The geometric calibration of the Planck satellite using point-source observations     

D. L. Harrison  F. van Leeuwen 《Monthly notices of the Royal Astronomical Society》2005,364(4):1441-1450

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The extragalactic submillimetre population: predictions for the SCUBA Half-Degree Extragalactic Survey (SHADES)     

Eelco van Kampen  Will J. Percival  Miller Crawford  James S. Dunlop  Susie E. Scott  Neil Bevis  Seb Oliver  Frazer Pearce  Scott T. Kay  Enrique Gaztañaga  David H. Hughes  Itziar Aretxaga 《Monthly notices of the Royal Astronomical Society》2005,359(2):469-480

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A halo-based galaxy group finder: calibration and application to the 2dFGRS     

Xiaohu Yang  H. J. Mo  Frank C. van den Bosch  Y. P. Jing 《Monthly notices of the Royal Astronomical Society》2005,356(4):1293-1307

We use the halo occupation model to calibrate galaxy group finders in magnitude limited redshift surveys. Because, according to the current scenario of structure formation, galaxy groups are associated with cold dark matter (CDM) haloes, we make use of the properties of the halo population in the design of our group finder. The method starts with an assumed mass-to-light ratio to assign a tentative mass to each group. This mass is used to estimate the size and velocity dispersion of the underlying halo that hosts the group, which in turn is used to determine group membership (in redshift space). This procedure is repeated until no further changes occur in group memberships. We find that the final groups selected this way are insensitive to the mass-to-light ratio assumed. We use mock catalogues, constructed using the conditional luminosity function (CLF), to test the performance of our group finder in terms of completeness of true members and contamination by interlopers. Our group finder is more successful than the conventional friends-of-friends (FOF) group finder in assigning galaxies in common dark matter haloes to a single group. We apply our group finder to the 2-degree Field Galaxy Redshift Survey (2dFGRS) and compare the resulting group properties with model predictions based on the CLF. For the ΛCDM concordance cosmology, we find a clear discrepancy between the model and data in the sense that the model predicts too many rich groups. In order to match the observational results, we have to either increase the mass-to-light ratios of rich clusters to a level significantly higher than current observational estimates, or to assume  σ₈≃ 0.7  , compared with the concordance value of 0.9.  相似文献   

Detection of DCO+ in a circumstellar disk     

E.F. van Dishoeck  W.-F. Thi  G.-J. van Zadelhoff 《Astrophysics and Space Science》2003,285(3-4):691-698

We report the first detection of DCO⁺ in a circumstellar disk. The DCO⁺ J=5–4 line at 360.169 GHz is observed with the 15 m James Clerk Maxwell Telescope in the disk around the pre-main sequence star TW Hya. Together with measurements of the HCO⁺ and H¹³CO⁺ J=4–3 lines, this allows an accurate determination of the DCO⁺/HCO⁺ ratio in this disk. The inferred value of0.035±0.005 is close to that found in cold pre-stellar cores and is somewhat higher than that measured in the envelope around the low-mass proto star IRAS 16293-2422. It is also close to the DCN/HCN ratio obtained for pristine cometary material in the jet of comet Hale-Bopp. The observed DCO⁺/HCO⁺ ratio for TW Hya is consistent with theoretical models of disks which consider gas-phase fractionation processes within a realistic 2-D temperature distribution and which include the effects of freeze-out onto grains. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The α-Monocerotids meteor outburst: the cross section of a comet dust trail     

P. Jenniskens  G. Docters van Leeuwen 《Planetary and Space Science》1997,45(12):1649-1652

One minute counts obtained during the meteor outburst of α-Monocerotids on November 22, 1995, are analyzed in order to examine the possibility of filamentary structure in the stream profile. None is found. It is argued that far-comet type outbursts are due to the Earth's passage through the dust trail of a long period comet, thus offering a direct means of studying such comet dust trails. Hence, the meteor stream activity curve is the first accurate cross section of dust densities through a comet dust trail.  相似文献   

Observations of the Hubble Deep Field South with the Infrared Space Observatory– II. Associations and star formation rates     

