2006/09/18 by A. R. Lopez-Sanchez, Á. R. López-Sánchez, C. Esteban +5 · 11 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Atomic physics #Dwarf galaxy #Ejecta #Emission spectrum #Excited state #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Physics #Spectral line #Stars #Stellar, planetary, and galactic studies #Supernova #astro-ph
paper · pdf · doi:10.1086/510112
published as Astrophys.J.656:168-185,2007 · 28 pages, 13 tables, 10 figures. Accepted for publication in ApJ
arxiv created 2006/09/18 · openalex publication_date 2007/02/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present echelle spectrophotometry of the blue compact dwarf galaxy NGC 5253 obtained with the VLT UVES. We have measured the intensities of a large number of permitted and forbidden emission lines in four zones of the central part of the galaxy. We detect faint C II and O II recombination lines, the first time that these are unambiguously detected in a dwarf starburst galaxy. The physical conditions of the ionized gas have been derived using a large number of different line intensity ratios. Chemical abundances of He, N, O, Ne, S, Cl, Ar, and Fe have been determined following standard methods. C ++ and O ++ abundances have been derived from pure recombination lines and are larger than those obtained from collisionally excited lines (from 0.30 to 0.40 dex for C ++ and from 0.19 to 0.28 dex for O ++ ). This result is consistent with a temperature fluctuation parameter ( t 2 ) between 0.050 and 0.072. We confirm previous results that indicate the presence of a localized N enrichment in certain zones of NGC 5253 and detect a possible slight He overabundance in the same zones. The enrichment pattern agrees with that expected for the pollution by the ejecta of Wolf-Rayet (W-R) stars. The amount of enriched material needed to produce the observed overabundance is consistent with the mass lost by the number of W-R stars estimated in the starbursts. We discuss the possible origin of the difference between abundances derived from recombination and collisionally excited lines (the so-called abundance discrepancy problem) in H II regions, finding that a recent hypothesis based on the delayed enrichment by SN ejecta inclusions seems not to explain the observed features.