1 00:00:00,430 --> 00:00:11,780 I sort of. Good afternoon, everybody. 2 00:00:11,780 --> 00:00:14,450 Can you hear me? Yes, I think you can. Good. Thank you. 3 00:00:14,450 --> 00:00:22,400 Welcome to the physics department and welcome to this 18th INSEE lecture, which will be given by Professor Jacqueline van Goal.com, 4 00:00:22,400 --> 00:00:28,220 who's been visiting as the relevant professor of astronomy at Columbia University in New York. 5 00:00:28,220 --> 00:00:36,980 So Professor Van Goal.com is a radio astronomer. She studies the distribution of neutral hydrogen gas around galaxies, and in particular, 6 00:00:36,980 --> 00:00:47,300 she's focussed her attention on the motions of that gas and what it can tell us about how galaxies are assembled and how they evolve. 7 00:00:47,300 --> 00:00:59,030 She did her Ph.D. in the capturing lab of the Rice University in Groningen in the Netherlands, and she went from that position, 8 00:00:59,030 --> 00:01:05,810 which is, I should say, one of the institutions in the world that sets the heart of this kind of world of work. 9 00:01:05,810 --> 00:01:12,590 So she was trained in a really intense environment that understands how to do this kind of work. 10 00:01:12,590 --> 00:01:21,440 And she went from there to the National Radio Astronomy Observatory in the United States, where this was in the early 1980s, 11 00:01:21,440 --> 00:01:28,610 where she went to work at something called the very large, very large array VLA in its early days. 12 00:01:28,610 --> 00:01:37,130 And she was one of the pioneers that made it possible to use that enormously powerful instrument to do this kind of work. 13 00:01:37,130 --> 00:01:39,770 It's not a trivial thing at all. 14 00:01:39,770 --> 00:01:49,010 It requires special techniques to be developed over and above those that were already in use at that facility in New Mexico at Socorro. 15 00:01:49,010 --> 00:01:54,770 That's where I met her in the early 1980s, when I too lived in the United States. 16 00:01:54,770 --> 00:02:01,790 She has been a faculty member at Columbia since 1988 and is widely recognised for her contributions. 17 00:02:01,790 --> 00:02:09,590 She's been a visiting professor at Berkeley University of California, Berkeley da Vinci professor at the China Institute in Groningen. 18 00:02:09,590 --> 00:02:16,850 She's a corresponding member of the Royal Dutch Academy, and she has two attributes in common with somebody else who's here. 19 00:02:16,850 --> 00:02:22,790 I can't quite see how I can see her now. In Belbin, who's a visiting professor in our department. 20 00:02:22,790 --> 00:02:29,480 She was a member of the Site Selection Advisory Panel for the square kilometre array. 21 00:02:29,480 --> 00:02:36,950 That is an enormously important role how to distribute this enormous future radio telescope across the globe. 22 00:02:36,950 --> 00:02:41,240 We all need to be grateful for all the people who are on that panel, and there weren't many. 23 00:02:41,240 --> 00:02:43,950 We have two in the room. 24 00:02:43,950 --> 00:02:52,880 And the other thing she shares in common with just the umbrella now is that she gave the length the GMC lectureship, if I can get it out. 25 00:02:52,880 --> 00:02:59,900 So the Jetski Lectureship marks the achievements of Karl Jetski, who was the first man to detect radio waves, 26 00:02:59,900 --> 00:03:04,640 extraterrestrial radio waves and launch the subject of radio astronomy. 27 00:03:04,640 --> 00:03:17,080 So it's my great pleasure to introduce Jacqueline van Goal.com to give the 18 10c lecture the role of gas in galaxy evolution. 28 00:03:17,080 --> 00:03:23,170 Thank you, Roger. So can you hear me? Yeah. OK, so my visit has already been fantastic. 29 00:03:23,170 --> 00:03:31,690 Thank you very much for this invitation. It's a wonderful opportunity and I have to confess I've never been to Oxford, so it's just amazing. 30 00:03:31,690 --> 00:03:37,510 It's really been very nice and I hope it will stay nice. So it was really good. 31 00:03:37,510 --> 00:03:42,340 So today I want to talk about the role of gas in galaxy evolution. 32 00:03:42,340 --> 00:03:45,880 Now you might think that gas is only a tiny part of your galaxy. 33 00:03:45,880 --> 00:03:52,060 And so maybe it's not that important, but it actually means galaxies need gas to grow. 34 00:03:52,060 --> 00:04:01,630 So I actually, although in Konia, I was a radio astronomer, I worked actually on star formation, not in neutral hydrogen gas and galaxies. 35 00:04:01,630 --> 00:04:10,210 But when I moved to the field, I actually started emitting somewhat of neutral hydrogen galaxies. 36 00:04:10,210 --> 00:04:17,500 And this is the image that really got me going. So this this is a picture from the L.A. Times. 37 00:04:17,500 --> 00:04:22,970 We made the news. And what you see here is this is a galaxy. 38 00:04:22,970 --> 00:04:28,240 We put the lights down and this is the galaxy is about the size of the Milky Way. 39 00:04:28,240 --> 00:04:37,210 So there's a huge galaxy there and what you see here are the stars. Now what you see around it is the neutral hydrogen gas. 40 00:04:37,210 --> 00:04:49,150 And so that shows that if you just used to looking at optically in a visible look at the stars, you actually see only a tiny portion of the universe. 41 00:04:49,150 --> 00:04:56,140 Galaxies may have a lot of gas around it. And so when I saw this picture, it was in the early 80s. 42 00:04:56,140 --> 00:05:03,670 I said, I want to make an H1 image of the universe. And so that has been my goal since then, and I haven't gotten very far yet. 43 00:05:03,670 --> 00:05:08,590 But today, I'll tell you a little bit about this, these efforts. 44 00:05:08,590 --> 00:05:13,110 So. So this was a very old fashioned view. 45 00:05:13,110 --> 00:05:23,370 We saw this neutral hydrogen. Nowadays, we know that many galaxies have, or maybe most have, a huge reservoir of hydrogen around us. 46 00:05:23,370 --> 00:05:27,720 So this is now again, this is sort of the size of the Milky Way. 47 00:05:27,720 --> 00:05:34,140 Right? It's tiny. It's just the stellar disk. And this is all the gas that we now know is around it. 48 00:05:34,140 --> 00:05:36,480 So that gas is in many different phases. 49 00:05:36,480 --> 00:05:44,580 It's only nice to test different temperatures and some of it is neutral and so that gas might and might get recycled. 50 00:05:44,580 --> 00:05:54,090 So the Milky Way might throw out some gas and it might fall back later, or it can be excreted from the gas that is in between the galaxies. 51 00:05:54,090 --> 00:06:03,540 And so today, I really want to talk about what happens, how galaxies get their gas so it might fall in and it might help sustain star formation. 52 00:06:03,540 --> 00:06:08,580 And sometimes they lose the gas or they lose this reservoir around it. 53 00:06:08,580 --> 00:06:14,610 And that's kind of star formation and they stop and they become red and that galaxies. 54 00:06:14,610 --> 00:06:18,420 So this will really be the story of my talk. 55 00:06:18,420 --> 00:06:23,730 Now I have to say a little bit about neutral hydrogen because they're actually not many people working on this topic, 56 00:06:23,730 --> 00:06:32,160 although right now there is a big renaissance going on. So the neutral hydrogen and hydrogen is the most abundant element in the universe. 57 00:06:32,160 --> 00:06:37,320 Of course, neutral atomic part is much smaller than that, but there is a lot of it around. 58 00:06:37,320 --> 00:06:44,700 And so if you you want to observe it, you have to make a big effort because the line emission is very weak. 59 00:06:44,700 --> 00:06:53,400 I'll get back to that. But just to know the actual content of a galaxy is not enough to say what's happening to that galaxies. 60 00:06:53,400 --> 00:07:02,100 I think that it's really making the images of the distribution of the gas and looking at the kinematics tells you what is really happening. 61 00:07:02,100 --> 00:07:10,950 And so I've been working on this for many, many years. And right now there is, as I said, there is a big renaissance going on very soon. 62 00:07:10,950 --> 00:07:18,960 So there's many different instruments that can do this work much better than the original archery, which I've been using until now. 63 00:07:18,960 --> 00:07:22,950 So there will be a lot of work on hydrogen imaging. 64 00:07:22,950 --> 00:07:26,280 So these are some of the instruments that are coming online. 