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A gravitational wave event, S190510g, which was classified as a binary-neutron-star coalescence at the time of preliminary alert, was detected by LIGO/Virgo collaboration on 2019 May 10. At 1.7 hours after the issue of its preliminary alert, we started a target-of-opportunity imaging observation in the Y band to search for its optical counterpart using the Hyper Suprime-Cam (HSC) on the Subaru Telescope. The observation covers a 118.8 deg2 sky area corresponding to $11.6\%$ confidence in the localization skymap released in the preliminary alert and $1.2\%$ in the updated skymap. We divided the observed area into two fields based on the availability of HSC reference images. For the fields with the HSC reference images, we applied an image subtraction technique; for the fields without the HSC reference images, we sought individual HSC images by matching a catalog of observed objects with the PS1 catalog. The search depth is 22.28 mag in the former method and the limit of search depth is 21.3 mag in the latter method. Subsequently, we performed visual inspection and obtained 83 candidates using the former method and 50 candidates using the latter method. Since we only have the one-day photometric data, we evaluated the probability of candidates being located inside the 3D skymap by estimating their distances with photometry of associated extended objects. We found three candidates are likely located inside the 3D skymap and concluded they could be a counterpart of S190510g, while most of the 133 candidates were likely to be supernovae because the number density of candidates was consistent with the expected number of supernova detections. By comparing our observational depth with a light-curve model of such a kilonova reproducing AT2017gfo, we show that early deep observations with the Subaru/HSC can capture the rising phase of the blue component of a kilonova at the estimated distance of S190510g (∼230 Mpc).

Post Extreme Adaptive-Optics (ExAO) spectro-interferometers design allows high contrast imaging with an inner working angle down to half the theoretical angular resolution of the telescope. This regime, out of reach for conventional ExAO imaging systems, is obtained thanks to the interferometric recombination of multiple sub-apertures of a single telescope, using single mode waveguides to remove speckle noise. The SCExAO platform at the Subaru telescope hosts two instruments with such design, coupled with a spectrograph. The FIRST instrument operates in the Visible (600-800nm, R~400) and is based on pupil remapping using single-mode fibers. The GLINT instrument works in the NIR (1450-1650nm, R~160) and is based on nulling interferometry. We present here how these photonic instruments have the unique capability to simultaneously do high contrast imaging and be included in the wavefront sensing architecture of SCExAO.

SCExAO at the Subaru telescope is a visible and near-infrared high-contrast imaging instrument employing extreme adaptive optics and coronagraphy. The instrument feeds the near-infrared light (JHK) to the integral-field spectrograph CHARIS. The spectropolarimetric capability of CHARIS is enabled by a Wollaston prism and is unique among high-contrast imagers. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. From measurements with the internal light source, we find that the image derotator (K-mirror) produces strongly wavelength-dependent crosstalk, in the worst case converting ~95% of the incident linear polarization to circularly polarized light that cannot be measured. Observations of an unpolarized star show that the magnitude of the instrumental polarization of the telescope varies with wavelength between 0.5% and 1%, and that its angle is exactly equal to the altitude angle of the telescope. Using physical models of the fold mirror of the telescope, the half-wave plate, and the derotator, we simultaneously fit the instrumental polarization effects in the 22 wavelength bins. Over the full wavelength range, our model currently reaches a total polarimetric accuracy between 0.08% and 0.24% in the degree of linear polarization. We propose additional calibration measurements to improve the polarimetric accuracy to

Professor Michitoshi Yoshida, who is based at Subaru Telescope of National Astronomical Observatory of Japan, is a lead scientist with J-GEM (the Japanese Collaboration for Gravitational- Wave Electro-Magnetic Follow-up) and throughout the course of his career in galactic study, has become increasingly interested in the active phenomena of the universe, such as gamma ray bursts (GRB). J-GEM is embarking on a research approach called multi-messenger astronomy, this method is based on the coordination between classical electromagnetic astronomy, new GW astronomy and particle astronomy, and is opening new opportunities for humans to investigate the Universe.

The choice of transmission grating can facilitate downsizing of a spectrograph and make it possible to achieve a perfect Littrow configuration. We are developing transmission gratings for next-generation instruments for the 8.2 m Subaru Telescope, the Thirty Meter Telescope (TMT), and other ground-based and space-borne telescopes. These include, a volume binary grating developed for an echelle grism (direct vision grating) for the Subaru Multi-Object InfraRed Camera and Spectrograph (MOIRCS); a reflector facet transmission (RFT) grating, a surface relief grating with sawtooth-shaped ridges of an acute vertex angle, expected to be deployed for the TMT Wide Field Optical Spectrograph (WFOS), and a hybrid grism for use as a medium-dispersion grism in MOIRCS, developed as a prototype of RFT grating. We describe the simulation results, fabrication methods, and experimental results of these prototype transmission gratings in this article.

The Subaru Telescope is an 8.2 m optical/infrared telescope constructed during 1991--1999 and has been operational since 2000 on the summit area of Maunakea, Hawaii, by the National Astronomical Observatory of Japan (NAOJ). This paper reviews the history, key engineering issues, and selected scientific achievements of the Subaru Telescope. The active optics for a thin primary mirror was the design backbone of the telescope to deliver a high-imaging performance. Adaptive optics with a laser-facility to generate an artificial guide-star improved the telescope vision to its diffraction limit by cancelling any atmospheric turbulence effect in real time. Various observational instruments, especially the wide-field camera, have enabled unique observational studies. Selected scientific topics include studies on cosmic reionization, weak/strong gravitational lensing, cosmological parameters, primordial black holes, the dynamical/chemical evolution/interactions of galaxies, neutron star mergers, supernovae, exoplanets, proto-planetary disks, and outliers of the solar system. The last described are operational statistics, plans and a note concerning the culture-and-science issues in Hawaii., 35 pages, 46 figures, 3 table, soon to be published in the Proceedings of the Japan Academy, Series B

