The sizes of broad emission line regions and black hole masses of double-peaked broad low-ionization emission line objects

In this paper, the sizes of the broad emission line regions (BLRs) and black hole (BH) masses of double-peaked broad low-ionization emission line emitters (DBP emitters) are compared using different methods: virial BH masses versus BH masses from stellar velocity dispersions, the size of BLRs from the continuum luminosity versus the size of BLRs from the accretion disc model. First, the virial BH masses of DBP emitters estimated by the continuum luminosity and linewidth of broad H beta are about six times (a much larger value, if including another DBP emitters, of which the stellar velocity dispersions are traced by the linewidths of narrow emission lines) larger than the BH masses estimated from the relation M-BH-sigma which is a more accurate relation to estimate BH masses. Second, the sizes of the BLRs of DBP emitters estimated by the empirical relation of R-BLR-L-5100 angstrom are about three times (a much larger value, if including another DBP emitters, of which the stellar velocity dispersions are traced by the linewidths of narrow emission lines) larger than the mean flux-weighted sizes of BLRs of DBP emitters estimated by the accretion disc model. The higher electron density of BLRs of DBP emitters would be the main reason which leads to smaller size of BLRs than the predicted value from the continuum luminosity.