65 00:07:26,280 --> 00:07:32,700 So first of all, there's a telescope in India that is like to very nurturing and has also just been upgraded. 66 00:07:32,700 --> 00:07:41,910 It's an amazing instrument. And then many new telescopes come online, escaped meerkat and aperitif that will do similar work. 67 00:07:41,910 --> 00:07:47,820 So in the very near future, you will hear a lot more about this topic. 68 00:07:47,820 --> 00:07:52,020 So why is it so difficult to measure this neutral hydrogen line? 69 00:07:52,020 --> 00:07:56,440 It's very simple. It's a highly forbidding transition, so you have few. 70 00:07:56,440 --> 00:07:59,310 This is sort of the shell structure of an atom. 71 00:07:59,310 --> 00:08:10,050 So the ground state of neutral hydrogen atom, there's proton and an electron, and they can either have parallel spins or opposite spins. 72 00:08:10,050 --> 00:08:16,800 And so if the electrons flip spins, it emits a tiny bit of energy. 73 00:08:16,800 --> 00:08:25,440 It's the 21 centimetre wavelength and it spins so that the wavelengths I observe it is radio telescopes. 74 00:08:25,440 --> 00:08:32,040 So just twenty one centimetre. And you say, Well, how often does this happen spontaneously? 75 00:08:32,040 --> 00:08:36,450 It happens about once every 10 million years for a given atom. 76 00:08:36,450 --> 00:08:44,550 So what a waste of my time to spend doing this. But so fortunately, if you look at the galaxy, there is many, many atoms. 77 00:08:44,550 --> 00:08:51,360 So in a typical column of atoms at any place in the galaxy can be 10 to the 20 atoms. 78 00:08:51,360 --> 00:08:55,950 So that is why you can actually do this observations. And so that's what I do. 79 00:08:55,950 --> 00:09:00,200 So I'll show you here one picture of the fairly large array telescopes. 80 00:09:00,200 --> 00:09:07,860 As Roger said, I'm in the early, early 80s, I arrived actually two months after the instrument came online. 81 00:09:07,860 --> 00:09:15,840 It was very exciting times. So it is a synthesis radio synthesis interferometry. 82 00:09:15,840 --> 00:09:25,290 So basically, since this wavelength is so long to get enough angular resolution to see detail, you need a very large telescope. 83 00:09:25,290 --> 00:09:30,210 Now, you cannot make a telescope that is the size, say, of Washington, D.C., 84 00:09:30,210 --> 00:09:34,380 which is what you would need to get the same resolution as the optical wavelengths. 85 00:09:34,380 --> 00:09:41,760 But what you can do is you can combine signals of different telescopes and use it as an interferometer. 86 00:09:41,760 --> 00:09:45,810 And so this is an interferometer with three different arms. 87 00:09:45,810 --> 00:09:54,120 And so if you wait eight hours, this arm have moved here that'll move there and that RF moves there, so you trace out a circle. 88 00:09:54,120 --> 00:10:00,750 And so that is like simulating a huge single dish and the feeling is even more special. 89 00:10:00,750 --> 00:10:04,720 So you can take these telescopes and move them out to different distance. 90 00:10:04,720 --> 00:10:10,500 There's a railroad own way, so you can actually go all the way to these mountains here that. 91 00:10:10,500 --> 00:10:19,650 Sets to resolution show the longest baseline is 30 kilometres, and you can combine all this data to make one image. 92 00:10:19,650 --> 00:10:24,840 So that's I will mostly be talking about results obtained with this telescope. 93 00:10:24,840 --> 00:10:28,680 OK, so what for me? 94 00:10:28,680 --> 00:10:32,820 The big question is today is not so much. How does the gas move? 95 00:10:32,820 --> 00:10:38,820 But how do galaxies grow in the largest scale structure of the universe? 96 00:10:38,820 --> 00:10:40,840 And so I'll show you some pictures of that. 97 00:10:40,840 --> 00:10:49,110 So if you look at the sky and you look at galaxies with a telescope, they are not uniformly distributed on the sky. 98 00:10:49,110 --> 00:10:56,020 But in fact, you will see that there is a very distinct, intrinsic, intricate web of galaxies. 99 00:10:56,020 --> 00:11:04,230 So you see filaments, you see clusters where many galaxies get into thousands of them and there is huge empty regions. 100 00:11:04,230 --> 00:11:11,460 And so this has been known for quite a while, both from theoretical simulations and from observations. 101 00:11:11,460 --> 00:11:17,970 And so the question is now what happens to the galaxies if they are at different locations in the cosmic web? 102 00:11:17,970 --> 00:11:30,930 So that's what I will be talking about. So here is the result of a simulation, and this is just this is at four different times after the Big Bang. 103 00:11:30,930 --> 00:11:38,610 So this is a simulation of only dark matter. So in case you don't notice, most of the universe consists of dark matter. 104 00:11:38,610 --> 00:11:46,770 We don't know what it is, but there is a lot of it there. And so the theorists really love making simulations of the distribution of this dark matter. 105 00:11:46,770 --> 00:11:51,990 It's actually pretty simple to do. You just know the laws of gravity. 106 00:11:51,990 --> 00:11:55,710 So this is very shortly after the Big Bang. 107 00:11:55,710 --> 00:12:05,400 The distribution is very, very uniform. It's very smooth. But then when you move on in time, you see that big holes develop and filaments. 108 00:12:05,400 --> 00:12:08,100 And so here this is the current time. 109 00:12:08,100 --> 00:12:16,560 So again, this this distribution of dark matter, you see that a fairly large empty regions, which we called for it actually knew by distance. 110 00:12:16,560 --> 00:12:20,670 About 95 percent of the local volume is Foyt. 111 00:12:20,670 --> 00:12:29,670 And so here is where the filaments get together to form. Clusters of galaxies might be thousands of galaxies zooming around very fast. 112 00:12:29,670 --> 00:12:32,070 So this is the dark matter. 113 00:12:32,070 --> 00:12:39,240 This is not to make the simulations of the galaxies in this dark matter is more difficult, but this is the distribution of the light. 114 00:12:39,240 --> 00:12:43,590 So that is so again, the galaxy to form follow the dark matter. 115 00:12:43,590 --> 00:12:47,850 And it's it's very clear now how do we know this is this? 116 00:12:47,850 --> 00:12:55,110 So I'll actually show you first one simulation from the A-lister simulation just to give you. 117 00:12:55,110 --> 00:12:59,100 Some idea of what a 3D structure looks like, 118 00:12:59,100 --> 00:13:10,320 so I'll just show you part of it and start out by showing the dark matter and then at some point it moves to showing the hot gas in this. 119 00:13:10,320 --> 00:13:15,840 So first you see these filaments form here and they grow bigger and bigger. 120 00:13:15,840 --> 00:13:27,340 So this is. Very shortly after the Big Bang, 1.2 million years after the Big Bang, so structures built up to become more massive. 121 00:13:27,340 --> 00:13:36,800 You see a very massive structure built up, this really grows can be a cluster. 122 00:13:36,800 --> 00:13:43,910 And then at some point I did switch, and it shows the gas in here, and so then green will be the coal. 123 00:13:43,910 --> 00:13:47,670 The gas and hot will be as gas gets really heated up. 124 00:13:47,670 --> 00:13:52,170 So here you see those gas in these filaments and can be very low density. 125 00:13:52,170 --> 00:13:57,350 But here there could be explosions, either supernovae going off or 18 feet back, 126 00:13:57,350 --> 00:14:07,940 or it can be clusters colliding with large amounts of the gas get heated up to very high temperatures, like 10 to eight or something. 127 00:14:07,940 --> 00:14:13,340 So just give you basically some idea of what the structure of the cosmic web looks like. 128 00:14:13,340 --> 00:14:21,110 It's very, very intricate. But so we'll download talk about is what the galaxies do in these structures. 129 00:14:21,110 --> 00:14:30,380 So how do we know that all this is happening? We have actually observations that show that this cosmic map exists. 130 00:14:30,380 --> 00:14:34,220 So this is now a two-dimensional slice of the universe. 131 00:14:34,220 --> 00:14:39,320 And what you see here is this is distance from us. 132 00:14:39,320 --> 00:14:45,920 So we're going back in time and the yellow points are all the galaxies. 133 00:14:45,920 --> 00:14:54,930 So if we know that the distance to the galaxies, we actually see that they are arranged in these filaments and into regions in between. 