ROXA: a new multi-frequency selected large sample of blazars with SDSS and 2dF optical spectroscopy

TL;DR

ROXA is a large, multi-frequency selected blazar catalog combining radio, optical, and X-ray data, significantly expanding known blazar samples and identifying new high-energy blazar candidates for future observations.

Contribution

This work introduces a new multi-frequency blazar catalog with 816 objects, including 173 newly identified blazars, demonstrating an effective selection method and enriching the sample for high-energy astrophysics.

Findings

High efficiency of blazar candidate selection (81% confirmed blazars)

Discovery of 173 new blazars, about 10% of known blazars

Identification of many new high-energy peaked BL Lac objects

Abstract

Context. Although Blazars are a small fraction of the overall AGN population they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray bands and have been shown to be the largest contaminant of CMB fluctuation maps. So far the number of known blazars is of the order of several hundreds, but the forthcoming AGILE, GLAST and Planck space observatories will detect several thousand of objects of this type. Aims. In preparation for these missions it is necessary to identify new samples of blazars to study their multi-frequency characteristics and statistical properties. Methods. We compiled a sample of objects with blazar-like properties via a cross-correlation between large radio (NVSS, ATCAPMN) and X- ray surveys (RASS) using the SDSS-DR4 and 2dF survey data to spectroscopically identify our candidates and test the validity of the selection method. Results. We present the Radio - Optical - X-ray catalog built at ASDC (ROXA), a list of 816 objects among which 510 are confirmed blazars. Only 19% of the candidates turned out to be certainly non-blazars demonstrating the high efficiency of our selection method. Conclusions. Our catalog includes 173 new blazar identifications, or about 10% of all presently known blazars. The relatively high flux threshold in the X-ray energy band (given by the RASS survey) preferentially selects objects with high fx / fr ratio leading to the discovery of new High Energy Peaked BL Lac (HBLs). Our catalog therefore includes many new potential targets for GeV-TeV observations.