The Impact of Merging on The Origin of Kinematically Misaligned and Counter-rotating Galaxies in MaNGA

TL;DR

This study investigates how galaxy mergers influence the misalignment between gas and stellar motions, revealing that merging increases kinematic misalignments and that counter-rotation is less often caused by merging.

Contribution

It provides new observational evidence linking galaxy mergers to kinematic misalignments and counter-rotation, using MaNGA data crossmatched with DESI surveys.

Findings

Merging galaxies have higher misalignment fractions than co-rotators.

Counter-rotators have lower merging fractions than misaligned galaxies.

Merging influences gas-stellar kinematic misalignments and counter-rotation phenomena.

Abstract

Galaxy mergers and interactions are expected to play a significant role leading to offsets between gas and stellar motions in galaxies. Herein we crossmatch galaxies in MaNGA MPL-8 with the Dark Energy Spectroscopic Instrument (DESI) Legacy Surveys and identify 311 merging galaxies that have reliable measurements of the $\Delta$PA, the difference between the stellar and gas kinematic position angles to investigate the impacts of merging on gas-stellar rotation misalignments. We find that the merging fractions of misaligned galaxies (30$^\circ$ $\leqslant$ $\Delta$PA $<$150$^\circ$) are higher than that of co-rotators ($\Delta$PA $<$ 30$^\circ$) in both quiescent and star-forming galaxies. This result suggests that merging is one process to produce kinematic misalignments. The merging fraction of counter-rotators ($\Delta$PA $\leqslant$ 150$^\circ$) is lower than that of misaligned galaxies in both quiescent and star-forming galaxies, while in the latter it is likely even lower than that of co-rotators. The orbital angular momentum transfer to the spins of stars and gas during merging and the tidal feature disappearance can lead to small merging fractions in counter-rotators. Numerous new stars that inherit angular momentum from gas after merging can further lower the merging fraction of star-forming counter-rotators.