 I hope you enjoyed your break, I hope you filled it up on beer, I hope you're ready for our next speaker. Our next speaker is a third year graduate student of the University of Washington. Our next speaker is not just a speaker, she is also a singer in a rock band. This rock band is called Night Lunch and its first album is coming out this winter. I should listen to it, it's amazing. Please join me in welcoming Natalie Nicholson. Hi, I'm Natalie Nicholson and I have this one dream. You go somewhere really dark, you're able to see the night, it's super, super cool. In particular I have three images of spiral galaxies and I'm particularly interested in these because the Milky Way that I mentioned before happens to be a spiral galaxy and they're the types of galaxies that I tend to look at because I'm interested in studying the evolution of our galaxy. And so we're going to talk a little bit about the components of a spiral galaxy and so I'm going to use a simplified diagram. I'm going to point out a few particular things. We have the disk which is made up mainly of young stars, those are going to be blue bigger stars and then you have the central, oh I have a little light right here, we have a central bulb that's usually made up of some older stars. Your globular clusters are living up in this dark matter halo, they're also made up of some older stars and then you have the nucleus and in that center of the galaxy you're going to have a supermassive black hole. Now supermassive black holes live in almost all galaxies because they're really, really small usually, they all have one and they are of particular interest to me but we'll get back to them in just a second. So the question that I really want to ask you, is a galaxy like a waffle, right? Because I don't think that when I showed you this diagram or when I showed you these gorgeous images of galaxies that you immediately thought, man, I really need to get an eye out after this, I am just craving some maple syrup, right? So how is the galaxy like a waffle? Well, right, we got that disk, we got our waffle disk, your butter, we got some marshmallow galactic clusters, I suggest adhering them with toothpicks. I actually showed this to my advisor earlier and she's like, why would you put marshmallows on that? On a waffle, that doesn't make any sense. So I'll get back to her comments on my research later. So we can also add some sprinkles, we got to add some stars to our disk, right? So we got young stars, blue sprinkles, old stars, red sprinkles. We've got the plate, that's going to be your halo. A regular plate is not going to be big enough, you might just need to put it on the table or on the floor like your whole house just has to represent the halo for your galaxy. And then this was actually not represented by anything but the super massive black hole, I just want to remind you, it's very important, it's there, it's living at the very center of your waffle galaxy. Where in the world did this come from? Why am I talking about waffles and galates? So, every summer for the last couple summers, I've been teaching a camp at the University of Washington. It's called Protostars Astronomy Camp and it's a camp for middle school girls, aged from, I guess, 11 to 14-ish. And they come and they spend two weeks with me and we learn about astronomy. And during the second week we talk about galaxies and we learn about the components of galaxies in exactly this way. This is actually a slide from this summer when we were putting together our galaxy waffles and this is a lovely example of a galaxy waffle plus the very nice diagram that I asked for of their galaxy waffle. And I'd like to particularly point out this instruction that I give them. Because even though I'm a grad student, which means I can't even possibly imagine thinking about having children, I know that if you were to give a bottle of syrup to a bunch of 12-year-olds, that would be mayhem, right? So they have to come up to me, they have to show me their galaxy waffle plus their lovely diagram to get syrup. And the syrup is representing the gas in the galaxy, right? Because that's what you're making your stars out of so there's going to be a lot more of this, et cetera, et cetera. So I was really excited about this. This is my second year that I've been doing it. And so I posted this photo exactly on Twitter and I was like really excited. I gave instructions on how to make the galaxy waffle and my advisor, like I mentioned, had some consent. So she was like, hey, you're serving your waffle wrong. It should be served in a fish bowl of syrup. And then in response to this, the chair of my department, the one who created that beautiful image in the question, was like, wait, you actually need a syrup fountain which is launching out from within the waffle. To which my advisor then retorted, also you need at least three fire hoses full of syrup. Just aim straight at the waffle. Here are the fire hoses of syrup. I ask you with our little waffle, oh wait, let me, right, let's get back to some science. Here was representing the gas in the waffle, in the galaxies. So where are we seeing this, where are we seeing all this gas? And really the dilemma here is that this is a bit too simplified, a diagram of the galaxy. So here's another beautiful image of a galaxy where you can actually see an example of a tidal stream due to a previous merger that happened with another galaxy. And the reason that you're able to see this stream is because there's enough gas, in fact enough gas that you're forming a little bit of stars in here, but there's enough gas that it's dented up for your eye to get out. But there's actually around really all galaxies in what's called the circumgalactic medium, which really just represents a gaseous halo that surrounds galaxies. And so if I were to update that simplified diagram that I showed you previously, it looks something like this. Where you have, you know, here's your disc of your galaxy, your supermassive black hole. Don't forget about it. It's right there in the center. And you have all of this gas that you can't see that's too diffuse to see coming into the galaxy from the ambient universe, coming out of the galaxy, do the energetics within it, and some of it which falls back out, and some of it which leaves the galaxy entirely. And all of this gas is really important for forming stars, for feeding the black hole. It's important to the evolution of these galaxies. How do I study these? I know that this video is actually not going to work because it's too big, so I'm going to move this. But I use simulations, which basically means that gravity and let time happen. And in particular, take into account the large-scale structure of the universe and run it just with dark matter, and then I'll find a halo of the mass that I'm interested of, Milky Way halo mass, and then I'll resimulate that. I'll zoom into that little region in my big box, and I'll throw in gas and the physics to make stars and the physics to make black holes, and I'll let that run for another 13.8 billion simulation years. And then I end up with a Milky Way mass galaxy. And this allows me to study the evolution of these galaxies. In particular, I use these simulations to study the circumgalactic media of Milky Way-like galaxies. And I say Milky Way-like because they're of the same mass, and some of them have this, some of them don't. But I'm looking at the circumgalactic