THE LICK AGN MONITORING PROJECT: BROAD-LINE REGION RADII AND BLACK HOLE MASSES FROM REVERBERATION MAPPING OF Hβ

Abstract

We have recently completed a 64-night spectroscopic monitoring campaign at\nthe Lick Observatory 3-m Shane telescope with the aim of measuring the masses\nof the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected\nmasses in the range ~10^6-10^7 M_sun and also the well-studied nearby active\ngalactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including\nNGC 5548) showed optical variability of sufficient strength during the\nmonitoring campaign to allow for a time lag to be measured between the\ncontinuum fluctuations and the response to these fluctuations in the broad\nHbeta emission. We present here the light curves for the objects in this sample\nand the subsequent Hbeta time lags for the nine objects where these\nmeasurements were possible. The Hbeta lag time is directly related to the size\nof the broad-line region, and by combining the lag time with the measured width\nof the Hbeta emission line in the variable part of the spectrum, we determine\nthe virial mass of the central supermassive black hole in these nine AGNs. The\nabsolute calibration of the black hole masses is based on the normalization\nderived by Onken et al. We also examine the time lag response as a function of\nvelocity across the Hbeta line profile for six of the AGNs. The analysis of\nfour leads to ambiguous results with relatively flat time lags as a function of\nvelocity. However, SBS 1116+583A exhibits a symmetric time lag response around\nthe line center reminiscent of simple models for circularly orbiting broad-line\nregion (BLR) clouds, and Arp 151 shows an asymmetric profile that is most\neasily explained by a simple gravitational infall model. Further investigation\nwill be necessary to fully understand the constraints placed on physical models\nof the BLR by the velocity-resolved response in these objects.\n