A magnified view of the ISM and star formation in a strongly lensed AGN hosting SMG at z = 2.6

Sub-mm Galaxies (SMGs) are among the most prolific star forming galaxies in the universe, with star formation rates (SFRs) up to 1000 Msun/yr. Our understanding of the nature of the dense star-forming interstellar medium (ISM) in these galaxies is still in its infancy, because it is difficult to access the spatial scales relevant for assessing the astrophysics of star formation in galaxies at high-z. ‘9io9’ is a strongly lensed SMG at z~2.6, with an intrinsic infrared luminosity exceeding 10^13 Lsun. The fact that it is strongly lensed allows us to examine the ISM on spatial scales of a few 100pc in a galaxy forming stars at several 1000 solar masses per year. We present new ALMA Band 4, 8 and 9 data tracing the molecular and atomic gas and thermal dust continuum in this object. We reveal evidence for a large star bursting molecular gas disc and possible molecular outflow, and present a study of the resolved dust temperature across the source (which also contains a radio-loud AGN). Our detection of both the 122 and 205um [NII] lines in 9io9, in combination with CI and CO(4-3), allow us to map the physical conditions of the ionised and molecular ISM across the source, providing a unique resolved insight into the nature of star formation at its most extreme at the peak epoch of galaxy assembly.