Characterizing the red optical sky background fluctuations from narrow-band imaging

TL;DR

This study investigates the spatial and temporal fluctuations of the sky background at ~9000A using narrow-band imaging data, which is crucial for designing future extremely large telescope instruments to detect faint distant galaxies.

Contribution

It provides the first characterization of sky background fluctuations at ~9000A over spatial and temporal scales relevant for next-generation telescopes.

Findings

Sky background fluctuations reach ~4 arcmin spatial scales.

Temporal variations occur over timescales of about an hour.

Results inform the design of fiber-fed instruments for E-ELT.

Abstract

The detection and characterization of the physical properties of very distant galaxies will be one the prominent science case of all future Extremely Large Telescopes, including the 39m E-ELT. Multi-Object Spectroscopic instruments are potentially very important tools for studying these objects, and in particular fiber-based concepts. However, detecting and studying such faint and distant sources will require subtraction of the sky background signal (i.e., between OH airglow lines) with an accuracy of ~1%. This requires a precise and accurate knowledge of the sky background temporal and spatial fluctuations. Using FORS2 narrow-band filter imaging data, we are currently investigating what are the fluctuations of the sky background at ~9000A. We present preliminary results of sky background fluctuations from this study over spatial scales reaching ~4 arcmin, as well as first glimpses into the temporal variations of such fluctuations over timescales of the order of the hour. This study (and other complementary on-going studies) will be essential in designing the next-generation fiber-fed instruments for the E-ELT.