2019 Fiscal Year Annual Research Report
The emergence of the supermassive black hole-galaxy mass relations at z > 1
| Project/Area Number |
18H01251
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SILVERMAN John 東京大学, カブリ数物連携宇宙研究機構, 准教授 (90573030)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | supermassive black holes / near-infrared / optical / galaxy evolution |
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| Outline of Annual Research Achievements |
The growth of supermassive black holes and their host galaxies are intimately linked which has important implications for astrophysics in general. Specifically, we are measuring the ratio of black hole mass and stellar mass of the host galaxy over a wide range of cosmic time (0.2 < z < 1.8) using the Hubble Space Telescope (HST) and the Hyper Suprime-Cam Strategic Survey Program (HSC-SSP). The host galaxy mass is determined by decomposing the rest-frame optical images into the quasar and host galaxy components using state-of-the-art analysis tools which carefully consider the influence of the instrumental point-spread function. In FY 2019 and 2020, we reported on the final results in four key studies (Ding et al. 2020a,b; Li et al. 2021 a,b). Two of these studies present the results of the decomposition including stellar masses, and structural properties of the host galaxies including their physical sizes for over 5000 quasars (0.2 < z < 0.8) from the HSC-SSP and 32 quasars at 1 < z < 2 using HST. These measurements demonstrate that supermassive black holes and their hosts maintain a constant mass ratio out to z ~ 1.8 thus indicating a co-evolutionary scenario. Interestingly, the scatter in the relation is also similar with cosmic time which can only be understood with black hole feedback affecting their host galaxies as supported by simulations.
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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
In FY2019, we included the sample of 5000 quasars at z < 1 that have optical imaging from the HSC-SSP. This allowed us to have a continuous sample from z~0.2 to z ~ 0.8 which improved upon the accuracy in the determination of the evolution rate of the ratio between black hole mass and galaxy stellar mass. We had to carry out extensive simulations to confirm the accuracy of the measurements and correct for any systematic offsets which were present for the faintest sources. To further understand the biases inherent in observation results, we had to construct a forward model of the sample which allowed us to correct for the additional biases. This was instrumental in deriving the intrinsic evolution rate. The extra work delayed the project by four months.
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| Strategy for Future Research Activity |
The publication of two key papers on supermassive black holes and their host galaxies (Li et al. 2021a, b) and an additional related effort by Kawinwanichakij et al. (2021) on the structural properties of the general galaxy population using the HSC-SSP are providing the data and measurements for two studies that further interpret the results. The first (Ding, Silverman et al.) compares the observational results from HSC and HST to a suite of state-of-the-art hydrodynamic simulations including MassiveBlack II, Illustris TNG and Horizon-AGN. This work will allow us to determine which simulations best match the evolutionary behavior of the mass ratio and its dispersion which can elucidate whether feedback from supermassive black holes is required. The second study (Silverman et al.) will examine the stellar masses and sizes of quasar hosts to compare with high redshift studies of the black hole mass - stellar velocity dispersion relation. This will put tight constraints on the development stage of their central mass concentration (i.e., bulge). Overall, we’ll have a comprehensive view of the relative growth between supermassive black holes and their host galaxies.
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