Bibcode
Rose, M.; Tadhunter, C. N.; Holt, J.; Ramos Almeida, C.; Littlefair, S. P.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 414, Issue 4, pp. 3360-3380.
Advertised on:
7
2011
Citations
17
Refereed citations
17
Description
We present spectroscopic observations of the type 2 quasar SDSS
J11311.05+162739.5 (z= 0.1732), which has the richest spectrum of
forbidden high-ionization lines (FHILs, e.g. [Fe VII], [Fe X], [Fe XI]
and [Ne V]) yet reported for an active galactic nucleus (AGN), as well
as unusually strong [O III] λ4363 emission. The study of this
object provides a rare opportunity to investigate the physical
conditions and kinematics of the region(s) emitting the FHILs. By
comparison with photoionization model results, we find that the FHIL
region has high densities (105.5 < nH <
108.0 cm-3) and ionization parameters (-1.5 <
log [U] < 0), yet its kinematics are similar to those of the
low-ionization emission-line region detected in the same object (full
width at half-maximum ˜360 ± 30 km s-1), with no
evidence for a significant shift between the velocity centroid of the
FHILs and the rest frame of the host galaxy. The deduced physical
conditions lie between those of the broad-line (nH >
109 cm-3) and narrow-line regions (nH
< 106 cm-3) of AGNs, and we demonstrate that
the FHIL regions must be situated relatively close to the illuminating
AGN (0.32 < rFHIL < 50 pc). We suggest that the inner
torus wall is the most likely location for the FHIL region, and that the
unusual strength of the FHILs in this object is due to a specific
viewing angle of the far wall of the torus, coupled with a lack of dust
on larger scales that might otherwise obscure our view of the torus.