The compact, ∼1 kpc host galaxy of a quasar at a redshift of 7.1

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C ii] fine-structure line and the underlying far-infrared (FIR) dust continuum emission in J1120+0641, the most distant quasar currently known ($z=7.1$). We also present observations targeting the CO(2–1), CO(7–6), and [C i] 369 μm lines in the same source obtained at the Very Large Array and Plateau de Bure Interferometer. We find a [C ii] line flux of ${F}_{[{\rm{C}}{\rm{II}}]}=1.11\pm 0.10$ Jy $\mathrm{km}\,{{\rm{s}}}^{-1}$ and a continuum flux density of ${S}_{227\mathrm{GHz}}=0.53\pm 0.04$ mJy beam−1, consistent with previous unresolved measurements. No other source is detected in continuum or [C ii] emission in the field covered by ALMA (~ 25''). At the resolution of our ALMA observations (0farcs23, or 1.2 kpc, a factor of ~70 smaller beam area compared to previous measurements), we find that the majority of the emission is very compact: a high fraction (~80%) of the total line and continuum flux is associated with a region 1–1.5 kpc in diameter. The remaining ~20% of the emission is distributed over a larger area with radius lesssim4 kpc. The [C ii] emission does not exhibit ordered motion on kiloparsec scales: applying the virial theorem yields an upper limit on the dynamical mass of the host galaxy of $(4.3\pm 0.9)\times {10}^{10}$ ${M}_{\odot }$, only ~20 × higher than the central black hole (BH). The other targeted lines (CO(2–1), CO(7–6), and [C i]) are not detected, but the limits of the line ratios with respect to the [C ii] emission imply that the heating in the quasar host is dominated by star formation, and not by the accreting BH. The star formation rate (SFR) implied by the FIR continuum is 105–340 ${M}_{\odot }\,{\mathrm{yr}}^{-1}$, with a resulting SFR surface density of ~100–350 ${M}_{\odot }\,{\mathrm{yr}}^{-1}$ kpc−2, well below the value for Eddington-accretion-limited star formation

A long-term view of tropical cyclone risk in Australia

Natural hazard risk is assessed by leveraging, among other things, the historical record. However, if the record is short then there is the danger that risk models are not capturing the true envelope of natural variability. In the case of tropical cyclones in Australia, the most reliable observational record spans less than 50 years. Here, we use a much longer (ca. 6000-year) chronology of intense paleo-cyclones and, for the first time, blend this information with a catastrophe loss model to reassess tropical cyclone wind risk in Northeast Australia. Results suggests that the past several decades have been abnormally quiescent compared to the long-term mean (albeit with significant temporal variability). Category 5 cyclones made landfall within a section of the northeast coast of Australia almost five times more frequently, on average, over the late Holocene period than at present. If the physical environment were to revert to the long-term mean state, our modelling suggests that under the present-day exposure setting, insured losses in the area would rise by over 200%. While there remain limitations in incorporating paleoclimate data into a present-day view of risk, the value of paleoclimate data lies in contextualizing the present-day risk environment, rather than complementing it, and supporting worst-case disaster planning

Binary quasars

Quasar pairs are either physically distinct binary quasars or the result of gravitational lensing. The majority of known pairs are in fact lenses, with a few confirmed as binaries, leaving a population of objects that have not yet been successfully classified. Building on the arguments of Kochanek, Falco & Munoz (1999), it is shown that there are no objective reasons to reject the binary interpretation for most of these. In particular, the similarity of the spectra of the quasar pairs appears to be an artifact of the generic nature of quasar spectra. The two ambiguous pairs discovered as part of the Large Bright Quasar Survey (Q 1429-053 and Q 2153-0256) are analysed using principle components analysis, which shows that their spectral similarities are not greater than expected for a randomly chosen pair of quasars from the survey. The assumption of the binary hypothesis allows the dynamics, time-scales and separation distribution of binary quasars to be investigated and constrained. The most plausible model is that the quasars' activity is triggered by tidal interactions in a galatic merger, but that the (re-)activation of the galactic nuclei occurs quite late in the interaction, when the nuclei are within 80+/-30 kpc of each other. A simple dynamical friction model for the decaying orbits reproduces the observed distribution of projected separations, but the decay time inferred is comparable to a Hubble time. Hence it is predicted that binary quasars are only observable as such in the early stages of galactic collisions, after which the quiescent super-massive black holes orbit in the merger remnant for some time.Comment: 12 pages, 12 figure

How neutral is the intergalactic medium surrounding the redshift z=7.085 quasar ULAS J1120+0641?

