Maximal compression of the redshift-space galaxy power spectrum and bispectrum
Maximal compression of the redshift-space galaxy power spectrum and bispectrum
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DOI：
10.1093/mnras/sty261
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发表时间：
2017-09
影响因子：
4.8
通讯作者：
D. Gualdi;M. Manera;B. Joachimi;O. Lahav
中科院分区：
文献类型：
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作者：
D. Gualdi;M. Manera;B. Joachimi;O. Lahav
我们探索了两种方法压缩红移空间星系功率谱和双谱相对于一组选定的宇宙学参数。这两种方法都涉及使用Karhunen-Lo 'eve算法将原始数据向量的维数（例如1000个元素）降低到所考虑的宇宙学参数的数量（例如7个）。在第一种情况下，我们在压缩数据向量上运行MCMC采样，以恢复1D和2D后验分布。第二种方法，大约快2000倍，在压缩前通过Fisher信息矩阵的对角化对参数空间进行正交化，无需MCMC采样即可获得后验分布。将这些方法用于未来的光谱红移调查，如DESI、Euclid和PFS，将大大减少计算精确协方差矩阵所需的模拟次数，同时减少约束功率的损失。我们考虑一个类似desi实验的红移箱。使用功率谱结合双谱作为数据矢量，两种压缩方法平均将68%可信区域分别恢复到标准MCMC采样结果的0.7%和2%以内。对于偏置参数b1、增长率f和标量振幅参数As，这些置信区间也比仅使用功率谱获得的置信区间分别小81%、80%和82%。
We explore two methods of compressing the redshift-space galaxy power spectrum and bispectrum with respect to a chosen set of cosmological parameters. Both methods involve reducing the dimension of the original data vector (e.g. 1000 elements) to the number of cosmological parameters considered (e.g. seven ) using the Karhunen–Lo`eve algorithm. In the first case, we run MCMC sampling on the compressed data vector in order to recover the 1D and 2D posterior distributions. The second option, approximately 2000 times faster, works by orthogonalizing the parameter space through diagonalization of the Fisher information matrix before the compression, obtaining the posterior distributions without the need of MCMC sampling. Using these methods for future spectroscopic redshift surveys like DESI, Euclid, and PFS would drastically reduce the number of simulations needed to compute accurate covariance matrices with minimal loss of constraining power. We consider a redshift bin of a DESI-like experiment. Using the power spectrum combined with the bispectrum as a data vector, both compression methods on average recover the 68 per cent credible regions to within 0.7 per cent and 2 per cent of those resulting from standard MCMC sampling, respectively. These confidence intervals are also smaller than the ones obtained using only the power spectrum by 81 per cent, 80 per cent, and 82 per cent respectively, for the bias parameter b1, the growth rate f, and the scalar amplitude parameter As.