We use the Spitzer Infrared Spectrograph ( IRS ) to study four infalling cluster galaxies with signatures of on-going ram-pressure stripping .
H _ { 2 } emission is detected in all four ; two show extraplanar H _ { 2 } emission .
The emission usually has a warm ( T \sim 115 - 160 K ) and a hot ( T \sim 400 - 600K ) component that is approximately two orders of magnitude less massive than the warm one .
The warm component column densities are typically 10 ^ { 19 } -10 ^ { 20 } cm ^ { -2 } with masses of 10 ^ { 6 } -10 ^ { 8 } M _ { \odot } .
The warm H _ { 2 } is anomalously bright compared with normal star-forming galaxies and therefore may be excited by ram-pressure .
In the case of CGCG 97-073 , the H _ { 2 } is offset from the majority of star formation along the direction of the galaxy ’ s motion in the cluster , suggesting it is forming in the ram-pressure wake of the galaxy .
Another galaxy , NGC 4522 , exhibits a warm H _ { 2 } tail approximately 4 kpc in length .
These results support the hypothesis that H _ { 2 } within these galaxies is shock-heated from the interaction with the intracluster medium .
Stripping of dust is also a common feature of the galaxies .
For NGC 4522 , where the distribution of dust at 8 \mu m is well resolved , knots and ripples demonstrate the turbulent nature of the stripping process .
The H \alpha and 24 \mu m luminosities show that most of the galaxies have star formation rates comparable to similar mass counterparts in the field .
Finally , we suggest a possible evolutionary sequence primarily related to the strength of ram-pressure a galaxy experiences to explain the varied results observed in our sample .