Dark matter halos and hidden clumps

11:45out of a review article about dark matter that's now, I think, eight or nine years old. On the left, that is a computer simulation uh of what we think a dark matter halo looks like. So, a dark matter halo is a gigantic uh blob of dark matter. That's the technical term for a giant blob of dark matter is a dark matter halo. >> This has nothing to do with Master Chief, I'm assuming, and Cortana. >> Uh I'm I'm No, it does not. I don't know I don't know what that is, but it definitely doesn't have to do with it. >> It's Halo is a best-selling Xbox game where there's a planet >> Oh, Halo. >> that's the ring.

12:25>> Oh, Master Chief. All right, sorry. It took me a second here. I was I was too focused on the on the picture. >> I I think I threw you off there. So, so on the on the on the left here, um this is our at the time this was our best guess at the this these clumps of dark matter uh in relation to where? >> Right. So, this is a again, it's a simulation on a on a supercomputer. Our galaxy in that picture would be at the center of the bright blob in the middle. And it would be much smaller than the size of this image. >> Okay. >> Got it. So, these what you're seeing is this dark matter halo that hosts our our galaxy. We think

13:06galaxies, for the most part, are inside of dark matter halos. And this is, in some sense, a prediction of our best theory of dark matter, which is that every galaxy, including our own, should be surrounded by an almost innumerable number of these small clumps of dark matter. >> It's almost like our galaxy is being insulated by these this dark matter as a way to incubate the like the the the existence and sustainability of the galaxies. >> Sure, you can think of it that way if you want. >> So, on the left, that's our simulation. And then on the right, we're looking at what looks almost like a like a a

13:48sphere imposed on a 2D like image. And And what are we looking at on the right? >> Right. So, on the right uh and that's what I That's why I like this figure so much. So, on the right, that is an a map of at the time all of the satellite galaxies of our galaxy that we knew of. >> Okay. >> So, you know, as as I said, we think galaxies reside inside of dark matter halos. And so, little galaxies that are orbiting around ours are inside of smaller dark matter halos. And that on the right is a map of the little galaxies that we knew of at the time. And what you see just looking from left to right is that there's a lot more

14:29clumps on the left that we don't see based on starlight, right? Those clumps, they don't have enough stars and gas in them for us to tell that they're there just by looking up and >> Mhm. >> assigning them a galaxy, right? So, they're completely dark, gigantic, so these are, you know, a million times to a billion times the mass of our sun, these enormous concentrations of dark matter, uh which we don't see. Because they have they they don't have enough stars or enough gas to be detected. >> This is so bizarre. Um and and okay, so just to just to make sure I'm tracking here, kind of what what's interesting is you sort of see on the left the the the bright spots are the clumps of dark

15:12matter. And it it it's almost there's almost a like a perfect one-to-one correlation with the galaxies in our right image, which would track with the thesis or idea that you mentioned, which is that we think galaxies are concentrated around these large clumps of dark matter. Am I getting that correct? >> Yeah, so the the idea is that, you know, galaxies, which are made of regular matter, they form inside of dark matter halos. So, the dark matter halo is there, it forms earlier than the galaxies because the regular matter is hot at the at early times. And so, the the dark matter is there, and then the the gas falls into it, and you form stars, and you

15:53form galaxies. >> Oh, it's like a pressure cooker for building galaxies. >> That's right, and life. >> And and life itself. Inter- So, so, in to some extent, one implication here is that the existence and the concentration of these these dark matter halos or clusters is a prerequisite for the formulation of stars and galaxy. >> I wouldn't say that it's a pre- pre-requisite for the formation of stars. What what what I would say is that our current theory, our best theory for what dark matter is, it explains galaxy formation partially by putting galaxies inside of dark

16:35matter halos. And it also predicts that there should be way more dark matter halos than we can see from their stars. >> It justifies its own existence almost. Um >> Well, you know, it's a it's a concrete prediction of the theory, and it turns out that if you change the particle physics of dark matter, you can completely change the properties of these clumps. >> And so, this is why as you talk about why it's an interesting area of research it by having a better model around you know, these dark matter clumps, etc., we can actually start to poke at

17:17its fun like it's fundamental component