HETDEX pilot survey for emission-line galaxies - I. Survey design,
  performance, and catalog
  We present a catalog of emission-line galaxies selected solely by their
emission-line fluxes using a wide-field integral field spectrograph. This work
is partially motivated as a pilot survey for the upcoming Hobby-Eberly
Telescope Dark Energy Experiment (HETDEX). We describe the observations,
reductions, detections, redshift classifications, line fluxes, and counterpart
information for 397 emission-line galaxies detected over 169 sq.arcmin with a
3500-5800 Ang. bandpass under 5 Ang. full-width-half-maximum (FWHM) spectral
resolution. The survey's best sensitivity for unresolved objects under
photometric conditions is between 4-20 E-17 erg/s/sq.cm depending on the
wavelength, and Ly-alpha luminosities between 3-6 E42 erg/s are detectable.
This survey method complements narrowband and color-selection techniques in the
search for high redshift galaxies with its different selection properties and
large volume probed. The four survey fields within the COSMOS, GOODS-N, MUNICS,
and XMM-LSS areas are rich with existing, complementary data. We find 104
galaxies via their high redshift Ly-alpha emission at 1.9<z<3.8, and the
majority of the remainder objects are low redshift [OII]3727 emitters at
z<0.56. The classification between low and high redshift objects depends on
rest frame equivalent width, as well as other indicators, where available.
Based on matches to X-ray catalogs, the active galactic nuclei (AGN) fraction
amongst the Ly-alpha emitters (LAEs) is 6%. We also analyze the survey's
completeness and contamination properties through simulations. We find five
high-z, highly-significant, resolved objects with full-width-half-maximum sizes
>44 sq.arcsec which appear to be extended Ly-alpha nebulae. We also find three
high-z objects with rest frame Ly-alpha equivalent widths above the level
believed to be achievable with normal star formation, EW(rest)>240 Ang.
