Although the link between activity in the nuclei of galaxy and galactic mergers has been under scrutiny for several years, it is still unclear to what extent and for which populations of active galaxies merger- triggered activity is relevant. The environments of AGN allow an indirect probe of the past merger history and future merger probability of these systems, suffering less from sensitivity issues when extended to higher redshifts than traditional morphological studies of AGN host galaxies. Here we present results from our investigation of the environment of radio selected sources out to a redshift z=2. We employ the first data release J-band catalog of the new near-IR Infrared Medium-Deep Survey (IMS), 1.4 GHz radio data from the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey and a deep dedicated VLA survey of the VIMOS field, covering a combined total of 20 sq. degrees. At a ux limit of the combined radio catalog of 0.1 mJy, we probe over 8 orders of magnitude of radio luminosity. Using the second closest neighbor density parameters, we test whether active galaxies inhabit denser environments. We find evidence for a sub-population of radio-selected AGN that reside in significantly overdense environments at small scales, although we do not find significant overdensities for the bulk of our sample. We show that radio-AGN in the most underdense environments have vigorous ongoing star formation. We interpret these results in terms of the triggering and fuelling mechanism of radio-AGN.

ABSTRACT
1. THE TRIGGERING OF RADIO-AGN
2. THE SA22 FIELD AND THE RADIO-AGN WITHIN IT
3. THE NEIGHBORHOODS OF RADIO-AGN
4. STAR FORMATION IN THE HOSTS OF RADIO-AGN
5. WHAT MAKES RADIO-AGN TICK?
REFERENCES

• Marios Karouzos(Department of Physics and Astronomy, Seoul National University)
• Myungshin Im(Department of Physics and Astronomy, Seoul National University)
• Jae-Woo Kim(Department of Physics and Astronomy, Seoul National University)
• Seong-Kook Lee(Department of Physics and Astronomy, Seoul National University)
• Scott Chapman(Department of Physics and Atmospheric Science, Dalhousie University)