Optical Surveys

In the traditional model of astronomical observation, individual or small teams of astronomers study a select class of objects in a small region of sky. However, some of the most exciting cosmological and astrophysical results in recent years have required the study of millions of galaxies over thousands of square degrees of sky. The Sloan Digital Sky Survey (SDSS), in which KIPAC played a small part, was the pioneer in large optical surveys, imaging over 50 million galaxies over 1/4 of the sky with 5 bands. This large survey has made possible the study of dark matter and dark energy on the largest scales, all the way down to the structure of the Milky Way galaxy at the smallest scales, with unprecedented precision.

KIPAC is a key partner in several next-generation large optical surveys, including the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST).  DES is an international project that surveyed 5000 square degrees of the southern sky from the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile, using the state-of-the-art Dark Energy Camera, which boasts 570 megapixels covering 2.2 square degrees. The five-year DES survey began in 2013 detected over 300 million galaxies, allowing precision measurements of the expansion history of the Universe to obtain dark energy constraints using galaxy cluster counts, baryon acoustic oscillations, and gravitational lensing. In addition, certain patches of the sky were reobserved with a short cadence for a complementary search for Type Ia Supernovae to be used as cosmological probes.

LSST is a very large project to image the entire southern sky every three nights with a new eight-meter class telescope, scheduled to go online in 2022. The LSST camera, construction of which is being led by scientists at KIPAC, will have more than three gigapixels, covering 3.5 square degrees with unprecedented image quality and survey efficiency. In addition to the precision dark energy science made possible by the wide field, extraordinary depth, and excellent image quality, the rapid survey ability will open up the entire southern sky to transient and variable studies on timescales from hours to years. The LSST will also be able to detect virtually all near-Earth objects that are potentially hazardous to life on Earth in the case of a collision, allowing several years to decades of warning.