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yuiop
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I have been reading this interesting article http://www.subarutelescope.org/Pressrelease/2006/09/13/index.html on one of the earliest galaxies that has ever been observed (z=6.96), that existed when the universe was just 760+/-15 million years old or about 6% of its current age. See also http://www.nature.com/nature/journal/v443/n7108/abs/nature05104.html
The article is very readable and nicely illustrated, but a couple of things puzzle me and I hope someone here can enlighten me. It describes the period of "recombination" when the universe transitions from an opaque period due to scattering of light by ions to a period when the universe becomes transparent when the ions combined to form hydrogen atoms. It then goes on to say that we do not see many galaxies at the early epoch (@760 million years) because neutral hydrogen absorbs the light from the early stars and they only later become visible when the young stars reionize the neutral hydrogen. That seems to contradict the earlier statement but maybe I am missing some important point??
Another issue is that they describe the early universe as being different to later epochs because of the relative rarity of galaxies in the early epoch. That would seem natural if all galaxies did not form simultaneously in the early universe and I would have thought that Malquist bias would be an additional factor at the enormous distances we are talking about here. See http://en.wikipedia.org/wiki/Malmquist_bias . However, they do not mention Malmquist bias anywhere in the article. Have they taken Malmquist bias into account and simply not mentioned it or is it a non issue in this context?
The article is very readable and nicely illustrated, but a couple of things puzzle me and I hope someone here can enlighten me. It describes the period of "recombination" when the universe transitions from an opaque period due to scattering of light by ions to a period when the universe becomes transparent when the ions combined to form hydrogen atoms. It then goes on to say that we do not see many galaxies at the early epoch (@760 million years) because neutral hydrogen absorbs the light from the early stars and they only later become visible when the young stars reionize the neutral hydrogen. That seems to contradict the earlier statement but maybe I am missing some important point??
Another issue is that they describe the early universe as being different to later epochs because of the relative rarity of galaxies in the early epoch. That would seem natural if all galaxies did not form simultaneously in the early universe and I would have thought that Malquist bias would be an additional factor at the enormous distances we are talking about here. See http://en.wikipedia.org/wiki/Malmquist_bias . However, they do not mention Malmquist bias anywhere in the article. Have they taken Malmquist bias into account and simply not mentioned it or is it a non issue in this context?
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