adsabs/WIESP2022-NER huggingface dataset:
Paper: 2016A&A...591A..74D (fulltext)
at high absolute RVs after subtracting out the main Gaussian components from the observed profiles. A wide component is very often found in H, while narrow components are occasionally found in [S II] and, with less confidence, in H as well. We have found several distinct pieces of evidence that such wide H wings arise from reflection of the Car spectrum (in agreement with previous studies), and that the reflecting dust is likely radially expanding to account for the observed asymmetry in these wings. Reflection nebulosity is also indicated by the level of sky continuum in places other than the Keyhole, notably near the Tr 14 core. The [S II] narrow components are instead suggestive of localized shocks, as also hypothesized for the diffuse X-ray emission already known in the region. We note that the observational data presented here were not originally taken with the purpose of studying the nebular emission. According to the Gaia -ESO Survey observing strategy, a number of fibers are routinely targeted at empty sky positions in order to eliminate the sky contribution from the stellar spectra. This study demonstrates the rich scientific content of the Gaia -ESO Survey data, even surpassing their intended objectives. Appendix A: Giraffe/HR15N instrumental line profile In Sect. 3.2 we examined best-fit residuals with amplitudes of 12% with respect to peak emission. Our ability to draw meaningful conclusions from such low-level features (in relative terms) in our data requires some detailed understanding of the instrumental response. We therefore examined Th–Ar calibration lamp spectra that are nearly simultaneous to some of the data studied here. These spectra are crowded in lines, and therefore only very few lines were isolated and bright enough to study their extreme tails down to less than 1% of peak. One such example is shown in Fig. A.1 , where the abscissa is transformed into a velocity scale to facilitate comparison with the results in Sect. 3.2 . In the same figure we show one-Gaussian (red) and two-Gaussian (blue) best-fit models to the lamp line profile, and their residuals. The one-Gaussian model is discrepant from the observed line profile at a level of 34% maximum. The two-Gaussian model residuals are much smaller, slightly exceeding 1% discrepancy. The profile obtained by convolving the lamp profile with a Gaussian with km s (e.g., a typical turbulent or thermal width), however, yields residuals of only 1% when fitted with only one Gaussian. At face value, this would suggest that by approximating the instrumental spectral response with a simple Gaussian we should expect spurious fit residuals on the order of 1% of peak emission. However, in Fig. 17 we observe that the oscillating residuals around zero velocity often exceed the 1% level (indicated by the horizontal dashed lines), and show a typical peak-to-peak RV interval of 3040 km s, while the residual oscillations in Fig. A.1 occur at the 12 pixel level (RV intervals 48 km