We present a detailed clustering analysis of a large K-band selected local galaxy sample,which is constructed from the 2MASS and the SDSS and consists of 82 486 galaxies with 10 < K < 13.5 and 0.01 < z < 0.1.The two-point correlation function of the magnitude-limited sample in real space at small scales is well described by the power law ξ(r) =(r/6.44 ± 0.23)-1.81±0.02.The pairwise velocity dispersion is derived from the anisotropic two-point correlation function and we find the dispersion σ12 = 685 ± 17 km s-1 if scale invariance is assumed,which is larger than values measured in the optical bands of the selected galaxy samples.We further investigate the dependence of the two-point correlation function and the σ12 on the g-r color and the K-band luminosity,and obtain similar results to previous works in optical bands.Comparing a mock galaxy sample with our real data indicates that the semi-analytical model cannot mimic the σ12 in observation,although it can approximate the two-point correlation function within measurement uncertainties.
Bin MaKe-Lai MengJun PanJia-Sheng HuangLong-Long Feng
除大气外,海洋对Chandler摆动具有重要的激发作用.利用Estimating the Circulation and Climate of the Ocean(ECCO)的海洋环流模式提供的流速场和洋底压力场资料,首次系统地研究了1980—2005年期间,太平洋、印度洋和大西洋对Chandler摆动激发的贡献.研究表明三大洋对Chandler摆动激发的贡献各不相同,太平洋激发能量约占观测激发能量的22.2%,在三大洋中最高,印度洋约占12.7%,大西洋最低,占7.1%左右.太平洋对Chandler摆动的激发能量可能受1982—1983年强ENSO事件的影响而显著提高.
Physical processes involving baryons could leave a non-negligible imprint on the distribution of cosmic matter.A series of simulated data sets at high resolution with identical initial conditions are employed for count-in-cell analysis,including one N-body pure dark matter run,one with only adiabatic gas and one with dissipative processes.Variances and higher order cumulants Sn of dark matter and gas are estimated.It is found that physical processes with baryons mainly affect distributions of dark matter at scales less than 1 h-1 Mpc.In comparison with the pure dark matter run,adiabatic processes alone strengthen the variance of dark matter by～10%at a scale of 0.1 h-1 Mpc,while the Sn parameters of dark matter only mildly deviate by a few percent.The dissipative gas run does not differ much from the adiabatic run in terms of variance for dark matter,but renders significantly different Sn parameters describing the dark matter,bringing about a more than 10%enhancement to S3 at 0.1 h-1 Mpc and z=0 and being even larger at a higher redshift.Distribution patterns of gas in two hydrodynamical simulations are quite different.Variance of gas at z=0 decreases by～30%in the adiabatic simulation but by～60%in the nonadiabatic simulation at 0.1 h-1 Mpc.The attenuation is weaker at larger scales but is still obvious at～10 h-1 Mpc.Sn parameters of gas are biased upward at scales <～4 h-1 Mpc,and dissipative processes show an～84%promotion at z=0 to S3 at 0.1 h-1 Mpc in contrast with the～7%change in the adiabatic run.The segregation in clustering between gas and dark matter could have dramatic implications on modeling distributions of galaxies and relevant cosmological applications demanding fine details of matter distribution in a strongly nonlinear regime.
