2024/01/09 by Li, Jianan, Wang, Ran, Pensabene, Antonio +17
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2401.04590
We present observations using the NOrthern Extended Millimetre Array (NOEMA) of CO and \rm H2O emission lines, and the underlying dust continuum in two quasars at z ∼ 6, i.e., P215-16 at z = 5.78 and J1429+5447 at z = 6.18. Notably, among all published CO SLEDs of quasars at z ∼ 6, the two systems reveal the highest and the lowest CO level of excitation, respectively. Our radiative transfer modeling of the CO SLED of P215-16 suggests that the molecular gas heated by AGN could be a plausible origin for the high CO excitation. For J1429+5447, we obtain the first well-sampled CO SLED (from transitions from 2-1 to 10-9) of a radio-loud quasar at z\gtrsim 6. Analysis of the CO SLED suggests that a single photo-dissociation region (PDR) component could explain the CO excitation in the radio-loud quasar J1429+5447. This work highlights the utility of the CO SLED in uncovering the ISM properties in these young quasar-starburst systems at the highest redshift. The diversity of the CO SLEDs reveals the complexities in gas conditions and excitation mechanisms at their early evolutionary stage.