%0 Journal Article
%T Are Wolf-Rayet Stars Able to Pollute the Interstellar Medium of Galaxies? Results from Integral Field Spectroscopy
%A Enrique P¨¦rez-Montero
%A Carolina Kehrig
%A Jarle Brinchmann
%A Jos¨¦ M. V¨ªlchez
%A Daniel Kunth
%A Florence Durret
%J Advances in Astronomy
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/837392
%X We investigate the spatial distribution of chemical abundances in a sample of low metallicity Wolf-Rayet (WR) galaxies selected from the SDSS. We used the integral field spectroscopy technique in the optical spectral range (3700£¿£¿¨C6850£¿£¿) with PMAS attached to the CAHA 3.5£¿m telescope. Our statistical analysis of the spatial distributions of O/H and N/O, as derived using the direct method or strong-line parameters consistent with it, indicates that metallicity is homogeneous in five out of the six analysed objects in scales of the order of several kpc. Only in the object WR404 is a gradient of metallicity found in the direction of the low surface brightness tail. In contrast, we found an overabundance of N/O in spatial scales of the order of hundreds of pc associated with or close to the positions of the WR stars in 4 out of the 6 galaxies. We exclude possible hydrodynamical causes, such as the metal-poor gas inflow, for this local pollution by means of the analysis of the mass-metallicity relation (MZR) and mass-nitrogen-to-oxygen relation (MNOR) for the WR galaxies catalogued in the SDSS. 1. Introduction Wolf-Rayet (WR) galaxies host very bright episodes of star formation characterized by the emission of broad WR bumps in their optical spectrum [1]. The two main bumps in the optical range are the blue bump, centered at a wavelength of 4650£¿£¿, produced by the emission from N V, N III, C III/C IV, and He II, and associated with WC and WN stars, and the red bump which is fainter, centered at 5800£¿£¿, produced mainly by C III and C IV, and associated with WC stars. The lines making up these bumps originate in the dense stellar winds from WR stars ejecting metals into the interstellar medium (ISM). The number of known WR galaxies has tremendously increased from the discovery of the first one (He 2¨C10: [2]), with different published catalogs [3¨C6], until the list of WR galaxies in the Sloan Digital Sky Survey (SDSS) by Brinchmann et al. [7] with around 570 objects with the identification of the WR bumps in their integrated spectra. There is increasing evidence that the most challenging problems for this kind of objects appear in the low metallicity galaxies. Although it is well documented that the number of WR stars and the intensity of the WR bumps are higher for higher metallicities [8], the values found in some low metallicity H II galaxies, such as IZw18 [9], are claimed to be much higher than those predicted by synthesis population models (e.g., [10]). Among the other important open issues regarding WR galaxies is the chemical enrichment of the ISM
%U http://www.hindawi.com/journals/aa/2013/837392/