Development and demonstration of an on-detector technique to limit the impact of atmospheric emission lines on near-infrared spectra
| dc.contributor.author | Grosson, Theodore | |
| dc.contributor.supervisor | McConnachie, Alan | |
| dc.contributor.supervisor | Venn, Kimberley Ann | |
| dc.date.accessioned | 2024-08-30T21:32:21Z | |
| dc.date.available | 2024-08-30T21:32:21Z | |
| dc.date.issued | 2024 | |
| dc.degree.department | Department of Physics and Astronomy | |
| dc.degree.level | Master of Science MSc | |
| dc.description.abstract | Observations in the near-infrared using large ground-based telescopes are limited by bright atmospheric emission lines, particularly the OH Meinel bands. These lines can saturate a spectrograph on the order of minutes, resulting in the loss of information at wavelengths containing the lines. OH lines also vary on the scale of minutes, so observations longer than this timescale cannot capture this variability. Both of these properties necessitate the use of short exposure times in order to perform accurate sky subtraction. To observe faint science targets, several short exposures must be coadded instead of taking a single long exposure. Because each exposure includes its own independent read noise, this results in an increase in the total noise of the coadded image. In this thesis I present a new method to achieve longer exposure times in near-infrared spectra without the saturation of these lines, while still preserving information about their variability so that sky subtraction can still be applied. This is accomplished by periodically resetting the pixels on an H2RG detector that contain bright lines while the rest of the detector continues integrating. This method is demonstrated on the McKellar Spectrograph, where we reset the emission lines from an arc lamp while still recording their flux. I show that, when comparing the resulting spectrum and its signal-to-noise to a more conventional observing mode, the only measurable systematic difference is a result of our imperfect setup and can be removed with a standard nonlinearity correction. This method does not have the drawbacks of other measures to mitigate the effects of OH lines, such as short exposure times or completely removing the information at the relevant wavelengths, and as such shows promise for potential future use at observatories. We advocate demonstrating this method on sky spectra at existing high-quality facilities in order to test its feasibility for use in sky subtraction schemes for premier modern spectrographs. | |
| dc.description.scholarlevel | Graduate | |
| dc.identifier.uri | https://hdl.handle.net/1828/20345 | |
| dc.language | English | eng |
| dc.language.iso | en | |
| dc.rights | Available to the World Wide Web | |
| dc.subject | Infrared detectors | |
| dc.subject | Spectroscopy | |
| dc.subject | OH lines | |
| dc.title | Development and demonstration of an on-detector technique to limit the impact of atmospheric emission lines on near-infrared spectra | |
| dc.type | Thesis |