The dust-obscured galaxies (DOGs) are an interesting AGN population since it is possibly in a very active and obscured phase during the co-evolution between a galaxy and a supermassive black hole. Recently we obtain 70 X-ray detected DOGs (eFEDS-DOGs) sample by combining HSC (optical), VIKING (NIR), WISE (MIR), and eFEDS (X-ray) data. Then, we can obtain the reliable DOGs sample in a dusty AGN phase since their SEDs show the power-law shape between optical and MIR, and they are detected by eROSITA suggesting that the objects have an AGN. However, the estimated logNH are smaller than 23, suggesting that the eFEDS-DOGs might not be in heavy obscured phase. Thus, to understand the rapidly growing phase of the SMBH-galaxy co-evolution, we need to assess the redshift and black hole masses. Here we propose optical spectroscopic observations of the eight eFEDS-DOGs with reliable photo-z and iAB ≤ 22 to decide their spectral redshifts, to estimate their SMBH masses, and to research the spectral evolution between the obscured AGN and the optically-thin quasars by assuming that the DOGs and quasars are in a gas-rich major merger scenario.
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