We present mid-infrared observations of comet P/2016 BA14 (PANSTARRS), which were obtained on UT 2016 March 21.3 at heliocentric and geocentric distances of 1.012 au and 0.026 au, respectively, approximately 30 hours before its closest approach to Earth (0.024 au) on UT 2016 March 22.6. Low-resolution ($\lambda$/$\Delta \lambda$~250) spectroscopic observations in the N-band and imaging observations with four narrow-band filters (centered at 8.8, 12.4, 17.7 and 18.8 $\mu$m) in the N- and Q-bands were obtained using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the 8.2-m Subaru telescope atop Maunakea, Hawaii. The observed spatial profiles of P/2016 BA14 at different wavelengths are consistent with a point-spread function. Owing to the close approach of the comet to the Earth, the observed thermal emission from the comet is dominated by the thermal emission from its nucleus rather than its dust coma. The observed spectral energy distribution of the nucleus at mid-infrared wavelengths is consistent with a Planck function at temperature T~350 K, with the effective diameter of P/2016 BA14 estimated as ~0.8 km (by assuming an emissivity of 0.97). The normalized emissivity spectrum of the comet exhibits absorption-like features that are not reproduced by the anhydrous minerals typically found in cometary dust coma, such as olivine and pyroxene. Instead, the spectral features suggest the presence of large grains of phyllosilicate minerals and organic materials. Thus, our observations indicate that an inactive small body covered with these processed materials is a possible end state of comets., Comment: Accepted for publication in Icarus

PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is a very wide- field, massively multiplexed, and optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed in the 1.3 degree-diameter field of view. The spectrograph system has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously deliver spectra from 380nm to 1260nm in one exposure. The instrumentation has been conducted by the international collaboration managed by the project office hosted by Kavli IPMU. The team is actively integrating and testing the hardware and software of the subsystems some of which such as Metrology Camera System, the first Spectrograph Module, and the first on-telescope fiber cable have been delivered to the Subaru telescope observatory at the summit of Maunakea since 2018. The development is progressing in order to start on-sky engineering observation in 2021, and science operation in 2023. In parallel, the collaboration is trying to timely develop a plan of large-sky survey observation to be proposed and conducted in the framework of Subaru Strategic Program (SSP). This article gives an overview of the recent progress, current status and future perspectives of the instrumentation and scientific operation.

We present the launch of the Hyper Suprime-Cam Legacy Archive (HSCLA), a public archive of processed, science-ready data from Hyper Suprime-Cam (HSC). HSC is an optical wide-field imager installed at the prime focus of the Subaru Telescope and has been in operation since 2014. While ~1/3 of the total observing time of HSC has been used for the Subaru Strategic Program (SSP), the remainder of the time is used for PI programs. We have processed the data from these PI programs and make the processed, high quality data available to the community through HSCLA. The current version of HSCLA includes data taken in the first year of science operation, 2014. We provide both individual and coadd images as well as photometric catalogs. The photometric catalog from the coadd is loaded to the database, which offers a fast access to the large catalog. There are other online tools such as image browser and image cutout tool and they will be useful for science analyses. The coadd images reach 24-27th magnitudes at $5\sigma$ for point sources and cover approximately 580 square degrees in at least one filter with 150 million objects in total. We perform extensive quality assurance tests and verify the photometric and astrometric quality of the data to be good enough for most scientific explorations. However, the data are not without problems and users are referred to the list of known issues before exploiting the data for science. All the data and documentations can be found at the data release site, https://hscla.mtk.nao.ac.jp/., Comment: 12 pages, 9 figures, submitted to PASJ. Data available at https://hscla.mtk.nao.ac.jp/

One of the key noise sources that currently limits high-contrast imaging observations for exoplanet detection is quasi-static speckles. Quasi-static speckles originate from slowly evolving non-common path aberrations (NCPA). The purpose of this work is to present a proof-of-concept on-sky demonstration of spatial Linear Dark Field Control (LDFC). The ultimate goal of LDFC is to stabilize the point spread function (PSF) by addressing NCPA using the science image as additional wavefront sensor. We combined spatial LDFC with the Asymmetric Pupil vector-Apodizing Phase Plate (APvAPP) on the Subaru Coronagraphic Extreme Adaptive Optics system at the Subaru Telescope. In this paper, we report the results of the first successful proof-of-principle LDFC on-sky tests. We present results from two types of cases: (1) correction of instrumental errors and atmospheric residuals plus artificially induced static aberrations introduced on the deformable mirror and (2) correction of only atmospheric residuals and instrumental aberrations. When introducing artificial static wavefront aberrations on the DM, we find that LDFC can improve the raw contrast by a factor of $3$--$7$ over the dark hole. In these tests, the residual wavefront error decreased by $\sim$50 nm RMS, from $\sim$90 nm to $\sim40$ nm RMS. In the case with only residual atmospheric wavefront errors and instrumental aberrations, we show that LDFC is able to suppress evolving aberrations that have timescales of $, Comment: Accepted for publication in Astronomy&Astrophysics. 13 pages, 11 figures, 2 tables

Many approaches to astronomical data reduction and analysis cannot tolerate missing data: corrupted pixels must first have their values imputed. This paper presents astrofix, a robust and flexible image imputation algorithm based on Gaussian Process Regression (GPR). Through an optimization process, astrofix chooses and applies a different interpolation kernel to each image, using a training set extracted automatically from that image. It naturally handles clusters of bad pixels and image edges and adapts to various instruments and image types. For bright pixels, the mean absolute error of astrofix is several times smaller than that of median replacement and interpolation by a Gaussian kernel. We demonstrate good performance on both imaging and spectroscopic data, including the SBIG 6303 0.4m telescope and the FLOYDS spectrograph of Las Cumbres Observatory and the CHARIS integral-field spectrograph on the Subaru Telescope., Comment: Published by the Astronomical Journal. 16 pages, 12 figures. The algorithm is implemented in the Python package astrofix, which is available at https://github.com/HengyueZ/astrofix

By combining integral field spectroscopy with extreme adaptive optics, we are now able to resolve objects close to the diffraction limit of large telescopes, exploring new science cases. We introduce an integral field unit designed to couple light with a minimal plate scale from the SCExAO facility at NIR wavelengths to a single-mode spectrograph. The integral field unit has a 3D-printed micro-lens array on top of a custom single-mode multi-core fiber, to optimize the coupling of light into the fiber cores. We demonstrate the potential of the instrument via initial results from the first on-sky runs at the 8.2 m Subaru Telescope with a spectrograph using off-the-shelf optics, allowing for rapid development with low cost.

