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Space Science

Speed Found to be Key to Galaxy Formation 61

QuantumCrypto writes "The All-wavelength Extended Groth strip International Survey (AEGIS), a collaborative effort involving nearly 100 scientists in half a dozen countries, revealed a new principle in the formation of all galaxies, from disk-like spirals, cloud-like ellipticals, and just irregulars. In essence the morphology of the galaxies depends on total mass involved and the internal speed it generates. 'By defining a new speed indicator, their analysis has managed to make sense out of very chaotic-looking objects,' said Sandra Faber, professor of astronomy and astrophysics at the University of California, Santa Cruz."
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Speed Found to be Key to Galaxy Formation

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  • AEGIS also reported that having their system in a particular galaxy offered +! radius detection of submerged galaxies.

    /ok that was horrible
    //back to work
  • by User 956 ( 568564 ) on Friday March 09, 2007 @03:07AM (#18286604) Homepage
    In essence the morphology of the galaxies depends on total mass involved and the internal speed it generates.

    Yeah, well, it all results in the eventual heat death of the universe, so what's the point really?
  • A lot of cosmology seems like common sense. All that "Hawking stuff" I found interesting that the first time I read about it was like a big Ok..and.. I could have told you that (except the black hole radiation part.. that's pretty good stuff). I could have told someone this while bs'ing over a beer in a bar while just joking around on crazy topics. More density = More gravity = More pull = Faster spin = Faster sorting = Faster final formation. Ok so you've got me on making the equation part, that's what
    • "A lot of cosmology seems like common sense.....I could have told someone this while bs'ing over a beer in a bar while just joking around on crazy topics."

      Yes, using the properties of galaxies to infer the early state of the primordial quantum flux of a dimentionless quantum dot that exploded into nothing to create everthing and everywhen will be a hot topic in bars tonight. /sarcasm
    • Wait. Let me guess. You're an engineer.
  • Simulations (Score:3, Interesting)

    by Tablizer ( 95088 ) on Friday March 09, 2007 @04:01AM (#18286786) Journal
    It would be interesting to see some simulations and animations of rotating spiral galaxies. We could never see that with actual galaxies because they move too slow from our perspective. A simulation will both test to see how accurate their models fit the real thing, and allow us to study how rotation works and spiral arms keep from winding "tighter", as it would otherwise seam. Maybe they could hilight a few reference stars so we can see how they move relative to the spiral arms. As an amature space artist, the movement of the arms relative to stars is a curious wonder that I cannot really visualize yet.
    • would they not have to model every star (or at least make an effort to properly model as many individual massive objects as possible) in order to make an accurate model?

      if you simplify it you will not learn anything.. if you assume for the sake of simplification an "evenly consistent galactic medium" then youre going to have problems imho.
      • would they not have to model every star (or at least make an effort to properly model as many individual massive objects as possible) in order to make an accurate model?

        Nah, it should be possible with a variation of particle physics.

        In fact, I'm going to be surprised if the behavior doesn't turn out to be fractal-ish in nature. Swirling gasses beget swirling particles beget planets swirling around a star swirling around a galaxy swirling around a megagalaxy swirling about, swirling about.

        Swirling, swirling, swirling. Soooo pretty.

        Aww, fuck, this coffee is not nearly strong enough... <swirl, swirl>

    • Re: (Score:3, Informative)

      by mdsolar ( 1045926 )
      I know Josh Barnes has produced some vidio of spirals rotating but I have not found it. Here are some more exciting merger simulation: http://www.ifa.hawaii.edu/~barnes/pressrel/mice/v i d301_04.mpg [hawaii.edu] and http://www.ifa.hawaii.edu/~barnes/pressrel/mice/v0 211d3.mpg [hawaii.edu] found at http://www.ifa.hawaii.edu/~barnes/research/interac tion_models/mice/index.html#modeling [hawaii.edu]. Models which concentrate on just rotation tend to be just two dimensional to save on computing. The are used to study secular evolution which could
    • by Gilmoure ( 18428 )
      If you took a video camera and pointed it at a distant spiral galaxy and then moved in real fast, you could get a video of it's formation, in reverse. You could then submit it to Funny Galaxy Videos show or sumt'ing.
    • by cbacba ( 944071 )
      Inside an arm, different objects can have relatively different speeds along the direction of the arm rotation. Also, objects can bob up and down as they go around. Different speeds can be achieved by slight variations and by the changes in gravitational attraction. The arm has got to move at the average speed and it's components generally have to move at this same velocity as it rotates - but some components may be ejected out of the arm. Essentially, each object in the arm is in orbit around the core b
  • I'm hereby announcing the creation of DISTASTEFUL. The organisation against the proDIgal, unnecesSarily conTrived and unnaturAlly nonsenSical abbreviaTion of projEcts and Federally fUnded estabLishments.
  • by ArcSecond ( 534786 ) on Friday March 09, 2007 @04:27AM (#18286862)
    According to Faber, the relation described in this study may reflect processes that began in the first fraction of a nanosecond after the Big Bang. "Galaxies began life as quantum fluctuations--tiny density fluctuations that created the seeds for the later coagulation of structure in the universe. When gravity took over, those seeds made galaxies, and we think that process is reflected in the Tully-Fisher relation," she said.

