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تسجيل مستخدم جديدPhysical properties of 15 quasars at $zgtrsim 6.5$
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Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only few quasars have been reported at $z > 6.5$ ($<$800 Myr after the Big Bang). In this work, we present six additional $z gtrsim 6.5$ quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 $z gtrsim 6.5$ quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of $zgtrsim$6.5 quasars show large blueshifts of the broad CIV 1549AA$,$emission line compared to the systemic redshift of the quasars, with a median value $sim$3$times$ higher than a quasar sample at $zsim$1; (2) we estimate the quasars black hole masses (M$rm_{BH}sim$0.3$-$5 $times$ 10$^{9}$ M$_{odot}$) via modeling of the MgII 2798AA$,$emission line and rest-frame UV continuum; we find that quasars at high redshift accrete their material (with $langle (L_{mathrm{bol}}/L_{mathrm{Edd}}) rangle = 0.39$) at a rate comparable to a luminosity-matched sample at lower$-$redshift, albeit with significant scatter ($0.4$ dex); (3) we recover no evolution of the FeII/MgII abundance ratio with cosmic time; (4) we derive near zone sizes; together with measurements for $zsim6$ quasars from recent work, we confirm a shallow evolution of the decreasing quasar near zone sizes with redshift. Finally, we present new millimeter observations of the [CII] 158 $mu$m emission line and underlying dust continuum from NOEMA for four quasars, and provide new accurate redshifts and [CII]/infrared luminosities estimates. The analysis presented here shows the large range of properties of the most distant quasars.
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