Scott Chapman

From the calendar

1) CCAT -- a 6-meter aperture submm-optimized telescope to be located at 5600m on Cerro Chajnantor in the Atacama, Chile -- is (almost) here! The telescope is shipping to Chile from Germany this year, and a first light 280GHz (1.1mm) instrument with a 1.3deg field called ModCam is in final characterization stages before deployment. Three further instruments are on schedule to deploy in early 2027: two imaging/polarimeters operating at 850um and 350um, and a line intensity mapping instrument targeting C+ in the z>6 EoR. Funding has been proposed to complete the final 3 instrument modules that Prime-Cam can support. Surveys across 7 science themes are being planned, and map making software is being developed with these science goals in mind.

2) Using a 30hr integration with the ALMA-ACA (21.0''×12.2''), we have uncovered a 75% excess CO(4-3) flux in the Protocluster SPT2349-56 at z=4.3, compared to the sum of individual sources detected in higher-resolution ALMA data (~1.0"). The missing flux is unlikely due to undetected faint sources but instead suggests that high-resolution ALMA observations might miss extended and low-surface-brightness gas. Such emission could originate from the circum-galactic medium (CGM) or the pre-heated proto-intracluster medium. If this molecular gas reservoir replenishes the star formation fuel, the overall depletion timescale will exceed 400Myr, reducing the requirement for the simultaneous SMG activity in SPT2349-56 (see Casey, C., 2016 ApJ...824...36 for the original framing of this issue). Our results highlight the role of an extended gas reservoir in sustaining a high star formation rate (SFR) in SPT2349-56, and potentially establishing the ICM during the transition phase to a mature cluster.