分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jiming Chen
Shamik Ghosh
Hao Liu
Larissa Santos
Wenjuan Fang
Siyu Li
Yang Liu
Hong Li
Jiaxin Wang
Le Zhang
Bin Hu
Wen Zhao
摘要： Constructing a fast and efficient estimator for the B-mode power spectrum of cosmic microwave background (CMB) is of critical importance for CMB science. For a general CMB survey, the Quadratic Maximum Likelihood (QML) estimator for CMB polarization has been proved to be the optimal estimator with minimal uncertainties, but it is computationally very expensive. In this article, we propose two new QML methods for B-mode power spectrum estimation. We use the Smith-Zaldarriaga approach to prepare pure-B mode map, and E-mode recycling method to obtain a leakage free B-mode map. We then use the scalar QML estimator to analyze the scalar pure-B map (QML-SZ) or B-mode map (QML-TC). The QML-SZ and QML-TC estimators have similar error bars as the standard QML estimators but their computational cost is nearly one order of magnitude smaller. The basic idea is that one can construct the pure B-mode CMB map by using the E-B separation method proposed by Smith-Zaldarriaga (SZ) or the one considering the template cleaning (TC) technique, then apply QML estimator to these scalar fields. By simulating potential observations of space-based and ground-based detectors, we test the reliability of these estimators by comparing them with the corresponding results of the traditional QML estimator and the pure B-mode pseudo-Cl estimator.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The spherical harmonic transform is a powerful tool in the analysis of spherical data sets, such as the cosmic microwave background data. In this work, we present a new scheme for the spherical harmonic transforms that supports both CPU and GPU computations, which is specially efficient on a large number of sky maps. By comparing our implementation with the standard Libsharp-HEALPix program, we demonstrate 2-10 times speedup for the CPU implementation, and up to 30 times speedup when a state-of-the-art GPU is employed. This new scheme's software package is available via an open source GitHub repository.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shamik Ghosh
Yang Liu
Le Zhang
Siyu Li
Junzhou Zhang
Jiaxin Wang
Jiazheng Dou
Jiming Chen
Jacques Delabrouille
Mathieu Remazeilles
Chang Feng
Bin Hu
Zhi-Qi Huang
Hao Liu
Larissa Santos
Pengjie Zhang
Zhaoxuan Zhang
Wen Zhao
Hong Li
Xinmin Zhang
摘要： AliCPT is the first Chinese cosmic microwave background (CMB) experiment which will make the most precise measurements of the CMB polarization in the northern hemisphere. The key science goal for AliCPT is the detection of primordial gravitational waves (PGWs). It is well known that an epoch of cosmic inflation, in the very early universe, can produce PGWs, which leave an imprint on the CMB in form of odd parity $B$-mode polarization. In this work, we study the performance of the component separation and parameter estimation pipelines in context of constraining the value of the tensor-to-scalar ratio. Based on the simulated data for one observation season, we compare five different pipelines with different working principles. Three pipelines perform component separation at map or spectra level before estimating $r$ from the cleaned spectra, while the other two pipelines performs a global fit for both foreground parameters and $r$. We also test different methods to account for the effects of time stream filtering systematics. This work shows that our pipelines provide consistent and robust constraints on the tensor-to-scalar ratio and a consistent sensitivity $\sigma(r) \sim 0.02$. This showcases the potential of precise $B$-mode polarization measurement with AliCPT-1. AliCPT will provide a powerful opportunity to detect PGWs, which is complementary with various ground-based CMB experiments in the southern hemisphere.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jiakang Han
Bin Hu
Shamik Ghosh
Siyu Li
Jiazheng Dou
Jacques Delabrouille
Jing Jin
Hong Li
Yang Liu
Mathieu Remazeilles
Wen Zhao
Pengjie Zhang
Zheng-Wei Li
Cong-Zhan Liu
Yong-jie Zhang
Chao-Lin Kuo
Xinmin Zhang
摘要： Cosmic microwave background radiation (CMB) observations are unavoidably contaminated by emission from various extra-galactic foregrounds, which must be removed to obtain reliable measurements of the cosmological signal. In this paper, we demonstrate CMB lensing reconstruction in AliCPT-1 after foreground removal, combine the two bands of AliCPT-1 (90 and 150~GHz) with Planck HFI bands (100, 143, 217 and 353~GHz) and with the WMAP-K band (23~GHz). In order to balance contamination by instrumental noise and foreground residual bias, we adopt the Needlet Internal Linear Combination (NILC) method to clean the E-map and the constrained Internal Linear Combination (cILC) method to clean the B-map. The latter utilizes additional constraints on average frequency scaling of the dust and synchrotron to remove foregrounds at the expense of somewhat noisier maps. Assuming 4 modules observing 1 season from simulation data, the resulting effective residual noise in E- and B-map are roughly $15~\mu{\rm K}\cdot{\rm arcmin}$ and $25~\mu{\rm K}\cdot{\rm arcmin}$, respectively. As a result, the CMB lensing reconstruction signal-to-noise ratio (SNR) from polarization data is about SNR$\,\approx\,$4.5. This lensing reconstruction capability is comparable to that of other stage-III small aperture millimeter CMB telescopes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jiakang Han
