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Jayanne English (STScI), A.R. Taylor (U. of Calgary), J.A. Irwin (Queen's U.), Canadian Galactic Plane Survey Collaboration
Neutral hydrogen ``worms'', which stream vertically from the mid-plane to high latitudes, may be conduits through which hot gas can escape into the halo. Using the Dominion Radio Astrophysical Observatory's (DRAO) Synthesis Telescope, as part of the Canadian Galactic Plane Survey, we have resolved an HI worm candidate. Although simulations have previously made general predictions, these data will constrain, for the first time, detailed numerical models of the dynamical processes generating disk-halo features.
After the incorporation of the data from the 26-m DRAO's single-dish telescope, the mosaic data cube has full information on all spatial scales down to a resolution limit of 1 arcmin and a velocity resolution of 0.82 km s-1. Thus we delineate Rayleigh-Taylor instability-like structures and can distinguish a 5 km s-1 line of sight velocity difference between the base and top of the worm. In general morphology, the worm is mushroom-shaped. Although it extends only a few hundred parsecs south of the midplane, the cap appears to be fragmenting. This may allow hot material from the stem's cavity, as well as UV photons, to escape to higher galactic latitudes.
The preliminary estimate of the observed minimum HI mass is 1.3 x 105 Msolar. Our initial thin-shell model, which assumes supernovae explosions drive this outflow, gives a minimum total energy of about 100 x 1051 ergs s-1.
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The author(s) of this abstract have provided an email address for comments about the abstract: jenglish@stsci.edu