The discovery of eight z ~ 6 quasars from Pan-STARRS1

Eduardo Bañados ,E A Magnier,R J Wainscoat,J Greiner,C Waters,K Chambers ,Linhua Jiang ,Fabian Walter ,William E Sweeney ,Bram Venemans ,R P Kudritzki ,N Kaiser,P A Price,A Weiß,Emanuele Paolo Farina ,J Tonry ,C W Stubbs,Hans─Walter Rix ,W S Burgett,Roberto Decarli ,Xiaohui Fan ,J S Morgan,Robert A Simcoe ,Ian D Mcgreer ,Gisella De Rosa ,E Morganson,N Metcalfe

doi:10.1017/s1743921314003172

Abstract

AbstractHigh-redshift quasars are unique probes of the evolution of supermassive black holes and the intergalactic medium at the end of the epoch of reionization. We present the optical spectra of eight new z ~ 6 quasars selected from the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1). Details of the selection strategy can be found in Bañados et al. (2014). With this work we increase the number of known quasars at z < 5.7 by more than 10%. The quasars discovered here span a large range of luminosities (19.6 ≤ zP1 ≤ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show weak or no Lyα emission line. We find a larger fraction of weak–line emission quasars than in lower redshift studies, although still based on low number statistics, this may imply that the quasar population could be more diverse than previously thought.

Highlights

High-redshift quasars provide us with unique information about the evolution of supermassive black holes (SMBHs) and the intergalactic medium (IGM) at early cosmic time
Pan-STARRS1 represents a fundamental step forward in high-redshift quasar searches for three reasons: 1) it covers two times the area observed with SDSS; 2) it goes significantly deeper (0.5 - 1 mag) than SDSS in the reddest bands where z ∼ 6 quasars are detected; and 3) the yP1-band facilitates the search of z ∼ 6 quasars and enables the search for luminous quasars beyond the SDSS limit, z > 6.5
Already in Morganson et al (2012) we discovered the first z ∼ 6 quasar selected from Pan-STARRS1

Summary

Introduction

High-redshift quasars provide us with unique information about the evolution of supermassive black holes (SMBHs) and the intergalactic medium (IGM) at early cosmic time. For more than a decade, several groups have searched for quasars at z > 5.7, establishing a sample of ∼60 quasars (e.g., Fan et al 2006b, Willott et al 2009) These quasars have played an important role in studies of the formation and evolution of SMBH and the IGM at the end of the epoch of reionization (e.g., Fan et al 2006a, Simcoe et al 2012, De Rosa et al 2013). These studies show that important changes are occurring in the IGM.

Pan-STARRS1 3π Survey

Quasar Candidates Selection

Results