The Sharpest Ultraviolet view of the star formation in an extreme
  environment of the nearest Jellyfish Galaxy IC 3418
  We present the far ultraviolet (FUV) imaging of the nearest Jellyfish or
Fireball galaxy IC3418/VCC 1217, in the Virgo cluster of galaxies, using
Ultraviolet Imaging Telescope (UVIT) onboard the ASTROSAT satellite. The young
star formation observed here in the 17 kpc long turbulent wake of IC3418, due
to ram pressure stripping of cold gas surrounded by hot intra-cluster medium,
is a unique laboratory that is unavailable in the Milkyway. We have tried to
resolve star forming clumps, seen compact to GALEX UV images, using better
resolution available with the UVIT and incorporated UV-optical images from
Hubble Space Telescope archive. For the first time, we resolve the compact star
forming clumps (fireballs) into sub-clumps and subsequently into a possibly
dozen isolated stars. We speculate that many of them could be blue supergiant
stars which are cousins of SDSS J122952.66+112227.8, the farthest star (~17
Mpc) we had found earlier surrounding one of these compact clumps. We found
evidence of star formation rate (4 - 7.4 x 10^-4 M_sun per yr ) in these
fireballs, estimated from UVIT flux densities, to be increasing with the
distance from the parent galaxy. We propose a new dynamical model in which the
stripped gas may be developing vortex street where the vortices grow to compact
star forming clumps due to self-gravity. Gravity winning over turbulent force
with time or length along the trail can explain the puzzling trend of higher
star formation rate and bluer/younger stars observed in fireballs farther away
from the parent galaxy.
