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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2404.05283 |
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| _version_ | 1866916197592727552 |
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| author | Schmidt, Tobias M. Bouchy, François |
| author_facet | Schmidt, Tobias M. Bouchy, François |
| contents | Achieving a truly accurate wavelength calibration of high-dispersion echelle spectrographs is a challenging task but crucially needed for certain science cases, e.g. to test for a possible variation of the fine-structure constant in quasar spectra. One of the spectrographs best suited for this mission is VLT/ESPRESSO. Nevertheless, previous studies have identified significant discrepancies between the classical wavelength solutions and the one derived independently from the laser frequency comb. The dominant parts of these systematics were intra-order distortions, most-likely related to a deviation of the instrumental line-spread function from the assumed Gaussian shape. Here, we therefore present a study focused on a detailed modeling of the ESPRESSO instrumental line-spread function. We demonstrate that it is strongly asymmetric, non-Gaussian, different for the two slices and fibers, and varies significantly along the spectral orders. Incorporating the determined non-parametric model in the wavelength calibration process drastically improves the wavelength calibration accuracy, reducing the discrepancies between the two independent wavelength solutions from 50m/s to about 10m/s. The most striking success is, however, that the different fibers and slices now provide fully consistent measurements with a scatter of just a couple m/s. This demonstrates that the instrument-related systematics can be nearly eliminated over most of the spectral range by properly taking into account the complex shape of the instrumental line-spread function and paves the way for further optimizations of the wavelength calibration process. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_05283 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Characterization of the ESPRESSO Line-Spread Function and Improvement of the Wavelength Calibration Accuracy Schmidt, Tobias M. Bouchy, François Instrumentation and Methods for Astrophysics Cosmology and Nongalactic Astrophysics Achieving a truly accurate wavelength calibration of high-dispersion echelle spectrographs is a challenging task but crucially needed for certain science cases, e.g. to test for a possible variation of the fine-structure constant in quasar spectra. One of the spectrographs best suited for this mission is VLT/ESPRESSO. Nevertheless, previous studies have identified significant discrepancies between the classical wavelength solutions and the one derived independently from the laser frequency comb. The dominant parts of these systematics were intra-order distortions, most-likely related to a deviation of the instrumental line-spread function from the assumed Gaussian shape. Here, we therefore present a study focused on a detailed modeling of the ESPRESSO instrumental line-spread function. We demonstrate that it is strongly asymmetric, non-Gaussian, different for the two slices and fibers, and varies significantly along the spectral orders. Incorporating the determined non-parametric model in the wavelength calibration process drastically improves the wavelength calibration accuracy, reducing the discrepancies between the two independent wavelength solutions from 50m/s to about 10m/s. The most striking success is, however, that the different fibers and slices now provide fully consistent measurements with a scatter of just a couple m/s. This demonstrates that the instrument-related systematics can be nearly eliminated over most of the spectral range by properly taking into account the complex shape of the instrumental line-spread function and paves the way for further optimizations of the wavelength calibration process. |
| title | Characterization of the ESPRESSO Line-Spread Function and Improvement of the Wavelength Calibration Accuracy |
| topic | Instrumentation and Methods for Astrophysics Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2404.05283 |