Poster Presentation

IMS High-z Quasar Survey and Future

Author(s): Yongjung Kim (Kyungpook National University), Myungshin Im (Seoul National University), Yiseul Jeon (FEROKA Inc.), Minjin Kim (Kyungpook National University), and IMS Team

Presenter: Yongjung Kim (Kyungpook National University)

We have been surveying for the past few years to identify faint quasars at high redshifts using the Infrared Medium-deep Survey (IMS). The IMS is a near-infrared imaging survey covering an area of about 120 square degrees. To eliminate the contaminants like late-type stars efficiently, we introduced (1) the advanced color selection by medium-band-based approach and (2) the probabilistic method using the corrected Akaike Information Criterion (AICc). Those two methods remarkably improve the selection efficiency of high-redshift quasars compared with the traditional color selection method. So far, 24 quasars have been newly discovered at redshifts between 4.6 and 6.3. Using these quasars, we studied quasar contribution to the ionizing background in the early universe, the growth of supermassive black holes and host galaxies, the evolution of quasar demography, and so on. We are planning to apply such techniques to the optical-to-infrared data from the upcoming surveys, such as 7DS, KS4, and SPHEREx. This will allow us to find the missing quasar population over the sky.