Two-micron spectrophotometry of Uranus and its rings     

P.D. Nicholson  T.J. Jones 《Icarus》1980,42(1):54-67

Multiaperture K photometry and 2.0- to 2.5-μm spectrophotometry of Uranus and its ring system are presented. The photometric results are used, together with a previously published measurement, to set limits on the geometric albedos of Uranus and the rings at ～2.2 μm: (0.74 ± 0.02) × 10(su?4) ≤ p_K (Uranus) ≤ (1.5 ± 0.3) × 10^?4, and (2.7 ± 0.6) × 10^?2 ≤ p_K (rings) ≤ (3.4 ± 0.1) × 10^?2. Reflectance spectra of Uranus and Uranus plus rings show features in the planet's spectrum which are attributed to gaseous CH₄ absorption, and a 2.20-μm feature in the combined spectrum which may be due to the rings. This feature is tentatively identified with either the 2.26-μm absorption feature of NH₃ frost, or the 2.2-μm OH band exhibited by certain silicate minerals. The results of JHK photometry of Uranus' satellite, Ariel (U1), indicate that the infrared colors of this object are very similar to those of the satellites U2, U3, and U4.  相似文献   

The use of the Coulter Counter for the Determination of Marine Primary Productivity     

Cushing  D. H.; Nicholson  H. F.; Fox  G. P. 《ICES Journal of Marine Science》1968,32(1):131-151

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New constraints on subduction zone structure in northern Cascadia     

T. Nicholson  M. Bostock  J. F. Cassidy 《Geophysical Journal International》2005,161(3):849-859

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Salt Waters of the Northern Apennine Foredeep Basin (Italy): Origin and Evolution     

Tiziano Boschetti  Lorenzo Toscani  Orfan Shouakar-Stash  Paola Iacumin  Giampiero Venturelli  Claudio Mucchino  Shaun K. Frape 《Aquatic Geochemistry》2011,17(1):71-108

The salt waters from the Emilia-Romagna sector of the Northern Apennine Foredeep have been investigated using major and trace element and stable isotope (δ²H, δ¹⁸O, δ³⁷Cl, δ⁸¹Br and ⁸⁷Sr/⁸⁶Sr ratio). Ca, Mg, Na, K, Sr, Li, B, I, Br and SO₄ vs. Cl diagrams suggest the subaerial evaporation of seawater beyond gypsum and before halite precipitation as primary process to explain the brine’s salinity, whereas saline to brackish waters were formed by mixing of evaporated seawater and water of meteoric origin. A diagenetic end-member may be a third component for mud volcanoes and some brackish waters. Salinization by dissolution of (Triassic) evaporites has been detected only in samples from the Tuscan side of the Apennines and/or interacting with the Tuscan Nappe. In comparison with the seawater evaporation path, Ca–Sr enrichment and Na–K–Mg depletion of the foredeep waters reveal the presence of secondary processes such as dolomitization–chloritization, zeolitization–albitization and illitization. Sulfate concentration, formerly buffered by gypsum-anhydrite deposition, is heavily lowered by bacterial and locally by thermochemical reduction during burial diagenesis. From an isotopic point of view, data of the water molecule confirm mixing between seawater and meteoric end-members. Local ¹⁸O-shift up to +11‰ at Salsomaggiore is related to water–rock interaction at high temperature (≈150°C) as confirmed by chemical (Mg, Li, Ca distribution) and isotopic (SO₄–H₂O) geothermometers. ³⁷Cl/³⁵Cl and ⁸¹Br/⁷⁹Br ratios corroborate the marine origin of the brines and evidence the diffusion of halogens from the deepest and most saline aquifers toward the surface. The ⁸⁷Sr/⁸⁶Sr ratio suggests a Miocene origin of Sr and rule out the hypothesis of a Triassic provenance of the dissolved components for the analyzed waters issuing from the Emilia-Romagna sector of the foredeep. Waters issuing from the Tuscan side of the Apennines and from the Marche sector of the foredeep show higher ⁸⁷Sr/⁸⁶Sr ratios because of the interaction with siliciclastic rocks.  相似文献   

Erratum to “on the inclination distribution of the jovian irregular satellites”[Icarus 158 (2002) 434-449]     

