COMICS medium-resolution Q-band spectroscopy

The medium-resolution Q-band grating provides a resolution of 2500 (0.66'' slit) and a dispersion of 0.002 μm/pixel. The spectrum is dispersed onto all 5 of the COMICS spectrograph's detectors, with large gaps between them. The grating tilt can be selected to vary the wavelength regions which fall on the detectors. We have now acquired an appropriate order-sorting pre-filter to observe the entire Q-band (from about 16 to 25 μm). Four grating positions are needed to completely cover this region.

The above figure is also available in a PDF format.

For convenience, each grating position (GP) is designated (corresponding to each row of the above figure, from top to bottom) New QM Short GP 1, New QM Short GP 2, New QM Long GP 1, and New QM Long GP 2 (please compare the above figure with the linked sky spectra actually observed).

There are two more figures available to help determine appropriate grating positions (qm-setting.pdf and qm-whole.png).

Sensitivity is still to be determined; however, it is thought to be similar to, or slightly better than, the sensitivity of the QM-short (16-21 μm) mode which was previously available (see below). This prediction is based upon the transmission spectrum of the new Q-wide order-sorting filter.


Old QM-short sensitivity

The point-source sensitivity of the QM grating varies with wavelengths and is shown in the following figure (1 sigma for 1 second of on-source integration time).

Reference: Old QM-short web page



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