The Circumgalactic H-alpha Spectrograph (CHαS) is a ground-based, narrowband optical integral field spectrograph designed to observe ultra-faint extended emission from ionized gas in the nearby universe. Commissioned for use as a facility instrument at MDM observatory, we are currently surveying nearby galaxies to produce deep H-alpha images and velocity maps, complemented with observations in other wavelengths. We present our work developing a robust analysis pipeline for CHαS, providing a toolkit to process images with densely-packed, spatially-resolved spectra. The pipeline includes techniques for astrometric refinement, wavelength mapping and distortion calibration of arrayed spectral images, as well as manipulations in Fourier space. With these, we are able to optimize our image registration and stacking procedures, sky background removal and spectral cube extraction for the tightly packed microlens array images. We highlight results using 5-10h deep image stacks and demonstrate results from cross-correlation with imaging and spectral data from other astronomical surveys.
The Circumgalactic Hα Spectrograph (CHαS) is a new narrowband integral field spectrograph optimized for observing faint emission from the ionized circumgalactic medium (CGM) of nearby galaxies. CHαS is deployed on the 2.4m Hiltner telescope at MDM Observatory in Arizona, where we are conducting an initial science survey collecting deep spectral imaging of 10 galaxies in Ha emission. Here we debut the commissioning of a blue channel, extending the spectral coverage to include Hβ and OIII emission. We present modeling for new narrowband filters that can tilt in order to center on different wavelengths, expanding our range of observable redshifts while limiting spectral overlap. Finally, we discuss the development of an actuated lenslet array mount to precisely shift the lenslet array across the focal plane, offsetting instrument flexure. CHαS will be an ideal test-bed for new focal plane and detector technologies as we develop it into a facility instrument at MDM Observatory.
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