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The detection of intergalactic H α emission from the Slug Nebula at z ∼ 2.3

Abstract : The Slug Nebula is one of the largest and most luminous Lyman-α (Ly α) nebulae discovered to date, extending over 450 kpc around the bright quasar UM287 at z= 2.283. Characterized by high surface brightnesses over intergalactic scales, its Ly α emission may either trace high-density ionized gas (`clumps') or large column densities of neutral material. To distinguish between these two possibilities, information from a non-resonant line such as H α is crucial. Therefore, we analysed a deep Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) observation of one of the brightest Ly α-emitting regions in the Slug Nebula with the goal of detecting associated H α emission. We also obtained a deep, moderate resolution Ly α spectrum of the nearby brightest region of the Slug. We detected an H α flux of F_{{H α }}= 2.62± 0.47 × 10^{-17} erg cm-2 s-1 (SB_{{H α }}=2.70± 0.48 × 10^{-18} erg cm-2 s-1 arcsec-2 at the expected spatial and spectral location. Combining the H α detection with its corresponding Ly α flux (determined from the narrow-band imaging), we calculate a flux ratio of {F_{Lyα }}/{F_{H α }}=5.5± 1.1. The presence of a skyline at the location of the H α emission decreases the signal-to-noise ratio of the detection and our ability to put stringent constraints on the H α kinematics. Our measurements argue for the origin of the Ly α emission being recombination radiation, suggesting the presence of high-density ionized gas. Finally, our high-resolution spectroscopic study of the Ly α emission does not show evidence of a rotating disc pattern and suggest a more complex origin for at least some parts of the Slug Nebula.
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https://hal-insu.archives-ouvertes.fr/insu-03747913
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Submitted on : Tuesday, August 9, 2022 - 8:43:05 AM
Last modification on : Thursday, November 24, 2022 - 5:02:58 PM
Long-term archiving on: : Thursday, November 10, 2022 - 6:04:06 PM

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Camille N. Leibler, Sebastiano Cantalupo, Bradford P. Holden, Piero Madau. The detection of intergalactic H α emission from the Slug Nebula at z ∼ 2.3. Monthly Notices of the Royal Astronomical Society, 2018, 480, pp.2094-2108. ⟨10.1093/mnras/sty1764⟩. ⟨insu-03747913⟩

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