08:05:05 Okay Hello, everyone. 08:05:07 Thank you for joining us. On Tuesday, the Milky Way. Week. And today, we have our first keynote. 08:05:19 Talk of the week, and it's by Professor Mary. 08:05:24 Mary is at Columbia University, and she has a lot many connections, who are here today at this at this for this program. 08:05:38 So, I am quite happy to be able to introduce her. 08:05:45 I think we all know about her 2012 review with Jess work, and 08:05:55 was a Josh peak. Yes. Okay. 08:05:59 And Mary was the first author and it has the seminal review with this beautiful 3d rendering of the mercury Halo that just kind of revolutionized our view of the Milky Way. 08:06:12 I won't go on about all of Mary's accomplishments, but I was really impressed to see a very nice and very, very visual. 08:06:27 Paper she put out about gas stripping of Milky Way Halo satellites, and I hope she talks about that today. So I'm going to turn it over to Mary and I also want to talk about our panel. 08:06:42 And today we have a panel discussion with with Mary Cortina besla admin Hodges cook. 08:06:50 Chris how and Frank event for. So Mary I am going to let you start. 08:06:55 Thank you for offering to give a keynote speaker. 08:06:58 Talk. 08:07:00 Okay, thanks very much been so I have a lot I was thinking about getting through today and so because of that, I would love to use as in poll but with KTP that's tricky, but just says very nicely set up a mentee poll for for me. 08:07:17 And so I'll go ahead and post that now. 08:07:21 And then this is basically just making sure I get to what everyone wants the most so if you have any opinion in terms of what is definitely covered I'll get to that slide and give you some more details on that but I wanted to post it right now in terms 08:07:35 of, you can vote for multiple things and then in a couple of slides I'll get to the one to describe those in more detail if you're like I don't understand this and wait till I get to that slide and we can we can talk about it. 08:07:49 So men t.com for everyone. 08:08:08 Okay, so the question I was asked to talk about today is what does the Milky Way tell us about the CGM my immediate reaction to this question is why is it not. 08:08:21 What, what does the CGM of the Milky Way. Tell us about it because I typically work more locally but indeed I understand why the question is such, just to set the scene just a little bit for everyone who comes from wide variety of red shifts and interests, 08:08:40 and we're talking about our Milky Way of course the Bard spiral galaxy. We're located about eight killer parasites out so whenever we're studying our CGM we have to consider that bias that's something young thing is an expert on and she'll be doing this 08:08:52 tutorial on Wednesday on this. We are set within a group environment. 08:08:58 It is a very low mass group though it's a loose group 3.2 times 10 to the 12 solar masses is the best local group mass estimate, we're talking about so really two large spirals in a large collection of dwarf galaxies, and then related to the question 08:09:13 that Justin young post this this last plot here is showing you stellar mass versus star formation rate this is from Glen Hawthorne and gearhead. 08:09:26 The cross here is showing the Milky Way. On this plot, and then they chose a bunch of SPSS analogs here as the red points. 08:09:33 So you can get an idea in terms of where it lies in overall star formation stellar mass space compared to other galaxies and the red and the red and the blue here. 08:09:43 The other point that you made which I decided to go ahead and add is that when you plot this in color, absolute magnitude space, this population spreads out dramatically so thats related to the question there posing is the Milky Way typical, I would say, 08:10:06 Make sure of course that you also pay attention to these people this week as you can see they're very clearly experts in the field, and I may get in trouble for this picture but anyway. 08:10:17 Just young Filippo are other people in terms of thinking about the observations in particular, I'm not the simulation people I don't mention here. I also don't have great pictures of them like I do, these, these this group. 08:10:41 Okay, so what does the Milky Way tell us about the CGM so I outlined several things that I would like to go through that I think the Milky Way in particular, says something about that you can easily do for other galaxies, and these options are what is 08:10:47 in that mentee pole I wasn't sure I would get through everything so I wanted to see if there was a clear. Oh, I definitely want you to cover this. So if you have if you care, you can go to that at the stage and make a vote and you can vote for multiple 08:11:00 things. I was going to right away sketch out the picture of the Milky Way with the cold high velocity codes, yet within 10 kilometer six of the disk, and most of the ionized gas we think to is close to the disk, but then an extended largely I nice Halo 08:11:17 medium with the measuring system coming through, but just nicely put up that picture already I was going to show off my zoom whiteboard skills and everything. 