THE NUCLEUS OF C16.16: ANOTHER CASE OF A DOUBLE-PEAKED ACTIVE GALACTIC NUCLEUSq

摘要

We study optical spectra in high and low activity states of the faint, distant Seyfert 1 galaxy C16.16. A strong stellar population contribution to the continuum is observed, even in the high-state spectrum. The low-ionization emission lines show large equivalent widths. Narrow-line ratios are used to parameterize and investigate the physical conditions in the narrow-line region. Photoionization models with nitrogen depletion, ionization continuum typical of an active galactic nucleus (AGN), and an ionization parameter U = 10~(-2.8) reproduce the observed narrow lines. The AGN continuum shows a strong variation, while the Balmer lines vary moderately. The Balmer lines have a broad and asymmetric component with double-peaked structure. Using the profiles of emission lines originated in a relativistic circular disk, we successfully fit the observed broad Ha profile. This disk component shows no variation in the observations. A variable, intermediate-width (～6000 km s~(-1)) Balmer component is also found. These two components seem to arise by different processes.