Numerical Coincidences and `Tuning' in Cosmology     

M.J. Rees 《Astrophysics and Space Science》2003,285(2):375-388

Fred Hoyle famously drew attention to the significance of apparent coincidences in the energy levels of the carbon and oxygen nucleus. This paper addresses the possible implications of other coincidences in cosmology. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

INGRID: A near-infrared camera for the William Herschel Telescope     

Christopher Packham  Keith L. Thompson  Almudena Zurita  Johan H. Knapen  Ian Smail  Robert Greimel  Daniel F. M. Folha  Chris Benn  rew Humphrey  Rene Rutten  David Ciardi  Matthieu Bec  Richard Bingham  Simon Craig  Kevin Dee  Derek Ives  Paul Jolley  Peter Moore  Marti Pi i Puig  Simon Rees  Gordon Talbot  Sue Worswick 《Monthly notices of the Royal Astronomical Society》2003,345(2):395-405

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The distribution of supermassive black holes in the nuclei of nearby galaxies     

Andrea Cattaneo  Martin G. Haehnelt  Martin J. Rees 《Monthly notices of the Royal Astronomical Society》1999,308(1):77-81

The growth of supermassive black holes by merging and accretion in hierarchical models of galaxy formation is studied by means of Monte Carlo simulations. A tight linear relation between masses of black holes and masses of bulges arises if the mass accreted by supermassive black holes scales linearly with the mass-forming stars and if the redshift evolution of mass accretion tracks closely that of star formation. Differences in redshift evolution between black hole accretion and star formation introduce a considerable scatter in this relation. A non-linear relation between black hole accretion and star formation results in a non-linear relation between masses of remnant black holes and masses of bulges. The relation of black hole mass to bulge luminosity observed in nearby galaxies and its scatter are reproduced reasonably well by models in which black hole accretion and star formation are linearly related but do not track each other in redshift. This suggests that a common mechanism determines the efficiency for black hole accretion and the efficiency for star formation, especially for bright bulges.  相似文献   

High-redshift galaxies, their active nuclei and central black holes     

Martin G. Haehnelt  Priyamvada Natarajan  & Martin J. Rees 《Monthly notices of the Royal Astronomical Society》1998,300(3):817-827

We demonstrate that the luminosity function of the recently detected population of actively star-forming galaxies at redshift z  = 3 and the B -band luminosity function of quasi-stellar objects (QSOs) at the same redshift can both be matched with the mass function of dark matter haloes predicted by standard variants of hierarchical cosmogonies for lifetimes of optically bright QSOs anywhere in the range 10⁶ to 10⁸ yr. There is a strong correlation between the lifetime and the required degree of non-linearity in the relation between black hole and halo mass. We suggest that the mass of supermassive black holes may be limited by the back-reaction of the emitted energy on the accretion flow in a self-gravitating disc. This would imply a relation of black hole to halo mass of the form M _bh ∝  v ⁵_halo ∝  M ^5/3_halo and a typical duration of the optically bright QSO phase of a few times 10⁷ yr. The high integrated mass density of black holes inferred from recent black hole mass estimates in nearby galaxies may indicate that the overall efficiency of supermassive black holes for producing blue light is smaller than previously assumed. We discuss three possible accretion modes with low optical emission efficiency: (i) accretion at far above the Eddington rate, (ii) accretion obscured by dust, and (iii) accretion below the critical rate leading to an advection-dominated accretion flow lasting for a Hubble time. We further argue that accretion with low optical efficiency might be closely related to the origin of the hard X-ray background and that the ionizing background might be progressively dominated by stars rather than QSOs at higher redshift.  相似文献   

Cumulative impacts of aggregate extraction on seabed macro-invertebrate communities in an area off the east coast of the United Kingdom     

Keith Cooper  Sin Boyd  John Aldridge  Hubert Rees 《Journal of Sea Research》2007,57(4):288-302

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A comparison of field-monitored and numerically predicted moisture movement in unsaturated soil     

H. R. Thomas  S. W. Rees 《国际地质力学数值与分析法杂志》1991,15(6):417-431

This paper presents the results of the application of a numerical model of flow of water in unsaturated soil to simulate real field behaviour. Numerical predictions are compared with field-monitored results as part of an assessment of the approach adopted. The numerical approach is based on a finite element solution of Richards' theoretical formulation, adopting a finite difference recurrence relationship to model the transient nature of the problem. The field results have been collected by British Gas in Kimmeridge clay at a site in Swindon. The simulation addressed the autumn wetting of the soil during 1983. Comparisons of volumetric moisture content readings from the field and numerical predictions give good correlation. It is concluded that the numerical model has adequately represented field behaviour over the depth of interest. Taken in conjunction with previous results, it is claimed that the model should now be capable of use in a predictive mode.  相似文献   

