2020A&A...635A..35B

Context. The OSIRIS Tunable Filter Emission Line Object (OTELO) survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution.
Aims. Here, we aim to determine the main properties and luminosity function (LF) of the [OIII] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys.
Methods. The selection and analysis procedures of ELS candidates obtained using tunable filter pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [OIII] emitters and the LF ([OIII]), including the main selection biases and uncertainties, are presented.
Results. From 541 preliminary emission-line source candidates selected around z=0.8, a total of 184 sources were confirmed as [OIII] emitters. Consistent with simulations, the minimum detectable line flux and equivalent width in this ELS sample are ∼5x10^–19erg/s/cm² and ∼6Å, respectively. We are able to constrain the faint-end slope (α=-1.03±0.08) of the observed LF ([OIII]) at a mean redshift of z=0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84%) of the morphologically classified [OIII] ELSs are disc-like sources, and 87% of this sample is comprised of galaxies with stellar masses of M*<10¹⁰M_☉.