The study of high-redshift active galactic nuclei (AGN) and their small-scale environment is necessary to investigate the different processes that control and influence the evolution of massive galaxies. In this paper we present a case study of cid₁253 (z=2. 15) and its companion galaxy using archive CO (3–2) and 340 GHz continuum observations with the Atacama Large Millimeter/submillimeter Array, supplemented by multi-wavelength photometry. Previous studies treated the system as a whole, without separating its components in order to match large-beam infrared observations. Our goal is to study cid₁253 and its companion separately by re-analysing the available archive data of the system. Based on our analysis, the companion galaxy is not only more gas-rich (MH2∼1011M⊙) but also has a higher dust mass, indicative of obscured star formation. Moreover, as cid₁253 is not detected at 340 GHz, it is possible that a large fraction of the unresolved, Herschel-detected infrared emission is associated with the companion, rather than cid₁253. The presented case study highlights the need to be more cautious with blended sources before drawing our conclusions and the necessity of high-resolution observations.
Fogasy et al. (Thu,) studied this question.