This research project aims to bring together and consolidate the cooperation of a group of researchers with deep-rooted expertises and skills in different areas close or directly related to the AGN phenomenon, and with important national and international collaborations. We plan to make significant contributions to the resolution of some of the most important challenges in the research frontiers of AGNs covering a large range of intrinsic luminosities (from LINERs to QSOs), accretion rates (low and high), scales (from the central SMBH to galaxy clusters), and redshifts (from the local volume to high-z objects), and for the first time integrating also the perspective allowed by numerical simulations. At the smallest scales, we plan to study the physical properties of the central engine specially in radio loud quasars, to determine the properties of the obscuring torus in LINERs and Seyferts, to test the Unified Model in Seyferts and to analyze the eventual disappearance of the BLR at the lowest AGN luminosities and/or accretion rates. At scales of the host galaxy, we plan to derive kinematical and stellar content properties of Seyferts and LINERs and relate them to the AGN fueling mechanisms, as well as to study the fueling and feedback of star formation and nuclear activity in nearby objects. At the largest scales, from close pairs to galaxy aggregations with tens of members, we plan to analyze the environments of radio galaxies and type 1 AGN.

More specifically, among the milestones we hope to achieve within the context of the research subproject untitled "Understanding nuclear activity in galaxies: from low to high accretion rates" are:

1. to determine the nature of the torus in nearby and local LINERS and search for signatures of its disappearance at low luminosities;
2.  to determine the eventual contribution of outflows in the broadening of permitted emission lines in type 1 LINERs;
3.  to analyse the kinematics and stellar populations in nearby AGN with top-ranked IFU and NIR spectroscopy;
4.  to analyse the dichotomy between Radio Loud and Radio Quiet quasars and the effect of the relativistic radio jets on the gas in the broad line emitting regions;
5. to study the importance of X-ray properties for discriminating pop. A and B quasars;
6.  to study the geometry and dynamics of nuclear outflows in the most highly accreting quasars;
7.  to analyse binary black holes in the context of mergers;
8.  to study the presence and type of AGN hosts in galaxy clusters.

These fundamental problems will be tackled with data at our disposal coming from state-of-the-art instrumentation, and with data we plan to gather partly within the framework of the scientific groups of projects for new incoming instrumentation at GTC.

Overall, this research project aims to benefit from a multi-wavelength, multi-technique approach: observations mainly in the optical, near- and mid- infrared, radio and X-rays together with numerical simulations. This approach will allow us to test the validity of the unified model for AGN, to study the structure and composition of the AGN torus, to quantify the true impact of AGN-induced outflows in their host galaxies, and to confirm whether or not galaxy interactions are the main triggering mechanism of luminous AGN. All the questions we plan to investigate are central or closely related to the key research fields and goals defined in the strategy reports of the Spanish RIA and in both the global European Science Vision for Astronomy and the Infrastructure Roadmap set up by the ASTRONET Board for European Astronomy. An important part of the research plan discussed here focuses on X-ray, IR and sub-mm astronomy, which are among the future directions observational Astrophysics is moving to. New and upcoming X-rays, IR and sub-mm instruments such as ATHENA, ALMA, the JWST and HARMONI on the E-ELT will be revolutionizing Astrophysics during the next decade. In that respect, the proposed coordinated project places us in a privileged position for leading research projects based on these facilities, as we are currently doing with the GTC, VLT and ALMA. On the other hand, the planned simulations should provide further insight into the relationship between the observed properties of galaxies and of the large scale structures in which they are immersed, thereby contributing towards improving our understanding of the baryon-dark matter connection.