2015ApJ...806..260F

We present Atacama Large Millimeter Array (ALMA) observations of two high-redshift systems (SMMJ02399-0136 at z₁∼ 2.8 and the Cloverleaf QSO at z₁∼ 2.5) in their rest-frame 122 µm continuum (ν_sky∼ 650 GHz, λ_sky∼ 450 µm) and [N ii] 122 µm line emission. The continuum observations with a synthesized beam of ∼0". 25 resolve both sources and recover the expected flux. The Cloverleaf is resolved into a partial Einstein ring, while SMMJ02399-0136 is unambiguously separated into two components: a point source associated with an active galactic nucleus and an extended region at the location of a previously identified dusty starburst. We detect the [N ii] line in both systems, though significantly weaker than our previous detections made with the first generation z (Redshift) and Early Universe Spectrometer. We show that this discrepancy is mostly explained if the line flux is resolved out due to significantly more extended emission and longer ALMA baselines than expected. Based on the ALMA observations we determine that ≥75% of the total [N ii] line flux in each source is produced via star formation. We use the [N ii] line flux that is recovered by ALMA to constrain the N/H abundance, ionized gas mass, hydrogen- ionizing photon rate, and star formation rate. In SMMJ02399-0136 we discover it contains a significant amount (∼1000 M_☉/yr) of unobscured star formation in addition to its dusty starburst and argue that SMMJ02399-0136 may be similar to the Antennae Galaxies (Arp 244) locally. In total these observations provide a new look at two well-studied systems while demonstrating the power and challenges of Band-9 ALMA observations of high-z systems.