We report the properties of the interacting S0 galaxy NGC 5195 ( M51B ) , revealed in a pixel analysis using the HST /ACS images in the F435W , F555W and F814W ( BVI ) bands .
We analyze the pixel color-magnitude diagram ( pCMD ) of NGC 5195 , focusing on the properties of its red and blue pixel sequences and the difference from the pCMD of NGC 5194 ( M51A ; the spiral galaxy interacting with NGC 5195 ) .
The red pixel sequence of NGC 5195 is redder than that of NGC 5194 , which corresponds to the difference in the dust optical depth of 2 < \Delta \tau _ { V } < 4 at fixed age and metallicity .
The blue pixel sequence of NGC 5195 is very weak and spatially corresponds to the tidal bridge between the two interacting galaxies .
This implies that the blue pixel sequence is not an ordinary feature in the pCMD of an early-type galaxy , but that it is a transient feature of star formation caused by the galaxy-galaxy interaction .
We also find a difference in the shapes of the red pixel sequences on the pixel color-color diagrams ( pCCDs ) of NGC 5194 and NGC 5195 .
We investigate the spatial distributions of the pCCD-based pixel stellar populations .
The young population fraction in the tidal bridge area is larger than that in other areas by a factor > 15 .
Along the tidal bridge , young populations seem to be clumped particularly at the middle point of the bridge .
On the other hand , the dusty population shows a relatively wide distribution between the tidal bridge and the NGC 5195 center .