The MASSIVE Survey -- XV. A Stellar Dynamical Mass Measurement of the
  Supermassive Black Hole in Massive Elliptical Galaxy NGC 1453
  We present a new stellar dynamical mass measurement ($M_\mathrm{BH}$) of the
supermassive black hole (SMBH) in NGC 1453, a fast-rotating massive elliptical
galaxy in the MASSIVE survey. We measure stellar kinematics in 135 spatial bins
in the central 1.5 kpc by 2 kpc region of the galaxy using high signal-to-noise
($S/N \sim 130$) spectra from the Gemini-North GMOS integral-field spectrograph
(IFS). Combining with wide-field IFS kinematics out to $\sim 3$ effective radii
and stellar light distributions from Hubble Space Telescope (HST) WFC3 images,
we perform Schwarzschild orbit-based mass modeling in the axisymmetric limit to
constrain the mass components in NGC 1453. The best-fit black hole mass is
$M_\mathrm{BH} =(2.9 \pm 0.4) 10^9 M_\odot$; the mass models without a central
black hole are excluded at the $8.7\sigma$ level. The NGC 1453 black hole lies
within the intrinsic scatter of the SMBH and galaxy scaling relations, unlike
three other galaxies hosting $\gtrsim 10^{10} M_\odot$ SMBHs in the MASSIVE
sample. The high-$S/N$ GMOS spectra enable us to determine 8 moments of the
Gauss-Hermite expansion of the line-of-sight velocity distributions (LOSVDs),
which are used as constraints in the orbit modeling. The stellar orbits in the
mass models are further constrained to produce negligible $h_9$ through
$h_{12}$ to minimize spurious behavior in the LOSVDs. We show that truncating
the series at $h_4$, as was often done in prior work, leads to a much weaker
constraint on the inferred $M_\mathrm{BH}$ for NGC 1453. Furthermore, we
discuss precautions and modifications that are needed to achieve axisymmetry in
triaxial orbit codes that use the Schwarzschild method to sample the start
space of stellar orbits in triaxial gravitational potentials.
