Collaborative Research: Halo Modeling Strikes Back: New Techniques to infer the Galaxy-Dark Matter Connection in the Presence of Environmental Effects

Yale University, New Haven CT

Investigators

Abstract

In the next decade, a number of innovative telescopic surveys will provide scientists with a wealth of precise data regarding galaxies and cosmology. This project aims to remove recently identified deficiencies in models of the relationship between galaxies and dark matter, necessary to interpret galaxy survey data. The researchers will develop, and make publicly available, an open-source software package that could be used to minimize systematic errors in interpreting galaxy data sets, leading to a better understanding of galaxy formation and evolution, and also paving the way for unbiased use of galaxy surveys in precision cosmology. Complementing this novel research program, this proposal includes contributions to K-12 science education, addressing the critical need for students to engage in STEM-related disciplines. At Yale, PI van den Bosch will develop a custom planetarium show for the Leitner Family Observatory and Planetarium on the topic of gravity, and tailored to 8th graders. At the University of Pittsburgh, PI Zentner will serve as an instructor in the Buhl Academy, a new program at the Carnegie Science Center Buhl Planetarium that pairs scientists with Pittsburgh area K-12 teachers. Halo occupation modeling models the probabilistic relation between galaxies and dark matter halos and is the premier tool for interpreting the clustering of galaxies. A standard assumption made in all halo occupation studies is that the mass of a dark matter halo completely determines the properties of its resident galaxy population. Mounting observational evidence indicates that galaxy properties, in particular star formation rates, are correlated with halo properties other than mass, such as halo age or concentration. This "galaxy assembly bias" (GAB) is a significant source of systematic error, both in efforts to understand galaxy evolution and in the precision cosmology program. In order to ensure the unbiased interpretation of forthcoming data, this proposal aims to develop the next generation halo occupation models that properly account for GAB. The researchers will identify the optimal set of observational diagnostics that can be used to infer the presence and strength of GAB, develop open-source software that properly accounts for GAB, and explore methods to mitigate the impacts of GAB by using alternative definitions of halo mass. They will apply these newly developed techniques to extant galaxy survey data, and make predictions for forthcoming surveys such as DES, eBOSS, DESI, LSST, EUCLID, and WFIRST.