High Velocity Gas Clouds in M 83 and M 51

ANN ARBOR, Mich.-- University of Michigan astronomers have found evidence for clouds of high-speed gases around galaxies that may help scientists understand the mysteries of similar material in our own Milky Way galaxy. Postdoctoral fellow Eric Miller and astronomy professor Joel Bregman presented their results Jan. 8 at the 203rd meeting of the American Astronomical Society in Atlanta, Georgia, where they described their studies of the faint radio and optical signals from two nearby galaxies.

Read the full press release

See the presentation from the American Astronomical Society meeting (4 pages, 463 kb, technical)

These results arise from my Ph.D. thesis work and are being prepared for refereed publication.


Additional Images


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Optical image of M 51, the Whirpool Galaxy, with the locations of the high velocity neutral hydrogen clouds shown by blue contours. Only four of the gas clouds are shown here for clarity. The gas clouds superimposed on the spiral arms of the galaxy are extended and likely related to the ongoing star formation in those regions of the galaxy, as stellar explosions drive material out of the disk of the galaxy.
Photo credit: University of Michigan and National Radio Astronomy Observatory

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Optical image of M 83, the Southern Pinwheel Galaxy, with the locations of the high velocity neutral hydrogen clouds shown by blue contours. Only the five clouds nearest the center are shown here for clarity. The gas clouds superimposed on the spiral arms of the galaxy are extended and likely related to the ongoing star formation in those regions of the galaxy, as stellar explosions drive material out of the disk of the galaxy. Horizontal black lines are an instrumental effect.
Photo credit: University of Michigan and National Radio Astronomy Observatory

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A cross-section of the neutral gas in M 83, with darker colors indicating more gas. The vertical axis shows the velocity of this material relative to our own solar system. Most of the emission is from the gas confined to the plane of the galaxy, with varying velocities indicating that the galaxy is rotating. The small feature identified by the crosshairs is a distinct cloud of neutral hydrogen moving 80 km/s faster than the bulk of the gas at that point in the disk. This velocity is similar to what we see for gas clouds near our own Galaxy, and the presence of such features in M 83 and M 51 suggests that the gas clouds in the Milky Way are nearby, probably produced by material ejected from the Galaxy by star formation regions.
Photo credit: University of Michigan and National Radio Astronomy Observatory
Last updated: Wed Apr 13 15:46:06 EDT 2005
email: milleric@umich.edu