Astronomy

Gazing Through the Dust

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Science  06 Nov 2009:
Vol. 326, Issue 5954, pp. 773
DOI: 10.1126/science.326_773a
CREDIT: IRAM, 30M RADIO-TELESCOPE

Galaxies undergoing vigorous bursts of star formation are often optically concealed by dust but appear luminous at longer wavelengths because the dust absorbs the light of the stars and re-emits it in the far infrared. If the galaxies are distant, they are detected at submillimeter wavelengths near Earth, because the far-infrared light gets stretched (or redshifted) by the cosmological expansion of the universe. In this way, hundreds of dusty, star-forming submillimeter galaxies have been detected over the past decade. Determining their precise distances from Earth, however, requires measuring a spectrum of their starlight, which is often too faint to detect.

As a proof of concept for circumventing this problem, Wei et al. used the new receiver at the IRAM 30-m radio telescope to look for CO emission lines—arising from the molecular gas that fuels star formation—from a submillimeter galaxy that was discovered in 1998 but for which it has not been possible to determine a distance. Their detection of two emission lines places the submillimeter galaxy SMM J 14009+0252 at redshift 2.93, or 11.4 billion light years away, and showcases a promising technique for determining the redshifts of submillimeter galaxies.

Astrophys. J. 705, L45 (2009).

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