OTELO

OSIRIS is the Spanish Day One instrument for the GTC 10.4m telescope. OSIRIS is a general purpose instrument for imaging, low-resolution long slit and multi-object spectroscopy (MOS). OSIRIS has a field of view of 8.6 x 8.6 arcminutes, which makes it ideal for deep surveys, and operates in the optical wavelength range from 365 through 1000 nm. The main characteristic that makes OSIRIS unique amongst other instruments in 8-10m class telescopes is the use of Tunable Filters. These allow selecting both the central wavelength and the width, thus providing narrow band imaging within the OSIRIS wavelength range.

OTELO, the key OSIRIS science project, is a deep emission line object survey to be performed with the OSIRIS Tunable Filters in selected atmospheric windows relatively free of sky emission lines. The observing strategy will allow studying a clearly defined volume of the Universe at a known flux limit. The total survey sky area is about 1 square degree distributed in different high latitude and low extinction fields with adequate angular separations. The result will result in 3D data cubes covering 150+180 Å wavelength intervals with spectral resolution of 700, from which spectra of the different sources will be retrieved. A 5σ depth of 1x10^-18 erg cm^-2s^-1 will make OTELO the deepest emission line survey to date. The expected number of emitters is of the order of 10⁴ and distributes as follows: 10% would be Hα star forming emitters up to a redshift 0.4, from which about 10% would correspond to low luminosity star forming galaxies; 70% would be star forming emitters detected at other optical emission lines up to a redshift 1.5; 5% Lyα emitters at redshifts up to 6.7, equivalent to 10% of the age of the Universe, 15% QSO and AGNs at different redshifts, and about 0.5% galactic emission stars. The spectra extracted from the data cubes will allow to deblend the Hα from the [NII]λ658.3,654.8 nm lines, thus allowing an estimation of the metal contents of the targets and the possibility to discriminate between the various AGN types. The expected depth and TF availability makes OTELO a truly unique emission line survey.

An auxiliary UBVRIJK broadband survey of the OTELO fields, currently under way, will allow, through photometric redshifts, the identification of the emission lines detected, as well as a morphological classification of the emitting sources.

The OTELO survey will be complemented with NIR spectroscopy of the high redshift targets using different instruments, and FIR (60-600 nm) images of some fields. The FIR data will be obtained via the HERSCHEL extragalactic survey that will employ some of the satellite guaranteed time to observe some OTELO fields. A fraction of the OTELO team is also part of the HERSCHEL extragalactic survey team.

OTELO Home Page

Last update December 1, 2005, by Héctor Castañeda