Title: Rings and Radial Waves in the Disk of the Milky Way

Abstract:
We show that in the anticenter region, between Galactic longitudes of $110^\circ<l<229^\circ$, 
there is an asymmetry in the main sequence star counts on either side of the Galactic plane 
using data from the Sloan Digital Sky Survey.  This asymmetry oscillates from more stars in the 
north at distances of about 2 kpc from the Sun to more stars in the south at 4-6 kpc from the 
Sun to more stars in the north at distances of 8-10 kpc from the Sun.  We also see evidence 
that there are more stars in the south at distances of 12-16 kpc from the Sun.  The three more 
distant asymmetries form roughly concentric rings around the Galactic center, opening in the 
direction of the Milky Way''s spiral arms.  The northern ring, 9 kpc from the Sun, is easily 
identified with the previously discovered Monoceros Ring.  Parts of the southern ring at 14 kpc 
from the Sun (which we call the TriAnd Ring) have previously been identified as related to the 
Monoceros Ring and others have been called the Triangulum Andromeda Overdensity.  The two 
nearer oscillations are approximated by a toy model in which the disk plane is offset by of the 
order 100 pc up and then down at different radii.  We also show that the disk is not azimuthally 
symmetric around the Galactic anticenter and that there could be a correspondence between 
our observed oscillations and the spiral structure of the Galaxy.  We suggest that the TriAnd 
and Monoceros Rings could be accreted satellites that form an outer disk.  More complex 
modeling is necessary to understand the observations.