Fig. 1 - Examples of the new galaxies discovered at z~1.
Posted on 03/14/2006 4:27:35 AM PST by PatrickHenry
A team of astronomers from France, the USA, Japan, and Korea, led by Denis Burgarella has recently discovered new galaxies in the Early Universe. They have been detected for the first time both in the near-UV and in the far-infrared wavelengths. Their findings will be reported in a coming issue of Astronomy & Astrophysics. This discovery leads to the first thorough investigation of early galaxies. Figure 1 shows some of these new galaxies.
The knowledge of early galaxies has made major progress in the past ten years. From the end of 1995, astronomers have been using a new technique, known as the “Lyman-break technique”. This technique allows very distant galaxies to be detected. They are seen as they were when the Universe was much younger, thus providing clues to how galaxies formed and evolved. The Lyman-break technique has moved the frontier of distant galaxy surveys further up to redshift z=6-7 (that is about 5% of the present age of the Universe). In astronomy, the redshift denotes the shift of a light wave from a galaxy moving away from the Earth. The light wave is shifted toward longer wavelengths, that is, toward the red end of the spectrum. The higher the redshift of a galaxy is, the farther it is from us.
The Lyman-break technique is based on the characteristic “disappearance” of distant galaxies observed in the far-UV wavelengths. As light from a distant galaxy is almost fully absorbed by hydrogen at 0.912 nm (due to the absorption lines of hydrogen, discovered by the physicist Theodore Lyman), the galaxy “disappears” in the far-ultraviolet filter. Figure 2 illustrates the “disappearance” of the galaxy in the far-UV filter. The Lyman discontinuity should theoretically occur at 0.912 nm. Photons at shorter wavelengths are absorbed by hydrogen around stars or within the observed galaxies. For high-redshift galaxies, the Lyman discontinuity is redshifted so that it occurs at a longer wavelength and can be observed from the Earth. From ground-based observations, astronomers can currently detect galaxies with a redshift range of z~3 to z~6. However, once detected, it is still very difficult to obtain additional information on these galaxies because they are very faint.
For the first time, Denis Burgarella and his team have been able to detect less distant galaxies via the Lyman-break technique. The team collected data from various origins: UV data from the NASA GALEX satellite, infrared data from the SPITZER satellite, and data in the visible range at ESO telescopes. From these data, they selected about 300 galaxies showing a far-UV disappearance. These galaxies have a redshift ranging from 0.9 to 1.3, that is, they are observed at a moment when the Universe had less than half of its current age. This is the first time a large sample of Lyman Break Galaxies is discovered at z~1. As these galaxies are less distant than the samples observed up to now, they are also brighter and easier to study at all wavelengths thereby allowing a deep analysis from UV to infrared to be performed.
Previous observations of distant galaxies have led to the discovery of two classes of galaxies, one of which includes galaxies that emit light in the near-UV and visible wavelength ranges. The other type of galaxy emits light in the infrared (IR) and submillimeter ranges. The UV galaxies were not observed in the infrared range, while IR galaxies were not observed in the UV. It was thus difficult to explain how such galaxies could evolve into present-day galaxies that emit light at all wavelengths. With their work, Denis Burgarella and his colleagues have taken a step toward solving this problem. When observing their new sample of z~1 galaxies, they found that about 40% of these galaxies emit light in the infrared range as well. This is the first time a significant number of distant galaxies were observed both in the UV and IR wavelength ranges, incorporating the properties of both major types.
From their observations of this sample, the team also inferred various information about these galaxies. Combining UV and infrared measurements makes it possible to determine the formation rate for stars in these distant galaxies for the first time. Stars form there very actively, at a rate of a few hundred to one thousand stars per year (only a few stars currently form in our Galaxy each year). The team also studied their morphology, and show that most of them are spiral galaxies. Up to now, distant galaxies were believed to be mainly interacting galaxies, with irregular and complex shapes. Denis Burgarella and his colleagues have now shown that the galaxies in their sample, seen when the Universe had about 40% of its current age, have regular shapes, similar to present-day galaxies like ours. They bring a new element to our understanding of the evolution of the galaxies.