08:11:40 But we have you have that scene and those slides are posted so you can get a general picture in your head from there. 08:11:34 In terms of what the options are in terms of what I'll talk about and what I'll just naturally go through in this order if there isn't a large preference. 08:11:43 First that the CGM clouds come in a very wide range of sizes and are multi phase and you could say well we know this from other galaxies as well. But we have direct evidence in the case of the Milky Way for this. 08:11:55 The mass and the CGM is not always as significant. 08:11:59 So this is important because of course one of the reasons the CGM has caught a lot of attention and Galaxy evolution is because we found that there's a lot of variance wrapped up in it. 08:12:10 Going to our local Milky Way and awesome 31 at some level, we're, we're finding there could be some discrepancy here either. Just locally or maybe at 00. 08:12:22 In general, interaction between the satellites and the CGM This is key because in the local environment we have a great census of the satellites and we also have the management system so we can watch that process directly. 08:12:36 There's also just more data to sort out the difference between a group medium and that of an individual galaxy and again we're talking about a very low mass group here. 08:12:46 But this is also something of interest to many people and myself and it's related to the paper I recently put out so but this is another, another option. 08:12:55 And then finally, we can learn about the halo magnetic field by looking at the clouds within our own Milky Way hailer Halo and this is something that I would like to advertise some work that a student is doing, if possible, and providing insight into 08:13:10 this, you should definitely talk to Brian games are on the observational side of this further though, as well. If I get to them. 08:13:18 Okay, um, can I ask now just if there's any clear bias in terms of the mentee pole. so yeah I just posted a JPEG, a screenshot of the results. It looks like the first place by, you know, the substantial margin is cloud sizes and multi-phase. 08:13:37 The second is, Oh, we got a few more bugs interaction between satellites and the CGM. 08:13:45 The third, I see is difference between CGM and group medium fourth is mass in the Milky Way and fifth is insight into magnetic field so almost exactly as you have written. 08:13:56 Okay, well maybe, maybe what I'll do is, 08:14:01 I might just go in order then, and then we'll see if I don't get to the, to the lat the data to sort out group medium and individual galaxy, we can always bring our panel into discuss this as well because some of them have thought about this pressure. 08:14:15 Okay, so let's talk about CGM clouds and the wide range of sizes, they have and the fact that we see that the Milky Way CGM is multi phase. Of course I have to show this plot at least once. 08:14:28 So this is showing the distribution of high velocity gas in our Milky Way Halo across the sky. And so what you're seeing here the shades are the neutral hydrogen, so the densest material ranging and density from about 10 to the eight to 10 to the 20 in 08:14:44 a trunk calm density. 08:14:46 trunk calm density. And then the circles here are representing ai ni gas detections in particular we have over six silicon lines and I he sees this is from learner Hawk at all I'm sorry I don't remember the other off, authors, and so what you can see 08:15:01 is that the gases multi-phase you see the multiple sizes here you see large complexes together with small clouds these little crosses here are the compact high velocity clouds detected with a more sensitive and higher resolution surveys on Twitter all 08:15:15 these crosses are, and you can see structures follow each other in velocity largely, we can look at the measurement system and we see the ionized gas largely has the same color as the dense gas detected and emission. 08:15:31 This is the tale of the magical extreme here so this is, this is the only complex here. That is a very large distance out in our Halo medium. So this would be 50 to 60 kilo parsecs and then going out to the tail. 08:15:45 The models and good Tina can talk about this more if people are interested, the tail has been found to extend even further towards the plane here, and also have be a distances potentially out to 100 kilometer six possibly even a little bit for further 08:16:01 out depending on the actual coming in for the first time model, etc. And so you can. The other thing is these complexes are very local there within 10 kilo per sec so mosey heights. 