ASTROPHYSICS: Glowing in the Wind

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Science  12 May 2006:
Vol. 312, Issue 5775, pp. 815a
DOI: 10.1126/science.312.5775.815a

Galactic winds, driven by violent bursts of star formation, are thought to spread elements heavier than hydrogen between galaxies and throughout the cosmos. The ashes of former stars thereby live on in later generations of stars and may affect galactic evolution. The loss of gas due to winds may starve galaxies of fuel and could affect the growth of different galaxy types. The nearby edge-on spiral galaxy M82 has the most thoroughly studied strong wind; this galaxy is undergoing a violent burst of star formation in its heart, which expels a bi-conical superwind of hot ionized gas.

By examining infrared images acquired with the Spitzer Space Telescope, Engelbracht et al. find that M82 is surrounded by a spherical halo of warm dust into which the hot wind penetrates. Spidery dust filaments emanate outward in all directions, extending well beyond the galaxy and its wind. The spectra reveal that aromatic hydrocarbons survive in the dust despite close proximity to the hot superwind. The unusually wide extent and spherical shape of the M82 dust cocoon suggest that the dust was driven out of the galaxy before the superwind commenced, and is thus more pervasive than previously thought; possible explanations include interactions with neighboring galaxies or alternative wind-related mechanisms. — JB

Astrophys. J. 642, L127 (2006).

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