We continue our empirical study of the emission line flux originating in the cool ( T \sim 10 ^ { 4 } K ) gas that populates the halos of galaxies and their environments .
Specifically , we present results obtained for a sample of galaxy pairs with a range of projected separations , 10 < { S _ { p } / kpc } < 200 , and mass ratios < 1:5 , intersected by 5,443 SDSS lines of sight at projected radii of 10 to 50 kpc from either or both of the two galaxies .
We find significant enhancement in H \alpha emission and a moderate enhancement in [ N II ] 6583 emission for low mass pairs ( mean stellar mass per galaxy , \overline { M } _ { * } , < 10 ^ { 10.4 } { M } _ { \odot } ) relative to the results from a control sample .
This enhanced H \alpha emission comes almost entirely from sight lines located between the galaxies , consistent with a short-term , interaction-driven origin for the enhancement .
We find no enhancement in H \alpha emission , but significant enhancement in [ N II ] 6583 emission for high mass ( \overline { M } _ { * } > 10 ^ { 10.4 } { M } _ { \odot } ) pairs .
Furthermore , we find a dependence of the emission line properties on the galaxy pair mass ratio such that those with a mass ratio below 1:2.5 have enhanced [ N II ] 6583 and those with a mass ratio between 1:2.5 and 1:5 do not .
In all cases , departures from the control sample are only detected for close pairs ( S _ { p } < 100 kpc ) .
Attributing an elevated [ N II ] 6583/H \alpha ratio to shocks , we infer that shocks play a role in determining the CGM properties for close pairs that are among the more massive and have mass ratios closer to 1:1 .