The colliding galaxy pair, NGC 5257-28, one of fourteen luminous infrared galaxies recently studied by the SMA.
Ultra-luminous galaxies reveal their secrets
5 Dec 2008
Ultraluminous infrared galaxies ('ULIRGs') shine with as much energy as one hundred or more of our Milky Way galaxies. Their most striking feature, however, is not their tremendous energy output but the fact that nearly all of their radiation is invisible, lying at infrared wavelengths. The source of this energy is intense star formation, and because that activity takes place within dust-filled clouds, the ultraviolet and visible light generated is absorbed by the dust grains and remitted in the infrared.
ULIRGs are thought to result from collisions between galaxies, and since collisions are common, ULIRGs and the slightly dimmer 'luminous infrared galaxies' could represent a period of stellar growth and enrichment that many galaxies (perhaps even our own galaxy) briefly experience, especially at early times in the age of the universe when collisions were common.
The connections between galaxy interactions and star formation, however, are poorly understood, in part because the obscuring dust makes it difficult to probe the small cores of the two merging galaxies.
Smithsonian Astrophysical Observatory (SAO) astronomers Christine Wilson, Glen Petitpas, Daisuke Iono, Alison Peck, Melanie Krips, and Tom Cox, together with ten colleagues, have just published the first in a landmark series of papers on luminous and ultraluminous galaxies using data obtained with SAO's Submillimetre Array (SMA). The SMA enabled the astronomers to measure for the first time the spatial distribution of the warm gas around luminous galaxies' cores.
The scientists reached two surprising conclusions.
First, they found that the ratio of the amount of gas to dust is about the same as it is in the Milky Way despite the very different level of star formation activity.
And second, they discovered that it is peak gas density, not the peak gas mass, which correlates with the region of maximum brightness. This suggests that the increased rate of star birth is the result of increased availability of gas as the fuel, a conclusion that is in direct contrast to the conventional wisdom that abundant gas increases the efficiency but not the rate of star birth.
The new paper, the first in a set that will analyse fourteen nearby galaxies, pioneers new, high spatial resolution diagnostics to provide new insights into these powerful cosmic beacons.
Adapted from information issued by the SAO / Hubble Space Telescope.
LATEST HEADLINES & TOP STORIES:
> Mysteries of our sister planet revealed
> Ultra-luminous galaxies reveal their secrets
> Astronomers use a supernova to look back in time
> It's official: Phoenix lander can no longer phone home
> DOWN TO EARTH: Cities of the Dead, Egypt
> A new player in space tourism
> Glittering giant of the southern skies
> Comet particles hint at Solar System's birth
> NASA puts escape rocket to the test
> Meet Mimas, Saturn's 'bullseye' moon
> Tiny satellite to study lightning link
> Do astronauts make good doctors?
> Shuttle Endeavour home
> Aussie seeds return from their space journey
> MAIN NEWS PAGE…
