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.
Abstract
We have developed an automated quick data analysis system for data quality assurance (QA) for Hyper Suprime-Cam (HSC). The system was commissioned in 2012–2014, and has been offered for ...general observations, including the HSC Subaru Strategic Program, since 2014 March. The system provides observers with data quality information, such as seeing, sky background level, and sky transparency, based on quick analysis as data are acquired. Quick-look images and validation of image focus are also provided through an interactive web application. The system is responsible for the automatic extraction of QA information from acquired raw data into a database, to assist with observation planning, assess progress of all observing programs, and monitor long-term efficiency variations of the instrument and telescope. Enhancements of the system are being planned to facilitate final data analysis, to improve the HSC archive, and to provide legacy products for astronomical communities.
Extensive air showers induced from high-energy cosmic rays provide a window into understanding the most energetic phenomena in the universe. We present a new method for observing these showers using ...the silicon imaging detector Subaru Hyper Suprime-Cam (HSC). This method has the advantage of being able to measure individual secondary particles. When paired with a surface detector array, silicon imaging detectors like Subaru HSC will be useful for studying the properties of extensive air showers in detail. The following report outlines the first results of observing extensive air showers with Subaru HSC. The potential for reconstructing the incident direction of primary cosmic rays is demonstrated and possible interdisciplinary applications are discussed.
Abstract
We use MMT spectroscopy and deep Subaru Hyper Suprime-Cam (HSC) imaging to compare the spectroscopic central stellar velocity dispersion of quiescent galaxies with the effective dispersion ...of the dark matter halo derived from the stacked lensing signal. The spectroscopic survey (the Smithsonian Hectospec Lensing Survey) provides a sample of 4585 quiescent galaxy lenses with measured line-of-sight central stellar velocity dispersion (
σ
SHELS
) that is more than 85% complete for
R
< 20.6,
D
n
4000 > 1.5 and
M
⋆
> 10
9.5
M
⊙
. The median redshift of the sample of lenses is 0.32. We measure the stacked lensing signal from the HSC deep imaging. The central stellar velocity dispersion is directly proportional to the velocity dispersion derived from the lensing
σ
Lens
,
. The independent spectroscopic and weak lensing velocity dispersions probe different scales, ∼3 kpc and ≳100 kpc, respectively, and strongly indicate that the observable central stellar velocity dispersion for quiescent galaxies is a good proxy for the velocity dispersion of the dark matter halo. We thus demonstrate the power of combining high-quality imaging and spectroscopy to shed light on the connection between galaxies and their dark matter halos.
We present the design and performance of the High Dispersion Spectrograph (HDS) of the Subaru Telescope. HDS is an echelle spectrograph located at the Nasmyth focus of the telescope. The collimated ...beam size is 272 mm, and the echelle is 300 mm by 840 mm in total size (
$31.6 \,\mathrm{gr} \,\mathrm{mm}^{-1}, R=2.8$
). HDS has two cross-dispersing gratings with
$400 \,\mathrm{gr} \,\mathrm{mm}^{-1}$
and
$250 \,\mathrm{gr} \,\mathrm{mm}^{-1}$
, which are optimized for the blue and red wavelength regions, respectively. The camera is of the catadioptric type system, consisting of three corrector lenses and a mirror. Two EEV-CCD’s with
$4100 \times 2048$
pixels and a pixel size of 13.5
${\mu \mathrm {m}}$
are used as the detector. A standard configuration with a
${0\rlap {.}{}^{\mathrm {\prime \prime }}4}$
slit gives a spectral resolution of
$R=90000$
, and a narrower slit width enables higher resolution of up to
$R \sim 160000$
. The spectrograph has sensitivities from 3000
${Å}$
to 1
${\mu \mathrm {m}}$
, and one exposure covers a range of 1500–2500
${Å}$
, depending on the wavelength region. The throughput of the telescope and the spectrograph, including the efficiency of the detector, is about 13% in 5000–6000
${Å}$
and about 8% at 4000
${Å}$
. The stability of the spectrograph and scattered light level are also reported.
