Eddington ratios of dust-obscured quasars at z ≲ 1: Evidence supporting dust-obscured quasars as young quasars

초록

Dust-obscured quasars have been suspected of being 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(Edd)) than those of unobscured quasars. However, their high dust obscuration poses challenges to accurately measuring their lambda(Edd) using commonly employed bolometric luminosity (L-bol) and black hole mass (M-BH) estimators based on the ultraviolet or optical luminosity. Recently, new estimators for L-bol and M-BH based on mid-infrared continuum luminosity (L-MIR) were established, 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(Edd) values of 30 dust-obscured quasars at z less than or similar to 1, the largest sample size to date, using the L-MIR-based L-bol and M-BH estimators. Our findings reveal that dust-obscured quasars exhibit significantly higher lambda(Edd) values compared to unobscured quasars. Moreover, we confirm that the enhanced lambda(Edd) 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 an earlier stage than unobscured quasars on the merger-driven galaxy evolutionary track.

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