Submillimeter galaxies are high redshift (z>1), high luminosity (L>=10^13 L_solar) galaxies with prodigious inferred star formation rates (~10^3 M_solar per year). It has been proposed that they are the progenitors of modern day elliptical galaxies. Redshifts are needed to measure temperatures, luminosities, and distances of the galaxies detected in submillimeter and millimeter-wave surveys. However, their star formation is highly obscured, making it difficult to determine their redshifts optically. We are building a millimeter-wave spectrometer, Z-Spec, to measure redshifts using rotational transitions of the carbon monoxide molecule, which are not subject to extinction.
The Z-Spec instrument will be used to detect CO rotational lines and also atomic fine-structure lines in submillimeter galaxies. The purpose of the instrument is to detect redshifts of submillimeter galaxy populations and introduce a new design for spectrometers intended for observing the far-infrared portion of the spectrum. The Z-Spec bolometer array and diffraction grating are cooled to 100 mK to achieve sufficient responsivity, low noise, and minimize thermal background.
The new design of Z-Spec incorporates a parallel plate waveguide grating architecture, rather than the free-space architecture. In the future, this will be very significant as its more compact design will allow for similar submillimeter spectrometers to be utilized for space-based missions.
The complete design can be found at:http://www.submm.caltech.edu/~bradford/publications/Z-Spec_SPIE02.pdf
Overview Collaborators
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