Speaker:
Wendy Freedman/Carnegie Observatories
Host Department:
Astronomy
Date: 09/20/2012
Time: 4:00 PM - 5:00 PM
Location: Dennison 807
Description:
THE CARNEGIE SUPERNOVA AND HUBBLE CONSTANT PROJECTS. I will discuss two ongoing projects: The Carnegie Supernovae Project (CSP), a long-term program using Type Ia supernovae to place constraints on the equation of state for dark energy; and The Carnegie Hubble Project (CHP), a new Spitzer Exploration Program aimed at measuring the Hubble constant to an accuracy of 2%. As part of the CSP, we have been extensively monitoring Type Ia supernovae, obtaining ultraviolet through near-infrared observations at low redshifts (z<0.08), and measuring the first near-infrared (I-band) Hubble diagram out to redshifts of 0.7. The CHP is calibrating the extragalactic distance scale in the mid-infrared (3.6 microns). Based on a geometric parallax calibration of Cepheids from the Hubble Space Telescope (and in future, from the European parallax satellite, GAIA), and with negligible reddening in the mid-infrared, this program is allowing us to re-measure the Cepheid distances to nearby galaxies, and calibrating Type Ia supernovae and other methods well out into the Hubble flow. I will discuss how this improved accuracy in the Hubble constant, in combination with new experiments like Planck, provides strong constraints on other cosmological parameters, such as the dark energy equation of state, w, and the numbers of neutrino species.
College of Literature, Science, and the Arts
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