The slowing down of galaxy disks in dissipationless minor mergers

Abstract

We have investigated the impact of dissipationless minor galaxy mergers on the angular momentum of the remnant. Our simulations cover a range of initial orbital characteristics and the system consists of a massive galaxy with a bulge and disk merging with a much less massive (one-tenth or one-twentieth) gasless companion which has a variety of morphologies (disk- or elliptical-like) and central baryonic mass concentrations. During the process of merging, the orbital angular momentum is redistributed into the internal angular momentum of the final system; the internal angular momentum of the primary galaxy can increase or decrease depending on the relative orientation of the orbital spin vectors (direct or retrograde), while the initially non-rotating dark matter halo always gains angular momentum. The specific angular momentum of the stellar component always decreases independent of the orbital parameters or morphology of the satellite, the decrease in the rotation velocity of the primary galaxy is accompanied by a change in the anisotropy of the orbits, and the ratio of rotation speed to velocity dispersion of the merger remnant is lower than the initial value, not only due to an increase in the dispersion but also to the slowing -down of the disk rotation. We briefly discuss several astrophysical implications of these results, suggesting that minor mergers do not cause a "random walk" process of the angular momentum of the stellar disk component of galaxies, but rather a steady decrease. Minor mergers may play a role in producing the large scatter observed in the Tully-Fisher relation for S0 galaxies, as well as in the increase of the velocity dispersion and the decrease in $v/\sigma$ at large radii as observed in S0 galaxies.

10 pages, 10 figures, accepted for publication in A&A

References in corpus (15)

• The SAURON project -- IX. A kinematic classification for early-type galaxies
• The structure of galactic disks: Studying late-type spiral galaxies using SDSS
• Multiple minor mergers: formation of elliptical galaxies and constraints for the growth of spiral disks
• The Nearly Universal Merger Rate of Dark Matter Haloes in Lambda-CDM Cosmology
• Kinematic properties of early-type galaxy haloes using planetary nebulae
• Properties of Bars and Bulges in the Hubble Sequence
• The mass distribution in early-type disk galaxies: declining rotation curves and correlations with optical properties
• The role of minor mergers in the recent star formation history of early-type galaxies
• Cold Dark Matter Substructure and Galactic Disks II: Dynamical Effects of Hierarchical Satellite Accretion
• Antitruncated Stellar Disks via Minor Mergers
• The Tully-Fisher relation for S0 galaxies
• On the Origin of Dynamically Cold Rings Around the Milky Way
• Tidal debris in elliptical galaxies as tracers of mergers with disks
• Testing the nature of S0 galaxies using planetary nebula kinematics in NGC 1023
• The haloes of merger remnants

Cited by in corpus (6)

• Formation of S0 galaxies through mergers. Evolution in the Tully-Fisher relation since $z\sim 1$
• MaNGA DynPop -- III. Stellar dynamics versus stellar population relations in 6000 early-type and spiral galaxies: Fundamental Plane, mass-to-light ratios, total density slopes, and dark matter fractions
• Evidence for Impact of Galaxy Mergers on Stellar Kinematics of Early-type Galaxies
• The dawn of disks: unveiling the turbulent ionised gas kinematics of the galaxy population at $z\sim 4-6$ with JWST/NIRCam grism spectroscopy
• Genesis of morpho-kinematic lopsidedness in minor merger of galaxies
• Beyond the stars: Linking H$\alpha$ sizes, kinematics, and star formation in galaxies at $z\approx 4-6$ with JWST grism surveys and $\text{geko}$