Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Galaxy rotational curves vs time

  1. Jan 13, 2019 #1
    Hello to everyone,

    I'm trying to find some data about the relation between galaxy age and rotational curve... until now without success.

    Are there any teams working on this? Are there any studies in this direction?

  2. jcsd
  3. Jan 13, 2019 #2


    User Avatar
    Science Advisor

    Welcome to PF.
    Radio observation of the hydrogen line from galaxies viewed side-on show two peaks due to the rate of rotation of the galaxy. From that the red shift of the galaxy as a whole can also be estimated.

    Can you be more specific about what you need? and why you need it?
  4. Jan 14, 2019 #3
    The interesting question is: do galaxies evolve to what we see nearby (more apparent mass than we can directly see) or they are like this from the beginning?
  5. Jan 14, 2019 #4
    I understand that the current consensus is there is no evidence of any significant evolution in. Rotation. curve profiles or dark matter content. Of spiral galaxies.
  6. Jan 14, 2019 #5


    User Avatar
    Gold Member

    I think your "." key is stuck.
  7. Jan 14, 2019 #6
    I think he meant to use his comma - "," - key...
  8. Jan 14, 2019 #7


    User Avatar
    Gold Member

    Actually, that wouldn't make any sense either. There is no reason for a "." OR a "," anywhere in that sentence.

    Ah. I see he's not a native English speaker. That's probably the heart of the issue. @TEFLing your English Is WAY better than my Thai :smile:
  9. Jan 28, 2019 #8


    User Avatar
    Gold Member

    This is an area of active study. Many teams of astronomers are actively trying to compare the oldest observable galaxies with modern galaxies.

    Leading theories of galaxy formation tend to predict that "modern" looking galaxies should only begin to be visible later in time since the Big Bang than they are actually observed. This is called the "Impossible Early Galaxy problem." As explained in the linked article:

  10. Jan 29, 2019 #9
    "The Impossibly Early Galaxy Problem" seems to imply that the hierarchical merger model of galaxy formation doesn't work and needs to be abandoned as the process by which galaxies form. Apart from this, there's a practical reason why there are no measurements of rotation curves of galaxies in the early universe; you can only get rotation curves of galaxies which are nearly edge-on to the line of sight of the observer. This means that the galaxies you want to observe have very low surface brightness due to interference from dust lanes. On top of that, as you go to further distances, the angular size of the galaxies get smaller, you have less spatial resolution in order to determine velocity as a function of radius - and that's worse in the radio region. So these selection effects make it impractical to make the observations...It's too bad, because that's a very interesting question!
    Last edited: Jan 29, 2019
  11. Jan 29, 2019 #10


    User Avatar
    Gold Member

    Another example of studies early galaxies, where as @alantheastronomer notes, properties other than rotation curves (such a velocity dispersion) are usually measured:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?