The GALAH Survey: Relative throughputs of the 2dF fibre positioner and the HERMES spectrograph from stellar targets

Abstract

We present an analysis of the relative throughputs of the 3.9-metre Anglo-Australian Telescope's 2dF/HERMES system, based upon spectra acquired during the first two years of the GALAH survey. Averaged spectral fluxes of stars were compared to their photometry to determine the relative throughputs of fibres for a range of fibre position and atmospheric conditions. We find that overall the throughputs of the 771 usable fibres have been stable over the first two years of its operation. About 2.5 per cent of fibres have throughputs much lower than the average. There are also a number of yet unexplained variations between the HERMES bandpasses, and mechanically & optically linked fibre groups known as retractors or slitlets related to regions of the focal plane. These findings do not impact the science that HERMES will produce.

arXiv comment14 pages, 10 figures. Accepted for publication in MNRAS

References in corpus (15)

• Astropy: A Community Python Package for Astronomy
• The 2dF Galaxy Redshift Survey: Spectra and redshifts
• Astrophysics Source Code Library
• The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)
• Galaxy and Mass Assembly (GAMA): survey diagnostics and core data release
• The GALAH Survey: Scientific Motivation
• The WiggleZ Dark Energy Survey: Survey Design and First Data Release
• Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
• The Anglo-Australian Observatory's 2dF Facility
• Performance of AAOmega: the AAT multi-purpose fibre-fed spectrograph
• APASS Landolt-Sloan BVgri photometry of RAVE stars. I. Data, effective temperatures and reddenings
• Multi-Object Spectroscopy Field Configuration by Simulated Annealing
• Long-term stability of fibre-optic transmission for multi-object spectroscopy
• Positioning errors and efficiency in fiber spectrographs
• Starbugs: all-singing, all-dancing fibre positioning robots

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• The GALAH Survey: Observational Overview and Gaia DR1 companion
• The Southern Stellar Stream Spectroscopic Survey ($S^5$): Overview, Target Selection, Data Reduction, Validation, and Early Science
• The GALAH survey: The data reduction pipeline
• Another super-dense sub-Neptune in K2-182 b and refined mass measurements for K2-199 b and c
• K2-HERMES II. Planet-candidate properties from K2 Campaigns 1-13
• First Light Results from the Hermes Spectrograph at the AAT