Early universe was less dusty than believed

Dec 09, 2013
Credit: Swinburne University of Technology

(Phys.org) —Dust may be more rare than expected in galaxies of the early Universe, according to an international research team, led by Swinburne University of Technology astrophysicist Dr David Fisher.

In a galaxy named IZw 18, the team measured the lowest dust mass of a galaxy that has ever been measured.

"It's not just that the dust mass is low. We found that the dust mass is 100 times smaller than would be expected based on commonly assumed theories," Dr Fisher said.

The galaxy, I Zw 18, is nearby, which makes it easier to study, but has properties that are very similar to galaxies of the high redshift Univese.

"It's an extreme galaxy in the local Universe, but it tells us a lot about a stage that almost all galaxies have gone through, so it gives us a picture of what the first galaxies look like."

Dr Fisher said the results imply that galaxies of the early Universe may have less dust than has been expected.

"This means, firstly, that they will look different than we expect and make different populations of stars than we expect. And secondly, that they will be much more difficult to observe, even with state-of-the-art facilities being built now such as the Atacama Large Millimeter/sub-millimeter Array (ALMA) of radio telescopes in northern Chile.

"IZw 18 is typical of very high redshift galaxies because it is very actively forming stars, and has a chemistry that is more like of the very early Universe with a very low abundance of metals and a lot of gas in the form of hydrogen," he said.

"Our result implies that current theories to describe the formation of stars when the Universe was very young are incomplete, and are built on invalid assumptions."

According to Dr Fisher, the amount of dust is very important for the formation of stars.

"What we think is going on, is that the harsh environment inside the galaxy we examined is adversely affecting the amount of in it.

"The radiation field measured inside I Zw 18 was roughly 200 times stronger than what we experience here in the Milky Way." Dr Fisher said that based on the findings, theories should be amended to account for environment in making stars.

The research is published in Nature.

Explore further: Galactic clusters low on hydrogen

More information: Paper: dx.doi.org/10.1038/nature12765

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Tuxford
3 / 5 (4) Dec 09, 2013
"Our result implies that current theories to describe the formation of stars when the Universe was very young are incomplete, and are built on invalid assumptions."

Indeed.
Widdekind
not rated yet Jan 18, 2014
I Z 18 appears to be interacting with a close companion dIrr galaxy (see HST or APOD)

mergers, triggering bursts of SF, could virialize into Spiral galaxies (since any two incident objects "must" have angular momentum, relative to their common barycenter)

maybe, dSph galaxies are isolated galactic clumps, of up to 1kpc in size, and 1e9-10Msol in mass; when they begin merging, they begin assembling all larger galaxies, e.g. dIrr. / Sp. (and if they then merge, on into Es) ?
Nestle
not rated yet Jan 18, 2014
the dust mass is 100 times smaller than would be expected based on commonly assumed theories
In steady state Universe model the red shift is the result of light scattering at the density fluctuations of vacuum and the Universe is roughly homogeneous at all distance scales. In Big Bang cosmology the matter formed in finely divided state, so that the lack of dust at distant areas of universe represents a stress for this theory (similar like many other examples presented here at PO). But the mainstream physics handles these indicia poorly, because they're not conclusive by itself and the contemporary physics is based on deterministic models, not on fuzzy logics. One thousand of 60% indicia doesn't count in the same way, like one 90% evidence, which slows down the progress of research. But are the physicists really motivated on speed of research, when their jobs and salaries depend on it? I seriously doubt it, until their money are going.

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