Far-Ultraviolet and Hα Imaging of Nearby Spiral Galaxies: The OB Stellar Population in the Diffuse Ionized Gas

摘要: We have compared Hα and far-ultraviolet (FUV) images of 10 nearby spirals, with the goal understanding contribution field OB stars to ionization diffuse ionized gas (DIG) in spiral galaxies. The FUV were obtained by Ultraviolet Imaging Telescope (UIT), using various ground-based telescopes. In all galaxies, FHα/FUIT flux ratio is lower DIG than H II regions. This likely an indication that mean spectral type for later Comparison NLyc/LUIT models evolving stellar populations shows population consistent either older single-burst or a steady state model constant star formation initial mass function (IMF) slope steeper α = 2.35. probably more realistic representation outside steep IMF simulates present-day expected does not necessarily indicate actually these galaxies M33, which has previously been investigated Hubble Space images. If types regions are same as M33 difference extinction between among then analysis suggests important sources most may be dominant source some correlated surface brightness both regions, although there large scatter faint due undersampling low total formed. often highest centers arms, also where brightest. can explained if greater fraction leakage interarm