The Infrared Medium-deep Survey. IX. Discovery of Two New $z\sim6$ Quasars and Space Density down to $M_{1450}\sim-23.5$ mag

We present the result of the Infrared Medium-deep Survey (IMS) $z\sim6$ quasar survey, using the combination of the IMS near-infrared images and the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) optical images. The traditional color-selection method results in 25 quasar candidates over $86$...

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Hauptverfasser: Kim, Yongjung, Im, Myungshin, Jeon, Yiseul, Kim, Minjin, Jiang, Linhua, Shin, Suhyun, Choi, Changsu, Hyun, Minhee, Jun, Hyunsung D, Kim, Dohyeong, Kim, Duho, Kim, Jae-Woo, Kim, Ji Hoon, Lee, Bumhyun, Lee, Seong-Kook, Molina, Juan, Pak, Soojong, Park, Won-Kee, Taak, Yoon Chan, Yoon, Yongmin
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Sprache:eng
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Zusammenfassung:We present the result of the Infrared Medium-deep Survey (IMS) $z\sim6$ quasar survey, using the combination of the IMS near-infrared images and the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) optical images. The traditional color-selection method results in 25 quasar candidates over $86$ deg$^{2}$. We introduce the corrected Akaike Information Criterion (AICc) with the high-redshift quasar and late-type star models to prioritize the candidates efficiently. Among the color-selected candidates, seven plausible candidates finally passed the AICc selection of which three are known quasars at $z\sim6$. The follow-up spectroscopic observations for the remaining four candidates were carried out, and we confirmed that two out of four are $z\sim6$ quasars. With this complete sample, we revisited the quasar space density at $z\sim6$ down to $M_{1450}\sim-23.5$ mag. Our result supports the low quasar space density at the luminosity where the quasar's ultraviolet ionizing emissivity peaks, favoring a minor contribution of quasars to the cosmic reionization.
DOI:10.48550/arxiv.2207.12282