134 00:14:54,930 --> 00:14:59,510 Then if you go to larger distances, you see that these patterns repeat. 135 00:14:59,510 --> 00:15:05,120 So the structure is the same everywhere. So these voids have don't change in size. 136 00:15:05,120 --> 00:15:10,850 They all are about the same. So this is what the the real universe looks like. 137 00:15:10,850 --> 00:15:20,390 This is what you see. OK, so now I want to talk a little bit about how galaxies form, 138 00:15:20,390 --> 00:15:27,110 and I'll basically give you a very brief recap of what a lot we've known for some while. 139 00:15:27,110 --> 00:15:35,730 So originally, when people started talking about this dark matter, they thought that galaxies grow by first. 140 00:15:35,730 --> 00:15:40,970 They have dark matter falling into halos and then the gas falls into this. 141 00:15:40,970 --> 00:15:47,060 Halos get heated up to about the furious temperature, and then it slowly cools and sellable in the disk. 142 00:15:47,060 --> 00:15:51,470 That's how you make a galaxy. And then by merging, you grow the galaxy. 143 00:15:51,470 --> 00:15:58,760 And so it turns out that the picture, which lasted until the early 2000s, was a little too simple. 144 00:15:58,760 --> 00:16:06,440 We now know that gas falls in along filaments, and sometimes it doesn't actually get heated up to the fuel temperature. 145 00:16:06,440 --> 00:16:12,650 But it is what is called cold mode accretion at full straight to the disk of the galaxies. 146 00:16:12,650 --> 00:16:18,590 And so now we think and this was, of course, already predicted by James php.ini in 1977. 147 00:16:18,590 --> 00:16:24,440 But now the simulations show that too. So what you see here? 148 00:16:24,440 --> 00:16:29,600 I don't know if you can see it actually very well. So this is the cold mode accretion. 149 00:16:29,600 --> 00:16:35,570 This is the accretion rate accretion rate density, and here is time. 150 00:16:35,570 --> 00:16:41,960 So this is very early in the universe. Galaxies grow mostly by in4 of gas. 151 00:16:41,960 --> 00:16:53,720 And then if you come to more recent times, the bigger halos get this effect that the gas get heated up and then settle slowly by cooling. 152 00:16:53,720 --> 00:17:00,860 So hot mode accretion becomes more important here, but you still see that cobalt accretion is very important. 153 00:17:00,860 --> 00:17:07,160 And then at the current time, you see that there is still an important part of mode accretion, 154 00:17:07,160 --> 00:17:14,420 but it's only especially in special halos and the special locations. 155 00:17:14,420 --> 00:17:20,680 And so what a prediction is, is that this you will see this. 156 00:17:20,680 --> 00:17:27,220 Only in the lower Miss Galaxy, so the smaller galaxies might still be growing by this circumpolar accretion, 157 00:17:27,220 --> 00:17:36,040 here you see the mass of the galaxy and here you see that around 10 to the straight unstinted 10. 158 00:17:36,040 --> 00:17:39,250 The warm moat accretion start dominating. 159 00:17:39,250 --> 00:17:46,150 So for the smaller galaxies, it's still important to have cold mode accretion and this is galactic environment. 160 00:17:46,150 --> 00:17:50,800 So this is the density of two galaxies around your galaxies. 161 00:17:50,800 --> 00:17:54,580 And this is the lowest density environment, is this voice. 162 00:17:54,580 --> 00:18:01,660 And so what you see here is that in forest, you expect actually that this cold mode accretion might still dominate. 163 00:18:01,660 --> 00:18:13,360 So I will first tell you something about observations of galaxies and voids, and then I'll go to galaxies in very high density regions in clusters. 164 00:18:13,360 --> 00:18:23,080 And then finally, I will tell you about a survey that we are doing with an upgraded fealy through a huge slice of the universe. 165 00:18:23,080 --> 00:18:31,240 So let me first tell you about for it. So these are the most empty regions in the nearby universe, and it's really in the local universe. 166 00:18:31,240 --> 00:18:35,140 What I'll first be talking about, because that's what we've been doing for a lot. 167 00:18:35,140 --> 00:18:41,020 So we there's a big optical survey of the entire sky. 168 00:18:41,020 --> 00:18:49,390 It's the Sloan Digital Sky Survey. And so we have two distribution of the galaxies nearby and so into it. 169 00:18:49,390 --> 00:18:56,200 We selected the first image region, which must be had to do a little bit of mass. 170 00:18:56,200 --> 00:19:02,860 We had to smooth the galaxy distribution and then find out really then to diffuse this. 171 00:19:02,860 --> 00:19:10,150 And then we had to find the largest distance from the filaments or the deepest densities in the fields. 172 00:19:10,150 --> 00:19:16,060 And then we looked and you said, if there is a galaxy we imaged and see what each one looks like. 173 00:19:16,060 --> 00:19:24,610 So here it is. So this is this is basically a distribution of the galaxies. 174 00:19:24,610 --> 00:19:32,470 And this is the density field that we derived in it. And then this is the distribution of the lowest density. 175 00:19:32,470 --> 00:19:38,320 So if you have wide and means it is furthest away from the filaments. 176 00:19:38,320 --> 00:19:43,540 So what you see here is so to pick these are really deepest under densities in the field. 177 00:19:43,540 --> 00:19:48,460 And so if you look at one of these places, boom, you find a galaxy and that is what it looks like. 178 00:19:48,460 --> 00:19:57,160 So that is how we did it. So then we observed a whole bunch in about sixty four, which we observed galaxies in these voyage. 179 00:19:57,160 --> 00:20:03,130 So here you see, this is the black is the distribution of the galaxies. 180 00:20:03,130 --> 00:20:08,170 Red is the distribution of the density field, and this is the galaxies we observed. 181 00:20:08,170 --> 00:20:15,790 And so we actually did this with a new back end at Westerberg telescope that you could probe a large instantaneous velocity range. 182 00:20:15,790 --> 00:20:23,350 So if you look at a galaxy, we can also see galaxies at the larger velocity and at a lower velocity which are 183 00:20:23,350 --> 00:20:29,590 in the filaments and that forms the control sample for the observations for it. 184 00:20:29,590 --> 00:20:32,680 So what two galaxies in four voids looked like? 185 00:20:32,680 --> 00:20:42,010 So people usually don't talk about it because there are so few galaxies, but they are the ones that are there are really interesting. 186 00:20:42,010 --> 00:20:50,540 So they're all very small, and most of them are blue, which means they are forming stars. 187 00:20:50,540 --> 00:20:58,610 OK. And so for those of you who know more about Galaxy, so if you look at the distribution of all galaxies in the nearby universe, 188 00:20:58,610 --> 00:21:08,240 for example, we slow and you look at the colour versus the luminosity you find at the galaxies are distributed into groups. 189 00:21:08,240 --> 00:21:09,590 There's the blue cloud. 190 00:21:09,590 --> 00:21:17,510 They are forming stars and then the this is the blue cloud and the more massive galaxies are in what's called the red sequence. 191 00:21:17,510 --> 00:21:21,560 So the red dots here are our first galaxies full. 192 00:21:21,560 --> 00:21:25,730 And so what you should notice is that all the galaxies are really small. 193 00:21:25,730 --> 00:21:30,380 We have no galaxies that are larger than three times 10 to 10 solar masses. 194 00:21:30,380 --> 00:21:39,740 Instead, they're all small, but I do spend the whole colourings, so we have actually one red Ford Galaxy. 195 00:21:39,740 --> 00:21:45,290 OK, but it's what is really interesting in these galaxies is the distribution of the neutral hydrogen. 196 00:21:45,290 --> 00:21:49,160 And here you have it. So this is here. 197 00:21:49,160 --> 00:21:54,950 You see an overlay of the neutral hydrogen contours on an optical image. 198 00:21:54,950 --> 00:22:04,430 And so what you see is for this just an example, these four galaxies, they all have very extended neutral hydrogen envelopes, 199 00:22:04,430 --> 00:22:11,060 which is so I think a typical galaxy in a slightly higher than city region would usually have a smaller extent, 200 00:22:11,060 --> 00:22:16,760 but still so much larger than the optical extent. So now have you two hydrogen envelopes? 