of these mergers. In this project, they will improve their simulations and compare the simulations with new observations. New telescopes, like the Large Synoptic Survey Telescope (LSST), are designed to study the smallest and faintest galaxies in the Universe. Many more colliding dwarf galaxies are soon to be discovered with these telescopes. The investigators will use their simulations to better understand the merger history of galaxies. This topic is important for understanding the history of formation of our own Milky Way galaxy. This collaborative project will leverage strong existing outreach efforts at both Columbia University and The University of Arizona. They will expand the TIMESTEP program, which reaches under-represented minorities and develops a community to support them throughout their academic careers. They will also support graduate students who produce popular YouTube videos, which answer top public astronomy questions.The investigators will improve their previous simulations by increasing mass resolution of the cosmological simulations and by modeling larger volumes of space. They plan to model dwarf galaxy pairs in the region near our Milky Way galaxy. They will dynamically match the models and explore the role of dwarf-dwarf galaxy mergers. The investigators will also create a simulated catalog of dwarf sub-halo pairs using the high-resolution, dark-matter-only, cosmological simulation. They will compare the observed dwarf galaxy pair counts with expectations of Lambda Cold Dark Matter cosmological models.