EDP Sciences
Free access
Volume 497, Number 1, April I 2009
Page(s) 103 - 108
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361/200911615
Published online 09 February 2009
A&A 497, 103-108 (2009)
DOI: 10.1051/0004-6361/200911615

Evidence of a pure starburst nature of the nuclear region of NGC 253

A. Brunthaler1, P. Castangia1, 2, A. Tarchi2, 3, C. Henkel1, M. J. Reid4, H. Falcke5, 6, and K. M. Menten1

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: brunthal@mpifr-bonn.mpg.de
2  INAF – Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
3  INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
4  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
5  Department of Astrophysics, Radboud Universiteit Nijmegen, Postbus 9010, 6500 GL Nijmegen, The Netherlands
6  ASTRON, Postbus 2, 7990 AA Dwingeloo, The Netherlands

Received 2 January 2009 / Accepted 30 January 2009

We present high-resolution spectral line and continuum VLBI and VLA observations of the nuclear region of NGC 253 at 22 GHz. While the water vapor masers in this region were detected on arcsecond and milliarcsecond scales, we could not detect any compact continuum emission with a 5$\sigma$ upper limit of ~1 mJy. The observations reveal that the water maser emission is not related to a possible low-luminosity active galactic nucleus but is almost certainly associated with star-formation activity. Not detecting any compact continuum source on milliarcsecond scales also questions the presence of a – previously assumed – active nucleus in NGC 253.

Key words: techniques: interferometric -- masers -- galaxies: starburst -- galaxies: individual: NGC 253

© ESO 2009