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 \pm 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 two observational position angles ( PA ) , with Lyman- \alpha  line flux of 1.06 \pm 0.19 \times 10 ^ { -17 } erg s ^ { -1 } cm ^ { -2 } .
The line flux is nearly a factor of four higher than in the archival MOSFIRE spectroscopic observations .
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 ) , and if confirmed would make this source the highest-redshift AGN yet found .
These observations from the Hubble Space Telescope thus clearly demonstrate the sensitivity of the FIGS survey , and the capability of grism spectroscopy to study the epoch of reionization .