A Kinematic Analysis of Ionised Extraplanar Gas in the Spiral Galaxies
  NGC 3982 and NGC 4152
  We present a kinematic study of ionised extraplanar gas in two
low-inclination late-type galaxies (NGC 3982 and NGC 4152) using integral field
spectroscopy data from the DiskMass H$\alpha$ sample. We first isolate the
extraplanar gas emission by masking the H$\alpha$ flux from the regularly
rotating disc. The extraplanar gas emission is then modelled in the
three-dimensional position-velocity domain using a parametric model described
by three structural and four kinematic parameters. Best-fit values for the
model are determined via a Bayesian MCMC approach. The reliability and accuracy
of our modelling method are carefully determined via tests using mock data. We
detect ionised extraplanar gas in both galaxies, with scale heights
$0.83^{+0.27}_{-0.40}\,\mathrm{kpc}$ (NGC 3982) and
$1.87^{+0.43}_{-0.56}\,\mathrm{kpc}$ (NGC 4152) and flux fraction between the
extraplanar gas and the regularly rotating gas within the disc of 27% and 15%
respectively, consistent with previous determinations in other systems. We find
lagging rotation of the ionized extraplanar gas in both galaxies, with vertical
rotational gradients $-22.24^{+6.60}_{-13.13} \,\mathrm{km\,s^{-1}\,kpc^{-1}}$
and $-11.18^{+3.49}_{-4.06}\,\mathrm{km\,s^{-1}\,kpc^{-1}}$, respectively, and
weak evidence for vertical and radial inflow in both galaxies. The above
results are similar to the kinematics of the neutral extraplanar gas found in
several galaxies, though this is the first time that 3D kinematic modelling of
ionised extraplanar gas has been carried out. Our results are broadly
consistent with a galactic fountain origin combined with gas accretion.
However, a dynamical model is required to better understand the formation of
ionised extraplanar gas.
