The host galaxy/AGN connection in nearby early-type galaxies

A. Capetti, B. Balmaverde
2006 Astronomy and Astrophysics  
[ABRIDGED] This is the third in a series of three papers exploring the connection between the multiwavelength properties of AGN in nearby early-type galaxies and the characteristics of their hosts. We selected 116 AGN candidates requiring a radio flux of 1 mJy. We classified the objects with HST images into "core" and "power-law" galaxies, on the basis of the nuclear slope of their brightness profiles. We used HST and Chandra data to isolate their nuclear emission to study the multiwavelength
more » ... haviour of their nuclei. The properties of the nuclei hosted by the 29 core galaxies were presented in Paper II. Core galaxies invariably host a radio-loud nucleus, with a median radio-loudness of Log R = 3.6 and an X-ray based radio loudness parameter of Log R,X = -1.3. Here we discuss the properties of the nuclei of the 22 "power-law" galaxies. They show a substantial excess of optical and X-ray emission with respect to core galaxies at the same level of radio luminosity. Conversely, their radio-loudness parameters, Log R ~ 1.6 and Log R,X ~ -3.3, are similar to those measured in Seyfert galaxies. Thus the radio-loudness of AGN hosted by early-type galaxies appears to be univocally related to the host's brightness profile: radio-loud AGN are only hosted by core galaxies, while radio-quiet AGN are found only in power-law galaxies. The brightness profile is determined by the galaxy's evolution, through its merger history; our results suggest that the same process sets the AGN flavour.
doi:10.1051/0004-6361:20054490 fatcat:6kp2fmxkqjaijl47frgext7y3i