Speaker
Description
Light emission from the atmosphere, known as airglow, is imprinted on all ground-based observations. Airglow is particularly strong and dense in near-infrared spectra, forming a forest of emission lines with fluctuating intensities. To ensure observations taken with ELT instruments are used to their full potential, an ELT working-group on sky-subtraction has been established by ESO in collaboration with instrument consortia so that airglow can be removed from science data to the required sub-percent accuracy.
The working group’s current focus is on the characterisation of airglow lines, as many molecular transitions are uncatalogued and their temporal and spatial variations are poorly constrained. We present the latest progress of this effort after 26h of VLT observations on CRIRES+ in the 1.2-1.8µm wavelength range. These deep and high-resolution (R ~ 100,000) observations allow us to showcase newly catalogued faint-lines that at lower resolution masquerade as a pseudo-continuum, and we discuss how they vary temporally and spatially over 10 minute and 10" scales respectively. Finally, we present the implications of this work on various ELT instruments, most notably MOSAIC, the ELT’s multi-object spectrograph.
