Eddington Ratios of Dust-obscured Quasars at $z\lesssim 1$: Evidence Supporting Dust-obscured Quasars as Young Quasars

Dust-obscured quasars have been suspected as the intermediate stage galaxies between merger-driven star-forming galaxies and unobscured quasars. This merger-driven galaxy evolution scenario suggests that dust-obscured quasars exhibit higher Eddington ratios (${\lambda }_{\mathrm{E}\mathrm{d}\mathrm{d}}$) than those of unobscured quasars. However, their high dust obscuration poses challenges to accurately measuring their ${\lambda }_{\mathrm{E}\mathrm{d}\mathrm{d}}$ using commonly employed bolometric luminosity ($L_{\mathrm{b}\mathrm{o}\mathrm{l}}$) and black hole (BH) mass ($M_{\mathrm{B}\mathrm{H}}$) estimators based on the ultraviolet (UV) or optical luminosity. Recently, Kim et al. (2023) established new estimators for $L_{\mathrm{b}\mathrm{o}\mathrm{l}}$ and $M_{\mathrm{B}\mathrm{H}}$ based on mid-infrared (MIR) continuum luminosity ($L_{\mathrm{M}\mathrm{I}\mathrm{R}}$), which are less affected by dust obscuration. These estimators enable the study of a large number of dust-obscured quasars across a wide redshift range. In this study, we measure the ${\lambda }_{\mathrm{E}\mathrm{d}\mathrm{d}}$ values of 30 dust-obscured quasars at $z\lesssim 1$, the largest sample size to date, using the $L_{\mathrm{M}\mathrm{I}\mathrm{R}}$-based $L_{\mathrm{b}\mathrm{o}\mathrm{l}}$ and $M_{\mathrm{B}\mathrm{H}}$ estimators. Our findings reveal that dust-obscured quasars exhibit significantly higher ${\lambda }_{\mathrm{E}\mathrm{d}\mathrm{d}}$ values compared to unobscured quasars. Moreover, we confirm that the enhanced ${\lambda }_{\mathrm{E}\mathrm{d}\mathrm{d}}$ values of dust-obscured quasars maintain consistency across the redshift span of 0 to 1. Our results strongly support the picture that dust-obscured quasars are in the earlier stage than unobscured quasars in the merger-driven galaxy evolutionary track.