Probing the interstellar medium of the quasar BRI0952-0115, an analysis of [CII], [CI], CO, OH, and H2O

Abstract: The extent of the effect of active galactic nuclei (AGN) on their host galaxies at high-redshift is not apparent and studying this effect in the distant universe is a difficult process as the mechanisms of tracing AGN activity can often be inaccurately associated with intense star formation and vice versa. Our aim is to better understand the processes governing the interstellar medium (ISM) of the quasar BRI0952-0952 at z = 4.432, specifically with regard to the individual heating processes at work and to place the quasar in an evolutionary context. We analyzed ALMA archival bands 3, 4, and 6 data and combined the results with high-resolution band-7 ALMA observations of the quasar. We detect C I, [C II], CO(5-4), CO(7-6), CO(12-11), OH, H2O, and we report a tentative detection of OH+. We update the lensing model from Kade et al. (2023) and use the radiative transfer code MOLPOP-CEP to constrain the properties of the CO, [CI], and [CII] emission and suggest different possible scenarios for heating mechanisms within the quasar. Modeling from the CO SLED suggests that there are extreme heating mechanisms operating within the quasar in the form of star formation or AGN activity; however, with the current data it remains unclear which of the two is the preferred mechanism. The updated lensing model suggests a velocity gradient across the [C II] line, suggestive of on-going kinematical processes within the quasar. We find that the H2O emission in BRI0952 is likely correlated with star-forming regions of the ISM. We use the molecular gas mass from [C I] to calculate a depletion time for the quasar. We conclude that BRI 0952-0952 is a quasar with a significant AGN contribution while also showing signs of extreme starburst activity, indicating that the quasar could be in a transitional phase between a starburst-dominated stage and an AGN-dominated stage.