Global properties of the population of Hii regions in NGC 7479 from photometric Hα imaging

摘要: We present a new high quality continuum-subtracted Hα image of NGC 7479. Using novel semi-automated technique we have determined the positions, angular sizes, and absolute fluxes over 1000 Hii regions constructed luminosi ty function for whole galaxy, showing that its slope is within published range spirals same morphological type. However NGC 7479 notable in bar shows unusually strong star formation along structure. This prompted us to undertake separate analyses disc. The disc luminosity (LF) clean bi-linear behaviour as found previously late-type spirals, with break at log L H\alpha = 38.6 erg s-1 , whereas LF much less regular form. difference not due small numbers bar, but reflects physical between properties their sets regions. show plots parameters selected shapes absence blending. derived galaxy-wide relations region set: diameter distribution function, versus volume number diameter, deduced global surface density scale length. Measuring integrated diffuse flux compare this computed ionizing escaping from population density-bounded regions, finding both terms energy balance geometry, hypothesis gives rise well borne out NGC 7479, significant fraction escapes completely into intergalactic medium.