Mass of a galaxy without dark matter and with dark matter

[Quarlep]

I am curious about mass of a galaxy without dark matter and with dark matter.I searched but I couldn't found.I ll be happy If you help me.

Thanks

 

[phinds]

Well, without dark matter there most likely would not BE any galaxy. although DM does not "clump" the way normal matter does, it has somehow accumulated into cosmologically massive blobs that then attract regular matter through gravitational attraction and the regular matter clumps into stars and planets and dust and the whole mess is a galaxy.

So asking what a galaxy would be like without the dark matter is a bit like asking how well someone could sing if they had no vocal chords.

 

[Quarlep]

Without dark matter I mean without dark matter mass my fault I forget mass

 

[phinds]

Without dark matter I mean without dark matter mass my fault I forget mass

Yes, that is exactly what I was talking about.

 

[mfb]

Without dark matter I mean without dark matter mass my fault I forget mass

How does that change the question?

For an existing galaxy, you can ask how much visible and how much invisible mass there are. The answer depends on the galaxy and the radius you consider (galaxies do not have sharp edges, especially in the dark matter distribution), but there are many galaxies where numbers are available online.

 

[wabbit]

I think the ratio of dark matter to matter is about the same in a typical galaxy (DM halo included) as the overall ratio of 85:15 but I could very well be wrong.

 

[phinds]

I think the ratio of dark matter to matter is about the same in a typical galaxy (DM halo included) as the overall ratio of 85:15 but I could very well be wrong.

The rabbit ? WRONG ? Not very likely

 

[wabbit]

Don't joke about the poor rabbit :) he's still recovering from almost loosing his legs in a black hole

 

[Quarlep]

Is that right isn't it 85/15

 

[Vanadium 50]

I think the ratio of dark matter to matter is about the same in a typical galaxy

There exist both DM-rich and DM-poor galaxies.

 

[phinds]

Is that right isn't it 85/15

do you not understand that 85:15 IS 85/15 or are you making a joke?

 

[phinds]

Don't joke about the poor rabbit :) he's still recovering from almost loosing his legs in a black hole

I TOLD you to stay away from those things !

 

[wabbit]

Yes mom, I won't do it again, promise:)

 

[wabbit]

There exist both DM-rich and DM-poor galaxies.

I was wondering about that, or something related rather - in galaxy collisions the matter tends to coalesce into a single galaxy after a while due I believe to some kind of friction - but with high enough collision velocity it seems that (some part of) the dark matter halos could just move through each other and continue on their way. If that does happen, not only would we be left with a DM poor merged galaxy, but also with stray haloes of dark matter zooming away without much matter left in them . Is that something that happens and if so do we see such stray halos (through lensing or other means)?

 

[mfb]

Well, there are objects like the bullet cluster where the distribution of dark matter differs significantly from the distribution of gas.
Stars also don't have much friction, so a complete separation of visible and dark matter would be odd.

 

[wabbit]

Thanks, I thought "some kind of friction" arising from matter-matter interaction (gas clouds maybe?) played a role in the merger process - but you re saying it's minor and essentially gravitational effects alone explain the process, did I get that right?

And yes I was thinking of the bullet cluster - though I don't recall seeing mention of stray halos escaping in that case, so I was freely extrapolating - perhaps a little too far : )

 

[phinds]

Thanks, I thought "some kind of friction" arising from matter-matter interaction (gas clouds maybe?) played a role in the merger process - but you re saying it's minor and essentially gravitational effects alone explain the process, did I get that right?

Actually, I think the dust interactions DO contribute an effect, it's just that stars/planets are so far apart that THEY don't hit each other.

 

[Quarlep]

do you not understand that 85:15 IS 85/15 or are you making a joke?

Yeah I understand it like that
Its not 85/15 then what it is.

 

[Quarlep]

I was watching House and there House said dark matter makes galaxies 6 times bigger mass.And I am curious about is that same for every galaxy ? Example a galaxy mass is m without dark matter.But with dark matter 6m.Is that true for all galaxies ? (85/15 near to 6 so I made a connection)

 

[phinds]

I was watching House and there House said dark matter makes galaxies 6 times bigger mass.And I am curious about is that same for every galaxy ? Example a galaxy mass is m without dark matter.But with dark matter 6m.Is that true for all galaxies ? (85/15 near to 6 so I made a connection)

Which part of post #10 did you not understand?

 

[Quarlep]

There exist both DM-rich and DM-poor galaxies.

So DM does not depend mass of galaxy.But this sound like stupid I guess.In quote I guess he means mass depend DM which less mass galaxies have Poor DM and heavier galaxies have Rich Dm

 

[Chronos]

The whole DM issue is confusing. Some galaxies appear to be rich in it, and others largely lacking. That suggests we may be missing an important clue.

 

[Quarlep]

I understand.Do you have any internet resources for that.This extra mass idea or DM rich DM poor stuff

 

[Chronos]

Examples include: http://arxiv.org/abs/astro-ph/0308518, A Dearth of Dark Matter in Ordinary Elliptical Galaxies; and http://arxiv.org/abs/1410.8141, Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster.
.

 

[Vanadium 50]

But this sound like stupid I guess

If you don't like what I said, provide a counterexample or counterargument, or at least ask a question. Don't just call it stupid. It's not just unhelpful. It's rude.

If you bothered to type "dark matter rich galaxies" in Google, you would have gotten 70,600 hits. If I were you, I'd do a bit more research before telling other people that they are wrong.

 

[wabbit]

I didn't read his post as calling you stupid , but saying the way he initially understood it sounded stupid. OP is clearly not using his first language here.

 

[Quarlep]

If you don't like what I said, provide a counterexample or counterargument, or at least ask a question. Don't just call it stupid. It's not just unhelpful. It's rude.

If you bothered to type "dark matter rich galaxies" in Google, you would have gotten 70,600 hits. If I were you, I'd do a bit more research before telling other people that they are wrong.

I didnt tell you stupid.If you understand like that I am very very sorry.

"I didn't read his post as calling you stupid , but saying the way he initially understood it sounded stupid. OP is clearly not using his first language here"

Wabbit is right.I tried to say this idea sounds like stupid And he is right again my first language is not english.

 

[Quarlep]

Examples include: http://arxiv.org/abs/astro-ph/0308518, A Dearth of Dark Matter in Ordinary Elliptical Galaxies; and http://arxiv.org/abs/1410.8141, Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster.
.

I read them and I found them interesting.But I want to ask something , this cases are extraordinary but this cannot be the hole story.I want to ask you in generally how DM affects mass of galaxy.there's 100 billion galaxies generally what can we say ?

 

[mfb]

The mass of the galaxy is a bit more than the mass of its dark matter. Where "a bit" depends on which galaxy you look at, but it is somewhere around 20% more on average.
Most of the mass in the universe is dark.

 

[Quarlep]

Lets suppose we have a galaxy mass 5m then dark matter mass will be 4m then total mass will be 9m so total mass is 2 times bigger then the galaxy mass in the average isn't it ?