| NSF Org: |
AST Division Of Astronomical Sciences |
| Recipient: |
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| Initial Amendment Date: | August 23, 2019 |
| Latest Amendment Date: | August 23, 2019 |
| Award Number: | 1910678 |
| Award Instrument: | Standard Grant |
| Program Manager: |
James Higdon
AST Division Of Astronomical Sciences MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | September 1, 2019 |
| End Date: | August 31, 2022 (Estimated) |
| Total Intended Award Amount: | $377,720.00 |
| Total Awarded Amount to Date: | $377,720.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
3720 S FLOWER ST FL 3 LOS ANGELES CA US 90033 (213)740-7762 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
University Park Campus SHS 371 Los Angeles CA US 90089-1342 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | EXTRAGALACTIC ASTRON & COSMOLO |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
The statistics of the peculiar velocity field of galaxy clusters (i.e., motions not related to expansion of the universe) are highly informative about the nature of dark matter, dark energy, and the theory of gravity. Currently, peculiar velocity measurements on large scales are limited to only the line-of-sight components of clusters, leaving most of the available information in the velocity field inaccessible to us. The yet-undetected transverse components can be traced through the cosmic microwave background (CMB) via two effects: (i) the Birkinshaw-Gull (BG) effect in CMB temperature, and (ii) the Kinetic Sunyaev-Zeldocivh (kSZ) effect in CMB polarization. In this research, we make a realistic assessment of the detectability of these signals with the near future CMB experiments, and also investigate the possibility of exploiting the statistics of these signals for cosmology. The PI will develop a creative educational product for K-12 students to promote awareness of and interest in physics and cosmology, in particular the physics of galaxy clusters and structure formation. K-12 teachers will be trained to use this educational product leveraging on existing relationships via the USC family of schools. The developed material will also be available online for all educators willing to download and use it.
The amplitude of both BG and kSZ effects are subdominant with respect to the primary CMB anisotropies and current instrumental noise levels. Aside from this, the signals can be confused with other emissions from within and outside the clusters, gravitational lensing effects, and uncertainties in clusters' physical description. Therefore, it is almost impossible to observe these effects for individual objects. Nevertheless, it is still possible to achieve a successful detection of them by employing novel statistical methods in the analysis of data. One example is to use pairwise statistical estimators which have been shown to significantly increase the detection signal-to-noise ratio. Throughout this project we will investigate the possibility of measuring these signals in the near future using the next generation of CMB surveys. We will provide forecast analyses through semi-analytical and numerical simulations of clusters and introduce proper map-filtering techniques and new statistical tools for this purpose. The current general interest in producing larger and deeper CMB surveys with improved intensity and polarization sensitivities makes this an appropriate time to further the study of peculiar velocities and inspect their cosmological implications.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This project focused the signatures of peculiar velocities in future CMB surveys.
We studied a number of implications of peculiar velocities, including non--gaussian signatures in the CMB maps, the gavitational moving lens effect, and the signatures in polarization of the Sunyaev-Zeldovich effect associated with galaxy clusters.
As for the peculiar motion of our own Galaxy:
We demonstrated that, with future high-resolution CMB experiments, it will be possible to attain a 10-to-20-sigma detection of the peculiar velocity of our own galaxy through the study of correlated harmonic modes. This provides an alternative venue to the use of the CMB dipole.
We also investigated the CMB bispectrum and trispectrum produced by the Galaxy peculiar velocitiy, and showed that it is not sufficiently prominent to bias non--gaussianity studies (induced by primordial perturbations). The non-gaussianity induced on the observation of extragalactic objects lie Sunyaev-Zeldovich clusters is also negligible.
We developed a fast, precise and efficient code for the boosting of the maps, which also properly takes into account the freqeuncy dependence of the signals to be boosted. Whenever possible, we compared it with other codes developed to this aim. We discuss pros and cons for each.
As for the moving lens detection and exploitation:
We developed Astropaint: a package aimed at painting any possible effect on a catalog of simulate halos with given location, distance, and mass. We used it to simulate the moving lens effect for future high resolution CMB experiments. We then created a set of correlated foreground maps, as well as lensed CMB, and studied to what extent the moving lens effect can actually be detected. We considered two methods: stacking and pairwise velocity determination. We determined the main source of limitation and the optimal mass/redshift cuts for all methods, for current and future experiments (CMB-S4, Simons Observatory, and CMB-HD).
We then proceeded to study the expected polarization signal in galaxy clusters at various redshifts. It is well known that the polarized Sunyaev-Zeldovich effect can be used to study the largest scales in the Universe as it conveys information on the CMB quadrupole at the location and redshift of a cluster.
We worked to create the first coherent simulations (of halos and CMB quadrupole at various redshifts) which allow to assess the detectability and exploitation of such signal in realistic setting. We are extending this work to include constraints relative to our own observed quadrupole, and the appropriate positioning of our Galaxy (which reduces the measurement possibilities).
As for broader impact:
We created a partnership with a group at EPFL (Switzerland) and contributed to develop a video for the general public, focusing on "scales in the Universe". The video, comprehensible by elementary school children, is now public. It can be found on youtube under the title: "Archaeology of Light - An Immersive Journey Through Space and Time".
Two USC postdocs, one graduate student and one undergraduate were involved in the activities described above.
Last Modified: 11/29/2022
Modified by: Elena Pierpaoli
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