THE 2014 ALMA LONG BASELINE CAMPAIGN: OBSERVATIONS OF THE STRONGLY LENSED SUBMILLIMETER GALAXY HATLAS J090311.6+003906 AT z = 3.042

We present initial results of very high resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the z = 3.042 gravitationally lensed submillimeter galaxy HATLAS J090311.6+003906 (SDP.81). These observations were carried out using a very extended configuration as part of Science Verification for the 2014 ALMA Long Baseline Campaign, with baselines of up to ∼15 km. We present continuum imaging at 151, 236, and 290 GHz at unprecedented angular resolutions as fine as 23 mas, corresponding to an unmagnified spatial scale of ∼180 pc at z = 3.042. The ALMA images clearly show two main gravitational arc components of an Einstein ring, with emission tracing a radius of ∼1.″ 5. We also present imaging of CO J = 10 − 9, J = 8 − 7, and J = 5 − 4 and H 2 O ?> ( 2 02 − 1 11 ?> ) line emission. The CO emission, at an angular resolution of ∼170 mas, is found to broadly trace the gravitational arc structures but with differing morphologies between the CO transitions and compared to the dust continuum. Our detection of H 2 O ?> line emission, using only the shortest baselines, provides the most resolved detection to date of thermal H 2 O ?> emission in an extragalactic source. The ALMA continuum and spectral line fluxes are consistent with previous Plateau de Bure Interferometer and Submillimeter Array observations despite the impressive increase in angular resolution. Finally, we detect weak unresolved continuum emission from a position that is spatially coincident with the center of the lens, with a spectral index that is consistent with emission from the core of the foreground lensing galaxy.