08:16:14 Within our Halo, and again you see this is complex see that the ionized gas follows the denser gas, and there's also some compact codes associated with this as well. 08:16:27 And so this is this fight itself shows that the clouds come in a wide range of sizes and are clearly multi phase because we're getting that medium both on top of the h1 clouds, as well as next to it showing it has this extended ionized medium around the 08:16:42 dense core. 08:16:43 This is a more recent data set from Victor at all showing the cost results of for the ionized gas and both all of these are an LS or velocity if you're interested I can show you a GSR version. 08:16:55 Later here you're seeing that we've filled in a number of sight lines and if you do an overlay. 08:17:01 with the h1, you find largely the same thing that most of the ionized gas is following what the cold densest gas is doing. This is one area that's particularly interesting in terms of it just being a large ionized complex without a lot of hh one at similar 08:17:17 velocities, but otherwise you generally see an h1 structure with the large ionized components. 08:17:27 I actually I wanted to mention to I'm actually happy to take questions during my talk, I know we haven't traditionally done this and slack is a place we can do this but if you want to raise your hand. 08:17:37 I'll just see you come up and I'll take your question I might wait till a pause point but I'm quite happy to take questions during the talk just for clarity or some other important thing you think should be mentioned or asked about now. 08:17:52 Okay and so then the advantage of the Milky Way though as you can keep going to our higher resolution and get very deep, and indeed when you do higher resolution observations you found in their clumps within the large clouds there's additional small clouds 08:18:07 around it. 08:18:16 These two examples here are from the Arecibo survey the alpha. So we're going about a factor of four to five better resolution was similar sensitivity to what you saw in that previous map in terms of the h1 cold h1 complexes. 08:18:23 This is the tale of complexity so we're at a z height of about two to four kilo per six. And so we're seeing that it's breaking up into the series of smaller clouds, but you also have some larger clouds present. 08:18:35 This is almost certainly complex Thea thought to be accreting on to the Milky Way disk. Currently, so this could be you know where it's currently breaking up, or you know, what we've talked about in the conference this could be also where we're seeing 08:18:49 some cooling going on as it slows and and it's pressure going fine and is able to start cooling. 08:18:55 So this is an interesting thing in terms of how we would actually sort out if there's actually some cooling going on, along with the destruction that we know is going on. 08:19:04 This is a tale of the mental extreme. As I said, we don't know the exact distance to this, but you know it's probably at least 100 kilo parsecs very clearly the destruction of CGM cold CGM client gas, but again, is it possible that we're also getting 08:19:20 some cooling going on there. 08:19:23 We can then look at the distributions of sizes, etc. Because we actually have a distance we can convert that to a physical size, work out of volume density. 08:19:33 medium. So the tale of complex see so lower Halo three few killer parsecs, we have a range of sizes from this sample about 25 to 100% volume densities about point oh 1.1 go through what people have found for these high velocity clouds. 08:19:55 And then this is showing you pressure that pressure assumption of of equilibrium and what you then get for that density of the halo assuming attend to six Calvin Halo medium, and then doing the same thing for the tail of the manual extreme. 08:20:09 It's further away. So you have larger size distribution and then you get much lower volume densities and lower pressures, as well, the halo densities here I would say are relatively high for what we would expect out there as well. 08:20:23 And so that just goes to show I mean, do we really think that the tail and mental extremism pressure equilibrium I'm not sure I was actually encouraged by what someone said that you commonly that assumption can work fine. 08:20:34 But I'd love to hear more about that. 08:20:37 So this is one example of, you know, where you can actually catalog individual clouds and look at their overall distribution of properties. You can go to even higher resolution though of course and the clumps just get smaller is generally what we find 08:20:53 and this is just a sampling of the work that's been done using synthesis arrays to get to even higher resolution. This is showing you a compact high velocity cloud where they point out some of the sub comes they see within that cloud. 