201 00:22:16,760 --> 00:22:25,700 And what so since we observe hydrogen one at a very specific wavelength, you also get the distribution of the motions of the gas. 202 00:22:25,700 --> 00:22:30,620 So Doppler shifts out of the gas moves towards us that get the wavelengths get a bit shorter. 203 00:22:30,620 --> 00:22:37,280 If it moves away from us, the wavelengths get a bit slower. So these are the falsity fields of the neutral hydrogen. 204 00:22:37,280 --> 00:22:43,070 And so one of the most interesting galaxies, I think, is this one. 205 00:22:43,070 --> 00:22:49,700 And here you get the blow up of this. So this is happened to be the first galaxy. 206 00:22:49,700 --> 00:22:53,900 The image that neutral hydrogen was immediately a big hit. 207 00:22:53,900 --> 00:23:01,820 So here you see the optical image. It's tiny. It's a very small galaxy and it's rotating like this. 208 00:23:01,820 --> 00:23:09,380 And this is the neutral hydrogen envelope, so it's sort of perpendicular to the optical image. 209 00:23:09,380 --> 00:23:14,540 And actually, it is rotating perpendicular to the stellar body. 210 00:23:14,540 --> 00:23:22,610 So this is what you would call a polar disk, and this has a lot of very interesting properties. 211 00:23:22,610 --> 00:23:31,160 So first of all, there's more mass in the disk in neutral hydrogen than there is in the stars. 212 00:23:31,160 --> 00:23:36,950 And second, this galaxy is a very thin, tiny galaxy. 213 00:23:36,950 --> 00:23:47,870 It doesn't have a bull's looks totally undisturbed. So and then third, we have been looking very hard to see if there is any stars in this. 214 00:23:47,870 --> 00:23:51,680 So we did very deep V observations. There's nothing there. 215 00:23:51,680 --> 00:23:56,000 It's just gas. So and here it is. 216 00:23:56,000 --> 00:24:01,490 This is a position for city profile. So there are no punk counterparts. 217 00:24:01,490 --> 00:24:11,000 So we think the tidal, if this would have been tidally created, it would have stirred up the stellar part of the galaxy. 218 00:24:11,000 --> 00:24:16,850 So it hasn't. So we think this might be an example of smooth accretion of gas. 219 00:24:16,850 --> 00:24:22,370 It's not disturbing the optical at all, which is bingo. That's what we hope to find. 220 00:24:22,370 --> 00:24:26,810 And here you see the location of this galaxy in the cosmic web. 221 00:24:26,810 --> 00:24:32,480 So this is the orientation of the matrix axis of this galaxy. 222 00:24:32,480 --> 00:24:36,140 So it is very close to a very small filament. 223 00:24:36,140 --> 00:24:45,650 And what we think is happening, if you look at this poll on this is that the gas is flowing out of the forehead onto the galaxy, 224 00:24:45,650 --> 00:24:49,550 which was just what was predicted by some people who do simulations. 225 00:24:49,550 --> 00:24:54,590 So this is a simulation of gas flows in it and here a filament. 226 00:24:54,590 --> 00:25:01,130 So we think that the gas is still creating the galaxy is still creating gas out of the void. 227 00:25:01,130 --> 00:25:04,940 OK, so now there's other interesting things it. 228 00:25:04,940 --> 00:25:11,240 In fact, our galaxy is close to one of the largest force we know about in the universe. 229 00:25:11,240 --> 00:25:18,230 And so there is in that void. There's also a tiny galaxy. It's called Caking two, four six, and it's sort of similar. 230 00:25:18,230 --> 00:25:26,360 It has. So you'd say it's one envelope that is slightly misaligned with the galaxy, so the major axis are not quite aligned. 231 00:25:26,360 --> 00:25:32,960 And if you look carefully at the velocity field, you see there are some irregularities in it. 232 00:25:32,960 --> 00:25:38,930 So we think again that this might be an example of a galaxy that still has the following in. 233 00:25:38,930 --> 00:25:45,770 OK. And another interesting thing they found in this point is that if you look at one galaxy, 234 00:25:45,770 --> 00:25:50,640 we found that there was actually a whole filament, a very thin filament of gas. 235 00:25:50,640 --> 00:25:57,360 And there are three galaxies in this filament. And I'll talk more about this velocity structure later. 236 00:25:57,360 --> 00:26:01,140 So several people have now been finding filaments in for it, 237 00:26:01,140 --> 00:26:08,820 which is again something that you expect that later on you have a void and then within there you form new filaments. 238 00:26:08,820 --> 00:26:17,250 So this is another example of that. So the conclusions from this sports survey were that by looking in for it, 239 00:26:17,250 --> 00:26:24,810 I think the most important thing is you select an interesting sample of galaxies, not all small there might all be accreting. 240 00:26:24,810 --> 00:26:28,770 They have very little miss simplicity, many of them. So these are galaxies. 241 00:26:28,770 --> 00:26:35,340 You are just looking at a low density part of the universe and the galaxies are still growing, slowly growing. 242 00:26:35,340 --> 00:26:42,870 So I think that's very, very interesting. And we have actually some other indications that void galaxies are fascinating. 243 00:26:42,870 --> 00:26:49,350 And I just want to show you this. There is a famous astrophysicist in Princeton, Jim Peebles, 244 00:26:49,350 --> 00:26:55,350 who has always been pointing out that there is like me, something's wrong with this Leibniz KDM. 245 00:26:55,350 --> 00:27:05,320 And what he pointed out is that in our local group, the most massive galaxies are actually not in the highest density regions of the galaxies, 246 00:27:05,320 --> 00:27:12,420 which is which is what you would expect if galaxies grow by merging the most massive ones to should go to high density. 247 00:27:12,420 --> 00:27:17,550 And so he said he had already three galaxies. This is the Super Bowl plane. 248 00:27:17,550 --> 00:27:23,370 And here are the three galaxies that all of you astronomers know well and two six nine four six 249 00:27:23,370 --> 00:27:32,010 M1A1 and fifty that are really in very low density and NGC six nine four six is important. 250 00:27:32,010 --> 00:27:36,210 It's really in for it now. I like this. 251 00:27:36,210 --> 00:27:45,060 So as an aside, John Garamendi pointed out that all these galaxies have no real boulders that have pseudo bulges, so they haven't been merging. 252 00:27:45,060 --> 00:27:54,750 And still, they're big. But if you are an H-1 astronomer, you know something else about these galaxies, which is that there's a six nine four six. 253 00:27:54,750 --> 00:28:03,570 This was one of the first two examples where here you see the optical and now in yellow, you see the H1, which is much more extended. 254 00:28:03,570 --> 00:28:05,730 So this one galaxy in a fault. 255 00:28:05,730 --> 00:28:14,190 So if you look at the very regular velocity field of this, guess that's way outside the optical and you take a slice through here. 256 00:28:14,190 --> 00:28:20,570 Then you see this gas follows a very nice rotation pattern, except he boom. 257 00:28:20,570 --> 00:28:27,230 It's shifted by 50 kilometres per second and here the same and here the same. 258 00:28:27,230 --> 00:28:33,170 So the idea is there are holes in the disk there and the guess is really displaced. 259 00:28:33,170 --> 00:28:39,710 So already most mine in 2007 said that it looks as if stuff is falling in. 260 00:28:39,710 --> 00:28:49,200 Now there's several examples of that where this has been noticed a long time ago, and no one has guessed displaced by 150 kilometres per second. 261 00:28:49,200 --> 00:28:53,600 And we don't know how it got displaced, where it could be because stuff is still falling in. 262 00:28:53,600 --> 00:28:58,430 So what I want to say is that it seems that there are galaxies that become 263 00:28:58,430 --> 00:29:04,910 latent and are still growing because they have gentle inflow of gas and the H1. 264 00:29:04,910 --> 00:29:14,070 So some of the sectors that now recently a very interesting paper appeared on the results of a Arecibo survey of over. 265 00:29:14,070 --> 00:29:23,660 But it also looked at force and what they noticed was that in it, they find filaments and what they call tendrils, which is the same thing. 266 00:29:23,660 --> 00:29:29,810 So what they noticed was that in these filaments, the galaxies grow bigger than they normally are, 267 00:29:29,810 --> 00:29:38,120 and they look undisturbed and they keep forming stars. So they're not going re-emerging, but they're probably going by in full of gas. 268 00:29:38,120 --> 00:29:43,520 So, so grateful for it. So now I'm going to completely switch topic. 