A new method for estimating the pattern speed of spiral structure in the
  Milky Way
  In the last few decades many efforts have been made to understand the effect
of spiral arms on the gas and stellar dynamics in the Milky Way disc. One of
the fundamental parameters of the spiral structure is its angular velocity, or
pattern speed $\Omega_p$, which determines the location of resonances in the
disc and the spirals' radial extent. The most direct method for estimating the
pattern speed relies on backward integration techniques, trying to locate the
stellar birthplace of open clusters. Here we propose a new method based on the
interaction between the spiral arms and the stars in the disc. Using a sample
of around 500 open clusters from the {\it New Catalogue of Optically Visible
Open Clusters and Candidates}, and a sample of 500 giant stars observed by
APOGEE, we find $\Omega_p = 23.0\pm0.5$ km s$^{-1}$ kpc$^{-1}$, for a local
standard of rest rotation $V_0=220$~km s$^{-1}$ and solar radius $R_0=8.0$~kpc.
Exploring a range in $V_0$ and $R_0$ within the acceptable values, 200-240 km
s$^{-1}$ and 7.5-8.5 kpc, respectively, results only in a small change in our
estimate of $\Omega_p$, that is within the error. Our result is in close
agreement with a number of studies which suggest values in the range 20-25 km
s$^{-1}$ kpc$^{-1}$. An advantage of our method is that we do not need
knowledge of the stellar age, unlike in the case of the birthplace method,
which allows us to use data from large Galactic surveys. The precision of our
method will be improved once larger samples of disk stars with spectroscopic
information will become available thanks to future surveys such as 4MOST.
