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The Atacama Compact Array as a survey machine of the early Universe

Hugo Messias
ALMA Observatory, Chile

As a follow-up machine to assess molecular gas and dust content of radio-detected galaxies or determine their redshift, the 12m-array component of ALMA will be the forefront facility. Less obvious is the early Universe discovery potential of its 7m-array component, the Atacama Compact Array (ACA, or Morita Array). With SKA and ngVLA being expected to provide countless radio "blobs" in the whole sky, there will be studies for which ACA will be the best option to pursue instead. Recently, a survey aiming to provide a statistical understanding of the hosts and environment of 36 high-redshift radio AGN candidates detected by ATCA was carried out with ACA at 1.3mm toward the ELAIS-S1 field. The initial results cover a variety of science cases highlighting the potential of ACA as a survey machine of rare luminous systems in the sky. Two observed examples of interest is one object at zsp = 1.58 showing a clear spatial offset between the jet-dominated millimetre continuum emission and that of the host’s molecular gas; but also the case of a local-Universe source showing a narrow jet-like region, as revealed by carbon monosulfide emission stretching 20 kpc out of the host galaxy. Likely the biggest surprise is the possible detection of the kinetic Sunyaev-Zel’dovich effect (kSZE) around four surveyed galaxies in the form of negative detections in the field. Simulations show that the majority of these are statistically significant, and less likely to be spurious. The post-pandemic future will tell, but this survey is already a showcase that ACA will also serve as a major follow-up machine of z>1 sources detected by radio facilities, and will help unveil numerous "unknown unknowns" in the process.

2022 July 13, 15:30

Online broadcast (Zoom)

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia