Discovery of Six Low-z, High-luminosity, and High-mass Quasars

Abstract This study presents the discovery of six low-redshift quasars, identified through spectral observations conducted with the RTT-150 telescope. These quasars, with redshifts ranging from 0.3 to 0.6, were selected incorporating their placement in the color–color diagrams and detection by ROSAT 2RXS, focusing on those resembling the spectral energy distribution of a quasar. Our analysis includes detailed modeling of their continuum and emission line properties, which allowed us to estimate their bolometric luminosities, central black hole masses, and Eddington ratios. The findings reveal that these quasars exhibit exceptionally high luminosities and high masses for their redshift values, making them rare examples in the low-redshift quasar population. The results contribute to our understanding of quasar characteristics and their role in probing the structure and evolution of the nearby universe. This research underscores the importance of continued exploration of low-redshift quasars to enhance our knowledge of cosmic evolution and the dynamics of supermassive black holes in the early universe.