Recovery and analysis of rest-frame UV emission lines in 2052 galaxies
  observed with MUSE at $1.5 < z < 6.4$
  [Abbreviated] Rest-frame UV emission lines probe physical parameters of the
emitting star-forming galaxies and their environments. The strongest main UV
line, Ly$\alpha$, has been instrumental in advancing the general knowledge of
galaxy formation in the early universe. However, observing Ly$\alpha$ emission
becomes increasingly challenging at $z \gtrsim 6$ when the neutral hydrogen
fraction of the CGM and IGM increases. Secondary weaker UV emission lines
provide important alternative methods for studying galaxy properties at high
redshift. We present a large sample of rest-frame UV emission line sources at
intermediate redshift for calibrating and exploring the connection between
secondary UV lines and the emitting galaxies' physical properties and their
Ly$\alpha$ emission. The sample of 2052 emission line sources with $1.5 < z <
6.4$ was selected through untargeted source detection in three-dimensional MUSE
data cubes. We searched optimally extracted 1D spectra of the full sample for
UV emission features via emission line template matching, resulting in a sample
of more than 100 rest-frame UV emission line detections. We show that the
detection efficiency of (non-Ly$\alpha$) UV emission lines increases with
survey depth, and that the UV emission line strength often correlate with the
strength of Ciii]. We measured the velocity offsets of resonant emission lines
with respect to systemic tracers as well as the electron density and the
gas-phase abundance. Lastly, using "PhotoIonization Model Probability Density
Functions" we find that the UV line emitters generally have ionization
parameter log10(U) $\approx$ -2.5 and metal mass fractions that scatter around
Z $\approx$ 10$^{-2}$, that is Z $\approx$ 0.66Z$\odot$. Value-added catalogs
of the full sample of MUSE objects studied in this work and a collection of UV
line emitters from the literature are provided with this paper.
