Evidence for Intermediate BLR of Reverberation-Mapped AGN PG 0052+251
  In this manuscript, we study properties of BLR of well-known
reverberation-mapped AGN, in order to find reliable evidence for intermediate
BLR. We firstly check properties of mapped AGN collected from literature in
plane of $\sHb^2/\sHa^2$ vs $\RHa/\RHb$. Commonly, virial BH masses based on
observed broad H$\alpha$ and H$\beta$ should be coincident. However, among the
mapped objects, PG0052 and NGC4253 are two apparent outliers in the plane of
$\sHb^2/\sHa^2$ vs $\RHa/\RHb$, which indicate BLRs of PG0052 and NGC4253 have
some special characters. Then based on the 55 public spectra of PG0052, BLR of
PG0052 is been carefully studied in detail. We find that line width ratio of
total observed broad H$\alpha$ to total observed broad H$\beta$ is $\sim$0.7,
which is much smaller than theoretical/observational value of $\sim$0.9.
Furthermore, flux ratio of total broad H$\alpha$ to total broad H$\beta$ is
about 6.8 (Balmer Decrement), which is not one reasonable value for BLUE quasar
PG 0052+251. Moreover, properties of line cores based on PCA technique confirm
there is one inner broad component and one seriously obscured intermediate
broad component in BLR of PG0052. If the seriously obscured intermediate BLR
was accepted, properties of PG0052 in the plane of $\sHb^2/\sHa^2$ vs
$\RHa/\RHb$ could be well reproduced, which indicates that the intermediate BLR
actually is well appropriate to mapped quasar PG 0052+251. Finally, the large
distance between inner component of BLR and intermediate component of BLR based
on CCF results rejects the possibility that the intermediate component is
probably extended part of inner component of BLR.
