S18B0137abst
S18B0137
We conducted submillimeter spectroscopy of z>6.5 QSO candidates as part of our systematic survey of high-redshift QSOs with ALMA. The goal of this survey is to discover new z>6.5 QSOs by detecting the high transition emission lines of carbon monoxide, CO(6-5) and CO(7-6), in the submillimeter spectra of QSO candidates selected by us from PanSTARRs1. Here, we propose FOCAS spectroscopy of 6 z>6.5 QSO candidates observed by us with ALMA. The ALMA spectra of these candidates show CO(6-5) emission lines redshifted to 6.9–7.2. In the spectra of one of our QSO candidates we detected two lines at >3σ, CO(6-5) and CO(7-6), at the same redshift (z=7.1). The CO emission is usually associated with star forming regions of quasars’ host galaxies and, therefore, does not provide the direct confirmation of the quasar identities of our candidates. The goal of the FOCAS observations is to confirm the quasar origin of our CO-detected QSO candidates by observing their quasar emission lines, such as the Lyα line. We note, that one of our CO-detected QSO candidates has been successfully confirmed to be a quasar at z=7.097 through detection of its Lyα line at the redshift similar to the redshift of its CO(6-5) line.
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