Design and development of MOSFIRE: the multi-object spectrometer for infrared exploration at the Keck Observatory

Abstract

MOSFIRE is a unique multi-object spectrometer and imager for the Cassegrain focus of the 10 m Keck 1 telescope. A refractive optical design provides near-IR (0.97 to 2.45 μm) multi-object spectroscopy over a 6.14' x 6.14' field of view with a resolving power of R~3,270 for a 0.7" slit width (2.9 pixels in the dispersion direction), or imaging over a field of view of 6.8' diameter with 0.18" per pixel sampling. A single diffraction grating can be set at two fixed angles, and order-sorting filters provide spectra that cover the K, H, J or Y bands by selecting 3rd, 4 th , 5 th or 6 th order respectively. A folding flat following the field lens is equipped with piezo transducers to provide tip/tilt control for flexure compensation at the 0.1 pixel level. A special feature of MOSFIRE is that its multiplex advantage of up to 46 slits is achieved using a cryogenic Configurable Slit Unit or CSU developed in collaboration with the Swiss Centre for Electronics and Micro Technology (CSEM). The CSU is reconfigurable under remote control in less than 5 minutes without any thermal cycling of the instrument. Slits are formed by moving opposable bars from both sides of the focal plane. An individual slit has a length of 7.1" but bar positions can be aligned to make longer slits. When masking bars are removed to their full extent and the grating is changed to a mirror, MOSFIRE becomes a wide-field imager. Using a single, ASIC-driven, 2K x 2K H2-RG HgCdTe array from Teledyne Imaging Sensors with exceptionally low dark current and low noise, MOSFIRE will be extremely sensitive and ideal for a wide range of science applications. This paper describes the design and testing of the instrument prior to delivery later in 2010.

z ∼ 2: An Epoch of Disk Assembly

“…The galaxies in SIGMA are located in the UDS, GOODS-S, and GOODS-N fields. Spectra were taken with the MOSFIRE spectrograph (McLean et al 2010(McLean et al , 2012 on the Keck I telescope as a part of the TKRS-2 survey (Wirth et al 2015) and were also published in Trump et al (2013) and Barro et al (2014). The slits were 0 7 wide and the spectral resolution wasR…”

A HIGH FRACTION OF Lyα EMITTERS AMONG GALAXIES WITH EXTREME EMISSION LINE RATIOS AT z ∼ 2*

“…The parent sample for this work consists of 315 galaxies in the redshift range 1.95 z 2.65 for which measurements (or upper McLean et al 2010McLean et al , 2012 on the Keck I telescope. An earlier version of this parent sample, with 219 galaxies, was described in detail by Steidel et al (2014), and we refer the reader to that paper for details of the MOSFIRE observations and data reduction.…”

Advances in instrumentation at the W. M. Keck Observatory

“…Commissioning is essentially complete at this time and on-sky performance meets our expectations. A detailed report is given in the paper in these proceedings by McLean et al [3] . MOSFIRE was developed for WMKO by UCLA, Caltech, and UCO, with funding from TSIP and a generous donation from Gordon and Betty Moore.…”