The Pan-STARRS1 z > 5.6 Quasar Survey. II. Discovery of 55 Quasars at 5.6 < z < 6.5

The identification of bright quasars at z greater than or similar to 6 enables detailed studies of supermassive black holes, massive galaxies, structure formation, and the state of the intergalactic medium within the first billion years after the Big Bang. We present the spectroscopic confirmation of 55 quasars at redshifts 5.6 < z < 6.5 and UV magnitudes -24.5 < M (1450) < -28.5 identified in the optical Pan-STARRS1 and near-IR VIKING surveys (48 and 7, respectively). Five of these quasars have independently been discovered in other studies. The quasar sample shows an extensive range of physical properties, including 17 objects with weak emission lines, 10 broad absorption line quasars, and 5 objects with strong radio emission (radio-loud quasars). There are also a few notable sources in the sample, including a blazar candidate at z = 6.23, a likely gravitationally lensed quasar at z = 6.41, and a z = 5.84 quasar in the outskirts of the nearby (D similar to 3 Mpc) spiral galaxy M81. The blazar candidate remains undetected in NOEMA observations of the [C ii] and underlying emission, implying a star formation rate M (circle dot) yr(-1). A significant fraction of the quasars presented here lies at the foundation of the first measurement of the z similar to 6 quasar luminosity function from Pan-STARRS1 (introduced in a companion paper). These quasars will enable further studies of the high-redshift quasar population with current and future facilities.

Automated summary

We confirm the existence of 55 quasars at redshifts 5.6 < z < 6.5 through optical and near-infrared surveys. Some notable sources include a potential gravitationally lensed quasar and a quasar located in the outskirts of the nearby spiral galaxy M81. These quasars will contribute to further studies of high-redshift quasar populations.