Nobeyama 45 m CO J = 1–0 observations of luminous type 1 AGNs at z ≈ 0.3

Abstract

We have performed CO J = 1–0 observations of 10 galaxies hosting luminous (Lbol > 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 (AV). 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 AV. This inconsistency may be due to overestimated AV values due to the lack of stellar absorption correction. Considering more reliable AV 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 AV to molecular gas mass proposed in the literature. This survey suggests that careful AV 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.