Abstract
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 [O III] 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 [O III] emitters and the LF ([O III]), 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 [O III] emitters. Consistent with simulations, the minimum detectable line flux and equivalent width in this ELS sample are ∼5 × 10−19 erg s−1 cm2 and ∼6 Å, respectively. We are able to constrain the faint-end slope (α = −1.03 ± 0.08) of the observed LF ([O III]) 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 [O III] ELSs are disc-like sources, and 87% of this sample is comprised of galaxies with stellar masses of M⋆ < 1010 M⊙.
Highlights
The analysis of the strength and profile of emission lines in galaxy spectra provides basic information about the kinematics, density temperature, and chemical composition of the ionised gas, allowing inferences about dust extinction, star-formation rate, and gas outflows
The aim of this study is to test the potential of OSIRIS Tunable Filter Emission Line Object (OTELO) for finding dwarf star-forming galaxies (SFGs) through the analysis of an [O III] emission-line sources (ELSs) sample at intermediate redshift in order to constrain its number density by probing the faint end of the luminosity function (LF)([O III]), and prepare the way for studying their intrinsic properties
We say that the deconvolution algorithm converges if a reliable theoretical spectrum is obtained from it, that is, if (i) the errors on the line fluxes obtained from the inverse deconvolution are below 50% of the line flux values, and (ii) the best theoretical continuum and equivalent width (EW) of the line, or lines, are within the limits of the corresponding parameters obtained from the simulations described in Sect
Summary
The analysis of the strength and profile of emission lines in galaxy spectra provides basic information about the kinematics, density temperature, and chemical composition of the ionised gas, allowing inferences about dust extinction, star-formation rate, and gas outflows. This enables spectral classification diagnostics between pure star-forming galaxies (SFGs) and hosts of active galactic nuclei (AGNs) independently of the galaxy mass. The detection and characterisation of sources with strong nebular emission lines (emission-line sources or ELSs) can provide a wealth of information about galaxy populations and the mechanisms that shape the galaxy-evolution process. Deep extragalactic surveys for finding faint ELSs, and model-based synthetic galaxy catalogues -with their synergies- are fundamental tools in tackling this problem
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