Narrow-band β images of star-formation regions in HII galaxies

Abstract

Aims.Create a catalog of images of HII galaxies and their individual star-formation regions in order to study the distribution of the gas emission and their underlying stellar continuum.Methods.We have used H narrow-band images of 43 selected HII galaxies obtained at ESO NTT 3.58 m telescope using the SUSI2 camera.Results.Surface photometric H fluxes and equivalent widths for all objects and star-formation regions are presented in this catalog. A myriad of filamentary structure were found in the pure H emission-line or continuum-subtracted images, probably attributed to expanding shells as a consequence of the star-formation activity. Our results indicate that the number of regions with high H equivalent width or young regions increase with the instrumental resolution, showing that the instrumental resolution is a bias to determine the cluster ages. Therefore, we showed that some of the observed giant HII regions may have been formed by ensembles of unresolved star forming regions or candidates to host Super Star Clusters. Pure H emission-line images, continuum contours and EW(H) maps showing the morphology of the gaseous and stellar emission in HII galaxies and their individual star-formation regions were obtained. All calibrated continuum and H emission line fluxes and the derived H equivalent width images are available in fits format from http://www.on.br/astro/etelles/HIIgalaxies/Hbeta/.. © 2007 ESO.