Thursday

Active galactic nuclei (AGN) exhibit broad emission lines (BELs) corresponding to a range of elements and ionisation states. Disk winds are commonly invoked as an explanation for these lines, arising from the broad-line region (BLR) of AGN. The emission lines produced in the BLR respond to changes in the ionising continuum with delays ranging from days to months. Associating these delays with light travel times then immediately provides an estimate of the size of the BLR. However, it is also possible to use carry out 2-D reverberation mapping, i.e. to estimate the line response to continuum variations as a function of both time-delay and velocity. The resulting response function (aka velocity-delay map) encodes key information about the geometry and kinematics of the BLR.

We have modified a Monte Carlo radiative transfer and ionisation code to predict the 2-D response functions for smooth (or "micro-clumped") rotating biconical disk wind models. This code has previously been used to explore YSOs, CVs and XRBs in addition to AGN and iteratively converges on a wind ionisation state and outflow spectrum taking into account self-shielding, multiple scattering and detailed atomic physics.

We show that, in general, positive line responses are very similar to those produced by purely rotationally-dominated flows. However, we also find that disk winds can produce significantly negative responses. Attempts to invert observational data to recover response functions will need to allow for this possibility. These negative reverberation signatures may provide a new way to distinguish rotating outflows from rotating disks.