The H$\alpha$ star formation main sequence in cluster and field galaxies
  at $z\sim1.6$
  We calculate H$\alpha$-based star formation rates and determine the star
formation rate-stellar mass relation for members of three SpARCS clusters at $z
\sim 1.6$ and serendipitously identified field galaxies at similar redshifts to
the clusters. We find similar star formation rates in cluster and field
galaxies throughout our range of stellar masses. The results are comparable to
those seen in other clusters at similar redshifts, and consistent with our
previous photometric evidence for little quenching activity in clusters. One
possible explanation for our results is that galaxies in our $z \sim 1.6$
clusters have been accreted too recently to show signs of environmental
quenching. It is also possible that the clusters are not yet dynamically mature
enough to produce important environmental quenching effects shown to be
important at low redshift, such as ram pressure stripping or harassment.
