A Northern Survey of Gamma-Ray Blazar Candidates

Abstract

In preparation for GLAST, we have compiled a sample of blazar candidates to increase the pool of well studied AGN from which GLAST counterparts will be drawn. Sources were selected with our Figure of Merit (FoM) ranking; thus, they have radio and X-ray properties very similar to the EGRET blazars. Spectroscopic confirmation of these candidates is in progress, and more than 70% of these objects have been identified as flat spectrum radio quasars and BL Lac objects. We present ~250 new optical blazar identifications based on McDonald Observatory spectroscopy, 224 with redshifts. Of these, 167 are in our FoM-selected set. To motivate the Gamma-ray nature of these objects, we analyzed the current release of the EGRET data for possible point sources at their radio positions. We develop two distinct methods to combine multiple EGRET observations of a sky position into a single detection significance. We report a detection of the signal of the set of blazar candidates in the EGRET data at the > 3 sigma level by both techniques. We predict that the majority of these blazar candidates will be found by GLAST due to its increased sensitivity, duty cycle and resolving power.