Quantifying the Fragility of Galactic Disks in Minor Mergers

Details Quantifying the Fragility of Galactic Disks in Minor Mergers Quantifying the Fragility of Galactic Disks in Minor Mergers

1995-10-09

arxiv.org/abs/astro-ph/9510052v1

Astrophys.J. 460 (1996) 121

Astronomy and Astrophysics

Astrophysics

LaTeX with AASTeX macros; text only. For PostScript with figures embedded, go to http://www.ucolick.org/~iwalker/ss/

Scientific paper

10.1086/176956

We perform fully self-consistent stellar dynamical simulations of the accretion of a companion ("satellite") galaxy by a large disk galaxy to investigate the interaction between the disk, halo, and satellite components of the system during a merger. Our fiducial encounter begins with a satellite in a prograde, circular orbit inclined thirty degrees with respect to the disk plane at a galactocentric distance of six disk scalelengths. The satellite's mass is 10% of the disk's mass and its half-mass radius is about 1.3 kpc. The system is modelled with 500 000 particles, sufficient to mitigate numerical relaxation noise over the merging time. The satellite sinks in only ~1 Gyr and a core containing ~45% of its initial mass reaches the centre of the disk. With so much of the satellite's mass remaining intact, the disk sustains significant damage as the satellite passes through. At the solar circle we find that the disk thickens ~60%, the velocity dispersions increase by $\Delta\mbox{\boldmath$\sigma$} \simeq (10,8,8)$ km/s to $(\sigma_R, \sigma_\phi, \sigma_z) \simeq (48, 42, 38)$ km/s, and the asymmetric drift is unchanged at ~18 km/s. Although the disk is not destroyed by these events (hence "minor" mergers), its final state resembles a disk galaxy of earlier Hubble type than its initial state, thicker and hotter, with the satellite's core enhancing the bulge. Thus minor mergers continue to be a promising mechanism for driving galaxy evolution.

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