2023PASJ...75..825M

We have performed CO J = 1-0 observations of 10 galaxies hosting luminous (L_bol > 10⁴⁶ erg s^–1) type 1 active galactic nuclei (AGNs) with the Nobeyama 45 m radio telescope. The targets are selected because they are expected to be rich in molecular gas based on their high nebular dust extinction (A_V). However, no significant CO emission lines were detected in any of the targets. The upper limits of the CO J = 1-0 luminosities are lower than expected given the molecular gas mass inferred from the nebular A_V. This inconsistency may be due to overestimated A_V values due to the lack of stellar absorption correction. Considering more reliable A_V values, the CO J = 1-0 non-detections by Nobeyama 45 m are natural. This suggests that our results do not contradict the conversion methods from A_V to molecular gas mass proposed in the literature. This survey suggests that careful A_V measurements as well as CO observations are still needed to improve the measurements or estimates of the molecular gas content of galaxies hosting luminous AGNs.