2017 Fiscal Year Research-status Report
The evolution of the stellar IMF with HSC strong lenses
| Project/Area Number |
17K14250
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Sonnenfeld Alex 東京大学, カブリ数物連携宇宙研究機構, 特任研究員 (40772827)
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | 100 new strong lenses / Stellar IMF |
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| Outline of Annual Research Achievements |
The main goal of this project is to use strong gravitational lensing to study the stellar initial mass function (IMF) of massive early-type galaxies out to redshift 1.The plan to achieve this goal consists in creating a large sample of strong lenses using photometric data from the Hyper Suprime-Cam (HSC) survey, following up the sample with spectroscopic observations, and using the sample of lenses to carry out a statistical study of the stellar IMF in the lens galaxies.
In FY2017, I discovered a sample of around 100 new lenses in HSC data. Roughly half of the lenses in this sample have been published, while the remaining half will be presented in a paper to be completed in FY2018. Thanks to the collaboration with Prof. Sherry Suyu, we have obtained spectra for 23 of these newly found lenses, using the instrument X-Shooter on VLT. This observational campaing was completed in February, and the spectra are now being analyzed.In parallel, I carried out a study of the stellar IMF of massive galaxies using a sample of known lenses at low redshfit, in combination with weak lensing measurements from HSC. The main result of this study, described in a paper recently submitted, is that the data is suggesting the presence of gradients in the stellar mass-to-light ratio of massive galaxies, which can be interpreted as gradients in the stellar IMF.
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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
I have obtained a large enough sample with all the necessary data to study the stellar IMF of massive galaxies at redshift around 0.5-0.5. Moreover, I have developed and tested a new statistical method for the combination of strong lensing measurements with weak lensing, according to the original plan.
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| Strategy for Future Research Activity |
The remaining steps for the completion of the project are combining all the data, carrying out the statistical measurement, and summarizing the results in a paper.The discovery of gradients in stellar mass-to-light ratio complicates the interpretation of strong lensing measurements, possibly limiting my ability to directly constrain the time evolution of the stellar IMF, which was the original goal of this research project. However, there is great interest among the extragalactic astronomy community in the issue of IMF gradients. The new sample of lenses from the HSC survey, due to the relatively high lens redshift, will allow to probe the IMF on larger scales compared to existing lens surveys, and therefore will enable me to investigate further how the stellar IMF varies spatially within individual galaxies.This is a very important question to answer in order to understand how massive galaxies form and evolve.
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| Causes of Carryover |
the reason is that the remaining amount from FY2017 is too small to be used to cover a purchase.
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[Journal Article] SDSS-IV MaNGA: The Spectroscopic Discovery of Strongly Lensed Galaxies2018
Author(s)
Talbot, Michael S.; Brownstein, Joel R.; Bolton, Adam S.; Bundy, Kevin; Andrews, Brett H.; Cherinka, Brian; Collett, Thomas E.; More, Anupreeta; More, Surhud; Sonnenfeld, Alessandro; Vegetti, Simona; Wake, David A.; Weijmans, Anne-Marie; Westfall, Kyle B.
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Journal Title
Monthly Notices of the Royal Astronomical Society
Volume: 477
Pages: 195-209
DOI
Peer Reviewed / Int'l Joint Research
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