0 Assigned ID: 346 ----- Attempting Submission 1 (Fri Apr 10 03:26:30 GMT 2015) ----- HST Phase I Proposal 346 (phase1_proposal.pdf.apt) successfully submitted. Receipt: # 346-1 ----- Attempting Submission 2 (Fri Apr 10 03:41:28 GMT 2015) ----- Observations and simulations both strongly suggest that AGN activity is triggered by one of two mechanisms. Either major mergers of gas-rich galaxies or secular disk instabilities within a galaxy force gaseous inflows and thus fuel the black hole in the center. HST imaging of AGN in the CANDELS and GOODS fields has recently been used to support the secular model in statistical significant samples of moderate luminosity AGN at redshifts z<2.0. However quasars, at higher luminosity and accretion rate, may instead be mainly triggered by the merger scenario which naturally allows for the extreme fueling rates. To date no such statistical study exists for the quasar population. We propose to build a large database of quasar images, selected from the HST archive, and use is to statisically constrain the major merger pair fraction of quasars above redshifts of z=0.5 to fill this gap. Using ACS, WFC3 and WFPC2 imaging, we will PSF subtract the quasar and its host galaxy in search for close companions. This technique has been successfully applied by our team to look for close companions in a small HST sample. This archival program will build the largest database of quasar imaging, comprising ~1000 quasar images observed in past HST programs, the majority of which do not have quasars as their primary targets, thus selected in an unbiased manner. We will not only be able to constrain the triggering mechanism of quasars, but also study the quasar host properties for indications of mergers. As a byproduct we will discover new lensed quasars and apply our findings to the quasar luminosity function. The final database will be made publicly available for further investigations. AGN/QUASARS 0 Regular false false false false false SUPPORTED