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[64.04] The High-Velocity NaI Cloud Complex Toward M81

J. T. Lauroesch, D. M. Meyer (Northwestern University), K. C. Roth (Gemini Observatory)

We have recently obtained long slit echelle observations of high velocity NaI absorption toward the core of the galaxy M81 using the Kitt Peak National Observatory 4-meter telescope. Our observations probe the neutral gas toward the core of the galaxy with a spatial resolution of ~1" and a spectral resolution of ~9 km/s, and we detect NaI absorption stretching more than 425 pc from the core. Previous observations of NaI toward the core of M81 and along the sightline to SN 1993J in M81 have shown absorption due to neutral gas at high positive velocities which is not associated with published HI 21cm emission at these positions. The NaI absorption toward the core is at velocities consistent with gas in the halo of M81 which has been tidally striped from M82. Our NaI data shows that this gas varies significantly in optical depth and in velocity over scales of <100pc, and we discuss how such absorption can arise in a ``clumpy'' extension to the M82 tidal tail.

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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.