Deep observational surveys at several wavelengths have shown that the early universe was a very different place than what we experience today. Space was crowded with newly-formed galaxies, those galaxies were forming stars at a prodigious rate - sometimes throughout the galaxy at once, and central black holes were rapidly consuming gas and stars in the innermost regions. Active sites were heavily enshrouded by dust, so today radiation is most easily detected in the far-infrared and sub-mm spectral regions, especially for objects at high redshift. The sub-mm grating spectrometer ZEUS-2, constructed by a team led by Dr. G. Stacey at Cornell University, is especially well-suited to studying these active regions of distant galaxies. It offers very high sensitivity, multi-object capability, and spectral resolution high enough to evaluate the conditions in the star-forming regions through the emission lines that are produced.
Dr. Stacey now intends to complete ZEUS-2 with a second Transition Edge Sensor (TES) detector array for the region 215/645 microns, as well as associated optics and electronics to operate this channel. The new capability opens spectral windows from 200 to 850 microns and samples several important lines of [N II], CO, and [CI], which are diagnostic of the physical conditions (temperature, density, etc.) in the emitting gas. Because the instrument is already fully functional in its single-array mode, the skills of Stacey's technical team are proven, and the goal of a two-detector system is relatively straightforward.
The TES arrays are cutting edge technology requiring the integration of key elements from industry, national centers, and academia. Indeed, the ZEUS instrument as a whole provides a fertile environment for the training of young scientists and students in state-of-the-art electronics and instrumentation, and undergraduate students will carry out several of the key aspects of the upgrade project. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.