how much dark matter in each galaxy? Is it related to age?

lenfromkits

Does anyone know if there is an understood correlation between the amount of dark matter we suspect in a galaxy and the age of the galaxy?

Basically, I am wondering if older galaxies tend to have more dark matter. But I need references to information on this, not just opinions :) Thanks.

rhyshanan

well i dont have time for referances but you question would relate to the longevity of stars.
dark matter is only dark because we cant see it. We cant see dark matter because there no light (stars) to eluminate them. So if older galaxies have less stars then yes, more dark matter. I think radio telescopes can detect dark matter (theoretically)

lenfromkits

Thanks rhyshanan. That sounds like a good theory. You wouldn't happen to know if they have already observed this pattern at all though would you? or have a key-word to search on? I'm trying to determine if a correlation has actually been observed or not yet.

rhyshanan

Well the only way people know dark matter exists is because of the gravity dark matter creates. things around dark matter will have strange orbits that signal that there must be an invisible object close by with gravity influancing the observerd object.
Our best telescopes can hardly see our own galaxy never mind other galaxies, so observing dark matter in distant galaxies is way out of our current capability

niceboar

From wiki
In astronomy and cosmology, dark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation.[1]

lenfromkits

Thanks again. I see. I'm hoping someone will know if there was a connection between calculated age of galaxies and the amount of dark matter that has been calculated for them.

lenfromkits

Thanks. I was wondering if there is a known connection between the 'amount' of dark matter that is inferred by these gravitational effects and the 'age' of the galaxy. Basically, is age correlated to the the extent to which we suspect dark matter exists there. (ie. I'm not really asking about what is dark matter or anything close to that... just about the age vs amount of dark matter predicted)

niceboar

Yes I know, and I don't know the answer to that, I was merely correcting the assertions that we can't see dark matter because stars don't shine on them. Dark matter doesn't interact with electromagnetism.

rhyshanan

I'm trying to say our current level of technology does not allow for us to answer this question. Maybe someone else will have another theory like. bigger galaxy more dark matter, but it will just be a theory becasue there is no way to know with the technology we have

lenfromkits

I see. Thanks. I believe that observations have been able to detect the 'speeds' at which stars orbit the galaxy center. These speeds for some reason do not match the 'predicted' speeds that they should traveling. They are travelling 'faster' than they should, thereby implying that there is additional gravity involved. Based on the observed speeds, they can calculate how much extra gravity would be need to cause these speeds.

So, based on what they do see of the speeds, they can estimate the amount of dark matter that exists there. The question is just, is this related to the age of the galaxy at all?

Thanks.

niceboar

Why not? You can measure the mass that should be there and the age of object and determine how much mass is seen, so you could find a correlation if there was one.

rhyshanan

i don't see how this is possble.

niceboar

Well you could look at the young, forming galaxies in the sky and compare them with the old galaxies. It's not an "age" per-say but it's relative.

Chronos

Dark matter distribution in the universe has been mapped by the Hubble telescope. See
http://news.bbc.co.uk/2/hi/6235751.stm

twofish-quant

Insufficient data to tell.

One problem is that if you want to see really old galaxy then it's dim enough so that it's hard to get galaxy rotation measurements.

lenfromkits

Okay, thanks. That makes sense. I guess of the list of younger/brighter galaxies, are we able to determine the age of them precisely enough that we could see if there's a correlation? Or would the ages be too vague?

DreadyPhysics

This can't be right. One of the first anomalies to suggest the existence of dark matter came from observing rotation curves of other galaxies and finding that they rotate differently than expected for the visible distribution of matter. This sort of measurement could give us a handle on the amount of dark matter present. The only problem is that we wouldn't be able to get a range of galaxy ages, as younger (more distant) galaxies would be hard to resolve.

And dark matter isn't simply dark because nothing is shining on it, it's fundamentally a different sort of matter.