The OTELO survey

I. Description, data reduction, and multi-wavelength catalogue

¹ Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
e-mail: bongio@iac.es
² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain
³ Asociación Astrofísica para la Promoción de la Investigación, Instrumentación y su Desarrollo, ASPID, 38205 La Laguna, Tenerife, Spain
⁴ Centro de Astrobiología (CSIC/INTA), 28850 Torrejón de Ardoz, Madrid, Spain
⁵ ISDEFE for European Space Astronomy Centre (ESAC)/ESA, PO Box 78, 28690 Villanueva de la Cañada, Madrid, Spain
⁶ Instituto de Astrofísica de Andalucía, CSIC, 18080 Granada, Spain
⁷ Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), 39005 Santander, Spain
⁸ Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁹ Grantecan S. A., Centro de Astrofísica de La Palma, Cuesta de San José, 38712 Breña Baja, La Palma, Spain
¹⁰ Centro de Estudios de Física del Cosmos de Aragón, Plaza San Juan 1, Planta 2, 44001 Teruel, Spain
¹¹ Instituto de Astronomía, Universidad Nacional Autónoma de México, México D.F., Mexico
¹² Departamento de Física, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, México D.F., Mexico
¹³ Ethiopian Space Science and Technology Institute (ESSTI), Entoto Observatory and Research Center (EORC), Astronomy and Astrophysics Research Division, PO Box 33679, Addis Abbaba, Ethiopia
¹⁴ Department of Astronomy & Astrophysics, University of Toronto, Canada
¹⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁶ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
¹⁷ European Southern Observatory, Alonso de Córdova 3107, Vitacura Casilla 19001, Santiago, Chile
¹⁸ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura Casilla 763 0355, Santiago, Chile
¹⁹ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen Ø, Denmark
²⁰ English Language and Foundation Studies Centre, University of Newcastle, Callaghan, NSW 2308, Australia
²¹ Sydney Institute of Astronomy, School of Physics, University of Sydney, NSW 2006, Australia
²² INAF, Telescopio Nazionale Galileo, Apartado de Correos 565, 38700 Santa Cruz de la Palma, Spain

Received: 24 April 2018
Accepted: 19 September 2018

Abstract

Context. The evolution of galaxies through cosmic time is studied observationally by means of extragalactic surveys. The usefulness of these surveys is greatly improved by increasing the cosmological volume, in either depth or area, and by observing the same targets in different wavelength ranges. A multi-wavelength approach using different observational techniques can compensate for observational biases.

Aims. The OTELO survey aims to provide the deepest narrow-band survey to date in terms of minimum detectable flux and emission line equivalent width in order to detect the faintest extragalactic emission line systems. In this way, OTELO data will complements other broad-band, narrow-band, and spectroscopic surveys.

Methods. The red tunable filter of the OSIRIS instrument on the 10.4 m Gran Telescopio Canarias (GTC) is used to scan a spectral window centred at 9175 Å, which is free from strong sky emission lines, with a sampling interval of 6 Å and a bandwidth of 12 Å in the most deeply explored EGS region. Careful data reduction using improved techniques for sky ring subtraction, accurate astrometry, photometric calibration, and source extraction enables us to compile the OTELO catalogue. This catalogue is complemented with ancillary data ranging from deep X-ray to far-infrared, including high resolution HST images, which allow us to segregate the different types of targets, derive precise photometric redshifts, and obtain the morphological classification of the extragalactic objects detected.

Results. The OTELO multi-wavelength catalogue contains 11 237 entries and is 50% complete at AB magnitude 26.38. Of these sources, 6600 have photometric redshifts with an uncertainty δ z_phot better than 0.2 (1+z_phot). A total of 4336 of these sources correspond to preliminary emission line candidates, which are complemented by 81 candidate stars and 483 sources that qualify as absorption line systems. The OTELO survey results will be released to the public on the second half of 2019.