Quasars are the most luminous non-transient objects known and as a result they enable studies of the Universe at the earliest cosmic epochs. Despite extensive efforts, however, the quasar ULAS J1120 + 0641 at redshift z = 7.09 has remained the only one known at z > 7 for more than half a decade. Here we report observations of the quasar ULAS J134208.10 + 092838.61 (hereafter J1342 + 0928) at redshift z = 7.54. This quasar has a bolometric luminosity of 4 × 10 times the luminosity of the Sun and a black-hole mass of 8 × 10 solar masses. The existence of this supermassive black hole when the Universe was only 690 million years old-just five per cent of its current age-reinforces models of early black-hole growth that allow black holes with initial masses of more than about 10 solar masses or episodic hyper-Eddington accretion. We see strong evidence of absorption of the spectrum of the quasar redwards of the Lyman α emission line (the Gunn-Peterson damping wing), as would be expected if a significant amount (more than 10 per cent) of the hydrogen in the intergalactic medium surrounding J1342 + 0928 is neutral. We derive such a significant fraction of neutral hydrogen, although the exact fraction depends on the modelling. However, even in our most conservative analysis we find a fraction of more than 0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are probing well within the reionization epoch of the Universe.

No abstract

Variable X-ray and γ-ray emission is characteristic of the most extreme physical processes in the Universe, and studying the sources of these energetic photons has been a major driver in astronomy for the past 50 years. Here we present multiwavelength observations of a unique γ-ray selected transient, discovered by Swift, which was accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z = 0.3534. Its high-energy emission has lasted much longer than any gamma-ray burst, while its peak luminosity was ∼100 times higher than bright active galactic nuclei. The association of the outburst with the cen-1 arXiv:1104.3356v1 [astro-ph.HE]

Aims. Our goal is to study gas properties in large-scale molecular outflows and winds from active galactic nuclei (AGNs) and starburst galaxies. Methods. We obtained high-resolution (1. 55 × 1. 28) observations of HCN, HCO + , HNC 1-0 and HC 3 N 10-9 of the ultraluminous galaxy (ULIRG) Mrk 231 with the IRAM Plateau de Bure Interferometer. Results. We detect luminous emission from HCN, HCO + and HNC 1-0 in the QSO ULIRG Mrk 231. All three lines show broad line wings -which are particularly prominent for HCN. Velocities are found to be similar (≈±750 km s −1 ) to those found for CO 1-0. This is the first time bright HCN, HCO + and HNC emission has been detected in a large-scale galactic outflow. We find that both the blueand red-shifted line wings are spatially extended by at least 0. 75 (>700 pc) in a north-south direction. The line wings are brighter (relative to the line center intensity) in HCN than in CO 1-0 and line ratios suggest that the molecular outflow consists of dense (n > 10 4 cm −3 ) and clumpy gas with a high HCN abundance X(HCN) > 10 −8 . These properties are consistent with the molecular gas being compressed and fragmented by shocks in the outflow. Alternatively, HCN is instead pumped by mid-IR continuum, but we propose that this effect is not strong for the spatially extended outflowing gas. In addition, we find that the rotation of the main disk, in east-west direction, is also evident in the HCN, HCO + and HNC line emission. An unexpectedly bright HC 3 N 10-9 line is detected inside the central 400 pc of Mrk 231. This HC 3 N emission may emerge from a shielded, dust-enshrouded region within the inner 40-50 pc where the gas is heated to high temperatures (200-300 K) by the AGN.