08:21:07 This is work where they looked at a long absorption line sight lines and found little dense clumps. And this is work where the, it's in the leading arm of the modeling system and the data has been the data has been combined with single dish results which 08:21:22 is key to really understand what's going on at all scales. So the top and these are sub are committed resolution. 08:21:30 So the top is showing you the highest resolution map. And then this is showing you what the single dish alone gives you right. So you can see the, the variety in terms of what you're seeing this is just the perks radio telescope This is combined with 08:21:44 the Compact Array data here. I'm going to sub art minute resolution and then when you're thinking about physical skills I know that's what the theorists one to know. 08:21:53 It totally depends on where the complex is, you can quote that you're getting to subpar sec levels but with that you have to be in that very lower Halo about one killer parsecs up once you get up to things that we think are more mentioned like system 08:22:07 getting out to interesting 50 killer parsecs type thing then you're right now we're limited to about five to 15% structures that we're getting down to. 08:22:22 So it totally depends on where you are in the hill in terms of what physical scale you're actually capturing and I'd be curious if the simulations actually expect a difference depending on the density in nature of the halo medium The clouds are moving 08:22:31 through, would you expect a difference in that relative size scale. 08:22:38 So in terms of the future of assessing Halo come size I just want to mention the gas cap survey. So this is going to cover 13,000 Square degrees of sky at 32nd resolution so this is what we need to really assess what's going on with the clump size distribution 08:22:56 across a large region of sky high resolution high sensitivity large region of sky and the results have started to come out for this, so far largely for the small Mendelian and cloud This is a paper bag and clued Griffis at all, we've added some, some 08:23:11 in layers to some film entry features in the small mentioned in cloud. So, this is, but this is also capturing the halo gas will be able to look at this, that comes size distribution and quite a bit of detail. 08:23:24 The come size distribution and quite a bit of detail. And I think what's key here is that we apply the same cataloguing method to both the simulations and the observation so we're actually comparing things one to one and seeing what what we see observational 08:23:38 II means physically. Are there any quick questions and then each one, and come size stuff. 08:23:46 Okay, I'm just continuing that in terms of the multi phase and size of features as the ionized gas so let me give you a quick overview of that. And there's many people in the audience that can say more about this, I apologize. 08:24:09 So going back to the six from fuse some back at all this gives you an idea the range of density for the oh six for the Milky Way Halo. We see everything from 10 to 13.5 to 10 to the 14.5. 08:24:22 This stuff would be associated with the management system this stuff would be lower Halo so again the thinking in his paper, and I think most people still think this is that this is the clouds interacting with that had Halo medium partially why you're 08:24:37 getting this, We can look at the silicon. 08:24:41 Lions This is the work of saying at all. I don't have a plot of victory at all showing the distribution for the high velocity gas for respect for the low velocity gas set aside to be in the halo as well. 08:24:53 And this is a type of variation we see in that silicon density so again we're seeing a fairly narrow distribution of densities in my opinion. 08:25:02 Going over 0.6 decks largely when you go across the sky and this just again shows you the wealth of information we can get for the Milky Way. We have so many sightlines that we can start to look at Cloud structure overall density variation, etc. 08:25:19 Then the tricky part is sorting out exactly where that gas is which is a big piece of work in itself. 08:25:28 Then in terms of zooming in and looking at the ionized gas structure at the smallest scales possible. What you can do is look at structures that have multiple sightlines within them and that's again I'm referencing Young's work but there's Chris Hawk, 08:25:43 on our panel did work with this related to globular clusters as well. 08:25:47 So in this case we're looking at stars within them 33 and using it to study the foreground gas. And so what she found is this type of variation, these are the points from the M 33 results using the stars there for the angular separation. 08:26:04 And then this is work from Collins at all looking at the silicon three. So again, I would I would argue this is not large variation on small scales I'll let just would you argue with that. 08:26:20 No, so I would say we don't see a lot of large scale variation in the ionized gas overall, and this physical separation here depends again exactly where you are 1% to one kilo per sec is roughly what we're looking at. 08:26:31 For the gas we detected along this sideline. 