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Thread: ultra compact dwarf galaxies formation problem

  1. #1
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    Default ultra compact dwarf galaxies formation problem



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    Default Re: ultra compact dwarf galaxies formation problem

    Nice. UCD's are beginning to look like the "brown dwarfs" of galaxies, bridging the gap between globs and "regular" dwarfs. Well, at least that's what came to my mind.

    I'll hush now...
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    Default Re: ultra compact dwarf galaxies formation problem

    Quote Originally Posted by bladekeeper View Post
    Nice. UCD's are beginning to look like the "brown dwarfs" of galaxies, bridging the gap between globs and "regular" dwarfs. Well, at least that's what came to my mind.

    I'll hush now...


    Have I been naughty lately? If so I certainly didn't enjoy it.....
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    Default Re: ultra compact dwarf galaxies formation problem

    Quote Originally Posted by not_Fritz_Argelander View Post


    Have I been naughty lately? If so I certainly didn't enjoy it.....
    Not a bit, but I have a habit of talking (typing) myself into a corner and not being able to work my way back out of it.

    But seriously, the UCD's did rather remind me of brown dwarfs being intermediate between low mass stars and high mass gas giants. It does seem, though, that UCD's are rather beyond the size of most globs to really be any manner of intermediary.

    Just thinking out loud.
    Bryan
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    Default Re: ultra compact dwarf galaxies formation problem

    Quote Originally Posted by bladekeeper View Post
    Not a bit, but I have a habit of talking (typing) myself into a corner and not being able to work my way back out of it.
    I make a point of doing that once a month. The idea is like

    Deliberate Mistakes · Finding Your Soul

    Or at least that's how I try to spin it.

    But seriously, the UCD's did rather remind me of brown dwarfs being intermediate between low mass stars and high mass gas giants. It does seem, though, that UCD's are rather beyond the size of most globs to really be any manner of intermediary.

    Just thinking out loud.
    And omega Cen and 47 Tuc could well be smallish UCGs! Metallicities indicate multiple waves of star formation for at least one of them. We had a thread on it some time ago that you may be remembering.

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    Default Re: ultra compact dwarf galaxies formation problem

    One would think that such dense star bearing regions would see more than their fair share of stellar collisions; the result of which should be more than their fair share of SNIA's as white dwarfs tip over the Chandrasekhar limit. A billion solar masses in a 600ly diameter volume. That is a busy place.

    Not including the Milky Way's central SMB...Is there a billion solar masses within a 600ly sphere at our galaxy's center?
    (600ly is only about 1/2 percent of the galaxy's diameter.)

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    Default Re: ultra compact dwarf galaxies formation problem

    Quote Originally Posted by Seeker725 View Post
    One would think that such dense star bearing regions would see more than their fair share of stellar collisions; the result of which should be more than their fair share of SNIA's as white dwarfs tip over the Chandrasekhar limit. A billion solar masses in a 600ly diameter volume. That is a busy place.

    Not including the Milky Way's central SMB...Is there a billion solar masses within a 600ly sphere at our galaxy's center?
    (600ly is only about 1/2 percent of the galaxy's diameter.)
    As far as your reasoning goes you're right. On density grounds alone it should be a lively place for mergers and SNs. But the think of it is that the spectral lines are quite broad indicating a very high velocity dispersion. That will, only partly, offset the effects of high density. High velocity dispersion means a narrower cross section for a collision to result in a merger and a wider cross section for non merging encounters.

    The density is orders of magnitude larger than at the center of the MW.
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