Measuring galaxy [O ii] emission line doublet with future ground-based wide-field spectroscopic surveys
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).
Origin : Publication funded by an institution
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