RT Journal Article T1 Discovery of a double ring in the dwarf galaxy Markarian 409 A1 Madore, B. F. A1 Noeske, K. A1 Cairós, L. M. A1 Papaderos, P. A1 Silich, S. A. A1 Gil De Paz, Armando AB We report the discovery of a double ring of emission-line regions around the nucleus of the blue compact dwarf galaxy Mrk 409 as seen by deep, ground-based Hα images. Echelle spectroscopy obtained at Magellan I with MIKE shows the presence of ionized gas flowing out of the galaxy from a very massive (≥7 × 10^6 M_☉) nuclear starburst with projected expansion velocities of ~50 km s-^1. Different scenarios for the formation of these rings are discussed. While the innermost, nuclear ring is most probably formed by the interaction of a starburst-driven shock with the surrounding interstellar medium, the origin of the outer ring is less clear. PB American Astronomical Society SN 0004-637X YR 2003 FD 2003-10-20 LK https://hdl.handle.net/20.500.14352/51798 UL https://hdl.handle.net/20.500.14352/51798 LA eng NO © 2003. The American Astronomical Society. All rights reserved. We acknowledge the referee (R. Buta) for his valuable comments. We thank the staff at the Palomar, LCO, Teide, NOT, and CAHA observatories for their help and support. This work has been financed by the Spanish PN de Astronomía y Astrofísica grants AYA2000-1790 and AYA2003-1676, the DFG grants FR325/50-1 and FR325/50-2, the CONACYT (Mexico) grant 36132-E, the EC Marie-Curie grant HPMF-CT-2000- 00774, and the NASA Galaxy Evolution Explorer mission. NO Programa Nacional de Astronomía y Astrofísica (PNAyA), España NO Geschäftsstelle der Deutschen Forschungsgemeinschaft (DFG), Alemania NO Consejo Nacional de Ciencia y Tecnologia CONACYT (Mexico) NO EC Marie-Curie Action NO NASA Galaxy Evolution Explorer mission NO Unión Europea (UE) DS Docta Complutense RD 2 sept 2025