Astron. Astrophys. 330, 435-442 (1998)

UCM1612+1308: a newly identified Blue Compact Galaxy ^*

M. Rego ¹, M. Cordero-Gracia ^{1, 2}, J. Gallego ¹ and J. Zamorano <sup>1

1</sup> Departamento Astrofsica, Facultad CC Fsicas, Universidad Complutense, E-28040 Madrid, Spain
² ETSI Aeronáuticos, Universidad Politécnica, E-28040 Madrid, Spain

Received 27 February 1997 / Accepted 16 September 1997

Abstract

UCM1612+1308 is a new emission-line galaxy identified in the context of the Universidad Complutense de Madrid (UCM) survey. This object was classified as Blue Compact Galaxy (BCG) from photometric data. A detailed spectroscopic study from new optical observations is presented now. The physical conditions and chemical composition are derived. The ionic abundances yield to a metallicity of and a very low nitrogen to oxygen abundances ratio, , supporting a primary nucleosynthesis origin for the nitrogen. The same value has been obtained for the sulfur to oxygen ratio. The comparison of the helium abundance with the oxygen and nitrogen abundances evidences a quickly enrichment of oxygen produced by massive stars. The ionizing cluster has been analyzed yielding a relatively low ionization parameter, , total number of stars, , stellar mass, , and gas mass . A lower limit of the dust mass, , has been obtained from the IRAS fluxes. The observed data and derived parameters, when interpreted with the evolutionary synthesis models by Leitherer & Heckman (1995), point out to an instantaneous burst with an age of

Key words: galaxies: individual (UCM1612+1308) galaxies: compact galaxies: abundances stars: formation

* Based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio del Roque de los Muchachos of the Instituto Astrofsico de Canarias.

Send offprint requests to: M. Rego

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations and data reduction
• 3. Physical conditions and chemical composition
  • 3.1. Electron temperatures and densities
  • 3.2. Heavy elements abundances
  • 3.3. Helium abundance determination
• 4. The ionizing source
  • 4.1. The ionization parameter and effective temperature
  • 4.2. The starburst population
  • 4.3. Mass of the ionized gas
  • 4.4. Mass of dust
• 5. The kinetic energy of the burst
• 6. Modeling the starburst
• 7. Summary and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
helpdesk.link@springer.de