ABSTRACT
We describe a weak lensing view of the downsizing of star-forming galaxies based on cross-correlating a weak lensing (
κ
) map with a predicted map constructed from a redshift survey. ...Moderately deep and high-resolution images with Subaru/Hyper Suprime-Cam covering the
DLS F2 field provide a
κ
map with 1 arcmin resolution. A dense complete redshift survey of the F2 field including 12,705 galaxies with
is the basis for construction of the predicted map. The zero-lag cross-correlation between the
κ
and predicted maps is significant at the 30
σ
level. The width of the cross-correlation peak is comparable to the angular scale of rich clusters at
, the median depth of the redshift survey. Slices of the predicted map in
redshift bins enable exploration of the impact of structure as a function of redshift. The zero-lag normalized cross-correlation has significant local maxima at redshifts coinciding with known massive X-ray clusters. Even in slices where there are no known massive clusters, there is a significant signal in the cross-correlation originating from lower mass groups that trace the large-scale of the universe. Spectroscopic
measurements enable division of the sample into star-forming and quiescent populations. In regions surrounding massive clusters of galaxies, the significance of the cross-correlation with maps based on star-forming galaxies increases with redshift from 5
σ
at
z
= 0.3 to 7
σ
at
the fractional contribution of the star-forming population to the total cross-correlation signal also increases with redshift. This weak lensing view is consistent with the downsizing picture of galaxy evolution established from other independent studies.
With an aim to study whether the close correlation between Na/H and Fe/H recently found in A-type stars further persists in the regime of B-type stars, the abundances of Na were determined for 30 ...selected sharp-lined late B-type stars (10000 K ≲ T
eff ≲ 14000 K) from the Na i 5890/5896 doublet. These Na abundances were then compared with the O and Fe abundances (derived from the O i
6156–8 and Fe ii 6147/6149 lines) showing anti-correlated peculiarities. It turned out that, unlike in the case of A-type stars, Na/H is roughly constant at a slightly subsolar level {Na/H ∼ −0.2 (±0.2)} without any significant correlation with Fe/H, which shows considerable dispersion ranging from ∼ −0.6 to ∼ +1.0. This may serve as an important observational constraint for understanding the abundance peculiarities along with the physical mechanism of atomic diffusion in upper main-sequence stars of late A- through late B-type including Am and HgMn stars.
Activity studies of solar-type stars, especially with reference to the status of our current Sun among them, have exposed the importance of (1) homogeneously selecting the sample stars and (2) ...reliably evaluating their activities down to a considerably low level. Motivated by these requirements, we conducted an extensive study on the activities of 118 solar-analog stars (of sufficiently similar properties to each other) by measuring the emission strength at the core of Ca II 3933.663 line (K line) on the high-dispersion spectrogram obtained by Subaru/HDS, where special attention was paid to correctly detecting the chromospheric emission by removing the wing-fitted photospheric profile calculated from the classical solar model atmosphere. This enabled us to detect low-level activities down to log
$R'$
$\sim$
$-$
5.4 (
$R'$
is the ratio of the chromospheric core emission flux to the total bolometric flux), by which we could detect subtle activity differences that were indiscernible in previous studies. Regarding the Sun, we found log
$R'_{\odot}$
$=$
$-$
5.33 near to the low end of the distribution, which means that it belongs to the distinctly low-activity group among solar analogs. This excludes the once-suggested possibility for the high frequency of Maunder-minimum stars showing appreciably lower activities than the minimum-Sun.
The abundances of alkali elements (Li, Na, and K) were determined from the Li I 6708, Na I 5682/5688, and K I 7699 lines by taking into account the non-LTE effect for 24 sharp-lined A-type stars (
$v ..._{\rm e}$
sin
$i$
$\lesssim$
50 km s
$^{-1}$
, 7000 K
$\lesssim$
$T_{\rm eff}$
$\lesssim$
10000 K, many showing Am peculiarities to different degrees), based on high-dispersion and high-
$S/N$
spectral data secured at BOAO (Korea) and OAO (Japan). We found a significant trend that
$A$
(Na) tightly scales with
$A$
(Fe) irrespective of
$T_{\rm eff}$
, which means that Na becomes enriched similarly to Fe in accordance with the degree of Am peculiarity. Regarding lithium,
$A$
(Li) mostly ranges between
$\sim$
3 and
$\sim$
3.5 (i.e., almost the same as or slightly less than the solar system abundance of 3.3) with a weak decreasing tendency with a lowering of
$T_{\rm eff}$
at
$T_{\rm eff}$
$\lesssim$
8000 K, though several stars exceptionally show distinctly larger depletion. The abundances of potassium also revealed an apparent
$T_{\rm eff}$
-dependence in the sense that
$A$
(K) in late-A stars tends to be mildly subsolar possibly with a weak anti-correlation with
$A$
(Fe) systematically decreasing from
$\sim$
5.0 (
$T_{\rm eff}$
$\sim$
8500 K) to
$\sim$
4.6 (
$T_{\rm eff}$
$\sim$
7500 K), while those for early-A stars remain near-solar around
$\sim$
5.0–5.2. These observational facts may serve as important constraints for any theory aiming to explain chemical anomalies of A-type stars.
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