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Astron. Astrophys. 329, 399-408 (1998)


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Dust in high-z radio-loud AGN *

A. Cimatti 1, W. Freudling 2, 3, H.J.A. Röttgering 4, R.J. Ivison 5 and P. Mazzei 6

1 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
2 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany
3 Space Telescope, European Coordinating Facility, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany
4 Sterrewacht, Huygens Lab., P.O. Box 9513, 2300 RA Leiden, The Netherlands
5 Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
6 Osservatorio Astronomico, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy

Received 20 May 1997 / Accepted 7 August 1997

Abstract

We present continuum observations of a small sample of high-redshift, radio-loud AGN (radio galaxies and quasars) aimed at the detection of thermal emission from dust. Seven AGN were observed with IRAM and SEST at 1.25 mm; two of them, the radio galaxies 1243+036 ([FORMULA]) and MG 1019+0535 ([FORMULA]) were also observed at 0.8 mm with the JCMT submillimetre telescope. Additional VLA observations were obtained in order to derive the spectral shape of the synchrotron radiation of MG 1019+0535 at high radio frequencies. MG 1019+0535 and TX 0211-122 were expected to contain a large amount of dust based on their depleted Ly [FORMULA] emission. The observations suggest a clear 1.25-mm flux density excess over the synchrotron radiation spectrum of MG 1019+0535, suggesting the presence of thermal emission from dust in this radio galaxy, whereas the observations of TX 0211-122 were not sensitive enough to meaningfully constrain its dust content. On the other hand, our observations of 1243+036 provide a stringent upper limit on the total dust mass of [FORMULA] M [FORMULA]. Finally, we find that the spectra of the radio-loud quasars in our sample ([FORMULA]) steepen between rest-frame radio and the far-infrared. We discuss the main implications of our results, concentrating on the dusty radio galaxy, MG 1019+0535.

Key words: galaxies: active – galaxies: ISM – radio continuum: galaxies – quasars: general – galaxies: G 1243+036; MG 1019+0535

* Partially based on observations obtained at the European Southern Observatory, La Silla, Chile

Send offprint requests to: A. Cimatti

© European Southern Observatory (ESO) 1998

Online publication: December 8, 1997
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