08:26:37 Okay, I'm either questions. Now, before I move on to the I'm going to move on to the math and the CGM. 08:26:47 We're getting great questions for the panel, so keep on going. Okay, I'll stop I'll just I'll just look for blue hands as my teaching, trying to be interactive is coming in here to tend to bring everyone in the mass in the CGM is not always as significant. 08:27:05 So this is related to when we look at the total amount of gas we're finding in the Milky Way Halo and then 31 at some level as well. We're not finding this much and right now I'm just taking the numbers from thing and all where she put everything worked 08:27:21 out that mass if you scale everything with the same numbers and have within 75 killed a parsecs, and it's a great event than value in all cases but for the Milky Way CGM. 08:27:34 We're finding generally a value that's tend to the nine solar masses are greater same thing and 31 is finding something similar and Chris can say more about that on the panel. 08:27:44 And then for cost Halo is of course an order of magnitude larger. 08:27:49 So, immediately there you say okay, there's something weird about the Milky Way. But these massive estimates are pretty dodgy, you could say as well. Right. 08:27:59 So you could put that but there's multiple other signs that the Milky Way is weird here's one that was suggested back with Tumlinson and all in 2011 just looking at the iOS six results and using the fuse those six results. 08:28:11 Just looking at a typical column density, the Milky Way was lying right about here and you can say well maybe that's where it was supposed to be and this is just a typical column then see detected, but already the Milky Way was starting to appear like 08:28:25 it was a little bit low compared to what was being found more recently for this type of temperature gas this has been done much more carefully by Hannah Bish and she has a beautiful new results video you can check out. 08:28:39 To find out more about this, but what the project did this was across our project that Justin, Josh Pekin young were involved with as well, and where you looked at matched Halo stars and QSO so they're both very close on the sky, and then looked at the 08:28:54 column density difference of the carbon for absorption. This little schematic is kind of showing you this is the inner region where we had the halo stars, and then going out to a very distant queue. 08:29:07 Way covering fraction of CGM carbon for is significantly down from other galaxies even from him 31 so the this shaded region is for the data for the other galaxies in terms of covering interaction with radius. 08:29:24 And here's depending depending on whether you count the measurement system. These are the points for the Milky Way just indicating that the covering traction in the outer Halo beyond eight kilo parsecs is very very low for the Milky Way compared to what 08:29:39 we see in other galaxies so another clear signature, that the Milky Way is somewhat low in terms of CGM content. 08:29:49 Then the other point in terms of the Milky Way potentially being odd, is that the cold h one gas is also less than other galaxies and with this. I've started with it I'm 31 data because Chris talked did a very nice paper here showing you the red are sightlines 08:30:05 lines for em 31 and showing what we have for, I hope you can read this is this is column density he might not be able to depending on big your screen is vs impact parameter distance. 08:30:18 And then this below is covering traction versus distance. And so you can see these are the cost Halo results a great points, they're very high we'll focus on within 100 kilo per six. 08:30:29 So very high values for the h1. 08:30:32 And then, in column density and then I'll for em 31 very down this is the mentoring system. And then in terms of covering traction as well. The cost halos points are higher for the Milky Way. 08:30:46 You can think about the high velocity clouds that have a 37% covering fraction for comes greater than this. 08:30:53 But when you, we now know that this gas because this was a northern survey This is almost all gases within 10 kilo parsecs so that would be a point, maybe about here, and here. 08:31:05 So again, and when you think about within 10 kilo parsecs when you're looking at other galaxies within 10 kilo parsecs very often you could almost be looking at this depending on what you're looking at exactly and that data is very limited. 08:31:26 But in general, this is not a isolated problem if you look at the deep h1 surveys Halo gas etc. We are not finding it an extended CGM medium above tend to the 18 in column. 