Hyper Suprime-Cam: Camera dewar design Komiyama, Yutaka; Obuchi, Yoshiyuki; Nakaya, Hidehiko ...
Publications of the Astronomical Society of Japan,
01/2018, Letnik:
70, Številka:
SP1
Journal Article
Recenzirano
Abstract
This paper describes the detailed design of the CCD dewar and the camera system which is a part of the wide-field imager Hyper Suprime-Cam (HSC) on the 8.2 m Subaru Telescope. On the 1.°5 ...diameter focal plane (497 mm in physical size), 116 four-side buttable 2 k × 4 k fully depleted CCDs are tiled with 0.3 mm gaps between adjacent chips, which are cooled down to −100°C by two pulse tube coolers with a capability to exhaust 100 W heat at −100°C. The design of the dewar is basically a natural extension of Suprime-Cam, incorporating some improvements such as (1) a detailed CCD positioning strategy to avoid any collision between CCDs while maximizing the filling factor of the focal plane, (2) a spherical washers mechanism adopted for the interface points to avoid any deformation caused by the tilt of the interface surface to be transferred to the focal plane, (3) the employment of a truncated-cone-shaped window, made of synthetic silica, to save the back focal space, and (4) a passive heat transfer mechanism to exhaust efficiently the heat generated from the CCD readout electronics which are accommodated inside the dewar. Extensive simulations using a finite-element analysis (FEA) method are carried out to verify that the design of the dewar is sufficient to satisfy the assigned errors. We also perform verification tests using the actually assembled CCD dewar to supplement the FEA and demonstrate that the design is adequate to ensure an excellent image quality which is key to the HSC. The details of the camera system, including the control computer system, are described as well as the assembling process of the dewar and the process of installation on the telescope.
Hyper Suprime-Cam: Filters Kawanomoto, Satoshi; Uraguchi, Fumihiro; Komiyama, Yutaka ...
Publications of the Astronomical Society of Japan,
08/2018, Letnik:
70, Številka:
4
Journal Article
Recenzirano
Abstract
We describe five broad-band filters and a narrow-band one for the Hyper Suprime-Cam (HSC) at the prime focus of the Subaru Telescope. Since the HSC is a practical successor to the ...Suprime-Cam (SC), our broad-band filter set follows the SC's SDSS g΄, r΄, i΄, z΄ filters, and Y filter, and the Hα filter is adopted as our first narrow-band filter. Filters for the HSC are quite large; therefore, they are constructed only by interference coatings. Based on a draft specification guided by that of SC's filters, we made prototype filters which were evaluated at a laboratory, and eventually used them in the actual HSC commissioning observation. Through this process, we learned that transmission measurement with a fine spatial sampling was crucial for reliable understanding of the filter characteristics, and this motivated us to develop an efficient measurement system. Since this measurement system is placed in the summit facility and functions semi-automatically, long-term monitoring of the performance of HSC filters will be achieved. We present in this paper the specifications that the HSC filter should meet, problems and solutions in filter implementation, issues found through the commissioning observing run, the new filter measurement system at the summit facility, and transmission curves and tables of the filters.
We developed a scan mirror mechanism (SMM) that enable a slit-based spectrometer or spectropolarimeter to precisely and quickly map an astronomical object. The SMM, designed to be installed in the ...optical path preceding the entrance slit, tilts a folding mirror and then moves the reflected image laterally on the slit plane, thereby feeding a different one-dimensional image to be dispersed by the spectroscopic equipment. In general, the SMM is required to scan quickly and broadly while precisely placing the slit position across the field-of-view (FOV). These performances are in high demand for near-future observations, such as studies on the magnetohydrodynamics of the photosphere and the chromosphere. Our SMM implements a closed-loop control system by installing electromagnetic actuators and gap-based capacitance sensors. Our optical test measurements confirmed that the SMM fulfills the following performance criteria: i) supreme scan-step uniformity (linearity of 0.08
%
) across the wide scan range (
±
1005
″
), ii) high stability (
3
σ
=
0.1
″
), where the angles are expressed in mechanical angle, and iii) fast stepping speed (26 ms). The excellent capability of the SMM will be demonstrated soon in actual use by installing the mechanism for a near-infrared spectropolarimeter onboard the balloon-borne solar observatory for the third launch,
Sunrise III
.
We present properties of moderately massive clusters of galaxies detected by the newly developed Hyper Suprime-Cam on the Subaru telescope using weak gravitational lensing. Eight peaks exceeding a ...signal-to-noise ratio (S/N) of 4.5 are identified on the convergence S/N map of a 2.3 deg{sup 2} field observed during the early commissioning phase of the camera. Multi-color photometric data are used to generate optically selected clusters using the Cluster finding algorithm based on the Multiband Identification of Red-sequence galaxies algorithm. The optical cluster positions were correlated with the peak positions from the convergence map. All eight significant peaks have optical counterparts. The velocity dispersion of clusters is evaluated by adopting the Singular Isothemal Sphere fit to the tangential shear profiles, yielding virial mass estimates, M{sub 500{sub c}}, of the clusters which range from 2.7 × 10{sup 13} to 4.4 × 10 {sup 14} M{sub ⊙}. The number of peaks is considerably larger than the average number expected from ΛCDM cosmology but this is not extremely unlikely if one takes the large sample variance in the small field into account. We could, however, safely argue that the peak count strongly favors the recent Planck result suggesting a high σ{sub 8} value of 0.83. The ratio of stellar mass to the dark matter halo mass shows a clear decline as the halo mass increases. If the gas mass fraction, f{sub g}, in halos is universal, as has been suggested in the literature, the observed baryon mass in stars and gas shows a possible deficit compared with the total baryon density estimated from the baryon oscillation peaks in anisotropy of the cosmic microwave background.
ABSTRACT We present properties of moderately massive clusters of galaxies detected by the newly developed Hyper Suprime-Cam on the Subaru telescope using weak gravitational lensing. Eight peaks ...exceeding a signal-to-noise ratio (S/N) of 4.5 are identified on the convergence S/N map of a 2.3 deg2 field observed during the early commissioning phase of the camera. Multi-color photometric data are used to generate optically selected clusters using the Cluster finding algorithm based on the Multiband Identification of Red-sequence galaxies algorithm. The optical cluster positions were correlated with the peak positions from the convergence map. All eight significant peaks have optical counterparts. The velocity dispersion of clusters is evaluated by adopting the Singular Isothemal Sphere fit to the tangential shear profiles, yielding virial mass estimates, , of the clusters which range from 2.7 × 1013 to 4.4 × 10 . The number of peaks is considerably larger than the average number expected from ΛCDM cosmology but this is not extremely unlikely if one takes the large sample variance in the small field into account. We could, however, safely argue that the peak count strongly favors the recent Planck result suggesting a high value of 0.83. The ratio of stellar mass to the dark matter halo mass shows a clear decline as the halo mass increases. If the gas mass fraction, fg, in halos is universal, as has been suggested in the literature, the observed baryon mass in stars and gas shows a possible deficit compared with the total baryon density estimated from the baryon oscillation peaks in anisotropy of the cosmic microwave background.
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