269 00:29:43,520 --> 00:29:50,930 I'm not going to the highest density regions of the universe, and so I'm going to look at the nearest cluster of galaxies. 270 00:29:50,930 --> 00:29:55,370 And so a cluster of galaxies. As I said, there might be thousands of galaxies. 271 00:29:55,370 --> 00:30:04,190 They move around very, very fast and they are filled with very hot gas like 10 to the eight degrees Dimension X ray. 272 00:30:04,190 --> 00:30:12,380 And so the question is what happens to these galaxy clusters? So in clusters, we often find galaxies that have completely stopped star forming. 273 00:30:12,380 --> 00:30:21,590 And so we have to find out what the reason is. One of the possible reasons is that the cold gas is being swept out by the hot gas. 274 00:30:21,590 --> 00:30:26,270 So this is a picture that we made of the vertical cluster. 275 00:30:26,270 --> 00:30:31,280 So what you see here is this is a picture of gas. There's only gas in this picture. 276 00:30:31,280 --> 00:30:36,290 So this is the Virgo cluster and this is the hot gas. What's been detected in X-ray? 277 00:30:36,290 --> 00:30:43,550 Yes, M87, which is the galaxy that the Event Horizon telescope imaged recently. 278 00:30:43,550 --> 00:30:49,160 So there's a black hole in the centre now, but this is a big galaxy. So it's very hot gas around it. 279 00:30:49,160 --> 00:30:55,460 And these are galaxies that we imaged in H1 one at a time. 280 00:30:55,460 --> 00:31:02,780 And what you see is the H1 disks in blue, but they've been blown up by a factor of 10 so that you can see them. 281 00:31:02,780 --> 00:31:07,790 Otherwise they would be. And so what you see is this picture tells actually a lot. 282 00:31:07,790 --> 00:31:14,750 So one of the things you see is that closer to the centre, these galaxies have very tiny H1 disks. 283 00:31:14,750 --> 00:31:18,530 Why further out there have a very large one disks. 284 00:31:18,530 --> 00:31:25,910 So that suggests that if a galaxy falls into this hot get, it actually gets stripped of the Gold Coast. 285 00:31:25,910 --> 00:31:27,380 So this is what we call Ramprasad. 286 00:31:27,380 --> 00:31:35,450 Stripping has been discussed for decades now, but I think by now we have very good evidence that that is really what is happening. 287 00:31:35,450 --> 00:31:38,030 And here you see some images of that. 288 00:31:38,030 --> 00:31:45,800 So here you see galaxies in the outskirts of Virgo that have this galaxy actually has a huge amount of gas, very large envelope. 289 00:31:45,800 --> 00:31:54,320 But then when you move in, you see here. And so again, the controls are neutral hydrogen and the image is the stars. 290 00:31:54,320 --> 00:31:59,330 And you see this galaxy, for example, has no neutral hydrogen on one side of it. 291 00:31:59,330 --> 00:32:04,340 And that is because it's falling into the hot gas. This galaxy is really interesting. 292 00:32:04,340 --> 00:32:09,380 It has a totally undisturbed stellar disk, but the gas is being pushed out. 293 00:32:09,380 --> 00:32:11,720 So that's what we call empiricist tipping. 294 00:32:11,720 --> 00:32:19,460 So this is a way for galaxies to completely lose their gas and maybe lose that reservoir of gas and stop forming stars. 295 00:32:19,460 --> 00:32:24,890 You see, other examples in these galaxies have only a little bit of neutral hydrogen right in the centre. 296 00:32:24,890 --> 00:32:31,010 So these different mythologies tell us a lot about at what stage they are of stripping, 297 00:32:31,010 --> 00:32:37,730 and we can now compare that to the stellar population synthesis to see when star formation stopped in this disks, 298 00:32:37,730 --> 00:32:44,030 and we can actually derive what orbits the galaxies followed before they fell into the cluster. 299 00:32:44,030 --> 00:32:51,290 So we've learnt a lot. And so one other picture that we made that we thought was very spectacular. 300 00:32:51,290 --> 00:33:03,200 So here again is Feargal, and we noticed there is a whole bunch of galaxies all at about the Fiero radius of the cluster that if you look careful. 301 00:33:03,200 --> 00:33:13,850 You see that I have tails in H1 here, you see them quite clearly, so this is a tail in H1 years until in H1. 302 00:33:13,850 --> 00:33:17,180 That are all pointing away from a central cluster. 303 00:33:17,180 --> 00:33:24,020 So we think that in this case, this indicates where RAM pressure stripping actually starts to be important. 304 00:33:24,020 --> 00:33:28,460 So it's the gas that's very loosely bound in the outer parts of the galaxies. 305 00:33:28,460 --> 00:33:34,220 And once they enter sort of the vireo radius of the cluster, they start losing the gas. 306 00:33:34,220 --> 00:33:43,140 It gets swept out. But then if you go even further out, you see very long tails. 307 00:33:43,140 --> 00:33:47,280 And so the question is, what is that the U.S? 308 00:33:47,280 --> 00:33:56,640 Hundreds of killed parsec and so that can have different origins, could be interactions, could still be a Christian, could be stripping. 309 00:33:56,640 --> 00:34:06,630 And so what I'm going to show you now is a movie that was made by Greg Bryant, who was in Oxford for quite a while before he moved to Columbia. 310 00:34:06,630 --> 00:34:10,920 And it's just a simulation of the gas and what you will see us. 311 00:34:10,920 --> 00:34:15,630 So it is basically what happens when galaxies fall into clusters. 312 00:34:15,630 --> 00:34:22,430 So here we go. So if it gets wide, it means the density is very, very high, 313 00:34:22,430 --> 00:34:29,080 so it's showing the density of the gas, so you see these galaxies falling in along filaments. 314 00:34:29,080 --> 00:34:34,330 And then if you look carefully, you see that a lot of guts get stripped out of the galaxy. 315 00:34:34,330 --> 00:34:40,120 But it felt full of holes. I hope you can see that. 316 00:34:40,120 --> 00:34:48,680 So this galaxies are being stripped if they go once through the cluster, they mostly lose all the gas. 317 00:34:48,680 --> 00:34:54,080 But in the in the filaments, you also see interactions and lots of things happening. 318 00:34:54,080 --> 00:34:58,580 So this actually looks really quite similar to what we observe. 319 00:34:58,580 --> 00:35:03,920 This is what happens to the guys in galaxies once again clusters. It's over. 320 00:35:03,920 --> 00:35:05,240 OK. 321 00:35:05,240 --> 00:35:13,370 So the conclusion of this is there's actually lots of different conclusion to this, but one is that repressed stepping plays a big role in clusters. 322 00:35:13,370 --> 00:35:19,760 And actually, it also plays a big role in groups, probably and in halos of galaxies. 323 00:35:19,760 --> 00:35:25,230 The smaller galaxies that fall into the halos of bigger galaxies might even get stripped. 324 00:35:25,230 --> 00:35:28,850 You see some evidence of that in halo of our own Milky Way, 325 00:35:28,850 --> 00:35:35,390 and quality of the data is now such that we can do simulations and compare exactly what is happening. 326 00:35:35,390 --> 00:35:40,610 We learn about the stage of disturbing and the future of these galaxies. 327 00:35:40,610 --> 00:35:44,780 OK, so now I want to talk a little bit about the future. 328 00:35:44,780 --> 00:35:51,230 And so first, I want to show you this picture that I like, but maybe it looks into a pretty low quality picture. 329 00:35:51,230 --> 00:35:56,510 But this is, I think, the start of making an H1 image of the universe. 330 00:35:56,510 --> 00:36:02,390 This is a result of high pass, which is low resolution neutral hydrogen survey. 331 00:36:02,390 --> 00:36:09,740 And what they show here is two slices in a universe at different philosophies, so one is further away than the other. 332 00:36:09,740 --> 00:36:15,380 And what they show is that red is galaxies that are unusually poor in gas. 333 00:36:15,380 --> 00:36:21,560 So to smooth over the distribution and blue is where there is an absence of gas. 334 00:36:21,560 --> 00:36:31,400 And so I think these images, if we could make them just for the whole universe, at least for large trip, it will tell us a lot about galaxy evolution. 335 00:36:31,400 --> 00:36:40,010 And I think for again, for the astronomers, the distribution of gas may actually tell you something about galaxy conformity. 336 00:36:40,010 --> 00:36:47,540 So there is an observation that if you look at a big galaxy, the smaller galaxies around it are not forming stars. 