Molecular Gas Dominated 50 kpc Ram Pressure Stripped Tail of the Coma
  Galaxy D100
  We have discovered large amounts of molecular gas, as traced by CO emission,
in the ram pressure stripped gas tail of the Coma cluster galaxy D100 (GMP
2910), out to large distances of about 50 kpc. D100 has a 60 kpc long,
strikingly narrow tail which is bright in X-rays and H{\alpha}. Our
observations with the IRAM 30m telescope reveal in total ~ 10^9 M_sun of H_2
(assuming the standard CO-to-H_2 conversion) in several regions along the tail,
thus indicating that molecular gas may dominate its mass. Along the tail we
measure a smooth gradient in the radial velocity of the CO emission that is
offset to lower values from the more diffuse H{\alpha} gas velocities. Such a
dynamic separation of phases may be due to their differential acceleration by
ram pressure. D100 is likely being stripped at a high orbital velocity >2200
km/s by (nearly) peak ram pressure. Combined effects of ICM viscosity and
magnetic fields may be important for the evolution of the stripped ISM. We
propose D100 has reached a continuous mode of stripping of dense gas remaining
in its nuclear region. D100 is the second known case of an abundant molecular
stripped-gas tail, suggesting that conditions in the ICM at the centers of
galaxy clusters may be favorable for molecularization. From comparison with
other galaxies, we find there is a good correlation between the CO flux and the
H{\alpha} surface brightness in ram pressure stripped gas tails, over about 2
dex.
