An OSIRIS/GTC survey of the AGN population of the intermediate redshift cluster ZwCl 0024.0+1652

We have performed a deep Halpha/[NII] survey of emission-line galaxies (ELG) in the intermediate-redshift cluster ZwCl 0024.0+1652 (z=0.395) using the red tunable filter of the OSIRIS instrument at GTC. Our final catalog comprises 174 robust cluster members, likely the largest sample of ELG in a cluster at intermediate redshift. Our observing technique allowed us to separate AGN from star-forming (SF) galaxies. On the one hand, we were able to detect and separate broad-line AGN (BLAGN). For narrow-line AGN (NLAGN), we used the standard diagnostic EWalphaN2 from Cid-Fernandes et al. (2010) to separate AGN from SF galaxies using the F([NII])/F(Halpha) ratio. We find that the count ratio BLAGN/NLAGN is approximately 0.64 (similar to the ratio Seyfert1/Seyfert2 in the local universe) and that (BLAGN+NLAGN)/ELG ~ 0.37. We have studied the evolution of the fraction of ELG vs. cluster-centric distance and local density, finding an increase of the activity in the intermediate density environment, close to the virial radius. This could suggest a trigger of activity induced by the interaction of galaxies with the intra-cluster medium (ICM). For the first time, we have been able to perform the study separately for SF galaxies and AGN.