We will present a new instrument, REACH (Rigorous Exoplanetary Atmosphere Characterization with High dispersion coronography) to realize very high spectral resolution, over R=100,000 at extreme contrast by combining the high-resolution spectrograph InfraRed Doppler (IRD) and the extreme adaptive optics instrument, SCExAO at the Subaru Telescope. REACH consists of mini-IFU like 7 single-mode fiber bundle located at a focus of SCExAO, a high-speed photometric monitoring camera, and a beam switching and feed system from the fiber bundle to IRD’s 2 single-mode fibers. We will provide an overview of the instrument and present the recent results from on-sky tests.

The Simultaneous-color Wide-field Infrared Multi-object Spectrograph (SWIMS) is one of the 1st generation facility instruments for the University of Tokyo Atacama Observatory (TAO) 6.5 m telescope currently being constructed at the summit of Cerro Chajnantor (5,640 m altitude) in northern Chile. SWIMS has two optical arms, the blue arm covering 0.9–1.4 µm and the red 1.4–2.5 µm, by inserting a dichroic mirror into the collimated beam, and thus is capable of taking images in two filter-bands simultaneously in imaging mode, or whole nearinfrared (0.9–2.5 µm) low-to-medium resolution multi-object spectra in spectroscopy (MOS) mode, both with a single exposure. SWIMS was carried into Subaru Telescope in 2017 for performance evaluation prior to completion of the construction of the 6.5 m telescope, and successfully saw the imaging first light in May 2018 and MOS first light in Jan 2019. After three engineering runs including the first light observations, SWIMS has been accepted as a new PI instrument for Subaru Telescope from the semester S21A until S22B. In this paper, we report on details of on-sky performance of the instrument evaluated during the engineering observations for a total of 7.5 nights.

Subaru Telescope, an 8­meter class optical telescope located in Hawaii, has been using a high ­availability commodity cluster as a platform for our Observation Control System for many years.1 A concerted attempt to virtualize this infrastructure using conventional virtual machines2 was eventually scuttled due to performance impacts on the observation software under sustained use. With the ascendance of container­-based virtualization, and its promise of high­-efficiency, we recently attempted this effort anew, and have found success with an approach that employs Linux (LXC) containers. This has provided immediate benefits in maintenance, risk ­management and availability. In this paper, we document our transition and discuss the rationale for this choice vs. the arguably more popular Docker containerization scheme. We list some of the issues we encountered and solved to realize a successful transition to containers. We have also recently converted our software stack to being based on Miniconda, a popular, open­source, cross­platform software distribution service. This move basically decoupled our software completely from the operating system platform, and provides a virtualized software stack with many desirable benefits. The combination of the LXC containers and Miniconda gives us an orthogonal three-­axis virtualization scheme with extreme flexibility. We present our system for managing Miniconda environments, the benefits that accrue, and how this three­-axis approach to virtualization has altered our deployment and management strategies.

Thirty Meter Telescope (TMT) plans to incorporate fully automatic CO2 snow cleaning in-situ process for its segmented primary mirror. Due to the size of the primary mirror, usual single hand-held narrow coverage CO2 snow cleaning wands are no longer feasible option, though existing 2 and 4 inch wide models provided design insight. A new, extra-wide linear coverage CO2 snow horn/nozzle arrangement has been successfully developed along with appropriate liquid CO2 bulk delivery system. Challenges of such design include large CO2 flow rates at pressures providing liquid state all the way to the spray nozzles, ensuring stable and uniform transition of liquid to solids, bulk CO2 storage in the facility and coordination of the cleaning process with other telescope daytime activities. Additionally, automated rotating cleaning arms inspired by the Subaru telescope have been designed to expeditiously cover area of the TMT primary mirror at controlled speeds and reasonable time. Results of the study optimizing the cleaning parameters and test of various hardware options and combinations with respect to optics cleaning efficiency are also described.

ULTIMATE-Subaru is a next large facility instrument project at Subaru telescope. We will develop a 14x14 sq. arcmin wide-field near-infrared (NIR) imager and a multi-object spectrograph with the aid of a ground- layer adaptive optics system (GLAO), which will uniformly improve the seeing by a factor of 2 over a wide field of view up to ~20 arcmin in diameter. We have developed system modeling of the GLAO and wide-field NIR instruments to define the system level requirements flow down from science cases and derive the system performance budgets based on the GLAO end-to-end numerical simulation and optical system models of the telescope and wide-field NIR science instruments. In this paper, we describe the system performance modeling of ULTIMATE-Subaru and present an overview of the requirements flow down.

Subaru telescope has been operating a high-contrast imaging instruments called Subaru coronagraphic extreme adaptive optics (SCExAO) which is used for exoplanet research. We are developing phase mask coronagraphs using photonic crystal wave plates inside the SCExAO. An eight-octant phase mask (8OPM) of three-layer achromatic structure has been fabricated as a second generation. It was designed for J and H band to reach 10-5 contrast, and Ks band to 10-4. A retardation and a coronagraphic performance of the 8OPM were confirmed almost as designed at 1550nm. An apodised (binary shaped) pupil to be used with the 8OPM was also studied to suppress diffracted light by the secondary shadow and spiders. We confirmed a performance of the combination of the apodizer and the 8OPM at visible wavelengths in a lab. We optimized the apodizer for a pupil of the SCExAO where we obtained a transmission of 50 % and a contrast of 10-4 the center and 10-6 at outer region. We manufactured the designed apodizer to be installed in SCExAO for infrared observations.

