Update on the Magellan InfraRed Multi-Object Spectrograph (MIRMOS)

The Magellan InfraRed Multi-Object Spectrograph (MIRMOS) will be a next generation multi-object (MOS) and integral field spectrograph (IFS) for the 6.5m Magellan telescopes at Las Campanas Observatory in Chile. MIRMOS will perform R~3700 spectroscopy over a simultaneous wavelength range of 0.886-2.404um (Y, J, H, and K bands) in addition to imaging over the range of 0.7-0.886um. Target selection in the MOS mode is achieved through a cryogenic mechanism capable of making up to 92 slits over a 13'x3' field of view (FoV). This mechanism can be reconfigured in real time to adjust slit widths for seeing conditions, change to a different mask, or form a long slit. The IFS mode of operation for MIRMOS will be achieved via an image slicer style integral field unit (IFU) which will provide an ~18"x26" FoV made up of 0.84"x26" slices. MIRMOS's design will allow it to address a wide range of science cases from performing spectroscopy of high-redshift galaxies as well as high signal-to-noise transmission spectroscopy of exoplanet atmospheres with the MOS/long slit mode, while also having the largest FoV IFS operating on a large telescope at these wavelengths. We will describe here the design of the MIRMOS instrument -- now at the end of the preliminary design phase.