STRONG FIELD-TO-FIELD VARIATION OF Lyα NEBULAE POPULATIONS AT z ≃ 2.3

Understanding the nature of distant Ly alpha nebulae, aka blobs, and connecting them to their present-day descendants requires constraining their number density, clustering, and large-scale environment. To measure these basic quantities, we conduct a deep narrowband imaging survey in four different fields, Chandra Deep Field South (CDFS), Chandra Deep Field North (CDFN), and two COSMOS subfields, for a total survey area of 1.2 deg(2). We discover 25 blobs at z = 2.3 with Ly alpha luminosities of L-Ly alpha = (0.7-8) x 10(43) erg s(-1) and isophotal areas of A(iso) = 10-60 square ''. The transition from compact Ly alpha emitters (LAEs; A(iso) similar to a few square '') to extended Ly alpha blobs (A(iso) > 10 square '') is continuous, suggesting a single family perhaps governed by similar emission mechanisms. Surprisingly, most blobs (16/25) are in one survey field, the CDFS. The six brightest, largest blobs with L-Ly alpha greater than or similar to 1.5x10(43) erg s(-1) and A(iso) > 16 square '' lie only in the CDFS. These large, bright blobs have a field-to-field variance of sigma(v) greater than or similar to 1.5 (150%) about their number density n similar to 1.0(-0.6)(+1.8) x 10(-5) Mpc(-3). This variance is large, significantly higher than that of unresolved LAEs (sigma(v) similar to 0.3 or 30%), and can adversely affect comparisons of blob number densities and luminosity functions (LFs) among different surveys. Our deep, blind survey allows us to construct a reliable blob LF. We compare the statistics of our blobs with dark matter halos in a 1 h(-1) Gpc cosmological N-body simulation. At z = 2.3, n implies that each bright, large blob could occupy a halo of M-halo greater than or similar to 10(13) M-circle dot if most halos have detectable blobs. The predicted variance in n is consistent with that observed and corresponds to a bias of similar to 7. Blob halos lie at the high end of the halo mass distribution at z = 2.3 and are likely to evolve into the similar to 10(14) M-circle dot halos typical of galaxy clusters today. On larger scales of similar to 10 comoving Mpc, blobs cluster where compact LAEs cluster, indicating that blobs lie in coherent, highly overdense structures.