2020 Fiscal Year Research-status Report
An Independent Test of the Hubble Constant Tension with Time-Delay Cosmography
| Project/Area Number |
20K14511
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Wong Kenneth 東京大学, カブリ数物連携宇宙研究機構, 特任研究員 (00794207)
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| Project Period (FY) |
2020-04-01 – 2022-03-31
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| Keywords | gravitational lensing / cosmology / extragalactic astronomy |
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| Outline of Annual Research Achievements |
In FY2020, I have had one refereed journal paper published as the corresponding author (Wong et al. 2020, MNRAS, 498, 1420), which has already received over 400 citations. I have also been co-author on 13 additional publications.
I primarily worked on the TDCOSMO project to measure the Hubble Constant (H0) using strong gravitational lensing time delays. I particular, I worked on lens modeling of the lensed quasar system WGD 2038-4008. I am leading one of two independent teams to predict the time delay of this lens (which has not yet been measured but is currently being monitored) using both a power-law and composite (stars+dark matter) model. The purpose of having two independent teams model this system is to evaluate systematic uncertainties associated with the choice of lens modeling codes and assumptions. At the moment, statistical uncertainties in the time-delay cosmography method are at a level where we are able to constrain H0 to a few percent, but systematic uncertainties are the primary limitation. This is a key test of one of the most important parts of the analysis, and will be submitted for publication shortly. I have also been awarded observing time on the Subaru telescope to measure redshifts of new lensed quasars.
I have also been co-chair of the Hyper Suprime Cam SSP Strong Lensing Working Group. We have published several papers with hundreds of newly-discovered strong lens candidates from the survey, and are in the process of obtaining redshifts for the most promising systems. We are also starting to explore machine learning-based lens search methods.
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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 |
I plan to finish my modeling of WGD 2038-4008 and co-author the paper as one of the two corresponding authors within the next few months. After finishing this project, there are two additional lensed quasars that will have preliminary models from a new automated pipeline being developed by a collaborator. I will conduct a more detailed modeling analysis of these in order to refine the results and make them usable for precision cosmology. This will probably be finished by the end of FY2021. I will also have observing time on the Subaru telescope in FY2021, and I will reduce and analyze the data obtained from these observations in order 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 intend to apply our existing methods to the full dataset once it is observed by the end of 2021. We are also developing multiple machine learning algorithms to supplement our current methods. I will also finish the analysis of a double source plane lens, the "Eye of Horus", using new environment spectroscopy from a collaborator. I will publish a preliminary lens model and analysis of the environment on this unique system.
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| Causes of Carryover |
Due to the travel restrictions imposed worldwide because of COVID-19, I have been unable to travel for collaboration meetings and conferences, which I had planned to do when I applied for funding. As a result, I have extra funds that have gone unused. If the travel restrictions are relaxed in FY2021, I intend to travel again for research purposes, but it is very difficult to predict right now.
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