CAREER: An order of magnitude improvement in measurements of the physical properties of dark matter

This program uses gravitationally-lensed quasars to study the nature of dark matter. By using high spatial-resolution spectroscopy, Nierenberg will measure positions and flux ratios for 200 multiply-lensed systems -- an order of magnitude increase in the existing number of similar measurements. These data will be used to determine the relative number of dark matter halos well below the mass threshold for galaxy formation, the presence of dark matter particles with high enough velocities to impact galaxy formation and galaxy clustering, and to confirm or exclude the existence of entirely dark halos. Research-integrated educational components include training and mentoring of a postdoctoral scholar and graduate students, a summer academy in STEM topics targeting 4th and 5th graders, course curriculum development in General Relativity, and public lectures series on Nierenberg’s research. Integral field spectroscopy with adaptive optics on multiple large-telescope facilities will be used by Nierenberg to constrain the distribution of dark-matter halos from the narrow emission-line flux ratios of quadruply lensed quasars, selected from Euclid and LSST imaging. Lens flux ratios are sensitive to the second derivative of the gravitational potential, offering unique sensitivity to the number and distribution of low-mass halos. A primary result from this work will be a definitive measurement of a possible turnover mass (at 106 solar masses) in the halo mass function, indicative of warm dark matter. The analysis approach is statistical, using forward modeling and Bayesian computing methods to evaluate the highly stochastic mapping of dark matter distribution parameters to predicted flux ratios. The educational components of this program are intertwined with the research themes, providing instruction and mentoring in the scientific method, scientific computing and dark matter research to students spanning elementary school through postdoctoral career phases. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.