Elasticsearch is one of solutions to monitor and analyze logs. Even with ALMA∗, observation logs are stored and anyone can look into it according to their purpose. For example, Hastings, which is a tool discovers the root cause of the defect, is utilized for ACA Correlator subsystem†. It queries logs to an ALMA Elasticsearch storing operational logs, analyzes specific messages which infer troubles, then outputs a result. Before the ALMA Elasticsearch was deployed, logs should have been collected manually in advance. Now the ALMA Elasticsearch has become available and we’ve known: 1) Elasticsearch can directly configure and access features by using REST API, 2) Logs taken even years ago can also be retrieved easily, 3) Elasticsearch’s major update didn’t cause much loss of time to change Hastings, 4) Python has several methods to manage Elasticsearch so that we can choose a favorite one. Therefore, we thought to apply Elasticsearch to the Subaru telescope‡. Size of Subaru logs are quite large but they are not stored in any database yet and just archived. We created a cluster system with Elasticsearch for the evaluation purpose and found ways to store data in a short time. We estimated the total ingestion time for 20 years of telescope status data to be at most 5 months. Our goal is to find a feasible cause of any defects in near real time, to predict any errors that may occur in near future, and to analyze communication between the telescope and observational equipment to optimize observations.

We present the current status and future plan of the instruments at the Subaru Telescope. The Hyper Suprime- Cam, which is a wide-field optical imager at the prime-focus and started the science operation in 2014, has been extensively used for a large survey program and general open use observations. The Prime Focus Spectrograph started the commissioning of the first subsystem, the Metrology Camera System, in 2018 and has been continuing the installation of the other subsystems. As the third system of the wide-field instrumentation suite, ULTIMATE-Subaru has started preliminary design for the GLAO system and conceptual designs for the science instruments. We will also present the status, upgrades, and future plan of the other facility instruments and visiting instruments.

The windscreen of the Subaru Telescope, which had been installed to prevent strong wind from directly hitting the telescope, was damaged and dropped out during the night operation at around 12:40 am, April 10, 2017. After that all observations at Subaru Telescope have been forced to be done without the windscreen. Due to the lack of the windscreen, the telescope would vibrate with strong wind, and the shape of the primary mirror would be deformed, thus the star image would become worse. Here we have investigated the effect of the lack of the windscreen statistically. The seeing at zenith at 500 nm was calculated from the FWHM of the star image obtained from the HSC on-site analysis software, and compared with the DIMM seeing at the east ridge of Maunakea simultaneously. Although the median seeing value varied by ~0.100 each year, the median seeing of DIMM before and after the incident is almost the same value (0.6100 and 0.6400), while the median seeing of HSC after the incident is ~0.0700 larger than before (0.6800 to 0.7500). The wind speeds at the telescope top ring, telescope center section, and outside the dome roof were investigated from the telescope telemetry data, and the correlations with the seeing were also investigated. Although the wind speed outside the dome did not change significantly before and after the incident, it was found that the wind speed inside the dome increased after the incident. Although it is not clear whether the degradation of the HSC seeing can be attributed to the absence of the windscreen, the seeing values over the last three years have statistically become ~10% worse than before.

FIRST, the Fibered Imager foR a Single Telescope, is a spectro-imager using single-mode fibers for pupil remap- ping, allowing measurements beyond the telescope diffraction limit. Integrated on the Subaru Coronagraphic Extreme Adaptive Optics instrument at the Subaru Telescope, it benefits from a very stable visible light wave- front allowing to acquire long exposure and operate on significantly fainter sources than previously possible. On-sky results demonstrated the ability of the instrument to detect stellar companions separated 43mas in the case of the Capella binary system. A similar approach on an extremely large telescope would offer unique scientific opportunities for companion detection and characterization at very high angular resolution.

With thousands of confirmed exoplanets, the era of discovery is giving way to that of characterization. Direct imaging is crucial, but extremely difficult due to high star-to-planet contrasts and high angular resolutions. Nulling interferometry, which suppresses contaminating starlight via destructive interference, aims to meet this challenge. A pathfinder of this technique is the GLINT nuller: a 6-baseline, spectrally dispersed pupil-remapping interferometer deployed at the Subaru telescope, in which a single photonic chip performs all the critical optical processes. We present the instrument, novel data processing based on self-calibrating methods, laboratory characterization and the latest on-sky results.

The Subaru Telescope recently celebrated its 20th year of operation. Despite that lengthy period of successful operation, it has never had a proper simulator for its telescope control system. This fact complicates the development and testing of observing scripts that need to send commands and receive realistic feedback from both telescope and instrument systems. The Subaru telescope control system was developed by a subcontractor and there was no requirement for it to be able to run in simulation mode. Furthermore, the source code is proprietary and is not accessible by current Subaru software engineers. These two facts greatly complicated the development of a telescope simulator. Prior to the current effort, the telescope simulator consisted of a “yes-man” interface, i.e., the rudimentary simulator would just respond that it received the command but would not simulate telescope motion or set any status items to provide feedback to the observing scripts. The telescope simulator developed in this effort currently simulates the following components: telescope and instrument rotator motion, focal station configuration, autoguide camera images and pointing errors, as well as facility hardware like dome shutters and mirror covers. We have plans to further refine all those components and implement features like simulated environmental conditions based on historical weather data. The simulator has already proven useful in testing observation scripts. In addition, the simulator will also be a good training aid for new telescope operators.

The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph designed for the prime focus of the 8.2m Subaru telescope. PFS will cover a 1.3 degree diameter field with 2394 fibers to complement the imaging capabilities of Hyper SuprimeCam. To retain high throughput, the final positioning accuracy between the fibers and observing targets of PFS is required to be less than 10 µ m. The metrology camera system (MCS) serves as the optical encoder of the fiber positioners for configuring of fibers. The MCS locates at the Cassegrain focus of the Subaru telescope to cover the whole focal plane with one 50M pixel CMOS sensor. The information from MCS will be fed into the fiber positioner control system for closed loop control. The MCS was delivered to Subaru Observatory in Apr. 2018 and it had two engineering runs in Oct. 2018 and Aug. 2019. The 1st engineering run concluded that the original mirror supports need to be improved to provide better image quality. The newly designed mirror supports were installed before the 2nd engineering run. The 2nd engineering run result shows that the MCS overall position accuracy is better than 4μm and the image processing time is less than 4 seconds. The MCS is ready for the system integration with other PFS components.

