We report measurements of trigonometric parallaxes for six high-mass star-forming regions in the Scutum spiral arm of the Milky Way as part of the BeSSeL Survey .
Combining our measurements with 10 previous measurements from the BeSSeL Survey yields a total sample of 16 sources in the Scutum arm with trigonometric parallaxes in the Galactic longitude range from 5 ^ { \circ } to 32 ^ { \circ } .
Assuming a logarithmic spiral model , we estimate a pitch angle of 19 { { \hbox to 0.0 pt { . } } ^ { \circ } } 8 \pm 3 { { \hbox to 0.0 pt { . } } ^ { \circ } } 1 for the Scutum arm , which is larger than pitch angles reported for other spiral arms .
The high pitch angle of the arm may be due to the arm ’ s proximity to the Galactic bar .
The Scutum arm sources show an average peculiar motion of 4 km s ^ { -1 } slower than the Galactic rotation and 8 km s ^ { -1 } toward the Galactic center .
While the direction of this non-circular motion has the same sign as determined for sources in other spiral arms , the motion toward the Galactic center is greater for the Scutum arm sources .