Peak star formation right where the collision is begining to take place

https://www.legacysurvey.org//viewer/?ra=18.8841&dec=-0.8525&layer=hsc-dr2&zoom=12&hsc-dr2-cosmos

If you look at the DR9 photometric z overlay you will see that these galaxies are not actually in the same part of space. The smaller one is much further away.