VLT adaptive optics imaging of QSO host galaxies and close environment at z ∼ 2 . 5 : results from a pilot program

We report on ESO–VLT near-IR adaptive optics imaging of one radio-loud (PKS 0113-283) and two radio quiet (Q 0045-3337 and Q0101-337) quasars at z > 2. In the first case we are able to resolve the QSO and find that it is hosted by an elliptical of absolute magnitude MK = −27.6. For the other two objects no extended emission has been unambiguously detected. This result, though restricted to a single object, extends up to z=2.5 the finding that cosmic evolution of radio-loud quasar hosts follows the trend expected for luminous and massive spheroids undergoing passive evolution. For Q0045-3337 our high resolution images show that it is located 1.2 arcsec from a K=17.5 foreground disc galaxy, which may act as gravitational lens, since the QSO most probably lies within the galaxy Einstein radius.