08:31:35 So it's very possible this is as equals zero problem in general and not just a milky way I'm 31 one. So this is something we can think about looking into more in the future, because these deep h1 surveys aren't still not finding this stuff that costs 08:31:50 halos is getting. 08:31:54 is getting. So in terms of the mass and the CGM not always been as significant, is this a generics equals zero problem is there an environment link, or is there still a problem with how we are comparing things that's possible we're just not don't have 08:32:08 it quite right in terms of how we're comparing being within the Milky Way and the local environment which has some velocity confusion problems we always need to deal with. 08:32:18 So, in the discussion afterwards if we want we can do a poll and what people think is potentially going on here. We'll see if people are interested in that. 08:32:28 Okay, I'm going to go on to the interaction of satellites with a CGM. And of course I have to show you this picture and I don't have to have an acknowledgement here because this is my old data which I still think is beautiful. 08:32:55 everyone. The management system the interaction of the management system with the Milky Way CGM This is a large management cloud small management cloud leading arm coming off here and the tail going off here. The clouds are moving in this direction, roughly, 08:32:58 right in this direction. 08:33:00 So, this is a very beautiful system in terms of studying how satellites loose or gases they interact with, with a CGM material and I actually only have this slide on this so we can talk about this more afterwards if you're interested, some of the data 08:33:16 we have that helps support what's going on with the ram pressure stripping the cloud interaction with the halo medium, each one cloud structure looking at head, tail codes. 08:33:31 This is, I met some of my work and also for at all the absorption lines I don't think Andy Fox was at this meeting but he's done beautiful work mapping the ionized gas distribution across the men link system. 08:33:40 And we find that there's a lot of mass presence, potentially, as well as a very high cross section, you can also then tell that there is some interaction with clouds with the halo medium is likely from from that work. 08:33:54 And then finally, from the simulations and particular LMC stripping simulations. This has worked by many are Salem, working with routine and besla, where you can see this with the observations the countries represent the stellar distribution and the gas 08:34:09 gases the shades. So you can see there's an offset between the gas, and the stars here, and this is a simulation where he's able to reproduce reproduce that offset of the gas from the stars with ram pressure stripping as the system plows through a milky 08:34:25 way Halo medium. So there's a lot we could talk about with this system but this is one where we're capturing it directly This is the process of how satellites lose their gas to a larger galaxy within the circumspect medium. 08:34:42 Okay, so then you can say what about the rest of them. So there's actually 119 dwarf galaxies now within two mega parsecs This is amazing. I mean, the number of dwarf galaxies in our local environment has increased substantially over the years and this 08:34:57 has been key in terms of understanding what those initial building blocks of galaxies look like, and understanding the missing satellites problem etc etc. 08:35:07 Understanding the missing satellites problem etc etc. But the other thing you can do with this is think about their gas content, and what is going on in terms of a satellite interaction with the halo medium. 08:35:15 And so this is something I did with Dan and research, a long time ago looked at the gas content of satellite galaxies relative to the Milky Way and I'm 31, but the time was right to do this again and others have done this as well but some rubbish. 08:35:32 Thinking back if you go way back people thought about this way, way back but now we have a huge set of satellites to think about this. And we can also think about okay what about the local group itself, what is a local group doing in terms of playing 08:35:45 a role. So this is showing you that distance to the Milky Way RM 31 whichever is actually closer. 08:35:53 And this is the variable radius blue is the Milky Way, and red is I'm 31. And so all of these open symbols represent non detections all of the field in symbols are detections. 08:36:06 And so what you can see is that within the variable radius of these galaxies. They're almost all non detections 80 of the 85 galaxies within the very old radio I am 31 of the Milky Way, do not have gas so there's a clear distant dependent mechanism potentially 08:36:23 potentially going on here to explain that fact right that we have all these galaxies are stripped or do not have gas any longer. And the ones that do have gas, these are largely more massive galaxies, these are the doors ellipticals of em 31 LMT SMC whether 08:36:41 you would even have these on the planets, these are very large Dorf galaxy. So those are the ones that are able to retain gas are largely the more massive satellites. 