NEWLY DISCOVERED z ∼ 5 QUASARS BASED ON DEEP LEARNING AND BAYESIAN INFORMATION CRITERION

초록

We report the discovery of four quasars with M-1450 greater than or similar to -25.0 mag at z similar to 5 and supermas-sive black hole mass measurement for one of the quasars. They were selected as promising high-redshift quasar candidates via deep learning and Bayesian information criterion, which are expected to be effective in discriminating quasars from the late-type stars and high-redshift galaxies. The candidates were observed by the Double Spectrograph on the Palomar 200-inch Hale Telescope. They show clear Ly alpha breaks at about 7000-8000 A, indicating they are quasars at 4.7 < z < 5.6. For HSC J233107-001014, we measure the mass of its supermassive black hole (SMBH) using its C Iv lambda 1549 emission line. The SMBH mass and Eddington ratio of the quasar are found to be similar to 10(8) M-circle dot and similar to 0.6, respectively. This suggests that this quasar possibly harbors a fast growing SMBH near the Eddington limit despite its faintness (L-Bol < 10(46) erg s(-1)). Our 100% quasar identification rate supports high efficiency of our deep learning and Bayesian information criterion selection method, which can be applied to future surveys to increase high-redshift quasar sample.

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