Quasar SDSS J142507.32+323137.4: dual AGNs?

Abstract

We analyze the optical spectrum of type 1 QSO SDSS J1425+3231. This object is interesting since its narrow emission lines, such as [O III]λλ4959, 5007, are double-peaked, and the line structure can be modeled well by three Gaussian components: two components for the two peaks (we refer to the peaks at low/high redshift as “the blue/red component") and another one for the line wing which has the same line center as that of the blue component, but is ∼ 3 times broader. The separation between the blue and red components is ∼500 km s−1 with the blue component being ∼2 times broader than the red one. The Hβ emission can be separated into four components: two for the double-peaked narrow line and two for the broad line which comes from the broad line regions. The black hole mass estimated from the broad Hβ emission line using the typical reverberation mapping relation is 0.85 × 108 M⊙, which is consistent with that derived from parameters of [O III]λ 5007 of the blue component. We suggest that this QSO might be a dual AGN system; the broad Hβ emission line is mainly contributed by the primary black hole (traced by the blue component) while the broad Hβ component of the secondary black hole (traced by the red component) is hard to be separated out considering a resolution of ∼2 000 for SDSS spectra or it may be totally obscured by the dusty torus.