The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50
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The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in spring 2011. Here we present the first results from this program, a measurement of the broad-line reverberation lag in the Seyfert 1 galaxy Mrk 50. Combining our data with supplemental observations obtained prior to the start of the main observing campaign, our data set covers a total duration of 4.5 months. During this time, Mrk 50 was highly variable, exhibiting a maximum variability amplitude of a factor of similar to 4 in the U-band continuum and a factor of similar to 2 in the H beta line. Using standard cross-correlation techniques, we find that H beta and H gamma lag the V-band continuum by tau(cen) = 10.64(-0.93)(+0.82) and 8.43(-1.28)(+1.30) days, respectively, while the lag of He II lambda 4686 is unresolved. The H beta line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core, consistent with an origin in a broad-line region (BLR) dominated by orbital motion rather than infall or outflow. Assuming a virial normalization factor of f = 5.25, the virial estimate of the black hole mass is (3.2 +/- 0.5) x 10(7) M-circle dot. These observations demonstrate that Mrk 50 is among the most promising nearby active galaxies for detailed investigations of BLR structure and dynamics.