The GALAH survey: the data reduction pipeline

Kos, Janez and Lin, Jane and Zwitter, Tomaz and Zerjal, Maruska and Sharma, Sanjib and Bland-Hawthorn, Joss and Asplund, Martin and Casey, Andrew R. and de Silva, Gayandhi M. and Freeman, Ken C. and Martell, Sarah L. and Simpson, Jeffrey D. and Schlesinger, Katharine J. and Zucker, Daniel and Anguiano, Borja and Bacigalupo, Carlos and Bedding, Timothy R. and Betters, Christopher and Da Costa, Gary and Duong, Ly and Hyde, Elaina and Ireland, Michael and Kafle, Prajwal R. and Leon-Saval, Sergio and Lewis, Geraint F. and Munari, Ulisse and Nataf, David and Stello, Dennis and Tinney, C. G. and Traven, Gregor and Watson, Fred and Wittenmyer, Robert A. (2017) The GALAH survey: the data reduction pipeline. Monthly Notices of the Royal Astronomical Society, 464 (2). pp. 1259-1281. ISSN 0035-8711

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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 (≲0.5 per cent) and scattered light (˜5 counts in a typical 20 min exposure), resolution across the field, sky spectrum properties, wavelength solution reliability (better than 1 km s-1 accuracy), and radial velocity precision.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version made available under License.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 18 May 2017 04:14
Last Modified: 15 Feb 2019 01:31
Uncontrolled Keywords: atmospheric effects; instrumentation: spectrographs; methods: observational; techniques: spectroscopic; surveys; stars: atmospheres
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1093/mnras/stw2064

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