ULTIMATE-Subaru ~ 究極のすばるへ ~

Japanese

For scientists

ULTIMATE-Subaru Overview for Scientists

ULTIMATE-Subaru is a project to develop a next-generation, wide-field adaptive optics (GLAO) system for the Subaru Telescope and to develop wide-field NIR instruments assisted by GLAO to maximize the NIR observational capabilities of Subaru in 2020s. Our simulations predict that Maunakea is ideally suited for GLAO and we can achieve FWHM=0.2-arcsec over ~20-arcmin in diameter at the median conditions in K-band. The ULTIMATE team has been discussing with the science community on the instrument plan since the launch of the project, and we concluded that the wide-field imager (WFI) received the highest scientific demands as the new/first instrument for ULTIMATE. Following the recommendations from the Project Definition Review in February 2016 and the Conceptual Design Review for ULTIMATE GLAO system in October 2018, we decided to take a “phased” approach to complete the ULTIMATE project:

Phase-1 (FY2025-): Complete the development of GLAO system by FY2025, and use MOIRCS (after its relocation to NsIR) as the first-light instrument for ULTIMATE. The goal of the ULTIMATE phase-1 (GLAO+MOIRCS) is to perform (1) pioneering science with GLAO imaging as preparatory work toward the ULTIMATE Phase-2, and (2) deep multi-object spectroscopy for high-redshift galaxies taking advantage of its enhanced sensitivity with GLAO.

Phase-2 (FY2027-): Complete the development of WFI by FY2027, and start a community-wide, SSP-class, large survey program by making full use of GLAO+WFI capabilities. The science team is developing the survey plan and strategy to maximize its science outputs. The unique advantages of ULTIMATE phase-2 are (1) narrow-band (NB), (2) medium-band (MB), and (3) broad-band K-band imaging with ~0.2-arcsec spatial resolution over the wide FoV. The plot here shows the K-band limiting magnitude and the survey area size of K-band imaging survey performed in the 21st centuty. By taking advantage of the wide FoV and enhanced sensitivity with GLAO, we can deliver unprecedentedly deep and wide imaging survey in K-band. Note that future wide-field infrared space telescopes (ESA's Euclid and NASA's Nancy Grace Roman Space Telescope) do not have sensitivity at λ>2um.

Adaptive Optics

ULTIMATE-Subaru Project is the combined effort of (1) the development of the Ground-Layor Adaptive Optics (GLAO) for Subaru, and (2) the planning and development of the next-generation instruments that will work with the GLAO. The first part (GLAO development) of the project was officially accepted as the NAOJ's "A" project in 2019.

According to our simulation, we expect to achieve FWHM=0.2-arcsec resolution in K-band in the moderate conditions of Maunakea. The histograms here show the probability distribution function of the image quality (in FWHM) in the case of natural seeing conditions (blue histogram) and in the case of GLAO (orange histogram), demonstrating a factor of ~2x improvement in the image quality.

The image here shows the 3-D design of the Wavefront Adapter Flange (WAF) for the GLAO. The development of the WAF starts from the NsIR platform by 2025, and subsequentlly to Cs in coordination with the Phase II timeline (below). We are also intensely working on the Laser Guide Star system, the Adaptive Secondary Mirror for GLAO, and the related systems.

Instruments

The second part of the project is the science instruments development. The GLAO for Subaru is expected to provide the median stellar FWHM of 0.2" to 0.3" over 14' FOV in K-band, which is the huge gain over the natural sky condition. We will prepare the instruments that can receive the benefit of GLAO to its maximum. We set three development phase (phase I -- III) for them.

Phase I Instrument -- MOIRCS and D-SHOOTER

The Phase 1 is the instrument for the GLAO performance verification. For the purpose, we will use MOIRCS by relocating it to the NsIR platform: visit the MOIRCS website for more detail about the detail of the instrument. Please note that the pixel scale of MOIRCS at NsIR platform will be changed to 0.105"/pix: the imaging field of view (FOV) will be 3'.6 × 6'.3, slightly smaller than the current size. The multi-object spectroscopy (MOS) function of MOIRCS will also be available, with the upgraded high-efficiency wide-band medium-resolution grisms. With the sharp image quality provided by the GLAO, we will enjoy the highest-sensitivity MOS spectroscopic performance among existing 8-10m class telescopes.

We are also planning to make the instrument called D-SHOOTER, the spectrograph that can simultaneously take data from optical to NIR. To make the D-SHOOTER the most powerful instrument among the similar one in the world, we are also planning to make a further upgrade to the GLAO hardware for D-SHOOTER so that we can even apply the AO correction to the optical wavelength using the technique called Laser Tomographic Adaptive Optics (LTAO). The LTAO technical feasibility project is already on-going under the collaboration with Tohoku University in Japan (the ULTIMATE-START project).

Phase II Instrument -- WFI

The Wide-Field Imager (WFI) will be the main GLAO instrument which fully make use of the benefit of the GLAO. The instrument has 14' × 14' FOV with the pixel sampling of 0.1"/pix (using 4 H4RG detectors). A suite of the broad-, medium-, narrow-band filters that are strategically designed will be available. The instrument will also allow the user filters. The WFI will be used as a workhorse instrument for a large imaging survey program.

The conceptual design study is intensely on-going. The image here shows the current sketch of the WFI optics (copyrighted by ULTIMATE team). The latest information and some more details about the specifications of the WFI is available here provided by K. Motohara et al.

Phase III Instrument -- Multi-IFU Instrument

As a final step of the instrument development, we are planning to have a powerful spectrograph which can pick up several targets from the wide FOV of the GLAO at Cs focus. A possible plan proposed is the fiber-fed deployable multi-Integral Field Uunit (IFU) system proposed by the Australian Astronomical Observatory. About 10 small IFUs, called STARBUG, will be moving around the surface of a glass plate on Cs to pick up targets. The light gathered by each STARBUG will be fed to the spectrograph via the high-throughput optical fibers. As there is no AO-corrected multi-IFU instrument in the world which can pick up targets across such a wide FOV of ULTIMATE-Subaru, it will be very powerful instrument for the spectroscopic survey of faint and relatively sparse objects such as clusters of young galaxies in the most distant universe.

The Phase III Instrument plan is still highly uncertain. We encourage YOU to propose your instrument for ULTIMATE-Subaru!!

Summary

Here is the summary of the preliminary instrument plan for ULTIMATE-Subaru.

Documentation

Publication
Study Reports
♣ Second Edition (version 2016/01/13)
　♦ Study report [PDF] (47 MB)
♣ First Edition (version 2012/08/07)
　♦ Study Report (Japanese only) [PDF] (28.5 MB)
　♦ Executive Summary (in English) [PDF] (55KB)
　♦ Executive Summary (in Japanese) [PDF] (690 KB)