Copyright by Athena Ranice Stacy 2011 - The University of Texas at ...

lower in average density (panel a in Fig. 3.2). The disk growth is halted at
nearly 2000 yr due to its gradual disruption through N-body dynamics of the
sinks. One of the sinks is ejected at ∼ 500 yr, after growing to only ∼ 1 M⊙.
The ejection occurs immediately following the merger of the two other sinks,
at a time when the three sinks are close together in the center of the disk
and subject to N-body dynamics. The sink accretes no more mass after its
ejection. It initially moves in a direction perpendicular to the disk plane at ∼
5 km s −1 with respect to the disk center of mass, and the maximum distance
between the two sinks approaches 3000 AU at approximately 2500 yr. This
increase in distance between the two sinks is mostly due to the motion of the
main sink, however. In this N-body interaction, the main sink gains a larger
velocity, initially moving with respect to the disk center of mass at ∼ 10 km
s −1 . It travels parallel to the disk plane and pulls the disk along with it. The
rapid motion of the main sink disrupts the high-density gas, which transforms
from a disk structure to a more diffuse tidal tail, eventually causing the total
measured disk mass to slightly decrease (Fig. 3.3). The rotational structure is
also disturbed, as indicated by a peak in χrad when the sink is ejected. After
approximately 3000 yr, the tidal tail begins to recompress, causing the dense
gas to be more dominated by radially inward motion. This is indicated by the
increase of χrad to ∼ 1 as well as an increase in the average disk density (Fig.
3.2).
From the solid red line in Figure 3.3, we also note a smooth early growth
of hot dense gas over the first 1000 yr. This begins almost as soon as the first
sink is formed, and the main sink thus provides an early source of heating.
This occurs as the gravitational potential of the sink, which grows to > 10 M⊙
in only 200 yr, heats the surrounding gas up to ∼ 7000 K, or cs 7 km s −1
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