We have developed an integral field unit (IFU) for the existing optical imaging spectrograph, Faint Object Camera And Spectrograph (FOCAS), on the Subaru telescope. FOCAS IFU finally saw a first light on March 2nd, 2018, and started the common use from 2019. In order to observe faint targets like distant galaxies, our IFU has a coarse sampling comparable to the best seeing size and high throughput. The field of view is 13.4 10.0 arcsec2 which is divided into 23 slices with the width of 0.435 arcsec. Our IFU has a slit separated by about 5.2 arcmin from an object field in order to simultaneously obtain a sky spectrum. We confirmed that the image quality is good enough for the 0.435-arcsec slice width and the best seeing size of 0.4 arcsec. Mean and median throughput of the IFU are respectively 85.0% and 87.3%. However some fields show lower throughput due to misalignment of the IFU optics and the worst throughput is 61.9% at one field corner. Flat fielding error is almost within ±3%, but worse errors are found at the low-throughput region. The worst error is 9% at the lowest throughput region.

The fabrication of the new medium-resolution grisms for MOIRCS onboard Subaru 8.2-m Telescope is presented. Our new grisms feature the state-of-the-art gratings that have very high efficiency and wide-spectral coverage manufactured by LightSmyth for the pulse-compression technology. The grating has the peak efficiency of over 96% and can cover the whole H-band wavelength range with over 90%. This is the first-time astronomical application case for the LightSmyth grating. We manufactured the custom-made H-band grism as well as the catalog product J-band grism with a bit less ideal performance. The cooling test of the grisms was done successfully, confirming the stability of the wave-front error over the cooling cycle. On-sky performance test of the new grisms were achieved in July 2020, and we have confirmed the high sensitivity as well as the amazing flatness of the throughput of these grisms. Though we cofirmed the existence of some faint ghosts of the 0-th order light as anticipated, the effect of them are confirmed to be negligible. We started offering the use of the grisms for Subaru community from August 2020.

We report the reflectivity of the Subaru Telescope's mirrors and these time evolutions measured with the Subaru Portable Spectrophotometer (SPS). Thanks to the capability of SPS, the absolute, spectroscopic reflectivity has been measured in-situ on the telescope since October 2017, and it becomes possible to understand and forecast the time evolution of the reflectivity degradation. We established a simple two factor model for the reflectivity degradation of the primary mirror which has coated with aluminum in 2017. From a study of CO2 cleaning with SPS, a part of dust on the mirror surface was found to be removed with CO2 cleaning, on the other hand, the roughness of the surface was found to become larger than before cleaning. The time evolution of the reflectivity of the primary mirror is now able to be forecasted. In parallel, we have applied SPS measurement to the infrared secondary mirror of the Subaru Telescope (IR M2) and found a significant loss of reflectivity in the visible wavelength in November 2018. IR M2 had been coated with silver in 2008 and used for over ten years. Although the original reflectivity of silver mirror is ~98% at 589 nm, there was ~50% in November 2018, and it was ~30% at in November 2019. One of the causes of the significant loss could be due to volcanic gas from the explosion of Kilauea in May 2018; however, it was hard to explain the continuing degradation in reflectivity through the following year. The reflectivity could not be recovered by any quick cleanings. We carried out recoating of IR M2 in November 2019. A three-factor model to explain the reflectivity degradation of IR M2 was considered. The model would help us to understand what happens on silver mirrors. On the other hand, unknown localized phenomenon such as a white spot was seen on the IR M2 mirror surface.

The Mid-Infrared Multi-field Imager for gaZing at the UnKnown Universe (MIMIZUKU) is developed as the first-generation mid-infrared instrument for the University of Tokyo Atacama Observatory (TAO) 6.5-m telescope. MIMIZUKU performs medium-band imaging and low-resolution spectroscopy in 2-38 microns and enables highest-spatial-resolution observations in the long-wavelength mid-infrared beyond 25 microns. In addition, MIMIZUKU has a unique opto-mechanical device called ‘Field Stacker’, which enables us to observe a distant (

Results of a conceptual design study of ULTAIMTE-Wide Field Imager (WFI) is presented. ULTIMATE-WFI is a near-infrared wide-field imager for the ground-layer adaptive optics system of the Subaru telescope (ULTIMATESubaru) which realizes a 0. 002 seeing size over 200diameter at the Cassegrain focus utilizing a deformable 2ndry mirror. WFI has a 15. 07×15. 07 FoV with a wavelength coverage of 0.9–2.5µm. The FoV is covered by four identical optics, each having a square field lens with 226mm on a side. Its effective FoV is 7. 02 on a side, and is covered by a HAWAII-4RG array detector with a pixel scale of 0. 0011/pix. Effective FoV will be 14. 04×14. 04 or 2070 in total. Spot sizes at a detector plane are less than 0. 001 over the wavelength coverage. Due to the large FoV, vignetting by the telescope structure occurs and an additional cold stop is necessary to block their thermal emission, which causes ~80% vignetting at the edge of the FoV. All the optics are contained in a cylindrical structure to be installed on the Cassegrain focus of the telescope, and kept under cryogenic temperature except for the field lenses. Gravitational deformation will be smaller than 1mm, and may have negligible impact on the final image quality., Ground-based and Airborne Instrumentation for Astronomy VIII, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus of the 8.2m Subaru telescope. PFS will cover 1.3 degrees diameter field with 2394 fibers to complement the imaging capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber positioners and fiducial fibers are located. In addition, the acquisition and guiding cameras (AGCs), the cable wrapper, the fiducial fiber illuminator, and viewer, the field element, and the telemetry system are located inside the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match those of the HSC’s Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations within the required accuracy. The delivery of PFI components started in 2017. After the verification of these components, the mechanical structure of the PFI is fully assembled in early 2019 and all Cobra positioners are integrated in summer 2020. A temperature controlled chamber with precise x-y scanner was setup for the verification of the fiber positioners. The testing of the target convergence performance of Cobra positioners is now in progress.

