THE LICK AGN MONITORING PROJECT 2011: REVERBERATION MAPPING OF MARKARIAN 50

The Lick AGN Monitoring Project 2011 observing campaign was carried out over\nthe course of 11 weeks in Spring 2011. Here we present the first results from\nthis program, a measurement of the broad-line reverberation lag in the Seyfert\n1 galaxy Mrk 50. Combining our data with supplemental observations obtained\nprior to the start of the main observing campaign, our dataset covers a total\nduration of 4.5 months. During this time, Mrk 50 was highly variable,\nexhibiting a maximum variability amplitude of a factor of 4 in the U-band\ncontinuum and a factor of 2 in the H-beta line. Using standard\ncross-correlation techniques, we find that H-beta and H-gamma lag the V-band\ncontinuum by tau_cen = 10.64(-0.93,+0.82) and 8.43(-1.28,+1.30) days,\nrespectively, while the lag of He II 4686 is unresolved. The H-beta line\nexhibits a symmetric velocity-resolved reverberation signature with shorter\nlags in the high-velocity wings than in the line core, consistent with an\norigin in a broad-line region dominated by orbital motion rather than infall or\noutflow. Assuming a virial normalization factor of f=5.25, the virial estimate\nof the black hole mass is (3.2+-0.5)*10^7 solar masses. These observations\ndemonstrate that Mrk 50 is among the most promising nearby active galaxies for\ndetailed investigations of broad-line region structure and dynamics.\n