PDRs4All

The Mid-Infrared Instrument (MIRI) is the imager and spectrograph covering wavelengths from 4.9 to 27.9 μm on board the James Webb Space Telescope (JWST). The MIRI Medium-Resolution Spectrometer (MRS) consists of four integral field units (IFU) and two wheels with three rotation settings, producing four spectral channels and three spectral sub-channels.. The 12 resulting spectral data cubes have different fields of view, spatial coverages, and spectral resolutions. The wavelength range of each cube partially overlaps with the neighboring bands, and the overlap regions typically show flux mismatches that have to be corrected by spectral stitching methods. The aim of stitching methods is to produce a single data cube incorporating the data of the individual sub-channels, which requires matching the spatial resolution and the flux discrepancies. We present Haute Couture , a novel stitching algorithm that uses nonnegative matrix factorization to perform a matrix completion, where the available MRS data cubes are treated as 12 sub-matrices of a larger incomplete matrix. Prior to matrix completion, we also introduced a novel preprocessing method to homogenize the global intensities of the 12 cubes. Our preprocessing consists of jointly optimizing a set of global scale parameters that maximize the fit between the cubes where spectral overlap occurs. We applied our novel stitching method to JWST data obtained as part of the PDRs4All observing program of the Orion Bar and produced a uniform cube reconstructed with the best spatial resolution over the full range of wavelengths.