Orbital parameters of stellar companions can be constrained by multi-epoch observations where the astrometric position relative to the host star is measured. Additionally, radial velocity (RV) measurements of the host star may constrain the companion mass. We describe two major advances for high contrast imaging systems that significantly improve estimation of orbital parameters and masses. First, well-calibrated fiducial satellite speckles are inserted in the science images by way of deformable mirror (DM) modulation to improve astrometric measurement accuracy. Second, radial velocity measurement of the companion light reveals its velocity along the line-of-sight. We describe how the two techniques, together, can efficiently constrain orbital parameters and masses, and can do so over a shorter observation time baseline than previously possible. We demonstrate our technique with the REACH (Rigorous Exoplanetary Atmosphere Characterization with High dispersion coronagraphy) instrument at the Subaru Telescope. REACH takes extreme adaptive optics corrected light via single mode fiber from the SCExAO instrument and injects it to the high-resolution (R

Subaru telescope is currently in the process of upgrading its laser guide star (LGS) system. The newest upgrade will have a TOPTICA SodiumStar laser source (operates at ~22W and 589nm) which is then sent to a laser launch telescope (LLT) just behind the secondary mirror of the telescope. In order to send the laser light to the LLT, a system of 6 mirrors has been designed to relay the laser light. Since the distances between these mirrors are quite large (the largest is ~9m), it was necessary to model the system in order to determine the correct placement and proper alignment procedure of each of these mirrors. For simplicity, the complete mirror relay system (including parts of the LLT up to the beam expander lens) has been modeled as an 8 mirror system in order to complete a tolerance analysis. The results of this analysis suggest that alignment of the system should be possible to do with a simple pinhole alignment procedure.

Institute of Astronomy, Graduate School of Science, the University of Tokyo is promoting the University of Tokyo Atacama Observatory Project, which is to construct an infrared-optimized 6.5m telescope at the summit of Co. Chajnantor (5640m altitude) in northern Chile. The high altitude and dry climate (PWV-0.5mm) realize transparent atmosphere in the infrared wavelength. The project is now approaching the final phase of the construction. Production of major components are almost completed: Production and preassembly test of a telescope mount and dome enclosure have been completed in Japan, and they are being transported to Chile. Three mirrors, the 6.5m primary, 0.9m secondary, and 1.1m-0.75m tertiary mirrors and their support systems have been all completed and tested in the USA. An aluminizing chamber have been fabricated in China, and its tests have been carried out in Japan. Development of two facility instruments, SWIMS and MIMIZUKU, are also completed. They were transported to the Subaru telescope, successfully saw the first light in 2018, and are confirmed to have the performance as designed. On-site construction work at the summit is now underway. Expansion of a summit access road from the ALMA concession was completed in 2019. Installation of foundation will follow, and then erection of the dome enclosure and a control building. The construction works are delayed by COVID-19, and we expect to complete the dome enclosure by Q3 of 2021. The telescope will be installed inside the dome and see the engineering first light by early 2022.

The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is a high-contrast imaging system installed at the 8-m Subaru Telescope on Maunakea, Hawaii. Due to its unique evolving design, SCExAO is both an instrument open for use by the international scientific community, and a testbed validating new technologies, which are critical to future high-contrast imagers on Giant Segmented Mirror Telescopes (GSMTs). Through multiple international collaborations over the years, SCExAO was able to test the most advanced technologies in wavefront sensors, real-time control with GPUs, low-noise high frame rate detectors in the visible and infrared, starlight suppression techniques or photonics technologies. Tools and interfaces were put in place to encourage collaborators to implement their own hardware and algorithms, and test them on-site or remotely, in laboratory conditions or on-sky. We are now commissioning broadband coronagraphs, the Microwave Kinetic Inductance Detector (MKID) Exoplanet Camera (MEC) for high-speed speckle control, as well as a C-RED ONE camera for both polarization differential imaging and IR wavefront sensing. New wavefront control algorithms are also being tested, such as predictive control, multi-camera machine learning sensor fusion, and focal plane wavefront control. We present the status of the SCExAO instrument, with an emphasis on current collaborations and recent technology demonstrations. We also describe upgrades planned for the next few years, which will evolve SCExAO —and the whole suite of instruments on the IR Nasmyth platform of the Subaru Telescope— to become a system-level demonstrator of the Planetary Systems Imager (PSI), the high-contrast instrument for the Thirty Meter Telescope (TMT).

Currently, two AO systems are operated at Subaru Telescope: AO188, which is a facility AO system, and SCExAO, which is a PI-type ExAO system operated behind AO188. In the next 5 year, large-scale upgrades are performed on AO188 for improving the AO performance and operation of AO188 and SCExAO and for the technical demonstration toward the future wide-field ULTIMATE-Subaru GLAO system at Subaru and an ExAO system at TMT, PSI. We are planning to upgrade the real-time control system, the LGS system, and bimorph DM. Also, a new NIR WFS, a LTAO WFS unit, and a beam-switching system will be installed into the Nasmyth IR platform. The installation of the LTAO WFS unit is a part of the ULTIMATE-START project, which implement a LTAO mode into AO188 and demonstrates technologies for the ULTIMATE-Subaru GLAO system. ULTIMATE-Subaru project aims at developing a next-generation, wide-field GLAO system and wide-field NIR instruments for Subaru Telescope, whose first light will be in FY2025.

ULTIMATE-Subaru Tomography Adaptive optics Research experimenT (ULTIMATE-START) is a laser tomography AO project on the Subaru telescope. The project is planned to achieve high Strehl Ratio AO correction in NIR bands, and moderate AO correction in visible bands above 600nm. An asterism of 4 laser guide stars (LGSs) will be launched from the laser launching telescope behind the secondary mirror. The tomography wavefront sensing unit with four 32$times$32 Shack-Hartmann wavefront sensors will be installed behind the current facility LGS AO system, AO188. The deformable mirror of AO188 will be upgraded to a 64$times$64 element DM. The corrected light will be fed to the optical integral field spectrograph, 3DII, and NIR camera and spectrograph, IRCS, through a beam switching optics for IR-side Nasmyth focus instruments under development. The first light of the laser launching system and wavefront sensing unit is planned in 2021.

