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VI. About the Poster

"The Hidden Lives of Galaxies" poster illustrates various facets of galaxies, both what is visible at optical wavelengths and what can be seen and revealed only at X-ray wavelengths. The central image is a composite X-ray (left-hand side) and optical (right-hand side) image of the Andromeda Galaxy. The optical image shows the familiar dust lanes and spiral arms. The X-ray image, taken from ROSAT data at 0.5-2.0 keV, shows individual sources and emission from gas in the galaxy. The inset shows a portion of the observations taken by the Chandra X-ray Observatory. The increased spatial resolution of the Chandra data now reveals many individual X-ray sources in the central region of the galaxy, as well as diffuse X-ray emission from hot gas.

On the right hand side of the poster is an illustration of the changing size and distance scale within the universe as we compare a planetary system to a neighborhood of stars in a stellar region, to a galaxy, and finally to a cluster of galaxies.

The lower left box shows the different types of galaxies — spiral, barred spiral, elliptical, irregular, and peculiar.

The lower right box illustrates and discusses the evidence for missing mass in galaxies as revealed by optical and X-ray observations. The left-hand plot compares the rotation curve of a galaxy to the velocities of planets in the solar system. The constant value for the velocities of stars in the outer reaches of the galaxy shows that there must be more mass in the galaxy than just the visible mass in order for the stars to remain bound to the galaxy. Likewise, the right-hand plot shows hot X-ray gas extending far beyond the visible image of the elliptical galaxy. Because this gas must be part of the galaxy, this too shows evidence for more matter than what is visible.

Poster Credits

"The Hidden Lives of Galaxies" poster was designed and assembled by Karen Smale, with additional artwork by Maggie Masetti. Also contributing were Gail Rohrbach, Brian Hewitt, and Steve Fantasia. Chief scientific consultant was Dr. Greg Madjeski, with additional assistance from Dr. Michael Lowenstein. Thanks also to Drs. Kimberly Weaver and William Pence for additional comments. The project was supervised by Dr. James Lochner.

The Chandra image of the nucleus of M31 is courtesy of Dr. Steve Murray, NASA/CXC/SAO. The rotation curve of the galaxy F563-1was provided by Dr. Stacy Mcgaugh, Univ. of Maryland. The optical image of NGC 4414 is from the Hubble Space Telescope, courtesy AURA/STScI/NASA, whereas the optical images M87, Centaurus A, Small Magellanic Cloud and NGC 1530 are copyright AURA/NOAO/NSF, used by permission. The image of M31 is copyright Bill Schoening, Vanessa Harvey, REU program/AURA/NOAO/NSF, used by permission for educational purposes.

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Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: Meredith Gibb
Responsible NASA Official: Phil Newman
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This page last updated: Wednesday, 01-Jun-2005 09:24:31 EDT