Talk:Reionization

Reionization and galaxy formation

The article says: reionization is the process that reionized the matter in the universe after the epoch of galaxy formation. But Graphical timeline of the Stelliferous Era shows the reionization phase starting at 100 million years after the Big Bang and completing before the formation of the first galaxies at 600 million years after the Big Bang. Which is correct ? Gandalf61 16:41, 23 January 2007 (UTC)

Never mind - found answer in Timeline of the Big Bang. Gandalf61 15:46, 27 January 2007

If Quasars existed during early Reionization epochs (20 > z > 5), then super-massive black holes (SMBH) existed to generate them. And if SMBH existed, then so did surrounding spheroidal proto-galaxies (proto-Ellipticals, proto-Spiral-Bulges). Also, if mega-mass SMBH existed, in the largest proto-galaxies; then intermediate-mass black holes (IMBH) existed, in "Nuclear [Star] Clusters (NC)", which seem to fill the same role, in smaller galaxies, as SMBH in the largest galaxies. Three-quarters of all galaxies have NCs; one-quarter have SMBH instead; see: http://www.eso.org/sci/meetings/2011/dynamics2011/Contributions/Neumayer.pdf. Thus, for every SMBH, three NC existed. Quasars represent sight-lines straight into the hearts of the earliest epochs of star formation ("Population III"). (Hypothetically, high resolution imaging would directly reveal the central SMBH, the structure of the relativistic jets, and at least the central core regions, of surrounding spheroidal star clusters.) Wikipedia seemingly has no article entry for NCs. Perhaps creating such a page, and linking it to this one, would improve this article, as well as Wikipedia's coverage of cosmology. 66.235.38.214 (talk) 04:19, 12 November 2012 (UTC)

According to Galaxy Formation & Evolution by Mo & van den Bosch (pp.58-60), "Ultra Compact Dwarf (UCD)" galaxies may be the biggest & brightest of Globular Clusters (GC); and, also, UCDs resemble NCs, albeit stripped of the latter's surrounding stellar halo. If so, the GC / UCD & NC are all spheroidal clusters of stars (of varying sizes) dating to the earliest epochs of star formation, i.e. they may be the first star formations, the first stellar structures. If so, then the emergence of Quasars, during the Reionization era (20 > z > 5), implies the co-occurring formation of the first star clusters, the largest of which also formed central SMBH, which generated AGNs, some of whose jets aimed towards earth, at present epoch ("here, now"), so being observed as those Quasars. Perhaps the article could be improved, by emphasizing the close connections, between AGNs and star formation? Inexpertly, i understand that the emergence of Quasars implies the co-emergence of GC-like spheroidal star clusters, some of which now reside in the centers of modern galaxies, at present epoch. Perhaps these connections could help improve the article coverage? 66.235.38.214 (talk) 06:35, 12 November 2012 (UTC)

Recombination disambiguation

I added the link back to the disambiguation page for the time being, as it give some explanation. I may write create a recombination stub in the next few days and redirect the link there. James McBride 09:14, 15 August 2007 (UTC)

My bad. I went back and looked at the previous version, and I guess I had looked at the wrong recombination. I thought the link had been removed, instead of redirected to the Big Bang timeline. James McBride 08:36, 16 August 2007 (UTC)

Adding more images

I would like to see a few more images in the article. In particular, the graph of the CMB polarization angular anisotropy map and an example Gunn-Peterson trough. A non-copyrighted version of the first should be possible, as it was generated by WMAP, but I only was able to find the image at other sites. James McBride 09:14, 15 August 2007 (UTC)

Current image deletion

I think editors should give serious consideration to deleting the image given at http://imagine.gsfc.nasa.gov/Images/sats_n_data/exhibit/reion.diagram.jpg 1) The universe does not become opaque at the surface of last scattering. It's called that for a reason, and it's not because the universe suddenly starts scattering - the universe becomes transparent then, not opaque (exception being specific neutral hydrogen absorption features as mentioned in the GP trough sections) 2) The universe does not become neutral either for that matter. It was neutral already, but ionized. It becomes unionized at that point, which is not the same as neutral 3) The universe does not become transparent again at reionization. It'd be opaque again, except that the free electron density is low enough that the Thomson scattering cross section remains low and the universe stays opaque. In other words, that diagram from NASA is pretty badly wrong in a number of fundamental points. I'd get rid of it myself, but I'd probably be accused of vandalism for getting rid of something from a reputable source, even when it's got fundamental errors in it —Preceding unsigned comment added by 91.84.172.216 (talk) 00:29, 21 February 2008 (UTC)

I agree that the language used is rather poor. There is some use of opaque and transparent in the sense used in the diagram in some of the literature, but I was initially rather confused by that. Perhaps the article would be stronger without the diagram. James McBride (talk) 02:42, 22 February 2008 (UTC)

I would agree. Having just approached the subject for the first time, I found the diagram misleading. Unless there are further comments to the contrary, I would suggest removing the image soon. 82.24.250.218 (talk) 21:39, 16 October 2008 (UTC)

I asked the NASA people to replace their erroneous image with a correct one, and after a few weeks they did, courtesy of their WMAP staff. Unfortunately I cannot add images to Wikipedia, according to the rules, because I haven't added 10 edits yet (I'm not "autoconfirmed"). Could somebody who is autoconfirmed please put the current version of http://imagine.gsfc.nasa.gov/Images/sats_n_data/exhibit/reion.diagram.jpg in the Wikemedia Commons and point to it from the Reionization page? Thanks in advance! Mike Pelizzari (talk) 22:22, 29 December 2009 (UTC)

Wow, that is great! I just uploaded the new version, and also made a couple of changes in the text you added to reflect the new image. James McBride (talk) 20:20, 30 December 2009 (UTC)

Name change

I suggest that the name of this entry should be changed to "Reionization event," to more clearly indicate its specific subject matter. --Steve, Sm8900 (talk) 14:53, 26 February 2010 (UTC)

Only if you have a reliable source that uses the term "reionization event". Seems to me that something that is spread over two phases, one of which lasts more than 800 million years, is more like a process than an event. Gandalf61 (talk) 15:21, 26 February 2010 (UTC)

I believe the two events are considered to be separate events. this article covers them as distinct though related events. I will try to find sources. --Steve, Sm8900 (talk) 16:01, 26 February 2010 (UTC)

Seeing your edit, I think I may understand the source of confusion. The universe started ionized. It became neutral during recombination. It was then reionized during a single period of time, lasting some hundreds of millions of years, known as reionization. I have frequently heard reionization called the "epoch of reionization," but almost never called the "reionization event." As such, I would strongly oppose any move to change the name to reionization event. James McBride (talk) 20:07, 26 February 2010 (UTC)

Well, how about a parenthetical note to indicate the topical area? Reionization is a word and scientific term with multiple uses and applications, like any other word in the English language. also, it can refer to a reionization process of any object or in any set of conditions. As an article title, it seems rather imprecise. An article title like "Reionization (cosmology)" or "Reionization (astrophysics)" might perhaps be more clear and accurate. --Steve, Sm8900 (talk) 14:57, 2 March 2010 (UTC)

I feel like the first sentence of the article makes clear the scope of the term as used in the article. As there is no other article on reionization, I am not sure what the purpose of renaming would be. Reionization would still redirect to reionization (cosmology) anyway. And, as a final note, the first non-cosmology hit for a simple search of reionization is on the 9th page. James McBride (talk) 04:07, 3 March 2010 (UTC)