Summary: The hosts of z = 2 QSOs
Itziar Aretxaga 1 , B.J. Boyle 2 and Roberto J. Terlevich 3
1 Max­Planck Institut f¨ur Astrophysik, Karl Schwarzschildstr 1, Postfach 1523, 85740
Garching, Germany
2 Anglo­Australian Observatory, PO Box 296, Epping, NSW 2121 Australia
3 Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ, UK
Abstract. We present results of the hosts of four high­redshift (z ß 2) and high
luminosity (MB ! ¸ \Gamma28 mag) QSOs, three radio­quiet one radio­loud, 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 rest­frame 2300 š A of at least
3 \Gamma 7 per cent of the QSO luminosity, and most likely around 6 \Gamma 18 per cent 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
radio­loud objects, but of QSOs as an entire class.
1 Introduction
The study of high redshift (z ß 2) QSOs offers a unique opportunity to in­
vestigate conditions in the early universe. In the currently favoured cold dark
matter cosmogony, this epoch corresponds to the period when normal galaxies
formed through hierarchical coalescence (Carlberg 1990), thereby giving rise to
enormous concentrations of gas in the center of the galaxies, which could feed

Source: Aretxaga, Itziar - Instituto Nacional de Astrofísica Óptica y Electrónica

Collections: Physics