We present our discovery of observational evidence for the coherence between galaxy rotation and the average line-of-sight motion of neighbors .
We use the Calar Alto Legacy Integral Field Area ( CALIFA ) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer ( PyCASSO ) platform , and the NASA-Sloan Atlas ( NSA ) catalog .
After estimating the projected angular momentum vectors of 445 CALIFA galaxies , we build composite maps of their neighbor galaxies on the parameter space of line-of-sight velocity versus projected distance .
The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies .
The signal of such dynamical coherence is significant for the neighbors within 800 kpc distance from the CALIFA galaxies , for which the luminosity-weighted mean velocity is as large as 61.7 \pm 17.6 km s ^ { -1 } ( 3.5 \sigma significance to bootstrap uncertainty ) when the angular momentum is measured at R _ { e } < R \leq 2 R _ { e } of each CALIFA galaxy .
In the comparison of the subsamples , we find that faint , blue or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright , red or kinematically well-aligned galaxies do .
Our results indicate that ( 1 ) the rotation of a galaxy ( particularly at its outskirt ) is significantly influenced by interactions with its neighbors up to 800 kpc , ( 2 ) the coherence is particularly strong between faint galaxies and bright neighbors , and ( 3 ) galaxy interactions often cause internal kinematic misalignment or possibly even kinematically distinct cores .