Mon. Not. R. Astron. Soc., 498, 3043-3059 (2020/October-3)
The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6.
MATTHEE J., PEZZULLI G., MACKENZIE R., CANTALUPO S., KUSAKABE H., LECLERCQ F., SOBRAL D., RICHARD J., WISOTZKI L., LILLY S., BOOGAARD L., MARINO R., MASEDA M. and NANAYAKKARA T.
Abstract (from CDS):
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.
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
galaxies: evolution - galaxies: high-redshift - dark ages, reionization, first stars - cosmology: observations
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