Delving into the Dark: Astronomical Probes of Dark Matter and Dark Energy

September 09, 2011

Modern models of the universe posit that it is composed in large part of as-yet unknown forms of matter and energy, dubbed dark matter (20% of the total) and dark energy (75%). A broad experimental, observational and theoretical research effort is under-way to discover the nature of these mysterious ingredients that dominate and shape the cosmos, with UC Santa Cruz physicists and astronomers playing a leading role. The research program of Assistant Professor Tesla Jeltema, the latest addition to the UC Santa Cruz Physics faculty, focuses precisely on astronomical probes of both dark matter and dark energy. The ultimate aim of Jeltema’s scientific work is to constrain models, gather information and eventually discover the nature of what “matters the most” in the universe.

Jeltema’s graduate work at MIT focused on the largest assemblies of matter in the universe, containing thousands of galaxies and thousands of billions of stars: clusters of galaxies. Under the supervision of X-ray astronomy pioneer Claude Canizares, Tesla studied the high-redshift cluster MS 1054-0321 with the new NASA X-ray telescope Chandra. This object, discovered with previous X-ray instruments but never observed in such fine detail, per se rules out a universe filled with matter only – thus pointing to some additional, unknown component. Jeltema showed that MS 1054-0321 is a merging cluster with features similar to the now-famous Bullet cluster: the gas density is offset from the matter density, as determined by weak lensing observations, implying that most matter in clusters is “dark”, and at most weakly interacting. While at MIT, Jeltema was also the first to quantitatively demonstrate that cluster structure and morphology evolve with redshift, in a way that depends on the underlying cosmological model.

Dr. Jeltema the joined Carnegie Observatories in Pasadena as a postdoctoral researcher. While continuing her work with X-ray observations, she extended her observational expertise to optical astronomy. In collaboration with John Mulchaey, she studied the question – crucial for star formation and galaxy evolution – of the impact of environment on galaxies, and in particular of small assemblies of galaxies known as “groups”. Jeltema led several observing runs at telescopes in Hawaii and Chile, emerging as a leading expert on groups of galaxies. In 2007, Dr. Jeltema joined the Astronomy Department at UC Santa Cruz as a Morrison Fellow, and expanded her expertise a third part of the electromagnetic spectrum: gamma rays.   As an associate member of the Fermi Collaboration and an active affiliate of the DEEP2 team, Jeltema was the first to put constraints on dark matter models via X-ray observations, and she played a pivotal role in several of the early Fermi searches for dark matter with gamma rays. She is also leading the Collaboration’s efforts to discover gamma ray emission from clusters of galaxies.

After receiving several faculty offers from around the world, including from Carnegie Mellon University in Pittsburgh, the University of Maryland, the University of Auckland in New Zealand and from the Max Planck Institute for Extraterrestrial Physics in Germany, Dr. Jeltema accepted a UC Santa Cruz offer as Assistant Professor in the Physics Department, a position she started in July 2011. Mother of a one-year old boy, Dr. Jeltema is actively committed to promoting the success of women in science and to fight the “leaky pipeline” phenomenon of women in academia. She is promoting and organizing several activities at UCSC, partly funded by the National Science Foundation, including the mentoring of female undergraduate students by female graduate students and inviting outstanding and successful women physicists from throughout the country for colloquia and more informal gatherings with local students. A competitive collegiate swimmer, Professor Jeltema enjoys pool and open-water swimming: she has swum three times from Alcatraz to San Francisco and once from the Golden Gate to the Bay Bridge, and she is the 2011 Pacific Masters Open-Water Champion in her age group. Balancing the demands and rewards of academic work, motherhood and an active lifestyle is the trademark of the latest addition to the ranks of the Physics Department at UC Santa Cruz.