南方基地知识库

NGC 5548 has been well spectroscopically monitored for reverberation mapping of the central kinematics by 19 campaigns. Using the maximum entropy method in this Letter, we build up a high-quality velocity-delay map of the H beta emission line in the light curves of the continuum and the line variations observed between 2015 and 2016. The map shows the response strength and lags of the velocity fields of the H beta-emitting regions. The velocity-delay structure of the map is generally symmetric, with strong red and blue wings at time lag tau less than or similar to 15 days, a narrower velocity distribution at tau greater than or similar to 15 days, and a deficit of response in the core. This is suggestive of a disk geometry of the broad-line region (BLR). The relatively weaker H beta response at the longer lags in the red side indicates anisotropic emission from the outer part of the BLR. We also recover the velocity-delay maps of NGC. 5548 from the historical data of 13 years to investigate the long-term variability of its BLR. In general, the BLR of NGC 5548 was switching between the inflow and virialized phases in the past years. The resultant maps of seven years reveal inflow signatures and show decreasing lags, indicating that the changes in the BLR size are related to the infalling BLR gas. The other four maps show potential disk signatures that are similar to our map.