The quasar ULAS J1120+0641 at redshift z=7.085 has a highly ionised near zone which is smaller than those around quasars of similar luminosity at z~6. The spectrum also exhibits evidence for a damping wing extending redward of the systemic Lya redshift. We use radiative transfer simulations in a cosmological context to investigate the implications for the ionisation state of the inhomogeneous IGM surrounding this quasar. Our simulations show that the transmission profile is consistent with an IGM in the vicinity of the quasar with a volume averaged HI fraction of f_HI>0.1 and that ULAS J1120+0641 has been bright for 10^6--10^7 yr. The observed spectrum is also consistent with smaller IGM neutral fractions, f_HI ~ 10^-3--10-4, if a damped Lya system in an otherwise highly ionised IGM lies within 5 proper Mpc of the quasar. This is, however, predicted to occur in only ~5 per cent of our simulated sight-lines for a bright phase of 10^6--10^7 yr. Unless ULAS J1120+0641 grows during a previous optically obscured phase, the low age inferred for the quasar adds to the theoretical challenge of forming a 2x10^9 M_sol black hole at this high redshift.Comment: 5 pages, 4 figures, accepted to MNRAS letter

No excess of bright galaxies around the redshift 7.1 quasar ULAS J1120+0641

We present optical and near-infrared imaging of the field of the z = 7.0842 quasar ULAS J112001.48+064124.3 taken with the Hubble Space Telescope. We use these data to search for galaxies that may be physically associated with the quasar, using the Lyman break technique, and find three such objects, although the detection of one in Spitzer Space Telescope imaging strongly suggests it lies at z ∼ 2. This is consistent with the field luminosity function and indicates that there is no excess of >L★ galaxies within 1 Mpc of the quasar. A detection of the quasar shortwards of the Lyα line is consistent with the previously observed evolution of the intergalactic medium at z > 5.5.SC acknowledges support from the NSF grant AST-1010004 and NASA HST grant GO-13033.06-A, RJM acknowledges ERC funding via the award of a consolidator grant, and BV has been supported by the ERC grant ‘Cosmic Dawn’.This is the final published version. It originally appeared in MNRAS at http://www.mnras.org/content/442/4/3454.full

Natural Variability and Warming Signals in Global Ocean Wave Climates

地球全体の波浪特性の変化傾向と自然変動の関係を解明 --地球温暖化の沿岸域への影響を定量化--. 京都大学プレスリリース. 2021-06-15.This paper presents a multivariate classification of the global wave climate into types driven by atmospheric circulation patterns. The primary source of the net long-term variability is evaluated based on historical wave simulations. Results show that the monsoon, extratropical, subtropical, and polar wave climate types of the Pacific and North Atlantic Oceans are dominated by natural variability, whereas the extratropical and subtropical wave climate types in the Indian Ocean, and the tropical wave climate types of the Atlantic and Pacific Oceans exhibit a global warming signal. In the Pacific sector of the Southern Ocean, strong natural variability may mask a global warming signal that is yet to emerge as being statistically significant. In addition, wave climate teleconnections were found across the world that can provide a framework for joint strategies to achieve the goals of climate adaption for resilient coastal communities and environments

The Ray Bundle method for calculating weak magnification by gravitational lenses

We present here an alternative method for calculating magnifications in gravitational lensing calculations -- the Ray Bundle method. We provide a detailed comparison between the distribution of magnifications obtained compared with analytic results and conventional ray-shooting methods. The Ray Bundle method provides high accuracy in the weak lensing limit, and is computationally much faster than (non-hierarchical) ray shooting methods to a comparable accuracy. The Ray Bundle method is a powerful and efficient technique with which to study gravitational lensing within realistic cosmological models, particularly in the weak lensing limit.Comment: 9 pages Latex, 8 figures, submitted to MNRA

Using globular clusters to test gravity in the weak acceleration regime

We have carried out a study of the velocity dispersion of the stars in the outskirts of the globular cluster Omega Centauri, finding that the velocity dispersion remains constant at large radii rather than decrease monotonically. The dispersion starts to be constant for an acceleration of gravity of a = 2.1e-8 cm/s/s. A similar result is obtained reanalyzing existing data for the globular cluster M15 where the profile flattens out for a = 1.7e-8 cm/s/s. In both cases the acceleration is comparable to that at which the effect of dark matter becomes relevant in galaxies. Explanations for this result within Newtonian dynamics exist (e.g. cluster evaporation, tidal effects, presence of dark matter) but require ad hoc tuning of the relevant parameters in order to make in both clusters the dispersion profile flat starting exactly at the same acceleration. We suggest that this result, together with a similar one for Palomar 13 and the anomalous behavior of spacecrafts outside the solar system, may indicate a breakdown of Newton's law in the weak acceleration regime. Although not conclusive, these data prompt for the accurate determination of the internal dynamics of as many GCs as possible.Comment: Accepted for publication on A&A Letters. Four pages + 2 figure