Valerio Carruba  Joseph A. Burns  Philip D. Nicholson 《Icarus》2003,162(1):230-231

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Modelling Dust in Galactic SEDs: Application to Semi-Analytical Galaxy Formation Models     

Laura Silva  Gian Luigi Granato  Alessandro Bressan  Cedric Lacey  Carlton M. Baugh  Shaun Cole  Carlos S. Frenk 《Astrophysics and Space Science》2001,276(2-4):1073-1078

We present the basic features and preliminary results of the interface between our spectrophotometric model GRASIL (which calculates galactic SEDs from the UV to the submm with a detailed computation of dust extinction and thermal reemission) with the semi-analytical galaxy formation model GALFORM (which computes galaxy formation and evolution in the hierarchical scenario, providing the star formation history as an input to our model). With these two models we are able to synthesize simulated samples of a few thousand galaxies for statistical studies of galaxy properties to investigate galaxy formation and evolution. There is good agreement with the available SED and luminosity function data. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Adaptive optics observations of small moons of saturn     

Britt R. Scharringhausen  Philip D. Nicholson  Thomas L. Hayward  Mitchell Troy 《Icarus》2003,162(2):385-390

We report near-infrared observations of Prometheus and Janus taken on 9 and 13 November 2000 (UT) with the Palomar Adaptive Optics System on the 5-m Hale telescope at Palomar Observatory. Dione, Rhea, and Tethys were used as guide “stars” for the adaptive optics system, and, though they were outside the isoplanatic patch of the region of interest, they allowed significant correction of the atmospheric turbulence.Prometheus, which is usually impossible to observe from the ground due to scattered light from the A ring, was imaged at superior conjunction with Saturn. At the time of the observations, the rings of Saturn were blocked by the southern limb of the planet while the moon passed just 0.35″ below the planet’s south pole. A K filter, in a methane absorption band, was used to suppress light from the disk of the planet, and template subtraction removed much of the scattered light from the A ring. Prometheus was found to be 21.9 ± 0.1° of mean longitude behind the position predicted by Voyager-era ephemerides, consistent with the orbital lag discovered during the 1995 ring-plane crossing.  相似文献   

Galaxy formation using halo merger histories taken from N-body simulations     

John C. Helly _&#;  Shaun Cole  Carlos S. Frenk  Carlton M. Baugh  rew Benson  Cedric Lacey 《Monthly notices of the Royal Astronomical Society》2003,338(4):903-912

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The 2dF Galaxy Redshift Survey: galaxy luminosity functions per spectral type     

Darren S. Madgwick  Ofer Lahav  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Steve Maddox  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,333(1):133-144

We calculate the optical b _J luminosity function (LF) of the 2dF Galaxy Redshift Survey (2dFGRS) for different subsets defined by their spectral properties. These spectrally selected subsets are defined using a new parameter, η , which is a linear combination of the first two projections derived from a Principal Component Analysis. This parameter η identifies the average emission- and absorption-line strength in the galaxy rest frame spectrum, and hence is a useful indicator of the present star formation. We use a total of 75 000 galaxies in our calculations, chosen from a sample of high signal-to-noise ratio, low-redshift galaxies observed before 2001 January. We find that there is a systematic steepening of the faint-end slope ( α ) as one moves from passive  ( α =-0.54)  to active  ( α =-1.50)  star-forming galaxies, and that there is also a corresponding faintening of the rest frame characteristic magnitude   M *-5 log₁₀( h )  (from −19.6 to −19.2). We also show that the Schechter function provides a poor fit to the quiescent (Type 1) LF for very faint galaxies  [ M _{b J}-5 log₁₀( h )  fainter than −16.0], perhaps suggesting the presence of a significant dwarf population. The LFs presented here give a precise confirmation of the trends seen previously in a much smaller preliminary 2dFGRS sample, and in other surveys. We also present a new procedure for determining self-consistent k -corrections, and investigate possible fibre-aperture biases.  相似文献   

Parameter constraints for flat cosmologies from cosmic microwave background and 2dFGRS power spectra     

Will J. Percival  Will Sutherland  John A. Peacock  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Stephen Moody  Peder Norberg  Bruce A. Peterson  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,337(3):1068-1080

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