HI 21 cm observation and mass models of the extremely thin galaxy FGC
  1440
  We present observations and models of the kinematics and distribution of
neutral hydrogen (HI) in the superthin galaxy FGC 1440 with an optical axial
ratio $a/b = 20.4$. Using the Giant Meterwave Radio telescope (GMRT), we imaged
the galaxy with a spectral resolution of 1.7 $\rm kms^{-1}$ and a spatial
resolution of $15" \times 13.5"$. We find that FGC 1440 has an asymptotic
rotational velocity of 141.8 $\rm kms^{-1}$ . The structure of the HI disc in
FGC 1440 is that of a typical thin disc warped along the line of sight, but we
can not rule out the presence of a central thick HI disc. We find that the dark
matter halo in FGC 1440 could be modeled by a pseudo-isothermal (PIS) profile
with $\rm R_{c}/ R_{d} <2$, where $R_{c}$ is the core radius of the PIS halo
and $R_{d}$ the exponential stellar disc scale length. We note that in spite of
the unusually large axial ratio of FGC 1440, the ratio of the rotational
velocity to stellar vertical velocity dispersion, $\frac{V_{Rot}}{\sigma_{z}}
\sim 5 - 8$, which is comparable to other superthins. Interestingly, unlike
previously studied superthin galaxies which are outliers in the
$log_{10}(j_{*}) - log_{10}(M_{*})$ relation for ordinary bulgeless disc
galaxies, FGC 1440 is found to comply with the same. The values of $j$ for the
stars, gas and the baryons in FGC 1440 are consistent with those of normal
spiral galaxies with similar mass.
