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Mock 2dF and SDSS galaxy redshift surveys 总被引:1,自引:0,他引:1
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The Effect of Central Baryonic Cores in Dark Halos on the Evaluation of Strong Lensing Probabilities
Jie WangNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2004,4(1):10-16
We present an estimate of the strong lensing probability by dark halos, with emphasis on the role of the baryonic matter arising purely from radiative cooling. We treat the contribution of the cooled baryons optimistically with all the cooled baryons confined within a central core, and including no feedback process from stellar evolution. Our two-component model provides a strong lensing probability that is in good agreement with the observed distribution of multiple images of quasars, provided that the cooled baryons are deposited within a spherical region of radius of 0.1 times the virial radius and follow an isothermal profile. It is pointed out that strong lensing may be used as an additional probe‘of baryon physics in dark halos though this may meanwhile complicate the test of the inner density profiles of dark matter in halos using the observed strong lensing probability. 相似文献
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Kyle T. Alfriend Srinivas R. Vadali Hanspeter Schaub 《Celestial Mechanics and Dynamical Astronomy》2001,81(1-2):57-62
Satellites flying in formation is a concept being pursued by the Air Force and NASA. Potential periodic formation orbits have been identified using Hill's (or Clohessy Wiltshire) equations. Unfortunately the gravitational perturbations destroy the periodicity of the orbits and control will be required to maintain the desired orbits. Since fuel will be one of the major factors limiting the system lifetime it is imperative that fuel consumption be minimized. To maximize lifetime we not only need to find those orbits which require minimum fuel we also need for each satellite to have equal fuel consumption and this average amount needs to be minimized. Thus, control of the system has to be addressed, not just control of each satellite. In this paper control of the individual satellites as well as the constellation is addressed from an astrodynamics perspective. 相似文献
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Uro Seljak † 《Monthly notices of the Royal Astronomical Society》2001,325(4):1359-1364
We analyse scale dependence of redshift-space bias b and β ≡ Ωm 0.6 / b in the context of the halo model. We show that linear bias is a good approximation only on large scales, for k <0.1 h Mpc−1 . On intermediate scales the virial motions of galaxies cause a suppression of the power spectrum relative to the linear one and the suppression differs from the same effect in dark matter. This can potentially mimic the effect of massive neutrinos, and the degeneracy can only be broken if the power spectrum is measured for k ≪0.1 h Mpc−1 . Different methods to determine β converge for k <0.1 h Mpc−1 , but give drastically different results on smaller scales, which explains some of the trends observed in the real data. We also assess the level of stochasticity by calculating the cross-correlation coefficient between the reconstructed velocity field divergence and the galaxies, and show that the two fields decorrelate for k >0.1 h Mpc−1 . Most problematic are galaxies predominantly found in groups and clusters, such as bright, red or elliptical galaxies, where we find poor convergence to a constant bias or β even on large scales. 相似文献