The Lick AGN Monitoring Project: Velocity-Delay Maps from the Maximum-Entropy Method for Arp 151

Understand

We present velocity-delay maps for optical H I, He I, and He II recombination lines in Arp 151, recovered by fitting a reverberation model to spectrophotometric monitoring data using the maximum-entropy method.

• H I response is detected over the range 0-15 days, with the response confined within the virial envelope.
• The Balmer-line maps have similar morphologies but exhibit radial stratification, with progressively longer delays for Hgamma to Hbeta to Halpha.
• The He I and He II response is confined within 1-2 days.