Unusual spectral energy distribution of a galaxy previously reported to be at redshift 6.68

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Abstract

Observations of distant galaxies are important both for understanding how galaxies form and for probing the physical conditions of the Universe at early times. It is, however, very difficult to identify galaxies at redshifts z > 5, because they are so faint and have few spectral characteristics. We previously reported1 the probable identification of a galaxy at z = 6.68, based on one line and an apparent break in the spectrum just shortwards of that, which we interpreted as Lyman α emission and the Lyman α break, where photons with shorter wavelengths are absorbed by the intervening neutral hydrogen gas. Here we present optical photometry that shows moderate detections of light in the B- and V-band images, which are inconsistent with the expected absence of flux shortwards of the Lyman α break for a galaxy at z > 5, and inconsistent with the previous flux measurement. Moreover, the spectral energy distribution for this object cannot readily be fitted by any known galaxy spectral template at any redshift, so the redshift is undetermined.

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Figure 1: Portions of the ground-based B, V and R images, smoothed by the size of the point spread functions, and the corresponding STIS image centred at galaxy A.
Figure 2: The observed spectral energy distribution of galaxy A.

References

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Correspondence to Hsiao-Wen Chen.

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