Direct evidence for Ly $\boldsymbol{\alpha }$ depletion in the protocluster core

Abstract We have carried out panoramic Lyα narrow-band imaging with Suprime-Cam on Subaru towards the known protocluster USS1558−003 at z = 2.53. Our previous narrow-band imaging in the near-infrared identified multiple dense groups of Hα emitters (HAEs) within the protocluster. We have now identifi...

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Published in:Monthly notices of the Royal Astronomical Society. Letters 2017-06, Vol.468 (1), p.L21-L25
Main Authors: Shimakawa, Rhythm, Kodama, Tadayuki, Hayashi, Masao, Tanaka, Ichi, Matsuda, Yuichi, Kashikawa, Nobunari, Shibuya, Takatoshi, Tadaki, Ken-ichi, Koyama, Yusei, Suzuki, Tomoko L., Yamamoto, Moegi
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Language:English
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Summary:Abstract We have carried out panoramic Lyα narrow-band imaging with Suprime-Cam on Subaru towards the known protocluster USS1558−003 at z = 2.53. Our previous narrow-band imaging in the near-infrared identified multiple dense groups of Hα emitters (HAEs) within the protocluster. We have now identified the large-scale structures across a ∼50 comoving Mpc scale traced by Lyα emitters (LAEs) in which the protocluster traced by the HAEs is embedded. On a smaller scale, however, there are remarkably few LAEs in the regions of HAE overdensities. Moreover, the stacking analyses of the images show that HAEs in higher-density regions show systematically lower escape fractions of Lyα photons than those of HAEs in lower-density regions. These phenomena may be driven by the extra depletion of Lyα emission lines along our line of sight by more intervening cold circumgalactic/intergalactic medium and/or dust in the dense core. We also caution that all the previous high-z protocluster surveys using LAEs as tracers would have largely missed galaxies in the very dense cores of the protoclusters where we would expect to see any early environmental effects.
ISSN:1745-3925
1745-3933
DOI:10.1093/mnrasl/slx019