Author(s): Kim, Seong Jin; Oi, Nagisa; Goto, Tomotsugu; Ikeda, Hiroyuki; Ho, Simon C-C; Shim, Hyunjin; Toba, Yoshiki; Hwang, Ho Seong; Hashimoto, Tetsuya; Barrufet, Laia; Malkan, Matthew; Kim, Helen K; Huang, Ting-Chi; Matsuhara, Hideo; Miyaji, Takamitsu; Pearson, Chris; Serjeant, Stephen; Santos, Daryl Joe D; Kim, Eunbin; Pollo, Agnieszka; Jeong, Woong-Seob; Wang, Ting-Wen; Momose, Rieko; Takagi, Toshinobu | Abstract: ABSTRACT The North Ecliptic Pole field is a natural deep-field location for many satellite observations. It has been targeted many times since it was surveyed by the AKARI space telescope with its unique wavelength coverage from the near- to mid-infrared (mid-IR). Many follow-up observations have been carried out, making this field one of the most frequently observed areas with a variety of facilities, accumulating abundant panchromatic data from the X-ray to the radio wavelength range. Recently, a deep optical survey with the Hyper Suprime-Cam (HSC) at the Subaru telescope covered the NEP-Wide (NEPW) field, which enabled us to identify faint sources in the near- and mid-IR bands, and to improve the photometric redshift (photo-z) estimation. In this work, we present newly identified AKARI sources by the HSC survey, along with multiband photometry for 91 861 AKARI sources observed over the NEPW field. We release a new band-merged catalogue combining various photometric data from the GALEX UV to submillimetre (sub-mm) bands (e.g. Herschel/SPIRE, JCMT/SCUBA-2). About ∼20 000 AKARI sources are newly matched to the HSC data, most of which seem to be faint galaxies in the near- to mid-infrared AKARI bands. This catalogue is motivating a variety of current research, and will be increasingly useful as recently launched (eROSITA/ART-XC) and future space missions (such as JWST, Euclid, and SPHEREx) plan to take deep observations in the NEP field.

Some supernovae such as pair-instability supernovae are predicted to have the duration of more than a year in the observer frame. To constrain the rates of supernovae lasting for more than a year, we conducted a long-term deep transient survey using Hyper Suprime-Cam (HSC) on the 8.2m Subaru telescope. HSC is a wide-field (a 1.75 deg2 field-of-view) camera and it can efficiently conduct transient surveys. We observed the same 1.75 deg2 field repeatedly using the g, r, i, and z band filters with the typical depth of 26 mag for 4 seasons (from late 2016 to early 2020). Using these data, we searched for transients lasting for more than a year. Two supernovae were detected in 2 continuous seasons, one supernova was detected in 3 continuous seasons, but no transients lasted for all 4 seasons searched. The discovery rate of supernovae lasting for more than a year with the typical limiting magnitudes of 26 mag is constrained to be 1.4^{+1.3}_{-0.7}(stat.)^{+0.2}_{-0.3}(sys.) events deg-2 yr-1. All the long-lasting supernovae we found are likely Type IIn supernovae and our results indicate that about 40% of Type IIn supernovae have long-lasting light curves. No plausible pair-instability supernova candidates lasting for more than a year are discovered. By comparing the survey results and survey simulations, we constrain the luminous pair-instability supernova rate up to z ~ 3 should be of the order of 100 Gpc-3 yr-1 at most, which is 0.01 - 0.1 per cent of the core-collapse supernova rate., 18 pages, 9 figures, 6 tables, accepted by The Astrophysical Journal

Characterisation of exoplanets is key to understanding their formation, composition and potential for life. Nulling interferometry, combined with extreme adaptive optics, is among the most promising techniques to advance this goal. We present an integrated-optic nuller whose design is directly scalable to future science-ready interferometric nullers: the Guided-Light Interferometric Nulling Technology, deployed at the Subaru Telescope. It combines four beams and delivers spatial and spectral information. We demonstrate the capability of the instrument, achieving a null depth better than 10−3 with a precision of 10−4 for all baselines, in laboratory conditions with simulated seeing applied. On sky, the instrument delivered angular diameter measurements of stars that were 2.5 times smaller than the diffraction limit of the telescope. These successes pave the way for future design enhancements: scaling to more baselines, improved photonic component and handling low-order atmospheric aberration within the instrument, all of which will contribute to enhance sensitivity and precision., Nulling interferometry is a technique combining lights from different telescopes or apertures to observe weak sources nearby bright ones. The authors report the first nulling interferometer implemented in a photonic chip doing spectrally dispersed nulling on several baselines, simultaneously.

ULTIMATE-Subaru is a next large facility instrument project at Subaru telescope. We will develop a 14x14 arcmin2 wide-field near-infrared (1.0-2.5μm) imager and a multi-object spectrograph with the aid of a ground- layer adaptive optics system (GLAO), which will uniformly improve the seeing by a factor of 2 over a wide field of view up to ~20 arcmin in diameter. The expected spatial resolution by the GLAO correction is about 0.2 arcsec FWHM in K-band under moderate seeing conditions at Subaru telescope. ULTIMATE-Subaru will provide a unique capability to realize wide-field and high spatial resolution survey observations in near infrared in the era of TMT. In this paper, we introduce the project overview including the GLAO and near-infrared instrument conceptual design. We also describe the future wide-field strategy at Subaru telescope with ULTIMATE-Subaru together with HSC and PFS.

We carried out optical high-resolution spectroscopy of T Tauri stars using the Subaru Telescope. Using archived data from the Keck Telescope and the Very Large Telescope, we detected forbidden lines of [S II] at 4069 A, in addition to those of [O I] at 5577 A and 6300 A, for 13 T Tauri stars. We consider that low-velocity components of these forbidden lines emanate from the wind associated with T Tauri stars. Using two flux ratios of the three lines, we simultaneously determined the hydrogen density and temperature of the winds. The winds of T Tauri stars have a hydrogen density of $2.5 \times 10^{6}$ cm$^{-3}$ - $2.5 \times 10^{9}$ cm$^{-3}$ and a temperature of 10800 -18000 K. The mass loss rates by the wind are estimated to lie in the range from $2.0 \times 10^{-10}$ M$_{\odot}$ yr$^{-1}$ to $1.4 \times 10^{-9}$ M$_{\odot}$ yr$^{-1}$. The mass loss rates are found to increase with increasing mass accretion rates. The ratio of the mass loss rate to the mass accretion rate is 0.001-0.1 for classical T Tauri stars and 0.1-1 for transitional disk objects.

