Research on the Galaxies Distribution in the Large-Scale Structure and Data-Integrated Access Service in the Virtual Observatory

Haijun Tian
2014 Publications of the Astronomical Society of the Pacific  
The thesis includes three parts: (1) redshift-space distortions on baryon acoustic oscillations (Tian et al. 2011); (2) spectroscopic target selection for extragalactic survey; and (3) design and implementation of job scheduling of Virtual Observatory Data Access System (VO-DAS). The peculiar velocities of galaxies distort the redshift space by the effect of linear squashing at large scales and the nonlinear effect named the "fingers-of-God" at small scales (Jackson 1972) . Through the linear
more » ... eory correlation function and its covariance, we predict the effect of compression at large scale will amplify and sharpen the baryon acoustic oscillations (BAO) feature near the line of sight (LOS). However, this effect becomes much weaker far from the LOS. In addition, the compression pushes the correlation function toward negative values along the LOS, and toward positive values in the transverse. This suggests the linear effect of the distortion contributes to the BAO, especially in the LOS. To validate our predictions, we constructed two kinds of simulations: one is extracted from the Millennium Simulation (MS) with small volume (500 Mpc h À1 ) and high resolution (2 Mpc h À1 ); the other is a suite of 100 particle-mesh (PM) dark-matter simulations with large volume (1 Gpc h À1 ) and low resolution (4 Mpc h À1 ). Splitting the sample into two-dimensional (2D) slices with various rotations, we investigated the 2D correlation functions in three situations: the real space, linear redshift space, the mixed linear and nonlinear redshift space, respectively. The results proved the existence of the sharpening and amplifying effects in the linear case, but the nonlinear distortion blurs all the features on the correlation function, even far from the LOS. This indicates that only the linear distortion can improve the BAO detection, and the nonlinear distortion is harmful. Finally, we analyzed the SDSS DR7 main-galaxy sample (MGS; Strauss et al. 2002) , splitting the sample into slices 2.5°on the sky in various rotations. Measuring 2D correlation functions in each slice, we see a sharp bump along the LOS. Using Mexican-hat wavelets, we localized it to ð110 AE 10Þ h À1 Mpc. At a particular wavelet scale and location, employing the variance of the wavelet transform, we estimated its significance at about 4σ. We also estimated that there is about a 0.2% chance of getting such a signal anywhere in the vicinity of the BAO scale from a power spectrum lacking a BAO feature. The small volume of SDSS MGS will lead to a large uncertainty in the measurement of BAO, since the error is inverse proportional to the square root of the sample volume. The need for more accurate measurement is driving the larger survey. The Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) in China can achieve a bigger redshift survey. The second part of thesis built two methods to select the targets, e.g., 4000 Å and Lyman break techniques. The former method is suitable for the early-type luminous red galaxies (LRGs; Eisenstein et al. 2001 ) and the latter for the late-type emission line galaxies (ELGs; Drinkwater et al. 2010) . With these methods, we finally constructed a sample of ∼500; 000 targets for the LAMOST commissioning. In the third part, we proposed and implemented a platform to integrate the astronomical resources to astronomers' fingertips, e.g., the Virtual Observatory Data Access System (VO-DAS). The advantages of the system are taken on several applications on the astronomical researches.
doi:10.1086/679565 fatcat:fjl6m3vylfeepayivuw7vcsf5q