Living with Neighbors. V. Better-aligned Spiral+Spiral Galaxy Pairs Show Stronger Star Formation

Enhanced star formation (SF) with star-forming neighboring galaxies bolsters the hydrodynamical contributions during paired interactions. Although the relative spin orientation between interacting galaxies can influence this effect, it has not been comprehensively explored. In this study, utilizing a meticulously curated sample of nearby (0.02 < z < 0.06) spiral+spiral pairs and an isolated control sample from Sloan Digital Sky Survey Data Release 7, coupled with Galaxy Zoo 2, and an approach to estimate spin–spin alignment (SSA), we systematically compare the impact of relative orientation, cos ξ , on interaction-induced SF. We reveal that SSA plays a pivotal role along with the conventionally recognized parameters of projected separation and SF of neighboring galaxies. Our results show an increase in SF augmentation as configurations transition from perpendicular ( cos ξ ∼ 0 ) to well aligned ( cos ξ > 0.7 ). This enhancement is especially pronounced when neighboring galaxies have higher SF, suggesting that hydrodynamical processes drive the effects of relative orientation. The heightened hydrodynamical friction, attributed to increased ram pressure and the propensity for prograde orbits in well-aligned pairs, is consistent with our findings.