Yoshiyuki Doi

Current performance and on-going improvements of the 8.2 m Subaru Telescope

An overview of the current status of the 8.2m Subaru Telescope constructed and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of Japan is presented. The basic design concept and the verified performance of the telescope system are described. Also given are the status of the instrument package offered to the astronomical community, the status of operation, and some of the future plans. The status of the telescope reported in a number of SPIE papers as of the summer of 2002 are incorporated with some updates included as of 2004 February. However, readers are encouraged to check the most updated status of the telescope through the home page, http://subarutelescope.org/index.html, and/or the direct contact with the observatory staff.

HyperSuprime: project overview

HyperSuprime is a next generation wide field camera proposed for the 8.3 m Subaru Telescope. The targeted field of view is larger than 1.5 deg in diameter, which will give us roughly 10 times increase of the survey speed compared with the existing prime focus camera (Suprime-Cam). An overview of the current status of the feasibility study is given.

High-resolution imaging polarimetry of HL Tau and magnetic field structure

We present high quality near infrared imaging polarimetry of HL Tau at 0.4 to 0.6 arcsec resolution, obtained with Subaru/CIAO and UKIRT/IRCAM. 3-D Monte Carlo modelling with aligned oblate grains is used to probe the structure of the circumstellar envelope and the magnetic field, as well as the dust properties. At J band the source shows a centrosymmetric pattern dominated by scattered light. In the H and K bands the central source becomes visible and its polarisation appears to be dominated by dichroic extinction, with a position angle inclined by � 40 ◦ to the disc axis. The polarisation pattern of the environs on scales up to 200 AU is consistent with the same dichroic extinction signature superimposed on the centrosymmetric scattering pattern. These data can be modelled with a magnetic field which is twisted on scales from tens to hundreds of AU, or alternatively by a field which is globally misaligned with the disc axis. A unique solution to the field structure will require spatially resolved circular polarisation data. The best fit Monte Carlo model indicates a shallow near infrared extinction law. When combined with the observed high polarisation and non-negligible albedo these constraints can be fitted with a grain model involving dirty water ice mantles in which the largest particles have radii slightly in excess of 1 µm. The best fit model has an envelope structure which is slightly flattened on scales up to several hundred AU. Both lobes of the bipolar outflow cavity contain a substantial optical depth of dust (not just within the cavity walls). Curved, approximately parabolic, cavity walls fit the data better than a conical cavity. The small inner accretion disc observed at millimetre wavelengths is not seen at this spatial resolution.

Mid-Infrared Spectral Energy Distribution of NGC 1068 with 0.″1 Spatial Resolution*

The central region of the Seyfert 2 galaxy NGC 1068 is imaged in the mid-infrared (MIR) using the Mid-Infrared Test Observation System on the 8.2 m Subaru Telescope. The oversampling pixel scale associated with the shift-and-add method shows 01 resolution images with a high dynamic range after deconvolution. Along with an extended structure at a position angle (P.A.) of -10° with higher surface brightness, another structure extends wider with lower surface brightness at a P.A. of 20°. The central peak elongates north-south with FWHM of 03 × 02. Spectral energy distribution (SED) of the central peak is fitted to have the silicate absorption feature of τ9.7 μm = 0.9 ± 0.3. This is half of the absorption expected from the near-infrared (NIR) feature of carbonaceous dust. This suggests a temperature gradient of the absorbing dust along the line of sight. Another possibility, which is not distinguishable here, is the size distribution of dust different from our Galaxy. Intrinsic luminosity of emission from the central peak is 3 × 1037 W. The SED shows a hint of the polycyclic aromatic hydrocarbon (PAH) emission features. Although a high spatial resolution MIR spectrum is required, it suggests that the PAH carriers near the active galactic nuclei (AGNs) are sheltered from the high-energy emission from the AGNs and that the AGNs have nuclear starbursts. For the NIR disklike structures, no counterparts are detected in the MIR. The nature of the structures remains unclear.

Near-infrared polarimeter for the Subarau telescope

We report the development and performance of a near-IR polarimeter for the Subaru 8.2m telescope. The polarimeter is currently used with one of the Subaru instruments, CIAO, the stellar coronagraphic imager with adaptive optics. CIAO is the instrument specialized to obtain high contrast images of faint objects in the vicinity of bright objects. For achieving both high spatial resolution and high dynamic range, the instrument is used wiht the Subaru adaptive optics and has a dedicated cold coronagraphic capability. The polarimeter comprises two components. One component consists of an achromatic half-waveplate, an achromatic quarter-waveplate, and a calibration wire grid. Both half- and quarter-waveplates are rotatable and retractable, while the calibrator is only retractable. This componetn is placed upstream of any opticla components including adaptive optics system, which minimizes the effect of various mirros on instrumental polarization. The other component consists of two anlayzers, a cold wire grid and acold Wollastron prism. These are placed in the filter wheels of CIAO cryostat and can be chosen. The whole system is remotely controlled.

Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

We present the photometric properties of a sample of infrared (IR) bright dust obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam (HSC) on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer (WISE), we discovered 48 DOGs with i−Ks > 1.2 and i− [22]> 7.0, where i, Ks, and [22] represent AB magnitude in the i-band, Ks-band, and 22 μm, respectively, in the GAMA 14hr field (∼ 9 deg). Among these objects, 31 (∼ 65 %) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show a NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma z = 1.99 ± 0.45, we calculated their total IR luminosity using an empirical relation between 22 μm luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5 ± 1.1) × 10L⊙, which classifies them as hyper-luminous infrared galaxies (HyLIRGs). We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 μm flux greater than 3.0 mJy and with i-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log φ = -6.59 ± 0.11 [Mpc]. The IR LF for DOGs including data obtained from the literature is well fitted by a double-power law. The derived lower limit for the IR LD for our sample is ρIR ∼ 3.8 × 10 [L⊙Mpc] and its contributions to the total IR LD, IR LD of all ultra-luminous infrared galaxies (ULIRGs), and that of all DOGs are > 3 %, > 9 %, and > 15 %, respectively. 2 Y. Toba et al. [Vol. ,

Near-infrared coronagraph imager on the Subaru 8m telescope

We introduce a near-infrared camera named coronagraph imager with adaptive optics (CIAO) mounted on the Subaru 8m telescope. Combined with the Subaru 36 elements adaptive optics (AO), CIAO can produce nearly diffraction limited image with approximately 0.07 arcsec FWHM at K band and high dynamic range imaging with approximately 10 mag difference at 1 arcsec separation under typical seeing conditions. We have carried out performance tests of imaging without and with coronagraph mask since its first light observation held on 2000 February. Because of limited weather conditions, the performance under best seeing conditions has not been tested yet. At a typical natural seeing condition of 0.4 - 0.8 arcsec, halo component of PSF using 0.2 - 0.8 arcsec mask can be reduced up to 70% comparing with that without mask using AO. Even after correction, residual wave front error has typically 1.2 rad2 which corresponds to the Strehl ratio of approximately 0.3 at K band. Such wave front errors degrades the image quality; this is a common problem of coronagraph on the ground-based telescope with non high-order AO. Nevertheless we emphasize that there are various advantages on our coronagraph: the clean PSF of CIAO, reduction of readout noise, and less effect of detector memory problem. Compared with coronagraphs on smaller telescopes, the PSF shape is sharper and it brings higher detectability of sources around bright objects.

Hyper Suprime-Cam: CCD readout electronics

Hyper Suprime-Cam is planned to employ about 120 2k×4k fully-depleted CCDs with 4 signal outputs for each. The data size of an image becomes larger than 2Gbytes. All of the CCDs are designed to be readout parallel within 20 seconds, and the readout noise is expected to be 5e. The frontend electronics will be mounted in a vacuumed cryostat, and connected to the backend electronics mounted on the outside of the cryostat. The frontend electronics includes entire analog circuits for CCD including CCD drivers, preamplifiers and ADC. The backend electronics consists of newly developed gigabit Ethernet modules combined with 2Gbytes memory modules, and several supporting boards. We will present the current status of the CCD readout electronics developments for HSC.

Test observation results from the mid-infrared imager MIRTOS for the Subaru Telescope

MIRTOS, Mid-IR Test Observation System, is a high spatial resolution mid IR (MIR) camera for the Subaru Telescope. It consists of two IR imagers. One is for MIR bands with a Si:As array with 320 by 240 pixels. It has 21 by 16 arcsec field of view (FOV) with a pixel scale of 0.067 arcsec. It also images the pupil of the telescope. The other is a near IR camera. A 256 by 256 InSb array with 0.028 arcsec/pixel is used to image 7 by 7 arcsec FOV at one corner of the MIR FOV. We apply Shift-and-Add (SAA) technique; a technique that shifts images detecting the displacements and adds them to cancel seeing. However it is often difficult to shift and add MIR images using a reference within because of low sensitivity in MIR for short exposure time. We solve this problem utilizing NIR images taken simultaneously as position references. We call this method two-wavelength shift-and-add (TWSAA). In this paper we show result from the test observations. 1) Pupil image was taken. It shows hot structures around the secondary mirror that are now planned to be covered by reflecting plates to direct the beam to the sky. 2) Correlation of motion between MIR peak position and NIR centroid position shows that NIR images can be used as TWSAA reference for MIR observations. 3) On a standard star and the core NGC 1068, SAA method was applied to reconstruct images. Resulting images show higher spatial resolution than previous observations.

The shutter and filter exchanger system of Hyper Suprime-Cam

The next generation wide field camera HSC (Hyper Suprime-Cam) on Subaru telescope is planned to cover 1.5 degree diameter field with a focal plane size about 650mm. To minimize the impact to the telescope, the design for the elements of the camera is constraint to the tight space and weight limits. In order to fit the available space, the screen winding shutter and petal shape filter exchanger are designed for the HSC. The CFRP is used for the structure to minimize the load. In this report, the design and analysis for the shutter and filter exchanger system will be presented. The result for the shutter membrane tests will also be discussed.