分类: 天文学 >> 天文学 提交时间: 2023-12-25
摘要: The small-scale linear information in galaxy samples typically lost during non-linear growth can be restored to a certain level by the density field reconstruction, which has been demonstrated for improving the precision of the baryon acoustic oscillations (BAO) measurements. As proposed in the literature, a joint analysis of the power spectrum before and after the reconstruction enables an efficient extraction of information carried by high-order statistics. However, the statistics of the post#2;reconstruction density field are difficult to model. In this work, we circumvent this issue by developing an accurate emulator for the pre-reconstructed, post-reconstructed, and cross power spectra (Ppre, Ppost, Pcross) up to k = 0.5 h Mpc1 based on the Dark Quest N-body simulations. The accuracy of the emulator is at percent level, namely, the error of the emulated monopole and quadrupole of the power spectra is less than 1% and 5% of the ground truth, respectively. A fit to an example power spectra using the emulator shows that the constraints on cosmological parameters get largely improved using Ppre+Ppost+Pcross with kmax = 0.25 h Mpc1 , compared to that derived from Ppre alone, namely, the constraints on (Ωm, H0, 8) are tightened by 41% 55%, and the uncertainties of the derived BAO and RSD parameters (, , f8) shrink by 28% 54%, respectively. This highlights the complementarity among Ppre, Ppost and Pcross, which demonstrates the efficiency and practicability of a joint Ppre, Ppost and Pcross analysis for cosmological implications.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Dark Energy Spectroscopic Instrument (DESI) will construct a large and precise three-dimensional map of our Universe. The survey effective volume reaches $\sim20\Gpchcube$. It is a great challenge to prepare high-resolution simulations with a much larger volume for validating the DESI analysis pipelines. \textsc{AbacusSummit} is a suite of high-resolution dark-matter-only simulations designed for this purpose, with $200\Gpchcube$ (10 times DESI volume) for the base cosmology. However, further efforts need to be done to provide a more precise analysis of the data and to cover also other cosmologies. Recently, the CARPool method was proposed to use paired accurate and approximate simulations to achieve high statistical precision with a limited number of high-resolution simulations. Relying on this technique, we propose to use fast quasi-$N$-body solvers combined with accurate simulations to produce accurate summary statistics. This enables us to obtain 100 times smaller variance than the expected DESI statistical variance at the scales we are interested in, e.g. $k < 0.3\hMpc$ for the halo power spectrum. In addition, it can significantly suppress the sample variance of the halo bispectrum. We further generalize the method for other cosmologies with only one realization in \textsc{AbacusSummit} suite to extend the effective volume $\sim 20$ times. In summary, our proposed strategy of combining high-fidelity simulations with fast approximate gravity solvers and a series of variance suppression techniques sets the path for a robust cosmological analysis of galaxy survey data.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We investigate using three-point statistics in constraining the galaxy-halo connection. We show that for some galaxy samples, the constraints on the halo occupation distribution parameters are dominated by the three-point function signal (over its two-point counterpart). We demonstrate this on mock catalogs corresponding to the Luminous Red Galaxies (LRGs), Emission-Line Galaxies (ELG), and quasars (QSOs) targeted by the Dark Energy Spectroscopic Instrument (DESI) Survey. The projected three-point function for triangle sides less up to 20$h^{-1}$ Mpc measured from a cubic Gpc of data can constrain the characteristic minimum mass of the LRGs with a precision of $0.46$ %. For comparison, similar constraints from the projected two-point function are $1.55$ %. The improvements for the ELGs and QSOs targets are more modest. In the case of the QSOs it is caused by the high shot-noise of the sample, and in the case of the ELGs, this is caused by the range of halo masses of the host halos. The most time-consuming part of our pipeline is the measurement of the three-point functions. We adopt a tabulation method, proposed in earlier works for the two-point function, to reduce significantly the required compute time for the three-point analysis.