SDSS J1619 with blue-shifted broad components in H$\alpha$ and in [O~{\sc iii}] having similar line width and velocity shifts: a recoiling SMBH candidate?

Abstract

In this Letter, we report a potential candidate of recoiling supermassive black hole (rSMBH) in SDSS J1619 based on similar velocity shifts and line widths of the blue-shifted broad components in H$\alpha$ and [O~{\sc iii}] doublet. The measured line width ratio between blue-shifted broad H$\alpha$ and broad [O~{\sc iii}] line is 1.06, if compared with common values around 5.12 for normal Type-1 AGN, indicating different properties of the blue-shifted broad components in SDSS J1619 from those of normal QSOs. The virial BH mass $M_{BHr}$ derived from the broad H$\alpha$ is consistent with the mass expected from the M_{BH}-\sigma relation. The similar velocity shifts and line widths of the blue-shifted broad components in H$\alpha$ and [O~{\sc iii}] and the virial BH mass derived from the H$\alpha$ broad line emissions that is consistent with the mass expected from the M_{BH}-\sigma~ relation, can be explained by a rSMBH scenario. Besides the rSMBH scenario, either the similar line widths of the blue-shifted broad components in H$\alpha$ and in [O~{\sc iii}] or the consistency between the virial BH mass and the mass expected from the M_{BH}-\sigma~ relation cannot be explained by the other proposed models in SDSS J1619.