Neutral hydrogen gas within and around NGC 1316
  We present MeerKAT observations of neutral hydrogen gas (HI) in the nearby
merger remnant NGC 1316 (Fornax A), the brightest member of a galaxy group
which is falling into the Fornax cluster. We find HI on a variety of scales,
from the galaxy centre to its large-scale environment. For the first time we
detect HI at large radii (70 - 150 kpc in projection), mostly distributed on
two long tails associated with the galaxy. Gas in the tails dominates the HI
mass of NGC 1316: 7e+8 Msun -- 14 times more than in previous observations. The
total HI mass is comparable to the amount of neutral gas found inside the
stellar body, mostly in molecular form. The HI tails are associated with faint
optical tidal features thought to be the remnant of a galaxy merger occurred a
few billion years ago. They demonstrate that the merger was gas-rich. During
the merger, tidal forces pulled some gas and stars out to large radii, where we
now detect them in the form of optical tails and, thanks to our new data, HI
tails; while torques caused the remaining gas to flow towards the centre of the
remnant, where it was converted into molecular gas and fuelled the starburst
revealed by the galaxy's stellar populations. Several of the observed
properties of NGC 1316 can be reproduced by a ~ 10:1 merger between a dominant,
gas-poor early-type galaxy and a smaller, gas-rich spiral occurred 1 - 3 Gyr
ago, likely followed by subsequent accretion of satellite galaxies.
