Elliptical galaxies not formed by merging
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bluemagi
This article comes from Science daily: June 1, 2016. The source is :Sissa Medialab. Summary of article: Using an "intuitive"approach, a new study confirms a recent hypothesis on the formation of galaxies, according to which larger elliptical galaxies formed in very ancient times through a process of local (in situ) star formation. This contradicts the current paradigm that they formed through the merging of spiral galaxies, a view which, despite being generally accepted by most of the scientific community, has been a source of theoretical inconsistencies. The study supports the in situ hypothesis, already proposed with theoretical models, basing itself only on the analysis and interpolation of new data collected by the Herschel instrument (in the infrared) integrated with Hubble data (in the ultraviolet), an innovative yet simple method. Interesting! BM.
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mlpeck
in response to bluemagi's comment.
Links:
Science Daily article: https://www.sciencedaily.com/releases/2016/06/160601083920.htm
Journal paper (arxiv version): http://arxiv.org/abs/1604.02507
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ElisabethB
moderator
in response to mlpeck's comment.
Tx mlpeck ! 😄
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StereoSpace
Interesting!
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vrooje
admin, scientist
I'm a bit confused by the link between the article and the paper. The article, which I think is mostly drawn from a press release about the paper, talks about elliptical galaxies and spiral galaxies and mergers; fine. But the paper is about the buildup of stellar mass via high-redshift star formation. The text of the paper itself never once mentions elliptical or spiral galaxies.
It does say that the star formation in galaxies at high redshift, which is what sets the mass characteristics of high mass galaxies, is more consistent with processes taking place in each individual galaxy (in situ processes) than with merger-driven star formation. They make the case that a lot of star formation occurring at these early times is heavily obscured by dust within galaxies, which explains why some of the methods that use ultraviolet light to observe star formation mis-classify the really strongly star-forming galaxies (UV light is strongly affected by dust).
It's a big jump to go from that to "ellipticals aren't formed by merging with spirals", though. Firstly, at the early times they're talking about, galaxies were much messier than they are today, and the traditional elliptical/spiral divide doesn't necessarily apply. Lots of rotating galaxies were "smooth" and spiral-free, and less rotation-dominated galaxies (that we might call "elliptical" according to that criterion) were bluer and had gas and dust and ongoing star formation -- all of which might lead to a different morphological classification. Secondly, in the earlier, less-expanded universe, things were closer together and interaction was pretty common, and there was so much available gas supply that a big merger wouldn't necessarily mean the morphology of the galaxy was forever changed. Disks could re-form, for example, so the paradigm that 2 spirals merge and form an elliptical via the destruction of both disks really doesn't have to be true at all, even for the most massive galaxies.
In short, I'm not sure there was an expectation that galaxies at z > 4 would follow the same morphological rules as galaxies we see today even before this paper was published, and while the paper does describe a study of star formation in the early universe, it doesn't make any claims about morphology. So I'm really not sure why the press release does.
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