Clumps in the solar neighborhood ’ s stellar velocity distribution could be caused by spiral density waves .
In the solar neighborhood , stellar velocities corresponding to orbits that are nearly closed in the frame rotating with a spiral pattern represent likely regions for stellar concentrations .
Via particle integration , we show that orbits can intersect the solar neighborhood when they are excited by Lindblad resonances with a spiral pattern .
We find that a two-armed spiral density wave with pattern speed placing the Sun near the 4:1 Inner Lindblad Resonance ( ILR ) can cause two families of nearly closed orbits in the solar neighborhood .
One family corresponds to square shaped orbits aligned so their peaks lie on top of , and support , the two dominant stellar arms .
The second family correspond to orbits 45 ^ { \circ } out of phase with the other family .
Such a spiral density pattern could account for two major clumps in the solar neighborhood ’ s velocity distribution .
The Pleiades/Hyades moving group corresponds to the first family of orbits and the Coma Berenices moving group corresponds to the second family .
This model requires a spiral pattern speed of approximately 0.66 \pm 0.03 times the angular rotation rate of the Sun or 18.1 \pm 0.8 km s ^ { -1 } kpc ^ { -1 } .