08:36:51 Just a quick zoom in on that pod just just shows you the names of all the satellites and shows you the wealth of data we have here, this this slope here this is due to the fact that we're using survey data that's the other reason to take this on again 08:37:04 we have deeper survey data, and this reduces this distance dependence with h1 mass that's why you see that line here of increasing limits. but all of the limits. 08:37:14 These are the lowest detected h1 masses. Right. And so we're at about 10 to the five. And these are the odd Dorf elliptical so almost all the limits except for just a couple are lower than any detected dwarf galaxy out there. 08:37:30 So then you can say okay this is a distant attempt dependent quenching mechanism, you can think of mechanisms that might cause that title forces, they're not strong enough at the large radio, of these dwarf galaxies including their pair galactic con and 08:37:44 their stellar distribution is not disturbed at all star formation stellar feedback, not on its own this some work by Emmerich at all and others have shown it's unlikely that they can quench from this alone. 08:37:57 And it's also not a distant dependent mechanism. Though there could be some link as a dork galaxies ghosts UFC gym the gas being compressed and star formation being triggered reorientation for the small ones. 08:38:11 And this is an important one to consider in the case of these doors because they are quite small, many of them, but the distance dependence immediately makes you wonder, okay but what is going on and consistent distance dependence. 08:38:24 This will be left to future surveys, do we actually see all Japan galaxies at much larger distances, then we can come back to bn ization, leading to the factory currently see for many of them at least. 08:38:39 And then as I'll talk about now ram pressure stripping the seems like the most likely mechanism in particular for the ones that are a little bit more massive So then the question is, is the CGM actually dense enough to do this to the dwarf galaxies, so 08:38:55 used to be in terms of thinking about the orbits of dwarf galaxies and especially around pressure stripping that there was only four dwarfs that we could do play this game with excluding them engineering system. 08:39:06 So, but now with Gaia, we have lots of proper motions, and we can get out orbit so this is Adrian price Wayland the models for this paper, where we calculated the halo density required at pair galactic Emperor instantaneous stripping so this is a very 08:39:21 simple estimate. 08:39:24 It's basically showing you, it has to be, it could be this dense but it could be even lower density right because you also are going to have some continuous stripping as a as a satellite to moving to the halo medium. 08:39:35 And we know that the halo medium is comfy, for instance, so this is a very simple estimate what Halo density would be required at para galactic confer instantaneous stripping. 08:39:46 And here you have that pair Galactica versus the halo density required. And so generally you're seeing a trend here right the lowest mass dwarf galaxies represented by the velocity dispersion are more only require very low Halo densities, where the more 08:40:02 massive doors require a bit higher Halo densities. What you can do is over plot the expectations for the halo density of the Milky Way and this comes from simulations. 08:40:13 What you have here the bread is the simulation of john at all. And this is, this has a massive we expect for the Milky Way at about 1.4 times 10 to the 12 solar masses and a variable radius going to 250 caliber six. 08:40:29 The blue is work that young worked on the foggy results and so this is a lower mass galaxy. It's at 4.9 times 10 to the 11, but it's useful to put on for comparison. 08:40:41 We're also showing here this is a very high resolution simulation that you get a wider spread in the types of densities you could potentially get with the higher resolution which was an interesting results in itself but not not something I'll talk about 08:40:56 here. But the bottom line in terms of stripping is that 80% are consistent with being stripped by a milky way Halo medium if you use the simulation that is more representative of the Milky Way the pig here, the vast majority could be stripped using this 08:41:12 simple calculation of what would we be required at para galactic and during its orbit. 