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  1. #1
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    Default A Completely Grown-Up Galaxy in the Young Universe



    Here is a blog entry which I recently wrote about a fully-grown elliptical galaxy that existed 10 billion years ago. Also in the blog entry there is a link to an article which I wrote on how to tell the age of a galaxy by its spectrum alone.

    A Completely Grown-Up Galaxy in the Young Universe
    Name: Eric
    Telescope: Meade 8" Starfinder Dob<br><a href="http://ericfdiaz.wordpress.com/">Eric Diaz's Journal</a><br><a href="http://ericfdiaz.webs.com/">Eric Diaz's Cosmos</a><br><br><a href=http://cleardarksky.com/c/Indianapoliskey.html> <img src="http://cleardarksky.com/c/Indianapoliscs0.gif?1"></a><br><br>

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  3. #2
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    HMMM. very interesting!!! thanks Makes you really sit and wonder???
    Do we really know what we think we do? I like the monkey-wrench line, very true
    So do you think its galaxy formation, or the age of the universe we should look at?
    or maybe something else entirely? Seems that logic isnt going to help!!

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    Yeah, curious. Perhaps something put it there in its fully formed state Or perhaps we'll end up with the same theory as now, but with some new special case where a galaxy like this can form early

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    Kinda what i thought!!

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    Quote Originally Posted by psonice View Post
    Yeah, curious. Perhaps something put it there in its fully formed state Or perhaps we'll end up with the same theory as now, but with some new special case where a galaxy like this can form early
    Another "special case" for the patchwork quilt called the "Big Bang."

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    ok ok at first i just thought it was interesting, but this is really puzzling me....
    how could this happen..... why, why?

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    This site provides this plot, powerfully portraying the dramatic decline, of UV radiation "blue-ward" of the 400nm H-K Break, as (simulated) galaxies age:


    "Elliptical galaxies, or the bulges of spirals, ... are assumed to have had most of their stars formed in a short period long ago, and undergone changes due only to stellar evolution since then (the condition of 'passive evolution'). As a sample calculation, here's a series of models of a rapid burst of star formation, from the code by Rocca-Volmerange & Guiderdoni, sampled at approximately 1-Gyr intervals."

    Some further factoids from the same said site:

    If the most powerful radio galaxies, seen to large redshift, are to be identified with normal elliptical galaxies seen at more recent epochs, and if their colors are generally dominated by starlight and not scattered nonthermal radiation...

    The upshot is that bright galaxies suffer major mergers at a rate 0.3-0.4 per Hubble time, with most of this concentrated in systems that are part of bound pairs... [cf. Milky Way & Andromeda on collision course in a few Gyr]


    The 'G-dwarf problem'; there are too few low-metallicity dwarfs in our galactic disk. The usual way out is to postulate introduction of new, pristine gas into the disk at a rate comparable to that of star formation... [prolonged period of "Disking Down" ??]

    The notion of quick bulge production with associated violent relaxation, followed by remaining gas collapsing to a disk with dissipation, then leisurely star formation and chemical evolution in the disk, stands up well...

    The monolithic collapse picture suggested by the results of ELS (and many subsequent ones) is appealing and explains the early appearance of some of the most massive galaxies... Luminous galaxies are found out to around z=5, and the color-absolute magnitude diagrams of clusters to z=1.5 are so narrow that they suggest the completion of major star formation very early on. A whole range of techniques describes the star-formating behavior of galaxies as one of downsizing (apparently first so called by Cowie et al. in 1996). One way of describing it is that the characteristic mass of star-forming galaxies has declined monotonically with time - it can also be described, of course, in terms of history as a function of mass. It is probably important that something closely analogous has been derived for the growth of black holes - the characteristic mass of actively accreting black holes, as seen in AGN, has been declining roughly in a parallel (and thus, perhaps, connected, fashion).
    Thus, the biggest & most massive "over-densities" were also, seemingly, the densest, so that they collapsed first (Top Down). Cf. Butcher-Oemler Effect:

    Butcher-Oemler effect

    The tendency of clusters of galaxies at greater distances (redshifts of about 0.4) to have a higher fraction of optically blue galaxies (mostly bright spirals and irregulars) than clusters of galaxies nearby. Although some astronomers suspect this may be only a selection effect, most believe the phenomenon is real and is probably related to the greater availability in the past of material from which new stars could form. The effect was first reported in 1978 by the American astronomers Harvey Raymond Butcher (1947-) and Augustus Oemler, Jr. (1954-).

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    The Molecular Universe -- from the Diffuse ISM to Planetary Systems also discusses in detail points pertinent to the OP.

    Also this abstract asserts similarly:

    The life cycle of the Interstellar Medium in other galaxies
    Volume: 73, Airborne Astronomy Symposium on the Galactic Ecosystem: From Gas to Stars to Dust
    Page: 121
    Authors: Knapp, G. R.
    Abstract: Gas in spiral galaxies cycles between the diffuse and dense phases as clouds collapse, form stars and are dispersed back into the ISM. Far infrared observations of continuum emission from interstellar dust and line emission from interstellar gas have revealed a wealth of information on the state of the ISM in galaxies of different morphological types. The analysis of these observations gives us information about the processes of star formation and about the evolution of the ISM. Star formation rates vary widely from galaxy to galaxy, with the rates in starburst galaxies being 10 - 100 times those in quiescent spiral galaxies. Far infrared spectroscopy of star-forming galaxies shows that the interstellar pressure increases with star formation rate. The structure of the interstellar medium in starburst galaxies is quite different from that of quiescent galaxies - much of the mass and volume are in HII regions and photodissociation regions. The size distribution of dust grains seems to depend on environment; small grains are abundant in the diffuse interstellar medium but not in dense molecular star forming regions. Quiescent spiral and elliptical galaxies contain a significant population of small grains, but starburst galaxies do not. Dwarf irregular galaxies also seem to contain few small grains; this may be the result of the higher UV flux in these galaxies. The star forming regions in dwarf irregulars also have a higher ratio of atomic to molecular gas than do those in the Galaxy. These results show that the ISM in galaxies of different morphological types reaches different equilibria, resulting in different modes of star formation and global galaxy evolution.

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    Default

    Another figure from this site:


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