OTELO survey: optimal emission-line flux determination with OSIRIS/GTC
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 \sigma depth of 10^-18
erg/cm^2/s and detecting objects of EW < 0.3 A, 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 H\alpha from [NII] lines by
analyzing the flux errors obtained. We simulated the OTELO data by
convolving a complete set of synthetic HII galaxies in EW with different
widths of the OSIRIS TFs. We estimated relative flux errors of the
recovered H\alpha and [NII]6583 lines. We found that, for the red TF, a
FWHM of 12 A and a sampling of 5 A is an optimal combination that allow
deblending H\alpha from the [NII]6583 line with a flux error lower than
20%. This combination will allow estimating SFRs and metallicities using
the H\alpha flux and the N2 method, respectively.