- #36
turbo
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Here is a link to a paper that identifies large, old, highly evolved galaxies in the HST UDF at z~3.Nereid said:small, yes; interacting, yes; but IIRC, the first HUDF papers were quite clear that the early structure appears to be quite different from that of the local universe!
http://scholar.google.com/url?q=http://arxiv.org/pdf/astro-ph/0405432
It may well be that structure in the UDF appears different from that of our local neighborhood, but before we read too much into that one (glorious!) image, let us consider some of the things that affect the usefulness of that image. First off, at high redshift, the most visible objects will be the ones with the most concentrated, perhaps violent, activity (mergers, starburst, etc). Galaxies with more uniform diffuse star distribution and a nondescript galactic core, like M33, will not be as easily detected in the UDF at high redshift, due to low contrast. Small galaxies with modest luminosities will be underrepresented simply because our instruments cannot detect them. Galaxies that are highly disturbed and energetic will be overrepresented, so if we see lots of oddballs at z~3-6, we should not be surprised - it is predictable and it should be expected. This selection effect can cause a strong bias, especially as we approach the limits of our instruments' capabilities. Additional biasing factors include surface brightness dimming, reddening from intergalactic dust, selection of filters for our instruments, and selection of noise-reduction algorithms in image processing, to name a few. Again, it's a great picture, but its value as a cosmological tool is limited by these factors, and probably dozens more that I haven't thought of.
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