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Title: Improving small-scale CMB lensing reconstruction

Abstract

Over the past decade, the gravitational lensing of the Cosmic Microwave Background (CMB) has become a powerful tool for probing the matter distribution in the Universe. The standard technique used to reconstruct the CMB lensing signal employs the quadratic estimator (QE) method, which has recently been shown to be suboptimal for lensing measurements on very small scales in temperature and polarization data. We implement a simple, more optimal method for the small-scale regime, which involves taking the direct inverse of the background gradient. We derive new techniques to make continuous maps of lensing using this "Gradient-Inversion" (GI) method and validate our method with simulated data, finding good agreement with predictions. For idealized simulations of lensing cross- and autospectra that neglect foregrounds, we demonstrate that our method performs significantly better than previous quadratic estimator methods in temperature; at $L=5000-9000$, it reduces errors on the lensing auto-power spectrum by a factor of $$\sim 4$$ for both idealized CMB-S4 and Simons Observatory-like experiments and by a factor of $$\sim 2.6$$ for cross-correlations of CMB-S4-like lensing reconstruction and the true lensing field. Finally, we caution that the level of the neglected small-scale foreground power, while low in polarization, is very high in temperature; though we briefly outline foreground mitigation methods, further work on this topic is required. Nevertheless, our results show the future potential for improved small-scale CMB lensing measurements, which could provide stronger constraints on cosmological parameters and astrophysics at high redshifts.

Authors:
ORCiD logo [1];  [2];  [3];  [4]
  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Univ. of Cambridge (United Kingdom)
  2. Univ. of Cambridge (United Kingdom)
  3. Princeton Univ., NJ (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1616086
Alternate Identifier(s):
OSTI ID: 1562597
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 100; Journal Issue: 2; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; cosmic microwave background; large scale structure of the universe

Citation Formats

Hadzhiyska, Boryana, Sherwin, Blake D., Madhavacheril, Mathew, and Ferraro, Simone. Improving small-scale CMB lensing reconstruction. United States: N. p., 2019. Web. https://doi.org/10.1103/PhysRevD.100.023547.
Hadzhiyska, Boryana, Sherwin, Blake D., Madhavacheril, Mathew, & Ferraro, Simone. Improving small-scale CMB lensing reconstruction. United States. https://doi.org/10.1103/PhysRevD.100.023547
Hadzhiyska, Boryana, Sherwin, Blake D., Madhavacheril, Mathew, and Ferraro, Simone. Mon . "Improving small-scale CMB lensing reconstruction". United States. https://doi.org/10.1103/PhysRevD.100.023547. https://www.osti.gov/servlets/purl/1616086.
@article{osti_1616086,
title = {Improving small-scale CMB lensing reconstruction},
author = {Hadzhiyska, Boryana and Sherwin, Blake D. and Madhavacheril, Mathew and Ferraro, Simone},
abstractNote = {Over the past decade, the gravitational lensing of the Cosmic Microwave Background (CMB) has become a powerful tool for probing the matter distribution in the Universe. The standard technique used to reconstruct the CMB lensing signal employs the quadratic estimator (QE) method, which has recently been shown to be suboptimal for lensing measurements on very small scales in temperature and polarization data. We implement a simple, more optimal method for the small-scale regime, which involves taking the direct inverse of the background gradient. We derive new techniques to make continuous maps of lensing using this "Gradient-Inversion" (GI) method and validate our method with simulated data, finding good agreement with predictions. For idealized simulations of lensing cross- and autospectra that neglect foregrounds, we demonstrate that our method performs significantly better than previous quadratic estimator methods in temperature; at $L=5000-9000$, it reduces errors on the lensing auto-power spectrum by a factor of $\sim 4$ for both idealized CMB-S4 and Simons Observatory-like experiments and by a factor of $\sim 2.6$ for cross-correlations of CMB-S4-like lensing reconstruction and the true lensing field. Finally, we caution that the level of the neglected small-scale foreground power, while low in polarization, is very high in temperature; though we briefly outline foreground mitigation methods, further work on this topic is required. Nevertheless, our results show the future potential for improved small-scale CMB lensing measurements, which could provide stronger constraints on cosmological parameters and astrophysics at high redshifts.},
doi = {10.1103/PhysRevD.100.023547},
journal = {Physical Review D},
number = 2,
volume = 100,
place = {United States},
year = {2019},
month = {7}
}

Journal Article:

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Cited by: 1 work
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Figures / Tables:

FIG. 1 FIG. 1: Map of the input (upper panel) and the GI-reconstructed convergence field (center panel), as well as the magnitude of the temperature gradient (lower panel) for a simulated small patch (1.707 x 1.707 deg2) of a CMB temperature ultra-low noise experiment with very bright galaxy clusters to better illustratemore » the reconstruction. A Wiener filter has been applied to the first two. A correlation between the convergence field maps is noticeable by eye as well corresponding to the regions where the magnitude of the gradient is largest.« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.