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The colours of z 2 QSO host galaxies Itziar Aretxaga 1 , Roberto J. Terlevich 2 , B.J. Boyle 3

Summary: The colours of z ß 2 QSO host galaxies
Itziar Aretxaga 1 , Roberto J. Terlevich 2 , B.J. Boyle 3
1 Max­Planck Institut f¨ur Astrophysik, Garching, Germany
2 Royal Greenwich Observatory, Cambridge, UK
3 Anglo­Australian Observatory, Epping, Australia
Abstract. Three high­redshift (z ß 2) and high luminosity (MB ! ¸
\Gamma28 mag for H 0
= 50Km s \Gamma1 Mpc \Gamma1 , q 0
= 0:5) QSOs, two radio­quiet
one radio­loud, were imaged in R, I and K bands. The luminosities,
colours and sizes of the hosts overlap with those of actively star­forming
galaxies in the local Universe. These properties give support to the young
host galaxy interpretation of the extended light around QSOs at high­
redshift. The rest­frame UV and UV­optical colours are inconsistent with
the hypothesis of a scattered halo of light from the active nucleus by a
simple optically­thin 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 in field
galaxies at similar redshifts and above. This might indicate that the QSO
phenomenon is preferentially accompanied by enhanced galactic activity


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


Collections: Physics