Our group works on topics in the frontiers of astronomy and astrophysics. Here are summaries of our most active areas of research:

• Cosmology and the large-scale structure of the Universe. We look at how galaxies in the universe are patterned to form clumps and clusters that are connected by thin filaments, almost like a cosmic sponge. One mysterious entity (dark matter) helps form the clumps, while another (dark energy) is starting to drive an accelerated expansion of these clumps away from each other. A main goal is to characterize the properties and behavior of both dark matter and dark energy. [Brownstein, Dawson, Mao, Wik, Zheng]
   
  
• Galaxy evolution and dynamics. Galaxies, such as our own Milky Way, can contain hundreds to hundreds-of-billions of stars (give or take!), as well as clouds of gas and dust, supermassive (and stellar mass) black holes, and dark matter. We look to see how galaxies were assembled and how they interact with each other, giving clues about the formation of stars, the chemical enrichment of the Universe, and the nature of dark matter. [Brownstein, Mao, Seth, Zasowski, Zheng]
   
  
• Galaxy nuclei and massive black holes. Most, if not all, galaxies harbor supermassive black holes. These exotic objects have the mass of millions to billions of stars packed into a region of space smaller than our solar system. We look at how these objects grow and influence the growth of their host galaxies. Their origin remains a mystery.... [Seth, Bromley, Wik]
   
  
• Stars in the Milky Way and the origins of elements. Stellar spectroscopy, or the detailed analysis of starlight in terms of its color, reveals the elements that make up stars. By studying how these elements are spread across different populations of stars in the Milky Way Galaxy, we can understand the origin of the periodic table, including carbon, oxygen, and other elements necessary for life on Earth. Spectroscopy also tells us about how the stars are moving, how old they are, and other properties that let us understand how the Milky Way formed and has changed over time. [Seth, Zasowski]
   
  
• Dark matter. Dark matter is known only from its gravitational influence on visible stars and gas. Its properties may be inferred from its effects galaxy clustering. A major goal of astronomy is to detect dark matter directly by catching a rare collision with normal atoms. Alternatively, dark matter may reveal itself in interactions that can lead to showers of high energy particles. So far there have been only tentative hints of detections. Thus, the search continues. [Brownstein, Gondolo, Mao, Sandick, Wik, Zhao]
   
  
• Planets. Amidst dark energy and dark matter, within galaxies and around stars, small particles of dust began to clump together to form planets. Our view of planets in the Universe has expanded from just a handful around our solar system to thousands seen around other stars. We are working to understand the mechanisms at play in the formation of planets, in particular of rocky planets like our own Earth. Is this process universal, and do we have company in the Universe? [Bromley]