Collaborative Research: Searching for Dark Matter Subhalos in Distant Strong Gravitational Lenses

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This project aims to transform the NSF facility ALMA, the Atacama Large Millimeter/submillimeter Array, into a powerful probe of the fundamental physics of dark matter and the astrophysics of galaxy formation, using an effect known as gravitational lensing first predicted by Einstein over a century ago. The main goal of the project is to quantify the properties of dark matter, the mysterious component of our Universe whose gravity binds galaxies together but which has eluded detection in collider experiments at our most advanced accelerators. Dark matter represents the most compelling evidence for new physics beyond the Standard Model of fundamental physics developed over 40 years ago and has therefore been the subject of intensive study, both theoretical and experimental, for many decades. Research supported by this grant will be incorporated into a program for integrating astronomy into 5th grade classrooms in Illinois, and undergraduates from underrepresented groups will participate in research activities under this project at Stanford.The research program involves a suite of theoretical, numerical, and observational research to lay the groundwork needed to translate ALMA observations of lensed dusty galaxies into constraints on the microphysical properties of dark matter. ALMA observations of gravitationally lensed galaxies will be used to search for substructure in the mass distributions of the lensing objects. Given the scale of ALMA data sets and the complexity of the lens modeling required to detect extremely subtle effects of low-mass substructure, this analysis will be performed on petascale computing facilities like NSF's Blue Waters using a novel analysis pipeline developed by the investigating team. Numerical simulations will be used to quantify the abundance of substructure expected in a variety of dark matter models that explore different physical characteristics of dark matter including various self-interactions, temperatures, and Compton wavelengths, using novel simulation software written by the investigating team. In addition, stacked optical/IR observations of detected dark matter subhalos will provide the most stringent bounds to date on the mean stellar mass - halo mass relation in the smallest galaxies, a crucial input for all models of galaxy formation.