medium of these galaxies, and in particular, I'm interested, as I've mentioned multiple times, in a supermassive black hole, and its possible effect, CGM on the circumgalactic medium. And I put this little asterisk at an instrument, Koshalos, which is on the Hubble telescope. You will all shout out. And it was able to look at this really diffused gas, finally, and we were able to start studying this kind of gaseous region that we haven't been able to study before. Studying the supermassive black hole with relation to the CGM is the supermassive black hole. This is called the M-sigma relation. It is of the galaxy that it lives in. In particular, it's the velocity dispersion of the bolt. We don't have to worry about that much, worry about that too much. What we're doing along this line here means that the supermassive black hole and the galaxy that it lives in must grow together. And your next question might be, well, how does it do that? And it kind of comes back to this idea of feedback. Now, feedback is the energy that is released by a black hole. When it starts to create material, right, it's eating up gas, it's starting to grow, and it can release this energy, and that energy can influence its surroundings. But that's actually kind of surprising. Our supermassive thread in an astrophysical journal was this comparison between a supermassive black hole size and a toast galaxy. And they compared it to the Cairo International Airport in the size of the Sahara Desert. It has enough influence on this long thing like the sigma relationship, must co-eval. I also know that galaxies depend on their CGM for their evolution as well. So that brings us kind of to the, really the crux of my research. The very basic, or the most basic, question that I'm trying to ask, you know, play a role in shaping the CGM. And I'm going to be honest with you. It does. So this is actually a plot for my own research where I'm showing that these are, this is the mass of metals in the CGM, and astronomers have a pretty simple definition of metals. It's anything that's not hydrogen. And I'm, there's a function for the galaxy and it's decreasing as you go out. And really the key things that I want you to notice about here, P0, GM1, GM2, GM3, those are just the names for different simulated galaxies. And the solid lines here are the simulations that I ran kind of normally, right? They had physics for star formation, they had gas in them, and they had physics for black holes. And then the dashed line, I moved the ability, basically I just said, no stars, you're not allowed to turn, you're not allowed to turn in the black holes. And so I removed black hole physics from those simulations and then I looked at this metal mass. And I noticed, hey, when I removed black holes, you're not getting as much metal out into the CGM. Oh, this little spike here, there's like a merger coming in, in that particular galaxy, which is interesting, but not what we're focusing on right now. And what is interesting is that this kind of points to this idea that the supermassive black hole is actually really vital to the evolution of the CGM, because it's moving all of this metal that's being created in the hearts of stars in the disk of the galaxy, and it's propagating them out into the CGM, meaning that without the black hole, we cannot shape the CGM, the way that it looks like, and the way that observers have seen it today. And that's, oh, yes. The way that observers have seen it today. In the summary, I leave you with instructions on how you can make your own galaxy wall holes. And I thank you all, and we'll take questions, right? Instructions. But actually, I'd like to point you to the instructions, right? This is where your CGM, the question is, so is the idea that the, you know, disk is creating a bunch of, all the stars in the disk are going supernova and they're creating a bunch of metals, and it's the idea that the supermassive black hole is then redistributing them for future star formation. And like, the idea is that the black hole is moving all of that gas out into the CGM, into that halo, but it's unlikely that that gas is going to form stars because it's too diffuse and it might be too energetic as well. Like, it might seem to pop to form stars So thank you for asking me about it. Leah, our previous speaker, asked me, I thought that black hole, and the whole point was that you can't escape energy, how can it be, you know, propagating this stuff into the CGM, and that's a great question. And it actually, I kind of glossed over that just for the sake of clarity, but a supermassive black hole, as it's a creating material, has an accretion, that's great. It has this material that hasn't quite reached the event horizon, so it hasn't fallen into that well where you can never return, right? It hasn't reached the point in the return, but it has this accretion, and all of that material is moving really, really, really fast, and it's shining really, really bright. Sometimes you hear the term, quizar or AGM, and that refers to black holes that are shining really brightly due to this really fast accreting material around it. It's something that hasn't totally fallen in yet, and it's moving really quickly, and therefore radiating a lot of energy away. Great question. So the question is, what data do we have to prove the existence of supermassive black holes, and, additionally, oh, what percentage of galaxies have supermassive black holes? So, the first part, there have been, I'm not a consumer, I'm not super great at this part, but I know that there are X-ray observations of the accretion of galaxies, as well as we've seen, at least in our own galaxy, the gravitational effects of supermassive black holes affecting the stars around it. As opposed to continuing on to the second half of your question, I don't know what the percentage is. Well, basically, if your galaxy is over, like, a billion times, 10 to the 9 or above, er, sorry, if it's, like, a billion times the mass of the sun or above, it's, like, our Milky Way is, uh, a trillion times. Any galaxy that size is definitely going to have a bigger, like, a really small galaxy. Gosh. The question is, what is inside the supermassive black hole presumably everything that it has accreted in its love? The models that I use, like, the, uh, cosmological simulations that I'm using and whether they're accurate and whether we can trust them, right, because we're putting particles in the box and kind of applying physics to them and the way that we compare them and kind of decide whether or not they are valid is by, uh, comparing them to observations. So the, actually, uh, so the simulations that I use are made in a code called Chandra. And this particular code is really good at matching particular relations that we see. They, it makes galaxies that look like galaxies that we can see. Uh, it's, you know, supermassive black, like, the relation just, the relation that I showed, like, the M-Sigma, it matches that with the galaxies that it makes. It matches some other relations. And due to those things, we say, okay, because we're making galaxies the way that we predict our own. You can see that they look. Now we can, you know, start to trust them as, all right, I'm going to use this trying to determine the physics that we have on here now. Well then, I think we're out of questions. Okay, well thank you very much. I hope to see you all there. Have a good night.