SDSS J022119.84+005628.4: A radio-loud narrow-line Seyfert I galaxy with star formation in its nucleus

The optical spectrum of SDSS J022119.84 + 005628.4 (R. A. = 02(h).21(m) 19.84(s), Dec = 00degrees56' 28.4", J2000; z = 0.399785+/-0.000558) is analyzed by multi-component profile modelling. The small flux ratio of [OIII](NC)/Hbeta (=0.78) = 1778.1 +/- 85.9 km s-(1) led us to identify SDSS J022119.84 + 005628.4 as a Narrow-line Seyfert 1 galaxy with RFe = 1.4(-1.0)(+1.0) and intermediate radio loudness, log R = 1.93. The continuum low jump at the Balmer limit might be contributed by a starburst component, which suggests that the object is a relatively young AGN with star-formation activity in its inner region. This provides a useful observational test of the AGN evolution. The low flux ratio of the narrow components, [O III]/Hbeta = 1.62, and the prominent [O II]lambda3727 emission, [O II]/[O III] = 2.24, suggests that there should be a group of AGNs different from Seyfert 2s when their broad line regions are obscured by the torus on the line of sight. A possible orientation effect is. suggested to interpret the observed Seyfert 1.5s-like spectrum of the object. The spectrum features prominent broad blue wings of both [OIII]lambdalambda4959 and 5007. After excluding other possible contributions, we conclude that the broad components are emitted by [0 111] itself. The material emitting the broad [0 111] line is probably situated in a transient line region (with a low electron density, n(e), < 10(7)cm(-3)) between the broad line region (BLR) and the narrow line region (NLR). The object can be classified as a "blue outlier" defined by Zamanov et al., according to its velocity shift v(r)([O III]) = -293.6 +/- 18.0 km s(-1), relative to the systematic velocity.