Very Long Baseline Array Imaging of Parsec-scale Radio Emissions in
  Nearby Radio-quiet Narrow-line Seyfert 1 Galaxies
  We conducted Very Long Baseline Array (VLBA) observations of seven nearby
narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz (18cm) with milli-arcsecond
resolution. This is the first systematic very long baseline interferometry
(VLBI) study focusing on the central parsec-scale regions of radio-quiet NLS1s.
Five of the seven were detected at a brightness temperature of >~5x10^6 K and
contain radio cores with high brightness temperatures of >6x10^7 K, indicating
a nonthermal process driven by jet-producing central engines as is observed in
radio-loud NLS1s and other active galactic nucleus (AGN) classes. VLBA images
of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear
structures. A large portion of the radio power comes from diffuse emission
components that are distributed within the nuclear regions (<~300 pc), which is
a common characteristic throughout the observed NLS1s. Jet kinetic powers
limited by the Eddington limit may be insufficient to allow the jets escape to
kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of
<~10^7 M_sun.
