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Strong field-to-field variation of Lyα nebulae populations at z ≃ 2.3

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Original languageEnglish
Pages (from-to)1654-1671
Number of pages18
JournalAstrophysical Journal
Volume719
Issue number2
DOIs
Publication statusPublished - 20 Aug 2010

Abstract

Understanding the nature of distant Lyα 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 Lyα luminosities of LLyα= (0.7-8) x 1043 erg s-1 and isophotal areas of Aiso = 10-60 □′′. The transition from compact Lyα emitters (LAEs; Aiso ∼ a few □′′) to extended Lyα blobs (Aiso > 10 □′′) 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 α ≳ 1.5 x 1043 erg s-1 and A iso > 16 □′′ lie only in the CDFS. These large, bright blobs have a field-to-field variance of συ ≳ 1.5 (150%) about their number density n ∼1.0+1.80.6 x 10-5 Mpc-3. This variance is large, significantly higher than that of unresolved LAEs (συ ∼ 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 ≳1013 M if most halos have detectable blobs. The predicted variance in n is consistent with that observed and corresponds to a bias of ∼7. Blob halos lie at the high end of the halo mass distribution at z = 2.3 and are likely to evolve into the ∼10 14 M halos typical of galaxy clusters today. On larger scales of ∼10 comoving Mpc, blobs cluster where compact LAEs cluster, indicating that blobs lie in coherent, highly overdense structures.

    Research areas

  • Galaxies: formation, Galaxies: high-redshift, Intergalactic medium

ID: 145366676