Testing the Cold Dark Matter Model by Constraining Dark Matter Substructure in Gravitational Lens Galaxies

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Most of the matter in the Universe is in the form of dark matter, whose presence we only observe through its gravity. All galaxies appear to be surrounded by large halos of dark matter. And dark matter dominates the gravitational field of galaxies and clusters of galaxies. Dark matter is dark because it does not emit or absorb light making it hard to study. In fact, astronomers do not yet know the true nature of dark matter. But understanding this will advance our understanding of the fundamental laws of physics.By studying the dark matter halos of galaxies, and how their gravity bends light from more distant sources (gravity lenses), astronomers can learn about the structure of the dark matter in the halos how they were formed. Various models to explain these things have been developed, and they can all be tested based on what actually happens in dark matter halos. This proposed study will use high-resolution images of gravity lenses to learn more about the structure of the dark-matter halos. The results will also help determine the type of particle dark matter is.The PI's institution serves students from underrepresented and/or underprivileged backgrounds. The Broader Impact part of this project will be to award promising undergraduate science and engineering majors (a minimum of six students over three years) a stipend to do research (allowing them to focus on studies and research rather than work part time jobs outside of school). The undergraduates will learn skills, and gain experiences, that are vital to STEM fields, while also producing valuable results for this project. Each year, students accepted to the program will work at the American Museum of Natural History (AMNH) during the summer. They will participate in a three-day workshop to acquire scientific computing skills, attend weekly meetings to discuss recent papers in astrophysics, and at the end of the summer will give a talk on their research at the AMNH "Physical Sciences REU Symposium". Finally, after the following fall semester the students will have the opportunity to attend and give a poster presentation of their research at the winter American Astronomical Society (AAS) meeting.This project clearly relates to NSF's mission to promote the progress of science. In addition, the "Broader Impact" portion of the project does this, and advances the national health, prosperity and welfare by helping to develop interest in, and educating, STEM activities among the next generation of diverse individuals.The existence of small dark matter substructure in galaxies is a key prediction of dark matter theories that remains largely untested. The project's goals are to test the Cold Dark Matter (CDM) paradigm by analyzing a sample of gravitational lenses observed at high resolution. The proposed project will evaluate methods to detect and characterize substructure in gravitational lens galaxies. In particular it will consist of observing lenses in the submillimeter electromagnetic spectral range. Galaxies with gravitational lenses are being discovered rapidly in this area. Using high-resolution observations (e.g. by the ALMA telescope array) of these galaxies, the PI and team will obtain unprecedented information on the dark matter distribution in galaxies. And because gravitational lensing directly exhibits the warping of space time by dark matter, a study of gravitational lens systems is a promising method to constrain generic particle properties of dark matter (independent of specific particle models). The team's primary goal is to show how this information can be used to constrain the detailed properties of dark matter substructure as a way of identifying the nature of dark matter itself.