The radio structure of the peculiar narrow-line Seyfert 1 galaxy candidate J1100+4421

Narrow-line Seyfert 1 galaxies (NLS1) are an intriguing subclass of active galactic nuclei. Their observed properties indicate low central black hole mass and high accretion rate. The extremely radio-loud NLS1 sources often show relativistic beaming and are usually regarded as younger counterparts of blazars. Recently, the object SDSS J110006.07+442144.3 was reported as a candidate NLS1 source. The characteristics of its dramatic optical flare indicated its jet-related origin. The spectral energy distribution of the object was similar to that of the gamma-ray detected radio-loud NLS1, PMNJ0948+0022. Our high-resolution European very long baseline interferometry network observations at 1.7 and 5 GHz revealed a compact core feature with a brightness temperature of greater than or similar to 10(10) K. Using the lowest brightness temperature value and assuming a moderate Lorentz factor of similar to 9, the jet viewing angle is less than or similar to 26 degrees. Archival Very Large Array data show a large-scale radio structure with a projected linear size of similar to 150 kpc reminiscent of double-sided morphology.