We propose to determine the location and kinematics of the high-ionization gas in the active galactic nucleus of Mrk 817 via broad emission-line reverberation mapping. Understanding the geometry and kinematics of the broad emission-line region is crucial (a) for identifying where disk winds are launched, (b) for identifying the driving mechanism, and (c) for understanding the radiative and kinetic outflows from nuclei that will allow us to assess the possible impact of AGN feedback on the host galaxy. Moreover, since the masses of the highest-redshift quasars are estimated based on scaling relationships involving the C IV 1549 emission line, the kinematics of the C IV line-emitting region must be known to assess the accuracy of such determinations. We propose to obtain 180 COS spectra of Mrk 817, one orbit approximately every other day for a year. This program is modeled after a similar highly successful and high impact monitoring program on NGC 5548 with COS in Cycle 21. The primary science goal is to determine the geometry and kinematics of the C IV and Ly alpha emitting regions. Mrk 817 is a higher luminosity and higher Eddington ratio source than NGC 5548 and therefore likely to have a strong disk wind, although our line of sight to the nucleus is unabsorbed. The NGC 5548 program showed that X-ray data are of critical importance in understanding the ionizing spectrum so accompanying low-cadence Chandra monitoring is also requested. A secondary science goal is continuum reverberation, and our request includes five additional observations with STIS to resolve current ambiguities about the contribution of diffuse broad-line region emission to the continuum.
- Pub Date:
- May 2020