[en] We measure alignments on scales of 1 Mpc h ^-1₇₁ for galaxies in Abell 1689 (z = 0.18) from an existing Hubble Space Telescope mosaic. We find evidence of galaxy alignment in the inner 500 h ^-1₇₁ kpc. The alignment appears to be stronger toward the center and is mostly present among the fainter galaxies, while bright galaxies are unaligned. This is consistent with a model where alignments originate from tidal locking.

[en] We present a deep and wide I luminosity function (LF) for galaxies in A1689 (z = 0.183) from a mosaic of Hubble Space Telescope WFPC2 images covering 10' on the side. The main result of this work is the detection of a steep upturn in the dwarf galaxy LF, with α ∼ -2. The dwarf-to-giant ratio appears to increase outward, but this is because giant galaxies are missing in the cluster outskirts, indicating luminosity segregation. The red sequence LF has the same parameters, within errors, as the total LF, showing that the faint end upturn consists of red quiescent galaxies. We speculate that the upturn is connected to the 'filling-in' of the red sequence at z < 0.4 and may represent the latest installment of 'downsizing' as the least massive galaxies are being quenched at the present epoch.

[en] We report the discovery of a luminous quasar, J1007+2115 at z = 7.515 (“Pōniuā‘ena”), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at z > 7.5, deep into the reionization epoch. The quasar is powered by a (1.5 ± 0.2) × 10⁹ M _⊙ supermassive black hole (SMBH), based on its broad Mg ii emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at z = 7.54, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of ≳10⁴ M _⊙ at z = 30. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Lyα line profile, and find that it is weaker than that of J1342+0928 and two other z ≳ 7 quasars. We estimate an IGM volume-averaged neutral fraction $⟨<!--\; ???\; -->x_{\mathrm{H}\mathrm{I}}⟩<!--\; ???\; -->={0.39}_{-<!--\; ???\; -->0.13}^{+0.22}$. This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 μm [C ii] emission line in J1007+2115 with the Atacama Large Millimeter/submillimeter Array; this line centroid yields a systemic redshift of z = 7.5149 ± 0.0004 and indicates a star formation rate of ∼210 M _☉ yr⁻¹ in its host galaxy.

[en] Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at z ≥ 7.5, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at z = 7.642, J0313−1806, the most distant quasar yet known. This quasar has a bolometric luminosity of 3.6 × 10¹³ L _⊙. Deep spectroscopic observations reveal a SMBH with a mass of (1.6 ± 0.4) × 10⁹ M _⊙ in this quasar. The existence of such a massive SMBH just ∼670 million years after the big bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in C iv and Si iv, with a maximum velocity close to 20% of the speed of light. The relativistic BAL features, combined with a strongly blueshifted C iv emission line, indicate that there is a strong active galactic nucleus (AGN)-driven outflow in this system. Atacama Large Millimeter/submillimeter Array observations detect the dust continuum and [C ii] emission from the quasar host galaxy, yielding an accurate redshift of 7.6423 ± 0.0013 and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of ∼200 M _⊙ yr⁻¹ and a dust mass of ∼7 × 10⁷ M _⊙. Follow-up observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.