337 00:36:47,540 --> 00:36:55,430 Why is the galaxy become red? Because it's gas. So apparently not only that galaxy lost that gas, but the surroundings too. 338 00:36:55,430 --> 00:36:56,780 And the opposite is true, too. 339 00:36:56,780 --> 00:37:03,680 If you see a big galaxy that's still forming stars since blue, the smaller galaxies in the Earth are also still forming stars. 340 00:37:03,680 --> 00:37:06,410 So an image of this could tell you why that is. 341 00:37:06,410 --> 00:37:15,140 It's just the neutral hydrogen reservoir around the galaxy, so just the large scale distribution of the gas, possibly. 342 00:37:15,140 --> 00:37:22,970 OK, so now I go to you. So this was all talking about the local universe really nearby stuff. 343 00:37:22,970 --> 00:37:30,950 Now I'm going to tell you a bit about evolution. So what do we know about evolution of of galaxies? 344 00:37:30,950 --> 00:37:38,660 And of course, so of galaxies? We know a lot. This is the evolution of the star formation rate and density in the universe. 345 00:37:38,660 --> 00:37:42,950 And so this is going back to about half the age of the universe. 346 00:37:42,950 --> 00:37:47,780 So this is redshift to you. And so you see that it peaks here. 347 00:37:47,780 --> 00:37:54,710 And then since then to allow the star formation rate drops dramatically. 348 00:37:54,710 --> 00:37:59,660 So in the last times, the star formation rate is dropping. 349 00:37:59,660 --> 00:38:07,250 And so the question is, why is that so this is really well known? But what do we know about a neutral hydrogen movement? 350 00:38:07,250 --> 00:38:13,010 So hydrogen is part of the gas reservoir. And so it could be that star is just galaxies. 351 00:38:13,010 --> 00:38:17,900 Just stop forming stars because they run out of gas. But what do we know? 352 00:38:17,900 --> 00:38:23,120 Not much. We know a lot about hydrogen density nearby. 353 00:38:23,120 --> 00:38:29,510 Because it's easy road map to home nearby universe, and then we know it at very large, large distances, 354 00:38:29,510 --> 00:38:35,520 but other hydrogen lines from the different excited little levels are shifted to the optical window. 355 00:38:35,520 --> 00:38:38,000 So we know that here here. 356 00:38:38,000 --> 00:38:47,150 So you see the Arabs here are actually very small, but this range between redshift zero and one, the error bars are enormous. 357 00:38:47,150 --> 00:38:52,010 And that actually indicates that we know very, very little about what's going on there. 358 00:38:52,010 --> 00:38:55,910 So the goal would be to try to observe that. 359 00:38:55,910 --> 00:39:01,340 And so that's what I've been doing for the last six years or so it's been. 360 00:39:01,340 --> 00:39:09,110 So this is an image of the H1 blind service that have been done so far. 361 00:39:09,110 --> 00:39:18,650 So what you see here is the offer of our service and our receiver survey covers. 362 00:39:18,650 --> 00:39:24,200 This is a fraction of the volume that a conference so nearby we know Will what whole sky. 363 00:39:24,200 --> 00:39:27,830 But if you go further and you see here the distribution of the galaxies, 364 00:39:27,830 --> 00:39:35,030 this cosmic map and you see there's one survey here and one survey here, that's the body survey that was done. 365 00:39:35,030 --> 00:39:41,720 We're supposed to work. And so this is not what we are doing. So this what's called the Chile survey and this was a pilot. 366 00:39:41,720 --> 00:39:51,770 So once we finish this, we go out a lot further and we know at least a little bit of what the galaxies to ultra large redshift. 367 00:39:51,770 --> 00:39:56,360 So it's called the chillis survey, huh? 368 00:39:56,360 --> 00:40:03,020 New Mexico has lots of Chile. You know, it's the Cosmos H1 large extragalactic survey. 369 00:40:03,020 --> 00:40:08,720 It's thousand to our space, the very large array after the upgrade. 370 00:40:08,720 --> 00:40:15,830 And it's basically it's sort of what a square kilometre array signed to be doing, but then much better and much easier. 371 00:40:15,830 --> 00:40:22,340 And it was when I started it, it was a pathfinder to the pathfinders. 372 00:40:22,340 --> 00:40:28,040 So right now, the past minutes are going to be a pathfinder for me, but that's how it happens. 373 00:40:28,040 --> 00:40:29,360 So this is a collaboration. 374 00:40:29,360 --> 00:40:37,970 One of the things that was interesting is that this is a really international collaboration, except there's nobody from Oxford. 375 00:40:37,970 --> 00:40:41,970 But other than that, there's there's lots of different countries, 376 00:40:41,970 --> 00:40:48,110 and one of the goals was to include people from all the past years that are being filled. 377 00:40:48,110 --> 00:40:51,440 So I suspect you have heard of square kilometre array. 378 00:40:51,440 --> 00:40:58,250 This is going to be this amazing telescope that will eventually come online and sort of a world telescope. 379 00:40:58,250 --> 00:41:00,980 So when that plan was made to build that, 380 00:41:00,980 --> 00:41:07,730 people started building smaller telescopes that would already do certain parts of the science with the escape. 381 00:41:07,730 --> 00:41:16,130 And those are the past finders. And so all these collaborators are actually most of them are part of one of the past funders. 382 00:41:16,130 --> 00:41:23,420 So there was sort of an interesting collaboration. So the main scientific motivation should now be totally clear to you. 383 00:41:23,420 --> 00:41:28,790 It's I want to know how galaxies grow as function of location in the cosmic web. 384 00:41:28,790 --> 00:41:34,960 So that's for me by far the most important. But of course, lots of one of the things you can do. 385 00:41:34,960 --> 00:41:39,890 And but one. So this is an observation from redshift zero two point four five. 386 00:41:39,890 --> 00:41:48,920 And it's just something I was pointing at one spot also. So this you can get morphology kinematics of individual galaxies. 387 00:41:48,920 --> 00:41:53,840 You can get the distribution total of each one in the universe. 388 00:41:53,840 --> 00:41:58,670 Lots of other things you can do. Um, so this is all pointing. 389 00:41:58,670 --> 00:42:04,340 So the Cosmos field is one of the best observed spots on the sky. 390 00:42:04,340 --> 00:42:09,380 So there's a large HST Hubble Space Telescope mosaic of this area. 391 00:42:09,380 --> 00:42:14,900 And so it's being observed at every imaginable wavelengths, except a neutral hydrogen. 392 00:42:14,900 --> 00:42:19,400 So we started doing it in neutral hydrogen and this is our pointing. 393 00:42:19,400 --> 00:42:24,320 We are not pointing at the centre because there is a strong radio source that mess up everything. 394 00:42:24,320 --> 00:42:26,240 So we just put it a bit off. 395 00:42:26,240 --> 00:42:33,980 But the strength of this field is that there is all these other observations that can help with the analysis of what we do. 396 00:42:33,980 --> 00:42:43,460 And so this is a plot of the sensitivity. So this is this alfalfa survey that was by far the most important in H1 until now. 397 00:42:43,460 --> 00:42:47,150 So that is that is in the local universe. 398 00:42:47,150 --> 00:42:53,540 These are different sensitivity functions. This is what we did in the pilot for this field. 399 00:42:53,540 --> 00:43:00,060 So that goes to a redshift point, too. And. 400 00:43:00,060 --> 00:43:05,760 This is the sensitivity that we get after some hours, so that goes to a rent of two point four five. 401 00:43:05,760 --> 00:43:17,670 So the reason we could do this was because the feel, which for a long time was the most powerful radio telescope that was around was in the late 90s. 402 00:43:17,670 --> 00:43:22,680 People realised this is electronics that is 30 years old so we can do much better. 403 00:43:22,680 --> 00:43:33,570 So they're actually upgraded it. And so while I've been doing much of my work with men of a total of six megahertz, you can fool the pilots. 404 00:43:33,570 --> 00:43:37,860 We could use 240 megahertz and now we use four and 18 megahertz. 405 00:43:37,860 --> 00:43:42,930 And it means that we can properties enormous velocity range all at once. 406 00:43:42,930 --> 00:43:50,760 And so since the the lines are so weak, you really want in one pointing to probe many, many galaxies. 407 00:43:50,760 --> 00:43:54,180 That's the advantage that you can have this large velocity cover. 