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dc.contributor.authorMcLure, Rossen_US
dc.contributor.authorDunlop, Jamesen_US
dc.contributor.authorKukula, Mareken_US
dc.contributor.authorBaum, Stefien_US
dc.contributor.authorO'Dea, Christopheren_US
dc.contributor.authorHughes, Daviden_US
dc.identifier.citationMon.Not.Roy.Astron.Soc. 308 (1999) 377-404en_US
dc.descriptionRIT community members may access full-text via RIT Libraries licensed databases:
dc.description.abstractWe present the first results from a major HST WFPC2 imaging study aimed at providing the first statistically meaningful comparison of the morphologies, luminosities, scalelengths and colours of the host galaxies of radio-quiet quasars, radio-loud quasars, and radio galaxies. We describe the design of this study and present the images which have now been obtained for approximately the first half of our 33-source sample. We also report and discuss the results of combining high-dynamic range PSF determination with 2-dimensional modelling to extract the key parameters of the host galaxies of these AGN; this is the first substantial study of quasar hosts in which it is proving possible to determine unambiguously the morphological type of the hosts of all quasars in the sample. A full statistical analysis is deferred until the complete sample has been observed, but within the sub-sample presented here we have already obtained some remarkably clean results. We find that the underlying hosts of all three classes of luminous AGN are massive elliptical galaxies, with scalelengths ~=10 kpc, and R−K colours consistent with old stellar populations. Most importantly this is the the first unambiguous evidence that, just like radio-loud quasars, essentially all radio-quiet quasars brighter than MR=−24 reside in massive ellipticals. This result removes the possibility that radio ‘loudness’ is directly linked to host galaxy morphology, but is however in excellent accord with the black-hole/spheroid mass correlation recently highlighted by Magorrian et al. (1998). To demonstrate this we apply the spheroid luminosity/spheroid mass/black-hole mass relations given by Magorrian et al. to infer the expected Eddington luminosity (and hence maximum expected nuclear R-band luminosity) of the putative black hole at the centre of each of the spheroidal host galaxies we have uncovered. Comparison of the predicted Eddington luminosities with the actual nuclear R-band luminosities produces a clear relationship, and suggests that the black holes in most of these galaxies are radiating at a few percent of the Eddington luminosity (although a few appear to be radiating close to the Eddington limit); the brightest host galaxies in our low-redshift sample are capable of hosting quasars with MR~=−28, comparable to the most luminous quasars at z~=3, if fueled at the Eddington rate. Finally we discuss our host-galaxy-derived black-hole masses in the context of the radio-luminosity:black-hole mass correlation recently uncovered for nearby galaxies by Franceschini et al. (1998). The radio loud AGN (both RGs and RLQs) lie on the Ptotal 5GHz : mbh relation, while the RQQs lie on the Pcore 5GHz : mbh relation. This finding may hold the key to identifying the physical origin of the radio-loud radio-quiet dichotomy (Refer to PDF file for exact formulas).en_US
dc.description.sponsorshipThis work was supported by PPARC through the award of a studentship to RJM, and the award of PDRAs to MJK and DHH. Support was also provided by NASA through GO program grant 6776 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555.en_US
dc.format.extent361930 bytesen_US
dc.publisherBlackwell Publishingen_US
dc.relation.ispartofseriesvol. 308en_US
dc.relation.ispartofseriesno. 2en_US
dc.subjectGalaxies - activeen_US
dc.subjectGalaxies - photometryen_US
dc.subjectInfrared - galaxiesen_US
dc.subjectQuasars - generalen_US
dc.titleA comparative HST imaging study of the host galaxies of radio-quiet quasars, radio-loud quasars and radio galaxies: Ien_US

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