Bin Hu
Shamik Ghosh
Siyu Li
Jiazheng Dou
Jacques Delabrouille
Jing Jin
Hong Li
Yang Liu
Mathieu Remazeilles
Wen Zhao
Pengjie Zhang
Zheng-Wei Li
Cong-Zhan Liu
Yong-jie Zhang
Chao-Lin Kuo
Xinmin Zhang
摘要： Cosmic microwave background radiation (CMB) observations are unavoidably contaminated by emission from various extra-galactic foregrounds, which must be removed to obtain reliable measurements of the cosmological signal. In this paper, we demonstrate CMB lensing reconstruction in AliCPT-1 after foreground removal, combine the two bands of AliCPT-1 (90 and 150~GHz) with Planck HFI bands (100, 143, 217 and 353~GHz) and with the WMAP-K band (23~GHz). In order to balance contamination by instrumental noise and foreground residual bias, we adopt the Needlet Internal Linear Combination (NILC) method to clean the E-map and the constrained Internal Linear Combination (cILC) method to clean the B-map. The latter utilizes additional constraints on average frequency scaling of the dust and synchrotron to remove foregrounds at the expense of somewhat noisier maps. Assuming 4 modules observing 1 season from simulation data, the resulting effective residual noise in E- and B-map are roughly $15~\mu{\rm K}\cdot{\rm arcmin}$ and $25~\mu{\rm K}\cdot{\rm arcmin}$, respectively. As a result, the CMB lensing reconstruction signal-to-noise ratio (SNR) from polarization data is about SNR$\,\approx\,$4.5. This lensing reconstruction capability is comparable to that of other stage-III small aperture millimeter CMB telescopes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jinyi Liu
Zeyang Sun
Jiakang Han
Julien Carron
Jacques Delabrouille
Siyu Li
Yang Liu
Jing Jin
Shamik Ghosh
Bin Yue
Pengjie Zhang
Chang Feng
Zhi-Qi Huang
Hao Liu
Yi-Wen Wu
Le Zhang
Zi-Rui Zhang
Wen Zhao
Bin Hu
Hong Li
摘要： AliCPT-1 is the first Chinese CMB experiment aiming for high precision
measurement of Cosmic Microwave Background B-mode polarization. The telescope,
currently under deployment in Tibet, will observe in two frequency bands
centered at 90 and 150 GHz. We forecast the CMB lensing reconstruction,
lensing-galaxy as well as lensing-CIB (Cosmic Infrared Background) cross
correlation signal-to-noise ratio (SNR) for AliCPT-1. We consider two stages
with different integrated observation time, namely "4 module*yr" (first stage)
and "48 module*yr" (final stage). For lensing reconstruction, we use three
different quadratic estimators, namely temperature-only, polarization-only and
minimum-variance estimators, using curved sky geometry. We take into account
the impact of inhomogeneous hit counts as well as of the mean-field bias due to
incomplete sky coverage. In the first stage, our results show that the 150 GHz
channel is able to measure the lensing signal at $15\sigma$ significance with
the minimum-variance estimator. In the final stage, the measurement
significance will increase to $31\sigma$. We also combine the two frequency
data in the harmonic domain to optimize the SNR. Our result show that the
coadding procedure can significantly reduce the reconstruction bias in the
multiple range l>800. Thanks to the high quality of the polarization data in
the final stage of AliCPT-1, the EB estimator will dominate the lensing
reconstruction in this stage. We also estimate the SNR of cross-correlations
between AliCPT-1 CMB lensing and other tracers of the large scale structure of
the universe. For its cross-correlation with DESI galaxies/quasars, we report
the cross-correlation SNR = 10-20 for the 4 redshift bins at 0.05
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The spherical harmonic transform is a powerful tool in the analysis of spherical data sets, such as the cosmic microwave background data. In this work, we present a new scheme for the spherical harmonic transforms that supports both CPU and GPU computations, which is specially efficient on a large number of sky maps. By comparing our implementation with the standard Libsharp-HEALPix program, we demonstrate 2-10 times speedup for the CPU implementation, and up to 30 times speedup when a state-of-the-art GPU is employed. This new scheme's software package is available via an open source GitHub repository.
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