Study of Active Galactic Nuclei in the OTELO Survey
Creators: name: Ramón Pérez, Marina
Publisher: name: Zenodo
Year: 2017
Subjects: AGN, OTELO, active galactic nuclei, survey, emission lines

description: This thesis focuses on the OTELO survey, an emission-line survey carried out with the tunable filters of the OSIRIS instrument at the Gran Telescopio CANARIAS, currently the largest fully steerable optical reflecting telescope in the world. The combined use of tunable filters, that allowed us obtaining 2D low-resolution spectroscopy of all the sources in the field, and a large diameter telescope, which reaches very deep limiting fluxes, is ideal for the search of faint emitters.<br> In particular, we have concentrated in the study of active galactic nuclei (AGN), one of the brightest and most intriguing objects in the Universe. Galaxies hosting an AGN show strong nuclear emission due to the accretion of material by the central supermassive black hole, according to the currently accepted paradigm. Their study provides invaluable information about the formation and evolution of galaxies in the Universe.<br> During this thesis, we have performed the reduction and calibration of OTELO data from scratch, a process that has required multiple iterations and the design of specific procedures. A deep multiwavelength catalogue of sources in the field has been obtained. The next step has been the selection of emission-line objects using the information gathered in the multiwavelength catalogue as well as the pseudo-spectra built for every source in the field, an unique tool only available when working with tunable filters. We have specifically focused on the Hα population at z ∼ 0.40, one of the most intense emission-lines in the optical spectrum of galaxies which can give valuable information about the star-formation and nuclear activity when present. After that, the selection of AGN has been performed with the use of four different methods, each targeting a different spectral range. Finally, we have analysed the AGN sample, in a study that included demographics, morphology, the search for luminous and ultra-luminous infrared galaxies (LIRGs/ULIRGs), the obtention of the Hα luminosity function at z ∼ 0.40 and an analysis of the environment at this redshift.<br> The main product of this thesis is OTELO’s deep, multiwavelength catalogue of emission-line objects, which will be the basis for future works. In addition, we have obtained reliable samples of Hα emitters and of AGN in the field. The analysis performed over the AGN population has allowed us to confirm previous results, such as the prevalence of late-type galaxies, the higher incidence of AGN in ULIRGs than in LIRGs or the effectiveness of the X-rays selection method for AGN, among many others. In addition, the Hα luminosity function (LF) obtained at z ∼ 0.40 has allowed us to extend the faint-end of previous LFs, reaching luminosities almost 1 dex fainter than those of previously published works. By characterizing the AGN sources at z ∼ 0.40, we have also been able to estimate the star-formation rate of star-forming galaxies at this redshift, as well as the contribution of AGN to the total luminosity.