[1] The team includes D. Burgarella, V. Buat, T.T. Takeuchi, S. Lauger, S. Arnouts, R.F. Malina (France), P.G. Pérez-Gonzales, K.D. Tyler, G.H. Rieke, T.A. Barlow, L. Bianchi, B.F. Madore, A.S. Szalay (USA), Y.-W. Lee, S.K. Yi (Korea), O. Ilbert (Italy).
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A long time ago, in a galaxy far, far away...
Two questions, though.
1) Under current theories of galaxy formation, is there any difference in the distribution of types of galaxies (globular, spiral, what not) for the earliest galaxies (i.e. did the mix of galaxies change over time)?
2) Is there enough "resolution" on these galaxies that we can get a rough sense of the mix of stars within them?
Cheers!
Huh?
...there were more little unicorns than you'd ever seen.....
The currently accepted model posits that elliptical galaxies are formed from coalescing and interacting spiral galaxies. This comes from the preferred locations of ellipticals (which are always near the center of a cluster of galaxies, as well as observations of some ellipticals which show recent signs of interacting with other galaxies. Elliptical galaxies are extremely red in color, which means that they are mostly older stars with no new star formation going on in them. They also are stripped of most of their gas, which also means that there will be no more star formation going on in them as well(that should help answer question number 2).
--Some people don't like hearing that the universe is older than a few thousand years.
I think only a very..very..small minority here and are they really worth tweaking?
PH explains this at some length--why don't you try reading what's posted?
If I were good in math, I would be an astronomer.
Really.
There are more than one would think, and they can be extremely vocal. Flame wars have arisen in the past between those who see an affront to their religious beliefs on the one hand, and those who see an affront to reason on the other (hence PH's exhortation).
and are they really worth tweaking?
That depends what you mean by "tweaking". Some would see the posting of this article as a tweak. Some would see my mention of young-Earth creationists as a tweak. Some would see any response to someone's objection to this article as a tweak. Some would see the uncompromising assertion of rigorous science and sane rationality in the face of an infantile, medieval Bible-idolatry as a tweak. Some would...er, ahem.
Is it worth posting this article, even though it may offend someone's sensibilities? Yes, it's damned interesting, and it impacts our conservatism in a positive way: philosophically, there is no point-of-view that can't benefit from a sense of scale.
Is it worth risking a divisive flame war to counter the opinions of the young-Earth creationists here? Yes, it is. Their writings constitute exhibit-A in the argument that FreeRepublic.com is a hotbed of anti-intellectualism and ignorance, and also in the argument that the conservative movement in general is hostile to science. To the extent that YEC opinions go unchallenged on FR, we yield to both those positions.
They take that into rigorous account: The Lyman Alpha Forest.
or on another hand photon decay theory may be in play.
There are many problems with that idea: Errors in Tired Light Cosmology.
For instance perhaps the other frequencies are beginning to be filtered out at those distances, or on another hand photon decay theory may be in play. What kind of tests could be developed that could determine this. Or are they just sticking with Doppler-redshift theory?
Every paper you see published in the field of extra galactic astronomy tests the model of an expanding universe in some manner, as pretty much everything you read in an paper these days depends on a prediction made by some aspect of that model. There are some papers out there that work pretty hard at trying to find other models (Arp et al), and they DO get published in well respected journals, but they are dismissed for various reasons (not statistically persuasive, rely on chance orientations, etc) by most of the field.
The important thing to remember is that first principles in most fields of astronomy come from things that are observed here on Earth (lab-observed physical relations and constants, spectra, etc), and then applied to outer space. So if no one has observed a photon decaying here, chances are it's not happening in outerspace.
--Is it worth posting this article, even though it may offend someone's sensibilities? Yes, it's damned interesting, and it impacts our conservatism in a positive way: philosophically, there is no point-of-view that can't benefit from a sense of scale.
The article's fine. The "tweaking" I was talking about was just the "now play nice" thing. If the aim of the article is to tweak the flat-earth'ers, it just seems like there are better things to do, not because I don't want to offend their sensibilities but just because they are a small and silly group of people who aren't worth wasting time on, IMHO. If the purpose of the posting to inform only there would have been no need for that little dig which kind of ruined the moment for me. :)
Sounds like someone has been to peecee boot camp.
bump
I'm a conservative christian....but I am also open to what science finds...I'm sure it will all come out in the wash someday soon....and we'll get all of our questions answered....until then I'm not going to sweat it....;-)
Frankly I think this is a Great Post.
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