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Session 4 - Low Luminosity AGN and Starburst Galaxies.
Display session, Monday, June 10
We present the first \sim arcsecond resolution far-ultraviolet (FUV, \lambda\sim1500Åimage of the nearby spectacular interacting galaxy pair NGC4038/4039. The observations were obtained by the Ultraviolet Imaging Telescope (UIT) in March 1995, as part of the Astro-2 mission on the Space Shuttle Endeavour. We detect significant FUV emission from this merger, despite extensive dust and molecular gas present in the system. The total FUV flux of the pair is \sim2.9 x 10^-13ergs cm^-2sec^-1Åor m_FUV\sim10.3. For an adopted distance of 19.8 Mpc, this corresponds to M_FUV\sim-21.2, a value typical of large spiral galaxies observed by UIT. The UV morphology is dominated by the starburst knots: little diffuse emission is present and star formation occurs mainly along two looping structures within the galaxies' disk remnants.
The FUV emission effectively traces the recent massive star formation. We identify 25 separate starburst regions, or knots in the system. We report on the number of young stars detected directly in each region, and estimate the total number of O and B stars present. Using comparison ground-based images made in the U, V, I, and K bands, we determine colors of the individual knots and compare these to star formation and dust extinction models to determine the overall properties of the starbursts in each region, e.g. mass functions, ages, and current star formation rates.
We briefly discuss the implications of these results to observations of other interacting galaxies, and to studies of the early universe where mergers occurred much more frequently.
Program listing for Monday