Physics Colloquium

"Measuring Dark Matter and Dark Energy with Gravitational Lensing"

Presented by Erin Sheldon, BNL

Tuesday, March 17, 2015, 3:30 pm — Large Seminar Room, Bldg. 510

Gravitational lensing is the bending of light as it passes massive bodies. The amount of deflection is directly related to the mass of the lensing body and the geometrical configuration of the lens-source system. Typical lens configurations involve a distant background galaxy lensed by a much closer foreground galaxy, or cluster of galaxies. The lensing effect can be used to infer the mass of the lens, both luminous and dark matter. Lensing, as a purely geometrical phenomenon has become the most important way to measure the distribution of dark matter in the universe. I will discuss measurements I have made of the dark matter distribution in galaxies and clusters of galaxies using the lensing phenomenon. These measurements, the most precise to date, are consistent with the predictions of the cold dark matter model. Dark energy has accelerated the expansion of the universe at late times, and thus alters the relationship between the observed redshift of galaxies and their true distance from us. Lensing is sensitive to this redshift-distance relationship, and thus dark energy, since the amount of light deflection depends on the relative distances of lens and source. I will discuss the Dark Energy Survey (DES), a survey of the southern sky, now ending our second year of data taking. DES surveys larger volumes of the universe, and probes farther back in time than previous lensing surveys. With DES we will establish lensing as a competitive method to study dark energy. I will discuss preliminary results from DES using galaxy clusters as lenses and distant background galaxies as sources. I will end with a discussion of the new Large Synoptic Survey Telescope (LSST) survey, of which BNL is a member. LSST is a successor of DES, now entering the construction phase. With LSST we will bring lensing to maturity as a probe of dark energy.

Hosted by: Morgan May

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