すばるHSCによる高速固有運動の測定に基づくコンパクト天体の研究

2022 Fiscal Year Annual Research Report

• Project/Area Number: 22J11959
• Allocation Type: Single-year Grants
• Research Institution: The University of Tokyo
• Principal Investigator: 邱 天 東京大学, 理学系研究科, 特別研究員(DC2)
• Project Period (FY): 2022-04-22 – 2024-03-31
• Keywords: White dwarf / Proper motion / Star forming history / Luminosity function

Outline of Annual Research Achievements

I have taken advantage of the Subaru Telescope, Hyper-Supreme Cam (HSC) to make precise proper motion measurements to explore those faint and high proper motion objects, combining with the Sloan Digital Sky Survey (SDSS). I have established a white dwarf catalogue by applying the reduced proper motion diagram to separate the white dwarf from the main-sequence stars. A black-body spectroscopic fitting has also been adopted to make validation and derive the temperature of white dwarfs, especially the low-temperature ones which can hardly be fitted with white dwarfs H/He models.
I have find a lot of extremely low-temperature white dwarf candidates lower than 5,000K. They are supposed to be the oldest population of stars, the fossil of our Milky Way Galaxy. We can measure the property of the white dwarfs to probe the information of the early time of the Galaxy. Besides, we can perfect the white dwarf cooling model at the red end.
Based on the white dwarf catalogue, I have made the white dwarf luminosity function (WDLF), which has been developed to recover the age and star formation history, such as that star burst will appear as a bump in the WDLF. Our WDLF shows a potential to include the intrinsic faint white dwarfs which has never been discovered in previous work.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

I have finished my work following the plan properly. The slightly change of the plan is due to that we have not obtained the time for spectroscopic observation to confirm our white dwarf candidates. So I have tried to make the white dwarf luminosity function instead, which is a more statistical way to study the white dwarfs rather than to probe the individual interesting objects.

Strategy for Future Research Activity

The following work is still on white dwarfs, I will try to probe the information from our white dwarf luminosity function. The star forming history is one of the most interesting destinations. We can trace the property of the stars in the early age. If we can confirm the low-temperature white dwarfs, I can support the data evidence to perfect the current white dwarf models for the oldest ones. The halo white dwarfs are also a good sample to study which are easier to distinguish from others due to the high proper motion, if we can find a coherent motion and similar properties such as metallicity. If it is possible, I am also planning to probe individual white dwarf with abnormal behaviours, such as weird motion, etc.