Density Wave Streaming Motions in Stars along the Sagittarius Spiral Arm

A magnitude-limited photographic survey of relative proper-motion components and B, V photometry of 1.3 × 106 stars brighter than apparent B magnitude 14.5 ± 0.5 in the fourth Galactic quadrant is converted into a distance-limited survey of 3.26 × 105 stars up to a distance of 500 pc. A streaming motion of 13.5 ± 0.5 km s-1 is detected in 4.1 × 104 Population I stellar candidates with an orbital perigalactic center located at 6.8 kpc ≤ R ≤ 7.2 kpc, with a Sun location Rsol = 8.5 kpc. A density perturbation of ~0.1 M⊙ pc-3 in the Galactic field potential at R0 ~ 6.8 kpc is interpreted as resulting from the density wave connected with the Sagittarius-Carina spiral arm. A set of 1.4 × 104 stars of mass ~1.5 ± 0.75 M⊙ identify a pitch angle of 10° ± 1° and a migration time from the Sagittarius spiral arm into the greater solar neighborhood of ~35 Myr.