The OTELO survey

A case study of [O III] λ4959,5007 emitters at ⟨z⟩ = 0.83

¹ Instituto de Radioastronomía Milimétrica (IRAM), Av. Divina Pastora 7, Núcleo Central 18012, Granada, Spain
e-mail: bongio@iram.es
² Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
³ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain
⁴ Asociación Astrofísica para la Promoción de la Investigación, Instrumentación y su Desarrollo, ASPID, 38205 La Laguna, Tenerife, Spain
⁵ Centro de Astrobiología (CSIC/INTA), 28692 ESAC Campus, Villanueva de la Cañada, Madrid, Spain
⁶ ISDEFE for European Space Astronomy Centre (ESAC)/ESA, PO Box 78, 28690 Villanueva de la Cañada, Madrid, Spain
⁷ Instituto de Astrofísica de Andalucía, CSIC, 18080 Granada, Spain
⁸ Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), 39005 Santander, Spain
⁹ Departamento de Física de la Tierra y Astrofísica, Instituto de Física de Partículas y del Cosmos, IPARCOS, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹⁰ Grantecan S. A., Centro de Astrofísica de La Palma, Cuesta de San José, 38712 Breña Baja, La Palma, Spain
¹¹ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, 05508090 São Paulo, SP, Brazil
¹² Instituto de Astronomía, Universidad Nacional Autónoma de México, 04510 Ciudad de México, Mexico
¹³ Departamento de Física, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, 07738 Ciudad de México, Mexico
¹⁴ Ethiopian Space Science and Technology Institute (ESSTI), Entoto Observatory and Research Center (EORC), Astronomy and Astrophysics Research Division, PO Box 33679, Addis Ababa, Ethiopia
¹⁵ Department of Astronomy & Astrophysics, University of Toronto, Toronto, Canada
¹⁶ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁷ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
¹⁸ DARK, Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, Copenhagen 2100, Denmark
¹⁹ English Language and Foundation Studies Centre, University of Newcastle, Callaghan, NSW 2308, Australia
²⁰ Sydney Institute of Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006, Australia
²¹ INAF, Telescopio Nazionale Galileo, Apartado de Correos 565, 38700 Santa Cruz de la Palma, Spain

Received: 15 June 2018
Accepted: 6 January 2020

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_⊙.