ISM Properties of a Massive Dusty Star-forming Galaxy Discovered at [zeta] similar to 7

Abstract

We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy to date, SPT-S J031132&minus;5823.4 (hereafter SPT0311&minus;58), at&nbsp;z=<strong>6.900</strong>&plusmn;<strong>0.002</strong>. SPT0311&minus;58 was discovered via its 1.4 mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an Atacama Large Millimeter/submillimeter Array 3 mm frequency scan that detected CO(6&ndash;5), CO(7&ndash;6), and&nbsp;[<strong>CI</strong>](2&ndash;1), and subsequently was confirmed by detections of CO(3&ndash;2) with the Australia Telescope Compact Array and&nbsp;[<strong>CII</strong>]&nbsp;with APEX. We constrain the properties of the ISM in SPT0311&minus;58 with a radiative transfer analysis of the dust continuum photometry and the CO and&nbsp;[<strong>CI</strong>]&nbsp;line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311&minus;58 is extremely massive, with an intrinsic gas mass of&nbsp;<strong><em>M</em>_gas</strong>=<strong>3.3</strong>&plusmn;<strong>1.9</strong>&times;<strong>10¹¹M_⊙</strong>. Its large mass and intense star formation is very rare for a source well into the epoch of reionization.