    I found this part really interesting. I know it is something pointed to already by fluctuations in the Cosmic Background Radiation, but the though that local variations at the smallest scales determined the structure of galaxies is really something to think on.

    • by anandsr ( 148302 )
      I don't understand how Tully Fisher relation comes about in GR+DM. It can come from MOND on the other hand. I don't understand why the article was totally silent on Dark Matter. Tully Fisher relation is very specific to Spiral galaxies, how did they apply it to other galaxy types without using any underlying theory. What was that theory, if it was not MOND or GR+DM.
    • by radtea ( 464814 )
      I know it is something pointed to already by fluctuations in the Cosmic Background Radiation, but the though that local variations at the smallest scales determined the structure of galaxies is really something to think on.

      The claim about the mass/combined-velocity[*] correlation being a reflection of big bang seeding of galaxies is really speculative. The fact that it applies to post-collisional galaxies suggests that the relationship is a product of galactic dynamics, not big bang cosmology. It's not im
  • by TMB ( 70166 ) on Friday March 09, 2007 @04:54AM (#18286966)
    For those interested in more details, it looks like the preprint is available at http://arxiv.org/abs/astro-ph/0702643 [arxiv.org].

    Originally TF was just a relationship between rotational speed and luminosity. Since luminosity is some measurement of stellar mass, it was proposed a few years ago that the true physical relationship was not with luminosity but with the total cooled baryonic mass (most of which is in the form of stars in most galaxies). So the Baryonic Tully Fisher relation was proposed, where they substituted the total mass of stars and gas instead of the luminosity. The relationship was tighter, indicating that this is closer to the fundamental relationship.

    This work now takes it one more step and uses a more physical measurement for the other variable. Rotational speed of a disk galaxy tells you how deep the potential well is, assuming that all of the motion is in the form of rotation. But if there are also disordered motions, then it's really a combination of the disordered and ordered motion that tell you how deep the potential is. So they've replaced the rotation velocity with a combination of rotational velocity and velocity dispersion - and voila, the relationship is even tighter!

    Very nice work.

    • Hey Mr. B, what's the status of actually relating the T-F/F-J (or whatever the unified relation is to be called now) to galaxy formation? It's been 5 1/2 years since I left extragalactic astronomy to become a hermit; but my last memory was that we hadn't gone very far in explaining the slope of the relation. Obviously it's steeper than one expects with a constant mass-to-light ratio and simple gravity (especially the Faber-Jackson relation, if you take stellar velocity dispersion on face value, which I gu
      • by TMB ( 70166 )
        My sense is that the mass-dependent mass-to-light ratio that you get in a cosmological context does get you the right slope for the TFR. The zero-point is actually the bigger issue - simulated disk galaxies rotate too fast given their stellar mass. However, this may have finally been resolved by better treatments of how supernova energy feeds back on the surrounding gas - there's some recent work by Fabio Governato and collaborators that looks pretty encouraging (eg. Monthly Notices of the Royal Astronomica
  • "Speed" like the last one here [wikipedia.org].

    I bet that's the cause for a lot of things! /p?

  • Irregular galaxies are 80% off in our clearance section.
  • I am to understand that our Galaxy rotates on its axis once ever 250 million years or so. If that is right, and the universe is 13 or 14 billion years old, then it would seem that we get this: age of Universe = 13,000,000,000 Years for one rotation of galaxy = 250,000,000 Total Rotations = age / rotation 52 Total Rotations since Universe began? First, is that about right? Second, if that is right then my question is how do galaxies obtain their distinctive
    • Re: (Score:2, Informative)

      by Anonymous Coward
      That's because the spiral is not caused by the rotation of the galaxy. It's caused by a (more slowly rotating) standing wave in spiral form in the disc. When the wave passes the matter in the disc, new bright young stars are formed and that's what you see.
      This was discovered in the 60's I believe.

      Tino Meinen
    • It's about right, the Milky Way may have formed as a disk more recently. One way to think about it is that the Sun has been around about 15 times since it formed for a motion of 200 km/s. A way to think about the morphologies of galaxies is to consider that stars form in response to the global potential. This is a hand wave, but you can see how it would not require a lot of mixing to get a fairly smooth distribution of stars. Bars may well be large-scale dynamical instabilities so that their shape, in a
  • I always knew that we were just figment of the imagination of some dude on drugs...
  • IANA Astronomer but would like to know if this chain of logic is possible, given the theory that galaxies that are brighter spin faster.

    Measure spin (average speed of local streaming)
    Get confirmation of our galactic shape (should be barred spiral) from that
    Get brightness based on spin
    Calculate total galactic output based on that
    Calculate brightness map of Milky Way seen from Earth
    Estimate how much matter is obscuring our view (make a dust map)

    And finally if it is possible to estimate average output for spec
  • Well, I guess that rules out smack, blow, dope, greenies, and roofies as keys to galaxy formation.
  • http://www.thunderbolts.info/ [thunderbolts.info] for info on galaxy formation, solar physics, and a bunch of other cool astrophysical stuff
    • And by info, you mean long discredited quack theories right? The electric universe theory which the site you linked to is widely dismissed by most physicists. It does however excite these people [fixedearth.com].

Somebody's terminal is dropping bits. I found a pile of them over in the corner.