Keck high-resolution spectroscopy of Mrk 335: constraints on the number of emitting clouds in the broad-line region

We present high-resolution (similar to 6 km s(-1)), high signal-to-noise ratio (similar to 400 at H alpha line centre) spectroscopy of Mrk 335, Cross-correlation (CC) analysis of the data yields a lower limit of similar to 3 x 10(6) for the number of emitting clouds in the broad-line region (BLR) of this object. This limit is applicable for clouds with T = 2 x 10(4) K and an optical depth of similar to 10(4) in their H alpha line, The result is obtained from the absence of a CC signal in the data and from extensive Monte Carlo simulations that show the minimum number of clouds necessary in order to prevent the creation of a delectable CC signal. The simulations can be used to test any BLR model which is based on a contribution from discrete sources provided that the individual emission profile of the sources and their distribution are given. Current BLR models based on stellar atmospheres of bloated stars can be ruled out, unless the linewidth of an individual star exceeds 100 km s(-1). The lower limit on the number of emitting clouds also provides constraints on traditional photoionization models for a system of clouds.