Physics and Astronomy Calendar

Superclusters represent the largest scale at which gravitational structure formation is important at the current epoch. Thus, the history of supercluster formation provides important constraints on theories of structure formation via gravitational collapse and the evolution of a substantial fraction of the baryons in the universe. Although such structures have been studied in the local universe, they remain largely unexplored at higher redshifts, where most observations have targeted only the densest cluster cores. By expanding observations to intermediate-density regimes at redshifts around one, we examine regions of intense galaxy transformation, including groups and filaments. To increase the sample of high-redshift superclusters, we have undertaken ORELSE, a multi-band survey of regions around a sample of twenty well-studied, rich clusters at z > 0.6. This survey consists of (1) deep optical photometry to identify potential structures; (2) extensive high-resolution spectroscopy to confirm structure members and study their stellar populations; (3) near-infrared imaging to obtain stellar masses and SEDs; (4) mid- and far-infrared imaging to study AGN, starbursts, and dust; (5) X-ray observations of the intracluster gas and AGN, and (6) radio observations to detect obscured star formation and AGN. We present some of the early results of this survey, including multiple new supercluster systems and properties of their galaxy populations. The importance of multi-wavelength observations to understand environmental effects on galaxy properties. star formation, and AGN is discussed.