Low-luminosity Seyfert nuclei in nearby galaxies

Broad Hα emission lines have been detected in the nuclei of many bright galaxies such as M81 and M87. These lines are similar to, but much weaker than, those seen in type 1 Seyfert nuclei and QSOs. If massive black holes are responsible for the broad lines and the immense luminosities of classical AGNs, continuity arguments suggest that they also produce the features observed at lower levels in the relatively ‘‘normal’’ galaxies studied here, especially since the intensity ratios of the narrow emission lines are like those expected from gas photoionized by dilute nonstellar (e.g., power‐law) radiation. The possible presence of massive black holes in nearby galaxies is consistent with the conclusion that the nucleus of our own Milky Way may harbor such an object.