Abstract
For more than fifty years, astronomers have mapped the neutral hydrogen gas
in the Galaxy assuming kinematically derived distances. We employ the distances
of nearby young stars, which trace the gas from which they formed, in
longitude-latitude-velocity space to map this gas without using kinematic
distances. We denote this new method "pattern matching". Analysis of simulated
spiral galaxies indicates that our pattern matching distances are 24% more
accurate than kinematic distances for gas within 15 kpc of the Sun. The two
methods provide similar agreement with parallaxes towards these masers,
although the kinematic method shows a small systematic offset in the distance
that is not present in the pattern matching distance. Using parallaxes and
velocities for masers, we show that this novel method, when matched with nearby
Cepheids, performs well compared to kinematics. This analysis is restricted to
sources that have a reasonably good match with a member of our Cepheid sample.
The distances derived here, and the associated map, have broad utility - from
improving our understanding of star formation and the dynamical structure of
the Galaxy, to informing 3-D dust maps.