Robert G. Mann  Seb Oliver  Ruth Carballo  Alberto Franceschini  Michael Rowan-Robinson  Alan F. Heavens  Maria Kontizas  David Elbaz  Anastasios Dapergolas  Evanghelos Kontizas  Gian Luigi Granato  Laura Silva  Dimitra Rigopoulou  J. Ignacio Gonzalez-Serrano  Aprajita Verma  Steve Serjeant  reas Efstathiou  Paul P. van der Werf 《Monthly notices of the Royal Astronomical Society》2002,332(3):549-574

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The universal mass accretion history of cold dark matter haloes     

Frank C.van den Bosch 《Monthly notices of the Royal Astronomical Society》2002,331(1):98-110

We use the extended Press–Schechter formalism to investigate the rate at which cold dark matter haloes accrete mass. We discuss the shortcomings of previous methods that have been used to compute the mass accretion histories of dark matter haloes, and present an improved method based on the N -branch merger tree algorithm of Somerville & Kolatt. We show that this method no longer suffers from inconsistencies in halo formation times, and compare its predictions with high-resolution N -body simulations. Although the overall agreement is reasonable, there are slight inconsistencies which are most easily interpreted as a reflection of ellipsoidal collapse (as opposed to spherical collapse assumed in the Press–Schechter formalism). We show that the average mass accretion histories follow a simple, universal profile, and we present a simple recipe for computing the two scale-parameters which is applicable to a wide range of halo masses and cosmologies. Together with the universal profiles for the density and angular momentum distributions of cold dark matter haloes, these universal mass accretion histories provide a simple but accurate framework for modelling the structure and formation of dark matter haloes. In particular, they can be used as a backbone for modelling various aspects of galaxy formation where one is not interested in the detailed effects of merging. As an example we use the universal mass accretion history to compute the rate at which dark matter haloes accrete mass, which we compare with the cosmic star formation history of the Universe.  相似文献   

The cosmic distance scale     

Sidney van den Bergh 《Astronomy and Astrophysics Review》1989,1(2):111-139

Summary The status of the cosmic distance scale problem in early 1989 is reviewed. Internally consistent distances to Local Group galaxies are given in Tables 5 and 6. Within the Local Group the distance scale is found to be 11±5% smaller than that previously adopted by Sandage and Tammann. Distances to nearby galaxies are used as stepping stones to the Virgo cluster. The interpretation of the Tully-Fisher observations of Virgo spirals is found to be ambiguous because it is not yet clear which spirals are cluster members and which are background objects. Distance estimates of the Virgo cluster obtained by different techniques are listed in Table 11. The distance modulus of the Virgo cluster is found to be 31.5±0.2, corresponding to a distance of 20±2 Mpc. The elliptical galaxies in the core of the Virgo cluster haveV ₀=1200±46 kms^–1, which corresponds toV _LG=1082±48 km s^–1. With an infall velocity of 250±50 km s^–1 this yields a cosmological redshiftV=1332±69 km s^–1, from which a Hubble parameter H₀=67±8 km s^–1 Mpc^–1 is obtained. Space Telescope observations of distant Cepheids, Tully-Fisher observations of spirals in the Hercules eluster, and interference filter observations of Virgo planetary nebulae in the light of [O_III], should soon result in a major improvement in the accuracy with which H₀ is known.  相似文献   

The SCUBA HAlf Degree Extragalactic Survey – III. Identification of radio and mid-infrared counterparts to submillimetre galaxies     

R. J. Ivison  T. R. Greve  J. S. Dunlop  J. A. Peacock  E. Egami  Ian Smail  E. Ibar  E. van Kampen  I. Aretxaga  T. Babbedge  A. D. Biggs  A. W. Blain  S. C. Chapman  D. L. Clements  K. Coppin  D. Farrah  M. Halpern  D. H. Hughes  M. J. Jarvis  T. Jenness  J. R. Jones  A. M. J. Mortier  S. Oliver  C. Papovich  P. G. Pérez-González  A. Pope  S. Rawlings  G. H. Rieke  M. Rowan-Robinson  R. S. Savage  D. Scott  M. Seigar  S. Serjeant  C. Simpson  J. A. Stevens  M. Vaccari  J. Wagg  C. J. Willott 《Monthly notices of the Royal Astronomical Society》2007,380(1):199-228

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Dynamic neural networks with data assimilation     

Henk van den Boogaard  Arthur Mynett 《水文研究》2004,18(10):1959-1966

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