  In a recent posting of a submitted paper Weatherley et al. re-analyse the
spectroscopic data from our observations of Abell 1835 IR 1916, a galaxy we
claimed to be at redshift z=10.0 (Pello et al., 2004, A&A, 416, L35). They
conclude that the emission line is not detected in their analysis. Although
their reduction procedure is accurate and robust, there are several differences
with ours. The most important one concerns the stacking of the spectral frames.
In the case of compact target sources [here: seeing-limited object,~3 pixels
FWHM in the spectral direction, on a 1" (~7 pixels) wide slit] spectral shifts
occur between individual frames. Our reduction corrects for this effect using a
nearby strong emission line from a compact reference object, as described in
Pello et al. However, Weatherley et al. neglect this effect. This difference
turns out to be crucial. E.g. adopting their combination scheme as closely as
possible but correcting for the spectral drifts we recover the line detection.
We conclude that more work is needed to fully understand the origin of our
differences. However, their non-detection claim needs further investigation and
cannot be uphold based on the arguments presented in their original version of
the paper. More information is beeing posted on
http://webast.ast.obs-mip.fr/people/roser/z10_spectroscopy_discussion. With
this material we also invite other researchers to re-analyse independently the
ISAAC spectroscopic observations.
