论文标题
圆形h $α$光谱仪（ch $α$ s）I。设计，工程和早期调试
The Circumgalactic H$α$ Spectrograph (CH$α$S) I. Design, Engineering, and Early Commissioning
论文作者
论文摘要
圆形H $α$光谱仪（CH $α$ S）是一个基于地面的光学集成场光谱仪，旨在检测附近宇宙中弥漫性电离气体的超生物延长发射。 CH $α$ S特别适合直接检测到低红色速度星系周围的近代培养基（CGM）的脆弱H $α$。它有效地将CGM的大区域映射为单一曝光，以附近的星系为目标（D $ <35 $ MPC），其中CGM有望填补视野。我们正在委托Ch $α$ S作为MDM天文台的设施工具。 CH $α$ S部署在Hiltner 2.4米望远镜的焦平面上，几乎利用望远镜的所有未覆盖的焦平面（10 Arcmin）进行宽场光谱成像。 Catadioptric设计提供了出色的宽场成像性能。 Ch $α$ S是使用Microlens阵列将视野划分为$ 60,000 $光谱的学生成像光谱仪。 CH $α$ S实现$ [1.3-2.8] $ arcseconds的角度分辨率和R $ = [10,000-20,000] $的解决能力。因此，光谱仪可以在$ 1-5 $ kpc（以10 MPC为单位）的尺度上解析结构，并将速度降低至15-30 km/s。 ch $α$ s有意在狭窄（30 Angstrom）带通道上运行；但是，它配置为调整中心波长并分别针对多种光学发射线。高衍射效率VPH光栅可确保跨配置的高通量。 CH $α$ S保持高度掌握和中等光谱分辨率，为在几毫米 - 拉力赛的顺序上绘制离散的超低表面亮度发射提供了理想的组合。
The Circumgalactic H$α$ Spectrograph (CH$α$S) is a ground-based optical integral field spectrograph designed to detect ultra-faint extended emission from diffuse ionized gas in the nearby universe. CH$α$S is particularly well suited for making a direct detection of tenuous H$α$ emission from the circumgalactic medium (CGM) surrounding low-redshift galaxies. It efficiently maps large regions of the CGM in a single exposure, targeting nearby galaxies (d $< 35 $ Mpc) where the CGM is expected to fill the field of view. We are commissioning CH$α$S as a facility instrument at MDM Observatory. CH$α$S is deployed in the focal plane of the Hiltner 2.4-meter telescope, utilizing nearly all of the telescope's unvignetted focal plane (10 arcmin) to conduct wide-field spectroscopic imaging. The catadioptric design provides excellent wide-field imaging performance. CH$α$S is a pupil-imaging spectrograph employing a microlens array to divide the field of view into $> 60,000$ spectra. CH$α$S achieves an angular resolution of $[1.3 - 2.8]$ arcseconds and a resolving power of R$ = [10,000 - 20,000]$. Accordingly, the spectrograph can resolve structure on the scale of $1-5$ kpc (at 10 Mpc) and measure velocities down to 15-30 km/s. CH$α$S intentionally operates over a narrow (30 Angstrom) bandpass; however, it is configured to adjust the central wavelength and target a broad range of optical emission lines individually. A high diffraction efficiency VPH grating ensures high throughput across configurations. CH$α$S maintains a high grasp and moderate spectral resolution, providing an ideal combination for mapping discrete, ultra-low surface brightness emission on the order of a few milli-Raleigh.
