Measuring galaxy [O ii] emission line doublet with future ground-based wide-field spectroscopic surveys Article - Novembre 2013

Johan Comparat, Jean-Paul Kneib, Roland Bacon, Nick J. Mostek, Jeffrey A. Newman, David J. Schlegel, Christophe Yèche

Johan Comparat, Jean-Paul Kneib, Roland Bacon, Nick J. Mostek, Jeffrey A. Newman, David J. Schlegel, Christophe Yèche, « Measuring galaxy [O ii] emission line doublet with future ground-based wide-field spectroscopic surveys  », Astronomy and Astrophysics - A&A, novembre 2013, A18. ISSN 0004-6361

Abstract

The next generation of wide-field spectroscopic redshift surveys will map the large-scale galaxy distribution in the redshift range 0.7 ≤ z ≤ 2 to measure baryonic acoustic oscillations (BAO). The primary optical signature used in this redshift range comes from the [Oii] emission line doublet, which provides a unique redshift identification that can minimize confusion with other single emission lines. To derive the required spectrograph resolution for these redshift surveys, we simulate observations of the [Oii] (λλ 3727, 3729) doublet for various instrument resolutions, and line velocities. We foresee two strategies for the choice of the resolution for future spectrographs for BAO surveys. For bright [Oii] emitter surveys ([Oii] flux 30 × 10-17 erg cm-2 s-1 like SDSS-IV/eBOSS), a resolution of R 3300 allows the separation of 90 percent of the doublets. The impact of the sky lines on the completeness in redshift is less than 6 percent. For faint [Oii] emitter surveys ([Oii] flux 10 × 10-17 erg cm-2 s-1 like DESi), the detection improves continuously with resolution, so we recommend the highest possible resolution, the limit being given by the number of pixels (4k by 4k) on the detector and the number of spectroscopic channels (2 or 3).

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