Near-infrared (NIR) high-resolution spectroscopy is a fundamental observational method
in astronomy. It provides significant information on the kinematics, the magnetic
fields, and the chemical abundances, of astronomical objects embedded in or behind
the highly extinctive clouds or at the cosmological distances. Scientific requirements
have accelerated the development of the technology required for NIR high resolution
spectrographs using 10 m telescopes. WINERED is a near-infrared (NIR) high-resolution
spectrograph that is currently mounted on the 1.3 m Araki telescope of the Koyama
Astronomical Observatory in Kyoto-Sangyo University, Japan, and has been successfully
operated for three years. It covers a wide wavelength range from 0.90 to 1.35 mu m
(the z-, Y-, and J-bands) with a spectral resolution of R = 28,000 (Wide-mode) and
R = 80,000 (Hires-Y and Hires-J modes). WINERED has three distinctive features: (i)
optics with no cold stop, (ii) wide spectral coverage, and (iii) high sensitivity.
The first feature, originating from the Joyce proposal, was first achieved by WINERED,
with a short cutoff infrared array, cold baffles, and custom-made thermal blocking
filters, and resulted in reducing the time for development, alignment, and maintenance,
as well as the total cost. The second feature is realized with the spectral coverage
of Delta lambda/lambda similar to 1/6 in a single exposure. This wide coverage is
realized by a combination of a decent optical design with a cross-dispersed echelle
and a large format array (2k x 2k HAWAII-2RG). The Third feature, high sensitivity,
is achieved via the high-throughput optics (> 60 %) and the very low noise of the
system. The major factors affecting the high throughput are the echelle grating and
the VPH cross-disperser with high diffraction efficiencies of similar to 83 % and
similar to 86 %, respectively, and the high QE of HAWAII-2RG (83 % at 1.23 mu m).
The readout noise of the electronics and the ambient thermal background radiation
at longer wavelengths could be major noise sources. The readout noise is 5.3 e(-)
for NDR = 32, and the ambient thermal background is significantly reduced to similar
to 0.05 e(-) pix(-1) sec(-1) at 273 K. As a result, the limiting magnitudes of WINERED
are estimated to be m(J) = 13.8 mag for the 1.3 m telescope, m(J) = 16.9 mag for the
3.6 m telescope, and m(J) = 19.2 mag for 10 m telescope with adoptive optics, respectively.
Finally, we introduce some scientific highlights provided by WINERED for both emission
and absorption line objects in the fields of stars, the interstellar medium, and the
solar system.
