Trigonometric parallaxes to star-forming regions within 4 kpc of the
  galactic center
  We report four trigonometric parallaxes for high-mass star-forming regions
within 4 kpc of the Galactic center. These measurements were made with the VLBA
as part of the BeSSeL Survey. By associating these sources kinematically with
large-scale features in CO and HI longitude-velocity diagrams, we begin to
outline some major features of the inner Milky Way: the Connecting arm, the
near and far 3 kpc arms, and the Norma arm. The Connecting arm in the first
Galactic quadrant lies closer to the Galactic center than the far 3 kpc arm and
is offset by the long-bar's major axis near its leading edge, supporting the
presence of an inner Lindblad resonance. Assuming the 3 kpc arms are a
continuous physical structure, the relative Galactocentric distance of its near
and far sides suggests highly elliptical streamlines of gas around the bar(s)
and a bar corotation radius, r_CR > 3.6 kpc. At a Galactic longitude near
10{\deg} and a heliocentric distance of about 5 kpc, the near 3 kpc arm and the
Norma arm intersect on a face-on view of our Galaxy, while passing at different
Galactic latitudes. We provide an accurate distance measurement to the W31
star-forming complex of 4.95 (+0.5;-0.43) kpc from the Sun, which associates it
with a bright CO feature belonging to the near 3 kpc arm.
