Abstract
Following our previous spectroscopic observations of $z>7$ galaxies with
Gemini/GNIRS and VLT/XSHOOTER, which targeted a total of 8 objects, we present
here our results from a deeper and larger VLT/FORS2 spectroscopic sample of
Wide Field Camera 3 selected $z>7$ candidate galaxies. With our FORS2 setup we
cover the 737-1070nm wavelength range, enabling a search for Lyman-$\alpha$ in
the redshift range spanning 5.06 - 7.80. We target 22 $z$-band dropouts and
find no evidence of Lyman-$\alpha$ emission. The upper limits on Lyman-$\alpha$
flux and the broad-band magnitudes are used to constrain the rest-frame
Equivalent Widths for this line emission. We analyse our FORS2 observations in
combination with our previous GNIRS and XSHOOTER observations, and suggest that
a simple model where the fraction of high rest-frame Equivalent Width emitters
follows the trend seen at $z=3-6.5$ is inconsistent with our non-detections at
$z\sim7.8$ at the 96\% confidence level. This may indicate that a significant
neutral HI fraction in the intergalactic medium suppresses Lyman-$\alpha$, with
an estimated neutral fraction $\chi_HI\sim0.5$, in agreement with other
estimates.
Users
Please
log in to take part in the discussion (add own reviews or comments).