Abstract

Lyman-alpha blobs are mysterious objects in the distant Universe extending over 50-100 kpc. Because these gigantic gas clouds have been detected only in optically thick and highly resonant Lyman-alpha emission, their power source remains a puzzle. Due to the rarity of blobs, the form of their evolution to the present day is also unknown. We are conducting multi-wavelength, deep, and large area surveys to identify tens of blobs at redshifts ~2-5. These surveys have now produced the first constraints on blob clustering, showing that blobs occupy massive halos likely to evolve into rich clusters today. Blobs are not only tracers of the most overdense environments at early times, but also may mark the sites of brightest cluster galaxy formation. By targeting the optically thin Halpha line, we have obtained the first measurements of gas kinematics in blobs, excluding strong outflows as the source of Lyman alpha emission.