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B. A. Buckalew, H. A. Kobulnicky (University of Wyoming)
We present narrowband HST imagery of the dwarf irregular starburst galaxy NGC 1569. The combination of this galaxy's proximity and the high spatial resolution of HST/WFPC2 provides us with an unprecedented look at the complex ionized gas distribution. We present a detailed study of the ionized gas and its excitation mechanism. We have determined the H\alpha/H\beta, [O~{\sc iii}]/H\beta, and [S~{\sc ii}]/H\alpha ratios for 3 pc bins across the entire galaxy. We mapped the positions of those ratios which have values larger than what is possible for photoionization mechanisms. We find that the percentage of ionized H\alpha gas attributed to non-photoionizing mechanisms is 19--15%, values 5--4 times larger than values from similar starburst galaxies. These non-photoionized points follow several arcs and filaments within the galaxy, suggesting that shocks are the prevalent non-photoionizing mechanism. We show that the mechanical luminosity produced from the starburst can easily explain the non-photoionized H\alpha luminosity. These data combined with the locations of Wolf-Rayet stars, star clusters, and radio-detected supernovae and with X-ray maps of the hot gas component allow us to determine which object is responsible for the shocks on a detection-by-detection basis. We detail below that most radio-detected SNR, some Wolf-Rayet stars, and the clusters of the main starburst around super star cluster A can explain the majority of the shocked H\alpha gas. This research was supported by NASA grant NRA-00-01-LTSA-052.
The author(s) of this abstract have provided an email address for comments about the abstract: mrk1236@uwyo.edu
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.