Z-Spec: a broadband, direct-detection, millimeter-wave spectrometer

Z-Spec is a broadband (195 310 GHz), direct-detection, millimeter-wave spectrometer with moderate resolution (R ~ 350) that we are building to observe CO rotational lines and atomic fine-structure lines in the recently discovered population of submillimeter galaxies. A large fraction of these sources cannot be identified optically and thus redshift determination is extremely difficult. The large instantaneous bandwidth of Z-Spec will allow measurement of redshifts up to z~4 via detection of two or more CO lines in a single spectrum. The spectrometer is based on a parallel-plate waveguide grating architecture that is substantially more compact than a conventional free-space grating system. The spectrometer and an array of 160 silicon nitride micromesh bolometers will be cooled to 100 mK to provide backgroundlimited sensitivity. In addition to measuring the redshifts of sources discovered in submillimeter continuum surveys, ZSpec will demonstrate a novel spectrometer concept well-suited for future far-infrared space missions.