Studies of type Ia supernovae (SNIa) first detected dark energy, a fundamentally weird component of the Universe that carries enormous implications for both cosmology and particle physics. This project will produce a better measurement of the properties of dark energy, including its equation of state and constraints on how much it could have changed over cosmic time. The PanSTARRS (Panoramic Survey Telescope and Rapid Response System) project will use an unprecedented combination of a 3.3 degree field of view and a 1.8 m collection aperture to increase some 30-fold the current sample of about 300 objects that crudely map out the history of cosmic expansion and the parameters of the dark energy. These new observations will have much higher quality, homogeneity, and freedom from systematic effects than has been heretofore possible.
But because it will not be possible to obtain spectra for the tens of thousands of SNIa that PanSTARRS will detect, Dr. Tonry's group has created a new powerful classifier with explicit freedom from assumptions about the nature of SNIa (such as the homogeneity of explosion, properties of enshrouding dust, or evolution with redshift). These automatic methods use precision light curves to measure both luminosity distance and redshift for each SNIa, and can determine whether a light curve is that of a SNIa or something else. The current project will use these techniques to classify the transient detections from PanSTARRS, estimate SNIa redshift and distance, and measure the time history of the expansion of the Universe to determine the properties of dark energy. It will also investigate exceptionally over- or under-luminous SNIa, and critically examine SNIa metallicity effects and the properties of dust extinction. Finally, this work will establish SNIa rates as a function of host galaxy star formation to search for SNIa subclasses arising from prompt or delayed white dwarf explosions.
Dark energy is apparently the main source of gravitation in the Universe, causing it to expand exponentially, and profoundly affecting galaxy formation and the creation of stars, planets, and people. A better measurement of dark energy will constrain particle physics theories, and affect our understanding of how galaxies and stars grew in the Universe. It is critical to carry out the most basic tests of isotropy and homogeneity, because it is certainly possible that we are being fooled by an even stranger Universe than we have dared to guess.
