| Project/Area Number |
20K14511
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 16010:Astronomy-related
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| Research Institution | National Astronomical Observatory of Japan (2021-2022)
The University of Tokyo (2020) |
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Principal Investigator |
Wong Kenneth 国立天文台, ハワイ観測所, 特任研究員 (00794207)
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| Project Period (FY) |
2020-04-01 – 2024-03-31
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| Project Status |
Granted (Fiscal Year 2022)
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| Budget Amount *help |
¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2021: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Keywords | gravitational lensing / cosmology / extragalactic astronomy / astrophysics |
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| Outline of Research at the Start |
My research uses strong gravitational lensing, a phenomenon where the gravity of a massive galaxy creates multiple images of a background object, to measure the expansion rate of the Universe. There is a growing discrepancy between different measurements of this expansion rate, depending on whether the measurement comes from observations of the early Universe (just after the Big Bang) or the late Universe (closer to the present time). Gravitational lensing provides an independent late-Universe measurement, and thus is a crucial test of whether this discrepancy may lead to new physics.
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| Outline of Annual Research Achievements |
In FY2022, I have had a refereed journal paper accepted for publication as the corresponding author (Wong et al. 2022, PASJ, 74, 1209), and I was one of the two primary authors of another accepted journal paper (Shajib et al. 2022, A&A, 667, 123). I was the second author on another submitted publication (Chan et al. 2023, MNRAS, submitted; arXiv:2304.05425).
I primarily worked on the TDCOSMO project to measure the Hubble Constant (H0) using strong gravitational lensing time delays. I was one of two independent teams that modeled the lensed quasar system WGD 2038-4008, with the goal of evaluating systematic uncertainties associated with the choice of lens modeling codes. Our results (Shajib et al. 2022) show that the predicted time delays between the teams agree to within ~1-sigma. I also obtained spectroscopy using the Subaru telescope to measure redshifts of four lensed quasar galaxies to make these useful for cosmology in the future as part of the TDCOSMO sample.
I am co-chair of the Hyper Suprime Cam SSP Strong Lensing Working Group. We have discovered hundreds of newly discovered strong lens candidates from the survey to date. I led a lens search through the latest HSC SSP data release (Wong et al. 2022) and discovered tens of new galaxy-scale lens candidates. I also mentored an undergraduate student, Yuichiro Ishida (Kyushu University), to develop a convolutional neural network (CNN) to search for lenses in HSC data. We will be on an upcoming publcation that compares the performance of different CNNs on a common test dataset (More et al., in preparation).
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
My research has been progressing at about the rate expected. Since I am working in international collaborations, the projects as a whole have been moving forward thanks to the efforts of both myself and other researchers, and we are continuously publishing new results and obtaining observing time on large telescopes. There have been minor delays in certain aspects of the various projects, but overall, the research is progressing at a reasonable pace.
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| Strategy for Future Research Activity |
As part of TDCOSMO, I am doing a detailed model of the gravitational lens DESJ0029-3814. A collaborator of mine has developed an automated pipeline
for preliminary modeling, and I will conduct a more refined analysis of this lens in order to make it usable for precision cosmology. I also am leading one of two teams modeling the lensed double-quasar, J1721+8842. Both of these new systems will provide additional constraints on H0 as part of the TDCOSMO sample. I will also continue to apply for observing time on the Subaru telescope in FY2023, to determine redshifts of several lensed quasars. These redshifts can then be used to analyze these systems in more detail for cosmological inference.
The HSC SSP Strong Lensing Working Group is continuing to develop new search methods for lenses in the survey data. I am continuing to work with undergraduate student Yuichiro Ishida (Kyushu University) on exploring CNNs for strong lens-finding when applying a lens-light subtraction step during preprocessing to see if this can improve the performance of the network. Yuichiro will lead a publication under my supervision detailing this work, which we hope to submit in FY2023.
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