  We present preliminary results from a programme to obtain multi-object
near-infrared spectroscopy of galaxies at redshifts $0.7<z<1.5$. We are using
the instrument CIRPASS (the Cambridge Infra-Red PAnoramic Survey Spectrograph),
in multi-object mode, to survey H-alpha in galaxies at $z\sim1$. We aim to
address the true star formation history of the universe at this epoch:
potentially the peak period of star formation activity. H-alpha is the same
star formation measure used at low redshift, and hence we can trace star
formation without the systematic uncertainties of using different calibrators
in different redshift bins, or the extreme dust extinction in the rest-UV.
CIRPASS has been successfully demonstrated in multi-object mode on the AAT and
WHT. Here we present preliminary results from one of our fields, the Hubble
Deep Field North, observed with the WHT. With 150 fibres deployed over an
unvignetted field of $\sim15$arcmin, we have several detections of H-alpha from
star forming galaxies at $0.8<z<1.0$ and present spectra of the seven brightest
of these. By pre-selecting galaxies with redshifts such that H-alpha will
appear between the OH sky lines, we can detect star formation rates of $5
h^{-2}_{70} M_{\odot} {\rm yr}^{-1}$ ($5 \sigma$ in 3-hours, $\Omega_M=0.3$,
$\Omega_{\Lambda}=0.7$). It appears that star formation rates inferred from
H-alpha are, on average, a factor of more than two higher than those based on
the UV continuum alone.

Astrophysics