Extensions around z=2 QSOs

Based on an R-band imaging survey of 6 high redshift (z~2) and high luminosity (M<-28mag) QSOs, we report the detection of extensions in two radio-quiet and one radio-loud QSO. The extensions are most likely due to the host galaxies of these QSOs, with luminosities of at least 3-7 per cent of the QSO luminosity. The most likely values for the luminosity of the host galaxies lie in the range $6-18 per cent of the QSO luminosity.Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.htm

Multicolour imaging of z= 2 QSO hosts

We present multicolour images of the hosts of three z=2 QSOs previously detected in R-band by our group. The luminosities, colours and sizes of the hosts overlap with those of actively star-forming galaxies in the nearby Universe. Radial profiles over the outer resolved areas roughly follow de Vaucouleur or exponential disk laws. These properties give support to the host galaxy interpretation of the extended light around QSOs at high-redshift. The rest-frame UV colours and upper limits derived for the rest-frame UV-optical colours are inconsistent with the hypothesis of a scattered halo of light from the active nucleus by a simple optically-thin scattering process produced by dust or hot electrons. If the UV light is indeed stellar, star formation rates of hundreds of solar masses per year are implied, an order of magnitude larger than field galaxies at similar redshifts and above. This might indicate that the QSO phenomenon (at least the high-luminosity one) is preferentially acompanied by enhanced galactic activity at high-redshifts.Comment: Accepted to be published in MNRAS. 11 pages, Latex, uses mn macros, also available at http://www.mpa-garching.mpg.de/~itzia

The hosts of z=2z=2 QSOs

We present results of the hosts of four high-redshift ($z \approx 2$) and high luminosity (M_B \lsim -28 mag) QSOs, three radio-quiet one radio-loud, imaged in R and K bands. The extensions to the nuclear unresolved source are most likely due to the hosts galaxies of these QSOs, with luminosities at rest-frame 2300\AA of at least 3-7% of the QSO luminosity, and most likely around 6-18% of the QSO luminosity. Our observations show that, if the extensions we have detected are indeed galaxies, extraordinary big and luminous host galaxies are not only a characteristic of radio-loud objects, but of QSOs as an entire class.Comment: 6 pages, 4 Figures, Latex, uses lamuphys.sty, also available at http://www.mpa-garching.mpg.de/~itziar To appear in the Proceedings of the ESO/IAC Conference on 'Quasar Hosts' ESO Astrophysics Symposia eds. D. Clements and I. Perez-Fourno