The GALAH survey

the data reduction pipeline

Janez Kos*, Jane Lin, Tomaž Zwitter, Maruška Žerjal, Sanjib Sharma, Joss Bland-Hawthorn, Martin Asplund, Andrew R. Casey, Gayandhi M. De Silva, Ken C. Freeman, Sarah L. Martell, Jeffrey D. Simpson, Katharine J. Schlesinger, Daniel Zucker, Borja Anguiano Jimenez, Carlos Bacigalupo, Timothy R. Bedding, Christopher Betters, Gary Da Costa, Ly Duong & 12 others Elaina Hyde, Michael Ireland, Prajwal R. Kafle, Sergio Leon-Saval, Geraint F. Lewis, Ulisse Munari, David Nataf, Dennis Stello, C. G. Tinney, Gregor Traven, Fred Watson, Robert A. Wittenmyer

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

We present the data reduction procedures being used by the GALactic Archeology with Hermes (GALAH) survey, carried out with the HERMES fibre-fed, multi-object spectrograph on the 3.9-m Anglo-Australian Telescope. GALAH is a unique survey, targeting 1 million stars brighter than magnitude V = 14 at a resolution of 28 000 with a goal to measure the abundances of 29 elements. Such a large number of high-resolution spectra necessitate the development of a reduction pipeline optimized for speed, accuracy, and consistency. We outline the design and structure of the IRAF-based reduction pipeline that we developed, specifically for GALAH, to produce fully calibrated spectra aimed for subsequent stellar atmospheric parameter estimation. The pipeline takes advantage of existing IRAF routines and other readily available software so as to be simple to maintain, testable, and reliable. A radial velocity and stellar atmospheric parameter estimator code is also presented, which is used for further data analysis and yields a useful verification of the reduction quality. We have used this estimator to quantify the data quality of GALAH for fibre cross-talk level (less than or similar to 0.5 per cent) and scattered light (similar to 5 counts in a typical 20 min exposure), resolution across the field, sky spectrum properties, wavelength solution reliability (better than 1 kms(-1) accuracy), and radial velocity precision.

Original languageEnglish
Pages (from-to)1259-1281
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Volume464
Issue number2
DOIs
Publication statusPublished - Jan 2017

Bibliographical note

Copyright 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. First published in Monthly Notices of the Royal Astronomical Society, 464(2), pp.1259–1281. The original publication is available at https://doi.org/10.1093/mnras/stw2064. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • atmospheric effects
  • instrumentation: spectrographs
  • methods: observational
  • techniques: spectroscopic
  • surveys
  • stars: atmospheres

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