AAS 205th Meeting, 9-13 January 2005
Session 26 Starbursts in Galaxies
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[26.03] O VI Emission in the Starburst Merger System NGC3256

R.C. Iping (the Catholic University of America), S.G. Neff, G. Sonneborn (NASA's GSFC), W.V. Dixon, R. Sankrit (Johns Hopkins University), B. Otte (University of Michigan)

We present our FUSE detection of O VI emission in NGC3256, an ongoing merger between two massive gas-rich disks and a good prototype for the type of interactions important in the earlier universe for building massive spheroids. O VI emission is observed in the velocity range -100 km/s to +300 km/s relative to the recession velocity of NGC 3256.

We interpret this coronal emission as evidence for shocks caused by the outflowing starburst superwind. We show how the cooling from O VI affects the overall energy balance in the superwind by comparing our O VI detection with models of expanding superbubbles / superwinds and with observations of the hotter (X-ray emitting) and cooler (optical line emitting) gas.

Previous searches have failed to detect O VI emission from starburst superwinds. These non-detections have been used to argue that radiative cooling is not important in removing kinetic energy from the superwinds, as well as that these winds play a major role in enriching the IGM. However, previous searches for O VI emission have generally looked at lower-mass starbursts, with low escape velocities and low-density haloes.

The detection of O VI emission in the NGC3256 superwind offers observational confirmation that in major mergers, surrounded by massive haloes, superwind material and energy may remain within the galaxy and not escape into the IGM. Assuming this result is typical for such mergers, this may have significant implications for the histories of both massive spheroids and the IGM.

We also detect Galactic OVI emission in our spectra. The strength of the emission indicates that it is from a supernova remnant shock wave.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.