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

Free access article

Issue		A&A Volume 440, Number 1, September II 2005


Page(s)		73 - 84
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20053113

A&A 440, 73-84 (2005)
DOI: 10.1051/0004-6361:20053113

Sample selection and hosts brightness profiles

A. Capetti¹ and B. Balmaverde²

¹ INAF - Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy
e-mail: capetti@to.astro.it
² Universitá di Torino, Via Giuria 1, 10125 Torino, Italy
e-mail: balmaverde@ph.unito.it

(Received 22 March 2005 / Accepted 27 April 2005)

Abstract
This is the first of a series of three papers exploring the connection between the multiwavelength properties of AGNs in nearby early-type galaxies and the characteristics of their hosts. We selected two samples, both with high resolution 5 GHz VLA observations available and providing measurements down to 1 mJy level, reaching radio-luminosities as low as 10¹⁹ W Hz^-1. We focus on the 116 radio-detected galaxies as to boost the fraction of AGN with respect to a purely optically selected sample. Here we present the analysis of the optical brightness profiles based on archival HST images, available for 65 objects. We separate early-type galaxies on the basis of the slope of their nuclear brightness profiles, into core and power-law galaxies following the Nuker's scheme, rather than on the traditional morphological classification (i.e. into E and S0 galaxies). Our sample of AGN candidates is indistinguishable, when their brightness profiles are concerned, from galaxies of similar optical luminosity but hosting weaker (or no) radio-sources. We confirm previous findings that relatively bright radio-sources ( $L_{{\rm r}} > 10^{21.5}$ W Hz^-1) are uniquely associated to core galaxies. However, below this threshold in radio-luminosity core and power-law galaxies coexist and they do not show any apparent difference in their radio-properties. Not surprisingly, since our sample is deliberately biased to favour the inclusion of active galaxies, we found a higher fraction of optically nucleated galaxies. Addressing the multiwavelength properties of these nuclei will be the aim of the two forthcoming papers.

Key words: galaxies: active -- galaxies: bulges -- galaxies: elliptical and lenticular, cD -- galaxies: nuclei -- galaxies: structure

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