408 00:43:54,180 --> 00:44:03,960 So you could early on, you could have said, I want to observe a galaxy a directive 2.5, but you wouldn't get a thousand hours to observe one galaxy. 409 00:44:03,960 --> 00:44:11,820 But in this case, we observe a whole comet. So we can get many galaxy sets, one that is really what the upgrade is. 410 00:44:11,820 --> 00:44:18,750 So that is that's what we are doing. And so we did lots of this, lots of interesting stories about this. 411 00:44:18,750 --> 00:44:23,640 So when we started to feel I had a telescope, the field didn't have a computer. 412 00:44:23,640 --> 00:44:27,710 Australia was building a telescope, but already had two computers. 413 00:44:27,710 --> 00:44:35,370 So we said, let's work together. So we did a calibration in New Mexico, and we shipped the data to Australia. 414 00:44:35,370 --> 00:44:43,440 And then Amazon came along and said, Could we use your data to demonstrate that Amazon is good for basic science? 415 00:44:43,440 --> 00:44:53,430 And we said, sure. So we are still getting entirely free computing on Amazon quite a few years later, which is amazing, but it's been very, very nice. 416 00:44:53,430 --> 00:44:58,620 So that's what's happening. So we're observing this thirty one thousand velocity channels. 417 00:44:58,620 --> 00:45:07,380 And so first show you the summary of what we found in this pilot, which only close to half to Richard Franks. 418 00:45:07,380 --> 00:45:12,660 So this is where the distribution of the known galaxies, which there was all this other data. 419 00:45:12,660 --> 00:45:19,320 As I said, optical data, direct points are detections. And so this is just 60 hours old, really. 420 00:45:19,320 --> 00:45:23,250 And the idea was that we wanted at the largest redshift. 421 00:45:23,250 --> 00:45:29,490 We wanted to be able to test what we locally knew as the most massive age amongst galaxies. 422 00:45:29,490 --> 00:45:33,720 So that's basically and that is also what we do for the larger survey. 423 00:45:33,720 --> 00:45:39,810 So and so here you see a summary actually of some of these results. 424 00:45:39,810 --> 00:45:45,510 So you see, this is a galaxy that is really nearby. I guess it's. 425 00:45:45,510 --> 00:45:49,830 About a year, and it has a huge one envelope, it's very disturbed. 426 00:45:49,830 --> 00:45:55,110 If you go to a larger redshift, you see interacting galaxies and this is a really good galaxy. 427 00:45:55,110 --> 00:46:00,690 So already here you see that the morphology is telling us some very interesting things. 428 00:46:00,690 --> 00:46:10,590 So that was good enough to convince the the time allocation committee of the field that they should give a thousand hours, which was great. 429 00:46:10,590 --> 00:46:20,550 OK. So we wrote in our proposal about the expected detection radius, and we calculated that in two totally independent ways. 430 00:46:20,550 --> 00:46:29,790 One was, we said, let's look at the distribution of masses in local universe and just assume that there is no evolution with redshift. 431 00:46:29,790 --> 00:46:35,490 And let's see what the distribution will be in this whole column out to a redshift of 0.5. 432 00:46:35,490 --> 00:46:40,550 How many galaxies will we detect? So that is this graph. 433 00:46:40,550 --> 00:46:53,180 Another way is to look at all the spectroscopic things, known galaxies, and there is a relation between colour and size of galaxies and each one mass. 434 00:46:53,180 --> 00:46:59,120 So we can look at the spectroscopic known galaxies and predict what each mass will be. 435 00:46:59,120 --> 00:47:03,410 And so that is this curve and this is the distribution of the galaxies. 436 00:47:03,410 --> 00:47:10,880 And so both mass estimates said that we should get about images of about 300 galaxies. 437 00:47:10,880 --> 00:47:15,080 It would be great. We aren't there yet, but we hope to get that eventually. 438 00:47:15,080 --> 00:47:20,120 So I'm not going to show you a few results of the first hundred eighty hours. 439 00:47:20,120 --> 00:47:26,630 That's a big one. And so what we did was we said, OK. 440 00:47:26,630 --> 00:47:32,570 In fact, I had a student who was about to graduate, and the student said, I really want to get some results. 441 00:47:32,570 --> 00:47:38,720 So she wanted to look here. So we'll get it. So the first question is, can you inherit 80 hours? 442 00:47:38,720 --> 00:47:42,590 Could you actually detect already galaxies at this redshift? 443 00:47:42,590 --> 00:47:46,860 So at that time, nobody really had gone beyond about this. 444 00:47:46,860 --> 00:47:54,500 They say we're no galaxies detected. So the first thing you can try is to do stacking. 445 00:47:54,500 --> 00:48:01,340 And so this is stacking at two different redshift. So basically, you don't detect individual galaxies, 446 00:48:01,340 --> 00:48:10,880 but you take the profile at the location of each galaxy that you know off and you shift it all to the same velocity and then you combine it. 447 00:48:10,880 --> 00:48:17,510 And so this is taking a direct shift of point one to. And this is sticking a directive two point three seven. 448 00:48:17,510 --> 00:48:26,210 And so lo and behold, he had one mass. So that is not the mean one mass of these galaxies about 1.8m central line. 449 00:48:26,210 --> 00:48:36,000 And this is three times then nine. So this is sort of what we hoped we would find that to mean h one mass would go up this redshift. 450 00:48:36,000 --> 00:48:43,670 Right? That is why just a star formation go down because they're running out of gas, so they should be more gas at higher redshift. 451 00:48:43,670 --> 00:48:53,900 And I was in March, I was in India. And so there they have this time metre radio telescope and they actually got an amazing result. 452 00:48:53,900 --> 00:48:59,720 They just started observing a year ago, they did the same same stacking game. 453 00:48:59,720 --> 00:49:09,170 So this is sticking around redshift of one. And they find that the H1 mass is one point eight times 10 to the 10. 454 00:49:09,170 --> 00:49:13,670 So it's really going up, and I think this looks like a pretty reliable result. 455 00:49:13,670 --> 00:49:18,380 So this was presented at the conference, but I've been very, very careful. 456 00:49:18,380 --> 00:49:25,730 This is a graduate student who did that. So this is the first, I think, reliable secondary result at a redshift one. 457 00:49:25,730 --> 00:49:33,050 And so it is completely consistent. There also have a striking result at a rate of two point thirty seven, which is consistent with ours. 458 00:49:33,050 --> 00:49:40,540 So there seems to be really an increase in mean H1 mass with redshift. 459 00:49:40,540 --> 00:49:50,830 So we hope so that's that's the first result that's really interesting now since we are looking at galaxies and I told you endless amounts about that, 460 00:49:50,830 --> 00:50:02,140 I'm so interested in pursuing that and actually being an undergrad who uses an algorithm to define the cosmic map in the Chile survey. 461 00:50:02,140 --> 00:50:07,750 This snake luber. So he used this programme dispersing to define it. 462 00:50:07,750 --> 00:50:17,230 And so we can now look. So one thing is he predicted, what four H-1 content we should see us see as a function of distance from the film, 463 00:50:17,230 --> 00:50:26,200 once again taking into account all the limits, etc. So he predict that indeed, the H1s goes up. 464 00:50:26,200 --> 00:50:31,420 If you go to larger distances from the filament, which is sort of what you expect if they move to the filaments, 465 00:50:31,420 --> 00:50:35,450 eventually the galaxies get decoupled from the gas. 466 00:50:35,450 --> 00:50:39,940 Right, that's the cosmic web detachment prediction. 467 00:50:39,940 --> 00:50:44,450 But so we can now they find this cosmic map for the Chile survey. 468 00:50:44,450 --> 00:50:48,670 And so these are results for a pretty low redshift. 469 00:50:48,670 --> 00:50:52,960 So the red dots are the galaxies that we detect. 470 00:50:52,960 --> 00:50:57,680 And so, for example, this is a galaxy that's the most isolated galaxy. 471 00:50:57,680 --> 00:51:03,730 It's the fourth galaxy. And you see it has a huge one envelope, which we really like. 472 00:51:03,730 --> 00:51:07,300 And so one of the things I'm really excited about, 473 00:51:07,300 --> 00:51:15,130 which we did last week is so the simulators and actually the several people here in Oxford 474 00:51:15,130 --> 00:51:21,910 to be doing to predict how galaxies will get formed with respect to the filaments. 