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Frenetic growth of supermassive black holes in the early universe

Mid-IR Astrometry

Mid-IR observing programmes would often benefit from absolute astrometry with subarcsecond accuracy, for example for comparing mid-IR images of galaxy nuclei or star-forming regions with images at other wavelengths. In this page we guide the user through the steps necessary to set up accurate absolute astrometry in the OT. The procedure at mid-IR wavelengths differs from that used in the optical because of low probability that two stars close enough to use the same guide star will be both bright at 10 or 20 microns.

Astrometry

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Telluric, flux and wavelength calibration

As at near-IR wavelengths, telluric standard star observations are required for mid-infrared spectroscopic observations to cancel telluric (atmospheric) absorption features in the data. The following is a guide to assist in selecting the most appropriate telluric standard stars. Two telluric standard observations must be included in the phase II definition for each observation lasting more than ~30 minutes, one airmass-optimized for measurement before the science target, and one for after the target.

Imaging Calibrations

Standard star observations are required for mid-IR imaging observations to allow the calibration of data onto a magnitude or flux scale. The following is a guide to assist in selecting appropriate flux standard stars. Two standard star observations must be included in the phase II definition for each observation lasting more than ~30 minutes, one airmass-optimized for measurement before the science target, and one for after the target. The Gemini staff member at the telescope will select one of these for baseline calibration, which will not be charged to the science program.

Mid-IR Spectroscopy Reduction

The midir package now includes a spectral reduction pipeline, msreduce. This can be used either with a spectrum of a single object or with two spectra, one of the science object and one of a telluric standard. In the former case a wavelength- (but not flux-) calibrated spectrum is produced, while in the latter case a flux-calibrated output spectrum can also be obtained. This section is a step-by-step description of the reduction process. The examples