Astron. Astrophys. Suppl. Ser. 139, 601-616

Extended radio emission in BL Lac objects

I. The images

P. Cassaro^1,5 - C. Stanghellini¹ - M. Bondi² - D. Dallacasa³ - R. Della Ceca ⁴ - R.A. Zappalà ⁵

Send offprint request: P. Cassaro,
e-mail: cassaro@ira.noto.cnr.it

1 - Istituto di Radioastronomia del CNR, C.P. 141, I-96017 Noto SR, Italy
2 - Istituto di Radioastronomia del CNR, Via Gobetti 101, I-40129 Bologna, Italy
3 - Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, I-40127, Bologna, Italy
4 - Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano, Italy
5 - Istituto di Astronomia dell'Università, Città Universitaria, viale Andrea Doria 6, I-95125 Catania, Italy

Received March 24; accepted July 28, 1999

Abstract:

We have observed 28 sources selected from the 1Jy sample of BL Lac objects (Stickel et al. 1991) with the Very Large Array (VLA) in A, B and D configurations at 1.36, 1.66 and 4.85 GHz, and/or with the Westerbork Synthesis Radio Telescope (WSRT) at 1.40 GHz. In this paper we present high sensitivity images at arcsecond resolution of the 18 objects showing extended structure in our images, and of another source from the FIRST (Faint Images of the Radio Sky at Twenty-cm) survey (Becker et al. 1995). In general our high sensitivity images reveal an amount of extended emission larger than previously reported. In some objects the luminosity of the extended structure is comparable with that of FR II radio sources. A future paper will be devoted to the interpretation of these results.

Key words: galaxies: active -- BL Lac objects: general -- radio continuum: galaxies