OTELO survey: optimal emission-line flux determination with OSIRIS/GTC

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Emission-line galaxies are important targets for understanding the chemical evolution of galaxies in the universe. Deep, narrow-band imaging surveys allow to detect and study the flux and the equivalent widths (EW) of the emission line studied. The present work has been developed within the context of the OTELO project, an emission line survey using the Tunable Filters (TF) of OSIRIS, the first generation instrument on the GTC 10.4m telescope located in La Palma, Spain, that will observe through selected atmospheric windows relatively free of sky emission lines. With a total survey area of 0.1 square degrees distributed in different fields, reaching a 5 σ depth of 10^(−18) erg/cm^(2) /s and detecting objects of EW < 0.3 Å, OTELO will be the deepest emission line survey to date. As part of the OTELO preparatory activities, the objective of this study is to determine the best combination of sampling and full width at half maximum (FWHM) for the OSIRIS tunable filters for deblending Hα from [N ii] lines by analyzing the flux errors obtained. We simulated the OTELO data by convolving a complete set of synthetic H ii galaxies in EW with different widths of the OSIRIS TFs. We estimated relative flux errors of the recovered Hα and [N ii]λ6583 lines. We found that, for the red TF, a FWHM of 12 Å and a sampling of 5 Å is an optimal combination that allow deblending Hα from the [N ii]λ6583 line with a flux error lower than 20%. This combination will allow estimating SFRs and metallicities using the Hα flux and the N2 method, respectively.
© 2011. The Astronomical Society of the Pacific. Artículo firmado por 13 autores. This work was supported by the Spanish Plan Nacional de Astronomía y Astrofísica under grant AYA2008-06311-C02-01. The Sloan Digital Sky Survey (SDSS) is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Max Planck Institute for Astronomy, Princeton University, the US Naval Observatory, and the University of Washington. Apache Point Observatory, site of the SDSS, is operated by the Astrophysical Research Consortium. Funding for the project has been provided by the Alfred P. Sloan Foundation, the SDSS member institutions, the National Aeronautics and Space Administration, the National Science Foundation, the US Department of Energy, and Monbusho. We thank the anonymous referee for all his/her constructive comments. Maritza A. Lara-López is supported by a Consejo Nacional de Ciencia y Tecnología and Secretaria de Educación Pública Mexican fellowships.
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