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Black Holes and Galaxy formation

  1. Aug 27, 2008 #1

    LowlyPion

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    http://blackholes.stardate.org/resources/articles/article.php?id=9

    This presupposes that dark matter and dark energy interactions play no role?
     
  2. jcsd
  3. Aug 29, 2008 #2
    Dark Energy didn't start playing a role in Cosmic history until roughly ~10 billion years after the big bang. Thus it doesn't have much to say about galaxy evolution (though it is important in the evolution of galactic clusters). As for Dark matter (DM), mmm, it seems like it would play some role, but I'm not sure.

    Warning: the following is just my educated guess.

    I'm guessing it plays more of a passive background role. The dark matter in a galaxy is really smoothly spread out and only becomes important (dynamically) a certain distance away. It's possible that that distance is located outside the bulge? Thus, within the bulge there is more normal matter (i.e. stars, gas), hence the focus on the black hole mass and the normal matter mass.

    Still, in the initial formation of galaxies DM is very important...so I don't think we can ignore DM entirely. Sorry for my inconclusive answer. I hope someone more knowledgeable will come to save the day.
     
  4. Aug 29, 2008 #3
    do we have a chicken/egg problem here?

    stars form in a galaxy and a galaxy forms around a black hole
    BUT you need a star to go boom to form a black hole

    so what came first a star or a galaxy

    or were there primal BHs or nongalaxy stars
     
  5. Aug 29, 2008 #4

    Janus

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    You don't need a star to go boom to form a black hole, all you need is enough mass packed into a small enough area. While some black holes are formed when stars go supernova, it is not the only way they can be formed.
     
  6. Aug 31, 2008 #5

    LowlyPion

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    I ran across this somewhat related article about stars forming close to massive black holes.

    http://www.sciam.com/article.cfm?id=how-stars-formed-near-black-hole&sc=rss
     
  7. Aug 31, 2008 #6

    Chronos

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    Black holes forming from stellar collapses may be fairly rare. Most supernova's blow off too much mass to collapse into a black nole. A neutron star is more likely.
     
  8. Sep 1, 2008 #7
    LowlyPion,
    That Sciam article is about something else entirely. It's about stars that form really close to the Super Massive Black Hole (SMBH). Here, "really close" means well within the SMBH's sphere of influence. A SMBH's sphere of influence is the volume in which most of the gravitational potential is due to the SMBH, not the surrounding stars,gas, and dark matter. Thus, the formation of these stars are directly affected by the SMBH's gravity.

    The strange thing about the relationship between galactic bulges and SMBH's--the subject of the article you initially linked to--is that most of the Bulge lies far outside of the SMBH's sphere of influence (a SMBH's sphere of influence is less than 100 ly while the bulge is several 1000 ly). Thus, how the relation came about is not immediately obvious.
     
  9. Sep 1, 2008 #8

    Chronos

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