Determination of the Even Harmonics in the Earth's Gravitational Potential     

D. G. King-Hele  G. E. Cook  Janice M. Rees 《Geophysical Journal International》1963,8(1):119-145

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On the excitation of suhvisual O1 λλ6300–6364 arcs at middle latitudes     

M. H. Rees 《Planetary and Space Science》1961,8(3-4):198-200

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Measurements of high latitude thermospheric winds by rocket and ground-based techniques and their interpretation using a three-dimensional,time-dependent dynamical model     

D. Rees  T.J. Fuller-Rowell  R.W. Smith 《Planetary and Space Science》1980,28(9):919-932

A three-dimensional, time-dependent model of thermospheric dynamics has been used to interpret recent experimental measurements of high altitude winds by rocket-borne and ground-based techniques. The model is global and includes a self-consistent treatment of the non-linear, Coriolis and viscosity terms. The solar u.v. and e.u.v. energy input provides the major energy source for the thermosphere. Solar u.v. and e.u.v. heating appear to be inadequate to explain observed thermospheric temperatures if e.u.v. heating efficiency (ε) lies in the range 0.3 < ε < 0.35. If the recent solar e.u.v. data are correct, then a value of ε between 0.4 and 0.45 would bring fluxes and observed temperatures into agreement. The Heppner (1977) and Volland (1978) models of high-latitude electric field are used to provide sources of both momentum (via ion drag) and energy (via Joule heating). We find that the Heppner Model CO (equivalent to Volland Model 1) is most appropriate for very quiet geomagnetic conditions (K_p ? 2) while Model A (equivalent to Volland Model 2) provides the necessary enhancement at high latitudes for conditions of moderate activity (K_p ～ 4). Even with the addition of a polar electric field, there still appears to be a shortage of high-latitude energy input in that model winds tend to be 10 m s^?1 poleward of observed winds under quiet or average geomagnetic conditions. This extra energy cannot be provided by enhancing the polar electric fields since the extra momentum would cause disagreement with the observed high latitude winds. High latitude particulate sources of relatively low energies, ~100 eV, seem the most likely candidates depositing their energy above about 200km. Relatively modest amounts of energy are then required, < 10¹⁰W global, to bring the model into agreement with both high- and mid-latitude neutral wind results.  相似文献   

The Doppler Imaging System: Initial observations of the auroral thermosphere     

D. Rees  A.H. Greenaway  R. Gordon  I. McWhirter  P.J. Charleton  Åke Steen 《Planetary and Space Science》1984,32(3):273-285

During December 1982, a novel Fabry-Perot interferometer—a Doppler Imaging System (DIS)— was used at Kiruna Geophysical Institute (KGI), Sweden (67.8°N, 21.2°E) to complement a series of coordinated observations of global thermospheric dynamics utilizing a number of conventional ground-based Fabry-Perot interferometers and the NASA Dynamics Explorer satellite. The DIS is an interferometer with two unique attributes : it has a luminosity or étendue more than one hundred times that of the conventional Fabry-Perot interferometer, and it is also capable of deducing a two-dimensional velocity field of a suitable line-emitting areal source by independently measuring the Doppler shift at a large number of points within the field of view. On 17 December 1982, a very large geomagnetic Storm Sudden Commencement (08.05 U.T.) preceded a major geomagnetic disturbance. During this disturbance, Northern Scandinavia was influenced by a strong eastward auroral electrojet for an extended period (10–19 U.T.). The DIS was able to observe the dynamical response of the upper thermosphere to this event in conjunction with a second Fabry-Perot interferometer (FPI) at KGI. Westward thermospheric winds of about 900 m s^?1 occurred during the disturbance and, at the peak of the disturbance, the combined DIS and FPI observations indicate that the thermospheric flow was quite chaotic. Fluctuations of the order of ± 150 ms^?1, associated with spatial scales of the order of 100 or 200 km occurred within the mean westward flow inside the 800 km diameter region observed from Kiruna.  相似文献