ABSTRACT
Through the use of a High Band Antenna (HBA) system, the Low Frequency Array (LOFAR) Two-Meter Sky Survey (LoTSS) is an attempt to complete a high-resolution 120-168 MHz survey of the northern celestial sky. To date, ~5 × 105 radio sources have been classified by LOFAR with most of them consisting of active galactic nuclei (AGNs). The strong AGN emissions detected by LoTSS, it is thought, are powered by supermassive black holes (SMBHs) at the center of galaxies. During an analysis of ~1,500 images of these AGNs, we identified 10 radio sources with radial spokes emitted from an unknown source. According to LOFAR, the radial spokes are artifacts due to calibration errors with no origin, and therefore they cannot be associated with an optical source. Our preliminary hypothesis for the artifacts was that they were produced by ionized jets emitted from quasi-stellar objects (QSOs). Specifically, that strong emissions from Type 1 broadline (BL) quasars were directed in the line of sight of the observer (i.e., LOFAR) and as a result produced the image artifacts. To test our hypotheses, we cross-referenced the ra and dec coordinates of the artifacts with the galactic coordinates indexed in the Sloan Digital Sky Survey (SDSS) and confirmed that the artifacts were associated with BL QSOs. Further analysis of the QSOs, moreover, demonstrated they exhibited prominent broad emission lines such as CIII and MgII, which are characteristic of Type 1 BL quasars. It is our interpretation, therefore, that the radial spokes characterized as artifacts by LOFAR were produced by the emission of Type 1 BL quasars in the line of sight of the radio telescope.
Approved by the Washington Academy of Sciences: 01 March 2021
Download Manuscript: LOFAR SDSS_AJP