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The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6

Abstract : CR7 is among the most luminous Ly α emitters (LAEs) known at z = 6.6 and consists of at least three UV components that are surrounded by Ly α emission. Previous studies have suggested that it may host an extreme ionizing source. Here, we present deep integral field spectroscopy of CR7 with VLT/Multi Unit Spectroscopic Explorer (MUSE). We measure extended emission with a similar halo scale length as typical LAEs at z ≍ 5. CR7's Ly α halo is clearly elongated along the direction connecting the multiple components, likely tracing the underlying gas distribution. The Ly α emission originates almost exclusively from the brightest UV component, but we also identify a faint kinematically distinct Ly α emitting region nearby a fainter component. Combined with new near-infrared data, the MUSE data show that the rest-frame Ly α equivalent width (EW) is ≍100 Å. This is a factor 4 higher than the EW measured in low-redshift analogues with carefully matched Ly α profiles (and thus arguably H I column density), but this EW can plausibly be explained by star formation. Alternative scenarios requiring active galactic nucleus (AGN) powering are also disfavoured by the narrower and steeper Ly α spectrum and much smaller IR to UV ratio compared to obscured AGN in other Ly α blobs. CR7's Ly α emission, while extremely luminous, resembles the emission in more common LAEs at lower redshifts very well and is likely powered by a young metal-poor starburst.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Friday, July 1, 2022 - 1:49:50 PM
Last modification on : Monday, July 4, 2022 - 3:33:59 AM

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Jorryt Matthee, Gabriele Pezzulli, Ruari Mackenzie, Sebastiano Cantalupo, Haruka Kusakabe, et al.. The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6. Monthly Notices of the Royal Astronomical Society, 2020, 498, pp.3043-3059. ⟨10.1093/mnras/staa2550⟩. ⟨insu-03711456⟩



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