475 00:51:21,910 --> 00:51:28,630 So if you have a filament that just collapses and is still thin, then it collapses from two directions and expensive to search. 476 00:51:28,630 --> 00:51:33,580 So you expect the angular momentum of the galaxy to be perpendicular. 477 00:51:33,580 --> 00:51:38,050 So the spin factor to be aligned with the filament two rotation is perpendicular. 478 00:51:38,050 --> 00:51:43,510 So the prediction is that the smaller galaxy spins that are aligned with the filament well. 479 00:51:43,510 --> 00:51:50,500 Eventually, the bigger galaxies will start merging, and the spin factor might change. 480 00:51:50,500 --> 00:51:59,470 So these are all pretty small galaxies. And what you see here is the so yellow is the orientation of the filaments. 481 00:51:59,470 --> 00:52:04,270 And if you look to the next to it, so I guess you can see it much better. 482 00:52:04,270 --> 00:52:08,050 Is this in yellow is the spin factor of the galaxies. 483 00:52:08,050 --> 00:52:17,320 And so if you make a histogram of the alignment, then you find that eight out of 10 are actually what you would call a light. 484 00:52:17,320 --> 00:52:27,070 So I think this is very cool. This is the first time this has been done in H1, and so eventually we will get 300 galaxies we can do this with. 485 00:52:27,070 --> 00:52:34,240 So that's that's really interesting. So now I come back to this filament that we found in Floyd a long time ago. 486 00:52:34,240 --> 00:52:42,010 So this is the three galaxies that we found. And so if you look at the velocity fields and you know how to interpret velocity fields, 487 00:52:42,010 --> 00:52:47,830 you see that for the three galaxies to commanders, here they flip. 488 00:52:47,830 --> 00:52:58,670 So it's rotating in this way, and the spin factor will be aligned with Finland, and that's true for all three. 489 00:52:58,670 --> 00:53:09,740 Optimists believe this. OK, so now, as I told you, I had one student who wanted to read it, and she said, I really want to discover something. 490 00:53:09,740 --> 00:53:17,270 So she looked at the wretched points, seven assists he may not. And she looked at all the galaxies that were predicted to have a large one mass. 491 00:53:17,270 --> 00:53:21,110 And so she detected this galaxy in neutral hydrogen. 492 00:53:21,110 --> 00:53:27,860 And so then this student immediately went to the large millimetre telescope in Mexico and looked for seal. 493 00:53:27,860 --> 00:53:37,550 And he finds odour. So this is the first detection of data on a emission directed mission at a rate of two point three seven six. 494 00:53:37,550 --> 00:53:44,330 So this is a fantastically interesting galaxy. So first, the H1 mass is three times and then it's very massive. 495 00:53:44,330 --> 00:53:49,880 The H2 mass is five times 10 percent. So ridiculous. It's really massive. 496 00:53:49,880 --> 00:53:58,700 And so here you see, this galaxy was known from its starburst and galaxy, its form of stars 80 solar masses per year. 497 00:53:58,700 --> 00:54:06,020 It's a massive galaxy. The stellar mass is eight times 22 percent, which is sort of interesting. 498 00:54:06,020 --> 00:54:13,310 So if you look at this more carefully, we say, Well, OK, is this galaxy unique in terms of its properties? 499 00:54:13,310 --> 00:54:19,640 So it is gas originated from, but here you see distribution of stellar mass versus H1 mass. 500 00:54:19,640 --> 00:54:25,310 And so the grey is the alfalfa found. 501 00:54:25,310 --> 00:54:30,980 This is our galaxy and here are of what they call H1 monsters. 502 00:54:30,980 --> 00:54:35,630 So those are very H1 rich galaxies. So it is gas rich, not unique. 503 00:54:35,630 --> 00:54:41,330 But now when you look and see, oh here again, results of different surveys, 504 00:54:41,330 --> 00:54:49,520 then it turns out it's only sort of the only other galaxies that have so much seal are from this FIPS survey, 505 00:54:49,520 --> 00:54:56,090 and that is a survey of galaxies at much higher redshift. So these galaxies are the richest one. 506 00:54:56,090 --> 00:55:04,640 So to see oh, content is really, really unusual. It usually in an utter way, and that is its star formation rate. 507 00:55:04,640 --> 00:55:11,420 So this is the star formation properties of galaxies, a function of stellar mass in the local universe, 508 00:55:11,420 --> 00:55:17,990 actually redshift point five to see this is our galaxy, it's forming stars way too fast. 509 00:55:17,990 --> 00:55:25,160 But though, if you look at Galaxy said at a redshift between 1.5 and two, you see that it fits right in. 510 00:55:25,160 --> 00:55:30,080 So this galaxy and its properties looks like the galaxy at a much higher rates. 511 00:55:30,080 --> 00:55:35,990 This is just again what we hope to find. So is one of the first results of chillies. 512 00:55:35,990 --> 00:55:44,960 That's really interesting. And of course, since I'm talking about spins, I asked again to look at a cosmic map around this galaxy. 513 00:55:44,960 --> 00:55:49,940 So it turns out this this H1 is aligned with a filament. 514 00:55:49,940 --> 00:55:59,090 And so if you look at the spin of this, if this galaxy, the spin is perpendicular to the filaments, so which is it's a big galaxy. 515 00:55:59,090 --> 00:56:07,190 So maybe that's just what some people expect. It's not aligned. It's been going for a while, but it's a fantastically interesting galaxy. 516 00:56:07,190 --> 00:56:14,510 So from this galaxy, you can say the first Asian image is it looks like it's a galaxy. 517 00:56:14,510 --> 00:56:16,820 It's very gas rich, very instrumenting. 518 00:56:16,820 --> 00:56:24,560 It has an unusually really unusual light SEO content, and it looks more like a clumpy disks they you see at higher redshift. 519 00:56:24,560 --> 00:56:28,820 So this might be near by example, but we can actually start studying that. 520 00:56:28,820 --> 00:56:34,280 So this is the first step to making a neutral hydrogen image of the universe. 521 00:56:34,280 --> 00:56:39,350 And so what can we conclude? So do I guess so? Conclusions and more questions? 522 00:56:39,350 --> 00:56:48,740 So I think one of the conclusions very careful is that maybe we find real evidence that the H-1 content of galaxies is increasingly stretched. 523 00:56:48,740 --> 00:56:53,270 We have no number of independent measurements that seem to suggest that. 524 00:56:53,270 --> 00:57:01,370 And it was already known that the molecular gas content of galaxies increases pretty rapidly and especially the ALMA telescope. 525 00:57:01,370 --> 00:57:11,600 Amazing results on that. So one question is, is the ratio of molecular gas to atomic gas changing with redshift? 526 00:57:11,600 --> 00:57:18,350 And so the indications that it is and I think one of the big questions is why is that and by how much? 527 00:57:18,350 --> 00:57:22,850 So this is really fantastic. So those are the conclusions. 528 00:57:22,850 --> 00:57:28,730 And I just want to end by telling you that we really live in interesting times. 529 00:57:28,730 --> 00:57:34,460 And the reason is that there's all these past findings that have started taking data. 530 00:57:34,460 --> 00:57:43,580 In fact, here in Oxford, there are amazing results using a telescope in South Africa and Meerkat Telescope, it is one of these past findings. 531 00:57:43,580 --> 00:57:49,850 It just started working. It's working better than anybody expected. It's really amazingly good. 532 00:57:49,850 --> 00:57:54,440 So this will go much deeper and will and has a much larger field of view. 533 00:57:54,440 --> 00:58:03,850 So there will be a real survey of H1. Eventually, I'll do a redshift of one, and ESCAP is an Australian up activists in the Netherlands, 534 00:58:03,850 --> 00:58:09,220 and they will both do a very large area of sky of nearby galaxies. 535 00:58:09,220 --> 00:58:18,940 So I think once these guys have got a data, we finally can maybe understand how galaxies grows at function of the location and of course, them. 536 00:58:18,940 --> 00:58:24,010 And then there's the square kilometre array, which will image galaxies attractive. 537 00:58:24,010 --> 00:58:29,080 And so we have to be a little patient, but eventually it will be there and it will be fantastic. 538 00:58:29,080 --> 00:58:40,006 So that's it. Stay tuned.