Kinematics and excitation of the ram pressure stripped ionized gas
  filaments in the Coma cluster of galaxies
  We present the results of deep imaging and spectroscopic observations of very
extended ionized gas (EIG) around four member galaxies of the Coma cluster of
galaxies: RB199, IC4040, GMP2923 and GMP3071. The EIGs were serendipitously
found in an H-alpha narrow band imaging survey of the central region of the
Coma cluster. The relative radial velocities of the EIGs with respect to the
systemic velocities of the parent galaxies from which they emanate increase
almost monotonically with the distance from the nucleus of the respective
galaxies, reaching -400 - -800 km/s at around 40 - 80 kpc from the galaxies.
The one-sided morphologies and the velocity fields of the EIGs are consistent
with the predictions of numerical simulations of ram pressure stripping. We
found a very low-velocity filament (v_rel = -1300 km/s) at the southeastern
edge of the disk of IC4040. Some bright compact knots in the EIGs of RB199 and
IC4040 exhibit blue continuum and strong H-alpha emission. The equivalent
widths of the H-alpha emission exceed 200 A, and are greater than 1000 A for
some knots. The emission line intensity ratios of the knots are basically
consistent with those of sub-solar abundance HII regions. These facts indicate
that intensive star formation occurs in the knots. Some filaments, including
the low velocity filament of the IC4040 EIG, exhibit shock-like emission line
spectra, suggesting that shock heating plays an important role in ionization
and excitation of the EIGs.
