Galaxies Are the Ultimate Recyclers, NASA's Hubble Confirms
ScienceDaily (Nov. 17, 2011) — Galaxies learned to "go green" early in the history of the universe, continuously recycling immense volumes of hydrogen gas and heavy elements to build successive generations of stars stretching over billions of years.
The color and shape of a galaxy is largely controlled by gas flowing through an extended halo around it. All modern simulations of galaxy formation find that they cannot explain the observed properties of galaxies without modeling the complex accretion and "feedback" processes by which galaxies acquire gas and then later expel it after chemical processing by stars. Hubble spectroscopic observations show that galaxies like our Milky Way recycle gas while galaxies undergoing a rapid starburst of activity will lose gas into intergalactic space and become "red and dead." (Credit: NASA; ESA; A. Feild, STScI)
This ongoing recycling keeps galaxies from emptying their "fuel tanks" and therefore stretches out their star-forming epoch to over 10 billion years. However, galaxies that ignite a rapid firestorm of star birth can blow away their remaining fuel, essentially turning off further star-birth activity.
This conclusion is based on a series of Hubble Space Telescope observations that flexed the special capabilities of its comparatively new Cosmic Origins Spectrograph (COS) to detect otherwise invisible mass in the halo of our Milky Way and a sample of more than 40 other galaxies. Data from large ground-based telescopes in Hawaii, Arizona, and Chile also contributed to the studies by measuring the properties of the galaxies.
This invisible mass is made up of normal matter -- hydrogen, helium, and heavier elements such as carbon, oxygen, nitrogen, and neon -- as opposed to dark matter that is an unknown exotic particle pervading space.
The results are being published in three papers in the November 18 issue of Science magazine. The leaders of the three studies are Nicolas Lehner of the University of Notre Dame in South Bend, Ind.; Jason Tumlinson of the Space Telescope Science Institute in Baltimore, Md.; and Todd Tripp of the University of Massachusetts at Amherst.
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Journal References:
1. T. M. Tripp, J. D. Meiring, J. X. Prochaska, C. N. A. Willmer, J. C. Howk, J. K. Werk, E. B. Jenkins, D. V. Bowen, N. Lehner, K. R. Sembach, C. Thom, J. Tumlinson. The Hidden Mass and Large Spatial Extent of a Post-Starburst Galaxy Outflow. Science, 2011; 334 (6058): 952 DOI: 10.1126/science.1209850
2. N. Lehner, J. C. Howk. A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in the Milky Way. Science, 2011; 334 (6058): 955 DOI:10.1126/science.1209069
3. J. Tumlinson, C. Thom, J. K. Werk, J. X. Prochaska, T. M. Tripp, D. H. Weinberg, M. S. Peeples, J. M. O'Meara, B. D. Oppenheimer, J. D. Meiring, N. S. Katz, R. Dave, A. B. Ford, K. R. Sembach. The Large, Oxygen-Rich Halos of Star-Forming Galaxies Are a Major Reservoir of Galactic Metals. Science, 2011; 334 (6058): 948 DOI:10.1126/science.1209840
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