Photometric AGN reverberation mapping (Haas et al.)

Vol. 535
In section 4. Extragalactic astronomy

Photometric AGN reverberation mapping - an efficient tool for BLR sizes, black hole masses, and host-subtracted AGN luminosities

by M. Haas, R. Chini, M. Ramolla, F. Pozo Nunez C. Westhues, R. Watermann, V. Hoffmeister, and M. Murphy, A&A 535, A73


A fundamental tool for measuring the mass of supermassive black holes (SMBH) in remote galaxies is reverberation mapping: the mass is determined from the virial relation, knowing the velocity (line-width) and the size of the broad line region (BLR) surrounding the black hole. Since this size cannot be measured directly, it is deduced from the time delay between direct emission of the central engine, and the reflected light emitted from the BLR gas. This method is usually done with spectroscopy, which is time consuming. The authors here propose to extend this method to photometric reverberation mapping which employs wide bandpasses to trace the AGN continuum and suitable narrow bands to trace the echo of the BLR gas clouds. They test the method on two local AGN and show that the BLR size can be measured within 10%, in spite of the dilution of the emission line in the narrow band. This method can help in measuring the mass of a large number of SMBHs, and also in probing cosmological models.