Improved data reduction procedure for the mid-infrared slit spectroscopy of AKARI/IRC LG2

Le résumé fourni par la source

The Infrared Camera (IRC) on board AKARI provides low-resolution spectroscopy (R = λ/Δλ ∼ 20–120) with three channels―NIR, MIR-S, and MIR-L. Among the observing modes of the IRC, LG2 slit spectroscopic data (17.5–25.7 μm) suffer from several instrumental artifacts, most notably contamination from the 0th and 2nd order light entering through the edge regions of the aperture mask. Because the relevant instrumental characteristics of the MIR-L channel had not been fully quantified, a standardized data-reduction procedure for LG2 slit spectroscopy was lacking. We present the first comprehensive study aimed at constructing a robust reduction method for AKARI/IRC MIR-L LG2 slit spectroscopy. Using spectroscopic observations of bright point-like sources, we examine the relative strengths of the 0th to the 1st order light as well as the efficiency profile of the 2nd order light for LG2. The slit width, slit efficiency―including corrections for diffraction-related energy loss― and the geometry of the MIR-L aperture mask are derived from imaging and spectroscopic measurements of the uniform zodiacal emission. Furthermore, we model the light contribution from the slit-less region and examine the stray-light contamination. Combining these analyses, we construct a reduction procedure that effectively removes artifacts, which could not be corrected previously, and enables accurate extraction of LG2 slit spectra, especially for extended objects. This work provides the first reliable framework for utilizing AKARI/IRC MIR-L LG2 slit spectroscopy in scientific studies.

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