Volume 585, January 2016
|Number of page(s)||19|
|Published online||16 December 2015|
The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: selecting emission line galaxies using the Fisher discriminant
1 CEA, Centre de Saclay, IRFU/SPP, 91191 Gif-sur-Yvette, France
2 Departamento de Fisica Teorica, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid, Spain
3 Instituto de Física Teórica, (UAM/CSIC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
4 Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
5 Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
6 Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, PR China
7 Department of Physics and Astronomy, University College London, Gower Street, London WC1E6 BT, UK
8 Department of Physics and Electronics, Rhodes University, PO Box 94, 6140 Grahamstown, South Africa
9 Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112, USA
10 Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000 México, D. F. Mexico
11 Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
12 Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, 200240 Shanghai, PR China
13 McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA
14 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, PR China
15 Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA
16 Institute of Cosmology & Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX, UK
17 Institutode Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18080 Granada, Spain
18 Campus of International Excellence UAM+CSIC, Cantoblanco, 28049 Madrid, Spain
Received: 7 May 2015
Accepted: 26 August 2015
We present a new selection technique of producing spectroscopic target catalogues for massive spectroscopic surveys for cosmology. This work was conducted in the context of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), which will use ~200 000 emission line galaxies (ELGs) at 0.6 ≤ zspec ≤ 1.0 to obtain a precise baryon acoustic oscillation measurement. Our proposed selection technique is based on optical and near-infrared broad-band filter photometry. We used a training sample to define a quantity, the Fisher discriminant (linear combination of colours), which correlates best with the desired properties of the target: redshift and [Oii] flux. The proposed selections are simply done by applying a cut on magnitudes and this Fisher discriminant. We used public data and dedicated SDSS spectroscopy to quantify the redshift distribution and [Oii] flux of our ELG target selections. We demonstrate that two of our selections fulfil the initial eBOSS/ELG redshift requirements: for a target density of 180 deg-2, ~70% of the selected objects have 0.6 ≤ zspec ≤ 1.0 and only ~1% of those galaxies in the range 0.6 ≤ zspec ≤ 1.0 are expected to have a catastrophic zspec estimate. Additionally, the stacked spectra and stacked deep images for those two selections show characteristic features of star-forming galaxies. The proposed approach using the Fisher discriminant could, however, be used to efficiently select other galaxy populations, based on multi-band photometry, providing that spectroscopic information isavailable. This technique could thus be useful for other future massive spectroscopic surveys such as PFS, DESI, and 4MOST.
Key words: methods: data analysis / galaxies: general / galaxies: star formation / galaxies: stellar content
© ESO, 2015
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