Optical morphology of distant RATAN-600 radio galaxies from subarcsecond resolution NOT images ^*

¹ Tuorla Observatory, FIN-21500 Piikkiö, Finland
² Special Astrophysical Observatory, Radio Astronomy Sector, 35147 Niznij Arkhyz, Karachey-Cherkessia, Russia
³ St. Petersburg Branch of the SAO, Radio Astronomy Laboratory, Pulkovskoe Shosse 65, 196140 St. Petersburg, Russia
⁴ Astronomical Institute of St. Petersburg University, 198904 St. Petersburg, Russia
⁵ National Radio Astronomical observatory, P.O. Box 0, Socorro, New Mexico 87801, U.S.A.

Send offprint request to: T. Pursimo

Received: 27 February 1998
Accepted: 7 September 1998

Abstract

We present direct imaging data of 22 ultra steep spectrum radio sources obtained at (or near) a subarcsecond seeing. The basic sample of 40 double radio sources was selected from the RATAN-600 catalogue. The FRII-structure has been confirmed with VLA and preliminary optical identifications which come from the 6 m-telescope. As the RATAN-600 flux limit at 3.9 GHz (≈ 10 mJy) is fainter than that of major surveys, the sample may have high-z contents. This is also suggested by the faint magnitudes in the Hubble diagram. The final aim is to create a homogeneous sample of high-z radio galaxies in a well defined strip around the sky, with faint radio limit and subarcsecond morphology down to . We could confirm 16 identifications down to  24. Most of the extended objects have multicomponent structures as expected from other surveys of high-redshift radio galaxies. We found five unresolved objects even with a subarcsecond seeing. Of the remaining six objects, three are extremely faint and the other three have such a complex environment that further observations are needed to confirm the optical identification.