Abstract
Galaxies at high redshifts provide a valuable tool to study cosmic dawn, and
therefore it is crucial to reliably identify these galaxies. Here, we present
an unambiguous and first simultaneous detection of both the Lyman-\alpha
emission and the Lyman break from a z = 7.512+/- 0.004 galaxy, observed in the
Faint Infrared Grism Survey (FIGS). These spectra, taken with G102 grism on
Hubble Space Telescope (HST), show a significant emission line detection
(6\sigma) in multiple observational position angles (PA), with total
integrated Ly\alpha line flux of 1.06+/- 0.12 e10-17erg s-1cm-2. The line
flux is nearly a factor of four higher than the previous MOSFIRE spectroscopic
observations of faint Ly\alpha emission at łambda = 1.0347\mum, yielding
z = 7.5078+/- 0.0004. This is consistent with other recent observations
implying that ground-based near-infrared spectroscopy underestimates total
emission line fluxes, and if confirmed, can have strong implications for
reionization studies that are based on ground-based Lyman-\alpha
measurements. A 4-\sigma detection of the NV line in one PA also suggests a
weak Active Galactic Nucleus (AGN), potentially making this source the
highest-redshift AGN yet found. Thus, this observation from the Hubble Space
Telescope clearly demonstrates the sensitivity of the FIGS survey, and the
capability of grism spectroscopy to study the epoch of reionization.
Description
[1605.06519] First results from Faint Infrared Grism Survey (FIGS): first simultaneous detection of Lyman-{\alpha} emission and Lyman break from a galaxy at z=7.51
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