The galaxy cluster Abell 1644 ($\bar{ z}=0.047$) is known for its remarkable spiral-like X-ray emission. It was previously identified as a bimodal system, comprising the subclusters, A1644S and A1644N, each one centered on a giant elliptical galaxy. In this work, we present a comprehensive study of this system, including new weak-lensing and dynamical data and analysis plus a tailor-made hydrodynamical simulation. The lensing and galaxy density maps showed a structure in the North that could not be seen on the X-ray images. We, therefore, rename the previously known northern halo as A1644N1 and the new one as A1644N2. Our lensing data suggests that those have fairly similar masses: $M_{ 200}^{ \rm N1}=0.90_{ -0.85}^{ +0.45} \times10^{ 14}$ and $M_{ 200}^{ \rm N2}=0.76_{ -0.75}^{ +0.37} \times10^{ 14}$ M$_\odot$, whereas the southern structure is the main one: $M_{ 200}^{ \rm S}=1.90_{ -1.28}^{ +0.89}\times 10^{ 14}$ M$_\odot$. Based on the simulations, fed by the observational data, we propose a scenario where the remarkable X-ray characteristics in the system are the result of a collision between A1644S and A1644N2 that happened $\sim$1.6 Gyr ago. Currently, those systems should be heading to a new encounter, after reaching their maximum separation.
Categories: astro-ph.GA astro-ph.CO