The characterization of exoplanets is critical to understanding planet diversity and formation, their atmospheric composition, and the potential for life. This endeavour is greatly enhanced when light from the planet can be spatially separated from that of the host star. One potential method is nulling interferometry, where the contaminating starlight is removed via destructive interference. The GLINT instrument is a photonic nulling interferometer with novel capabilities that has now been demonstrated in on-sky testing. The instrument fragments the telescope pupil into sub-apertures that are injected into waveguides within a single-mode photonic chip. Here, all requisite beam splitting, routing, and recombination are performed using integrated photonic components. We describe the design, construction, and laboratory testing of our GLINT pathfinder instrument. We then demonstrate the efficacy of this method on sky at the Subaru Telescope, achieving a null-depth precision on sky of ∼10−4 and successfully determining the angular diameter of stars (via their null-depth measurements) to milliarcsecond accuracy. A statistical method for analysing such data is described, along with an outline of the next steps required to deploy this technique for cutting-edge science.

We carried out deep H$\alpha$ narrowband imaging with 10 hours net integrations towards the young protocluster, USS1558$-$003 at $z=2.53$ with the Subaru Telescope. This system is composed of four dense groups with massive local overdensities, traced by 107 H$\alpha$ emitters (HAEs) with stellar masses and dust-corrected star formation rates down to $1\times10^8$ M$_\odot$ and 3 M$_\odot$yr$^{-1}$, respectively. We have investigated the environmental dependence of various physical properties within the protocluster by comparing distributions of HAEs in higher and lower densities with a standard Kolmogorov--Smirnov test. At 97\% confidence level, we find enhanced star formation across the star-forming main sequence of HAEs living in the most extreme `supergroup', corresponding to the top quartile of overdensities. Furthermore, we derive distribution functions of H$\alpha$ luminosity and stellar mass in group and intergroup regions, approximately corresponding to 30 times and 8 times higher densities than the general field. As a consequence, we identify by 0.7 and 0.9 dex higher cutoffs in H$\alpha$ luminosity and stellar mass functions in the dense groups, respectively. On the other hand, HAEs in the intergroup environment of the protocluster show similar distribution functions to those of field galaxies despite residing in significant overdensities. In the early phase of cluster formation, as inferred from our results, the densest parts in the protocluster have had an accelerated formation of massive galaxies. We expect that these eventually grow and transform into early-type galaxies at the bright end of the red sequence as seen in present-day rich clusters of galaxies., Comment: Accepted for publication in MNRAS, 24 pages, 17 figures, 5 tables

Prior statistical knowledge of the atmospheric turbulence is essential for designing, optimizing and evaluating tomographic adaptive optics systems. We present the statistics of the vertical profiles of $C_N^2$ and the outer scale at Maunakea estimated using a Slope Detection And Ranging (SLODAR) method from on-sky telemetry taken by RAVEN, which is a MOAO demonstrator in the Subaru telescope. In our SLODAR method, the profiles are estimated by a fit of the theoretical auto- and cross-correlation of measurements from multiple Shack-Haltmann wavefront sensors to the observed correlations via the non-linear Levenberg-Marquardt Algorithm (LMA), and the analytic derivatives of the spatial phase structure function with respect to its parameters for the LMA are also developed. The estimated profile has the median total seeing of 0.460$^{\prime\prime}$ and large $C_N^2$ fraction of the ground layer of 54.3%. The $C_N^2$ profile has a good agreement with the result from literatures, except for the ground layer. The median value of the outer scale is 25.5m and the outer scale is larger at higher altitudes, and these trends of the outer scale are consistent with findings in literatures., Comment: 11 pages, 10 figures, submitted to MNRAS

The discovery of extremely zirconium- and lead-rich surfaces amongst a small subgroup of hot subdwarfs has provoked questions pertaining to chemical peculiarity in hot star atmospheres and about their evolutionary origin. With only three known in 2014, a limited search for additional `heavy-metal' subdwarfs was initiated with the Subaru telescope. Five hot subdwarfs having intermediate to high surface enrichment of helium were observed at high-resolution and analyzed for surface properties and abundances. This paper reports the analyses of four of these stars. PG1559+048 and FBS 1749+373, having only intermediate helium enrichment, show strong lines of triply ionized lead. PG1559+048 also shows a strong overabundance of germanium and yttrium. With more helium-rich surfaces, Ton 414 and J17554+5012, do not show evidence of heavy-metal enrichment. This limited survey suggests that extreme enrichment of `heavy metals' by selective radiative levitation in hot subdwarf atmospheres is suppressed if the star is too helium-rich., Accepted to publish in MNRAS

We describe the current performance of the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument on the Subaru telescope on Maunakea, Hawaii and present early science results for SCExAO coupled with the CHARIS integral field spectrograph. SCExAO now delivers H band Strehl ratios up to ~0.92, extreme AO corrections for optically faint stars, and planet-to-star contrasts rivaling that of GPI and SPHERE. CHARIS yield high signal-to-noise detections and 1.1—2.4 micron spectra of benchmark directly-imaged companions like HR 8799 cde and kappa And b that clarify their atmospheric properties. We show how spectra and astrometry for kappa And b lead to a reevaluation of this object's nature. Finally, we briefly describe plans for a SCExAO-focused direct imaging campaign to directly image and characterize young exoplanets, planet-forming disks, and (later) mature planets in reflected light.

We introduce novel gratings for next generation instruments of the TMT (Thirty Meter Telescope), the 8.2 m Subaru telescope, other ground-based and space-borne telescopes. The reflector facet transmission (RFT) grating which is a surface relief grating with sawtooth shaped grating lattice of an acute vertex angle, is developed for the WFOS of the TMT. The hybrid grism (direct vision grating) for the MOIRCSof the 8.2m Subaru Telescope is developed as a prototype of the RFT grating. The volume binary grating is developed for a high-dispersion echelle grism of the nuMOIRCS as the first light instrument of the ULTIMATE Subaru. We also developing a silicon grism for the MIMIZUKU of the 6.5m telescope of the University of Tokyo Atacama Observatory in Chile and a quasi-Bragg (QB) immersion grating.