Development of a near-infrared high-resolution spectrograph (WINERED) for a survey of bulge stars

Abstract

Abstract. We are developing a new near-infrared high-resolution (R[max] = 100,000) and high-sensitive spectrograph WINERED, which is specifically customized for short NIR bands at 0.9-1.35 µm. WINERED employs an innovative optical system; a portable design and a warm optics without any cold stops. The planned astrometric space mission JASMINE will provide precise positions, distances, and proper motions of the bulge stars. The missing components, the radial velocity and chemical composition will be measured by WINERED. These combined data brought by JASMINE and WINERED will certainly reveal the nature of the Galactic bulge. We plan to complete this instrument for observations of single objects by the end of 2008 and to attach it to various 4-10m telescopes as a PI-type instrument. We hope to upgrade WINERED with a multi-object feed in the future for efficient survey of the JASMINE bulge stars.Keywords. Galaxy: bulge, infrared: stars, stars: abundances, stars: atmospheres, instrumentation: spectrographs, techniques: spectroscopic, techniques: radial velocitiesWe are developing a new NIR high-resolution spectrograph WINERED (=Warm INfrared Echelle spectrograph to Realize Extreme Dispersion) by employing two novel approaches (Ikeda et al. 2006). First, WINERED employs warm optics with no cold stop, which can be realized by limiting the wavelength range to short NIR bands of 0.9-1.35 µm. Second, WINERED employs an immersion grating of ZnSe or ZnS, resulting in a high resolving power of R max = 100,000, despite its compactness (1,500 × 500 × 500 mm). These two approaches make WINERED portable and easy to build, align, and maintain. Therefore, the total cost and time can be significantly reduced as compared with an entirely cooled classical echelle spectrograph. Warm opticsIn the short NIR region (λ 1.35 µm), the ambient thermal and sky backgrounds are negligible if compared to the readout noise (Ikeda et al. 2006, Kondo et al. 2006. It means that the cooling of entire optics is not necessary as long as we remain in this short NIR region. WINERED employs warm (room temperature) optics except for the camera system that includes the detector array (Fig. 1). The narrow wavelength range significantly increases the performance of the AR coating on the optical elements, e.g., R < 1% per surface is possible, while R > 5 % per surface is inevitable at some wavelengths for 1.0−5.5 µm broad band AR. This leads to a significant throughput improvement for WINERED which uses a large number of refractive optics for the aberration-free design. 510https://www.cambridge.org/core/terms. https://doi