Speaker
Description
By using deep radio source catalogs currently available, we present a new blazar candidate catalog, BROS, which includes 56314 sources located at declination $\delta > -40^{\circ}$ and outside the Galactic Plane ($|b| > 10^{\circ}$). We picked up flat-spectrum radio sources of $\alpha > -0.5$ ($\alpha$ is defined as $F_{\nu} \propto \nu^{\alpha}$) from 0.15 GHz TGSS and 1.4 GHz NVSS catalogs. Then, we identified their optical counterparts by cross-matching with the Pan-STARRS1 data.
Color-color and color-magnitude plots for the selected flat-spectrum radio sources clearly showed two populations, “quasar-like” and “elliptical-galaxy-like” sequences. We emphasize that the latter population emerged for the first time and is missed by previous CRATES catalog because of the higher radio flux threshold.
We found that the color-magnitude relation of nearby bright elliptical galaxies up to z=0.3 follows the “elliptical-galaxy-like" sequence. The index of the logN-logS distribution for this sample is $1.44\pm0.06$, supporting the interpretation of "nearby" because the measurement is consistent with a value for a static Euclidean universe.
This BROS catalog is useful to search for electromagnetic counterparts of ultra-high-energy cosmic rays as well as PeV neutrions recently detected by IceCube, thus a powerful catalog in the era of multi-messenger astronomy. We also emphasize that this BROS catalog includes nearby ($z \leq 0.3$) BL Lac objects, a fraction of which would be TeV emitters and detectable by future Cherenkov Telescope Array. We will soon make this catalog available once published.
