The Sciences

Galaxies So Near, Yet So Far

Cosmic VarianceBy Sean CarrollJan 13, 2010 3:00 PM


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You might have heard the news out of last week's American Astronomical Society meeting, that the Hubble Space Telescope had found evidence for the most distant galaxies yet discovered. Using the newly-installed Wide Field Camera 3, HST did a close-up examination of some likely candidates in the Ultra Deep Field, and found galaxies at redshifts of 7 or 8 (meaning the universe is now 8 or 9 times bigger than it was when the light was emitted). That corresponds to about 600 million years after the Big Bang, which pushes back the era of galaxy formation quite a bit. But wait! Over at Science News, Ron Cowen points out that a team led by Rychard Bouwens and Garth Illingworth of UC Santa Cruz already has a paper on the arxiv that uses similar techniques to identify three galaxies with a redshift of 10, corresponding to only 450 million years after the Big Bang. And, as Cowen mentions in a blog post, the paper was available since last month.

Constraints on the First Galaxies: z~10 Galaxy Candidates from HST WFC3/IR Authors: R.J. Bouwens, G.D. Illingworth, I. Labbe, P.A. Oesch, M. Carollo, M. Trenti, P.G. van Dokkum, M. Franx, M. Stiavelli, V. Gonzalez, D. Magee Abstract: The first galaxies likely formed a few hundred million years after the Big Bang. Until recently, it has not been possible to detect galaxies earlier than ~750 million years after the Big Bang. The new HST WFC3/IR camera changed this when the deepest-ever, near-IR image of the universe was obtained with the HUDF09 program. Here we use this image to identify three redshift z~10 galaxy candidates in the heart of the reionization epoch when the universe was just 500 million years old. These would be the highest redshift galaxies yet detected, higher than the recent detection of a GRB at z~8.2. The HUDF09 data previously revealed galaxies at z~7 and z~8... [snipped]

So why are galaxies at redshift 8 considered news, if galaxies at redshift 10 have already been discovered? As Charlie Petit talks about at the Knight Science Journalism Tracker, the difference seems to be that the former were announced at a press briefing, while the latter just appeared on arxiv. For better or for worse, conventional science journalism has been cut back to the point where most reporters have no choice but to wait for press releases to appear to write a story. They don't have the resources to scan through arxiv postings every day -- and even if they did, the precious newsworthy nuggets are rather sparsely scattered through the mass of Kuhnian normal science. And let's not even think about the idea that journalists should spend time (and money) going to lots of conferences and talks and chatting with scientists about what's hot in their fields these days -- the resources just aren't there. There is some room for blogs to help out here. A blog by a respectable scientist can point to interesting stories that didn't appear in any press releases, and journalists can follow up. (I know it's happened here before.) But the thing about blogs is that they're remarkably non-systematic; bloggers mention things because they personally find them interesting, not because they feel a duty to the wider public. The nature of journalism is changing rapidly, and it's not clear how things will eventually shake out. I certainly hope that we continue to enjoy the work of people like Cowen, who make the extra effort to find good science stories and spread them widely.

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