The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet
  Reference Atlas (MEGaSaURA) I: The Sample and the Spectra
  We introduce Project MEGaSaURA: The Magellan Evolution of Galaxies
Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises
medium-resolution, rest-frame ultraviolet spectroscopy of N=15 bright
gravitationally lensed galaxies at redshifts of 1.68$<$z$<$3.6, obtained with
the MagE spectrograph on the Magellan telescopes. The spectra cover the
observed-frame wavelength range $3200 < \lambda_o < 8280$ \AA ; the average
spectral resolving power is R=3300. The median spectrum has a signal-to-noise
ratio of $SNR=21$ per resolution element at 5000 \AA . As such, the MEGaSaURA
spectra have superior signal-to-noise-ratio and wavelength coverage compared to
what COS/HST provides for starburst galaxies in the local universe. This paper
describes the sample, the observations, and the data reduction. We compare the
measured redshifts for the stars, the ionized gas as traced by nebular lines,
and the neutral gas as traced by absorption lines; we find the expected bulk
outflow of the neutral gas, and no systemic offset between the redshifts
measured from nebular lines and the redshifts measured from the stellar
continuum. We provide the MEGaSaURA spectra to the astronomical community
through a data release.
