  The spectral investigation of the triply ionized gold (Au IV) has been
carried out in the wavelength region of 500--2106 {\AA}. The gold spectra were
photographed at the National Institute of Standards and Technology (NIST, USA)
on a 10.7-m normal incidence vacuum spectrograph (NIVS) using a sliding spark
source as well as on a 3-m NIVS at the Antigonish laboratory in Canada with a
triggered spark source. Our analysis is theoretically supported by the
pseudo-relativistic Hartree-Fock (HFR) formalism with superposition of
configuration interactions implemented in Cowan's suite of codes. Radiative
transition parameters are also calculated using HFR+CPOL (core-polarization
effects) model and multiconfiguration Dirac-Hartree-Fock (MCDHF) approach, and
their comparisons are used to evaluate the transition rate data. All the
previously reported levels of the $5d^{8}$, $5d^{7}6s$, and $5d^{7}6p$
configurations are confirmed, except one and three are newly established. The
missing $^{1}S_{0}$ level of $5d^{8}$ is now established at 55277.8 cm$^{-1}$.
A total of 981 observed lines (E1-type) classified to 1031 transitions,
including 133 newly identified, enabled us to optimize 139 energy levels.
Several astrophysically important transitions, forbidden (M1- and E2-types)
lines of $5d^{8}$ and $5d^{7}6s$, are provided with their Ritz wavelengths and
radiative parameters. A critically evaluated set of energy levels, observed and
Ritz wavelengths along with their uncertainties, transition rates, and
uniformly-scaled intensities of Au IV lines have been presented. Also, large
scale atomic data to compute opacity of Au IV in the kilonova ejecta have been
supplemented in this work.
