Deep rest-frame far-UV spectroscopy of the giant Lyman α emitter 'Himiko'

J. Zabl, Hans Ulrik Nørgaard-Nielsen, J. P. U. Fynbo, P. Laursen, M. Ouchi, P. Kjaergaard

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Abstract

We present deep 10 h VLT/XSHOOTER spectroscopy for an extraordinarily luminous and extended Ly alpha emitter at z = 6.595 referred to asHimiko and first discussed by Ouchi et al., with the purpose of constraining the mechanisms powering its strong emission. Complementary to the spectrum, we discuss near-infrared imaging data from the CANDELS survey. We find neither for He II nor any metal line a significant excess, with 3 σ upper limits of 6.8, 3.1, and 5.8 x 10-18 erg s-1 cm-2 for C IV λ 1549, He II λ 1640, C III] λ 1909, respectively, assuming apertures with 200 km s-1 widths and offset by -250 km s-1 w.r.t. to the peak Ly α redshift. These limits provide strong evidence that an AGN is not a major contribution to Himiko's Ly α flux. Strong conclusions about the presence of Pop III star formation or gravitational cooling radiation are not possible based on the obtained He II upper limit. Our Ly alpha spectrum confirms both spatial extent and flux (8.8 +/- 0.5 x 10-17 erg s -1 cm-2) of previous measurements. In addition, we can unambiguously exclude any remaining chance of it being a lower redshift interloper by significantly detecting a continuum redwards of Ly α, while being undetected bluewards.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume451
Issue number2
Pages (from-to)2050-2070
ISSN0035-8711
DOIs
Publication statusPublished - 2015

Keywords

  • Stars: Population III
  • Galaxies: high-redshift
  • Galaxies: individual: Himiko
  • Galaxies: star formation

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