Dynamical Modeling of Kinematically Decoupled Galaxies: Structural Components

Abstract

We present the results of dynamical modeling of two galaxies with inconsistent kinematics -- PGC 35706 and LEDA 2220522 -- using data from the MaNGA integral-field spectroscopic survey and deep photometry from the DESI Legacy Imaging Surveys. The Schwarzschild orbit-superposition method in the axisymmetric approximation was employed to identify structural components based on the orbital circularity parameter ${\lambda }_z$. Three components have been identified in the galaxies: a spheroidal (bulge/halo) component and co-rotating and counter-rotating stellar disks. The spheroidal component dominates by mass in both galaxies: about 60\% in PGC 35706 and 51\% in LEDA 2220522; the contributions of the co-rotating and counter-rotating disks are 29\% and 9\% in PGC 35706 and 30\% and 18\% in LEDA 2220522, respectively. The kinematics of the ionized gas in both galaxies is consistent with the rotation of the counter-rotating disk, indicating that it formed from externally accreted gas with opposite angular momentum. The results support a scenario in which counter-rotating disks form through gas accretion from the intergalactic medium or through minor mergers with gas-rich satellites. This work demonstrates the effectiveness of the Schwarzschild method for studying the complex kinematic structure of galaxies and their formation history.

16 pages, 9 figures, 1 table; published in Astrophysical Bulletin