08:41:20 Okay, so this is the satellites are important just for tracking the process and how the gas is stripped. And the other thing the satellites are important for is just telling us there is a halo medium out to larger Ada right so that we start to constrain 08:41:35 relative distribution of the halo medium with distance from the Milky Way. 08:41:42 But the other thing to consider right is that we are part of a group. Okay, so what is going on in terms of there being a local group Halo medium, and what role can that play, what can we learn about it from the satellites for instance and and also other 08:41:58 mechanisms although I'm going to let other people step in with with mentioning other mechanisms largely that we can sort out the group and Galaxy medium. 08:42:09 Okay, in terms of what we would expect for a local group Halo medium young showed this on Monday. This is a local group simulation of news at all. And I'm told that I had a speed collaboration with Martin spire and he said they were doing with Philip 08:42:25 Richter, and others I'm sure are doing simulations of local groups now so that is great because when I was surprised when I was looking into the simulations that were available. 08:42:35 I wasn't finding a lot later than this in terms of local group simulation but this does a nice job of showing you that, depending on the temperature the gas, you do expect this medium to extend between the galaxies and surrounding it, etc. 08:42:51 So you have to expect that this medium would also play a role in stripping dwarf galaxy so that's what we considered we considered. Do it does this extended local group medium play a potential role and stripping the dwarf galaxies as well. 08:43:06 This is the model that Adrian price Wayland set up for a paper where you have these are the visual radio of the Milky Way and I'm 31, and then all the dwarfs are shown by the symbols the detections and the non detections. 08:43:20 And then this gray line represents our local group surface that we use so this is representing a local group burial radius, and then we examine the relationship between gas content in this local group burial radius where we set zero as the surface, local 08:43:40 group surface or the local group veil radius. And so what you find is indeed when in this would be zero. So this would be the local groups surface here, so these are within the local group surface. 08:43:48 These are beyond in general what that local group surface finds is that you do find even more of the galaxies without gas or within that local group surface, and it's about the same number that detected. 08:44:01 So again I mean it's not a huge result at five verses at right in terms of it now and come to see more of the local group galaxies without gas, but it makes sense that you wouldn't have an additional quenching roll from that local group medium so it's 08:44:18 it's some evidence potentially that there is this local group medium that is also playing a role in stripping the satellites. So when tests is to consider what we see for other systems, do we see a group medium playing a role in general. 08:44:34 And when we compare things, the saga survey for instance, they're finding, they're serving galactic analogs, and they're finding that 108 of 127 satellites are 86% are star forming. 08:44:49 And for us, it's much, much lower right we have 29% star for me. So again, they don't quite have the data to look at where the ones that are in a group environment yet, and generally most of them are very clearly not at least in their early paper they 08:45:04 weren't, but this could potentially point that okay for some reason the Milky Way being in a group environment is providing an additional level of quenching. 08:45:14 And so that's why we have so many that are already quenched compared to what they're finding for other systems. 08:45:20 The other thing I wanted to mention, and that is the work though, in terms of thinking about access X ray absorption and so far there hasn't been any excess found along that local group access so in terms of of that result that's an interesting counter 08:45:36 to there being an abundant local group medium within the hot gas that's prob there. 08:45:43 And I have a student thinking about what you find for other systems this year she just started her work at Columbia and she's looking at what do we find for local spirals let's look at the gas content of local spiral, the satellites around local spirals 08:45:58 and see if we can distinguish if there's a difference between what we find for the Milky Way and the local group. 08:46:06 Okay, I'm. How much time do I have them. 08:46:11 Um, you have about, I would say you have 15 minutes up to, oh really yeah okay, that seems like too much but okay. 13 minutes. Yeah, well I can let it, I've been buzzing through stuff pretty quickly so I'm happy just to let it go to discussion but since 08:46:27 I do have a little bit more time I will say something about the insight into the magnetic field part. 08:46:34 So in terms of the insight into the magnetic field I wanted to mention some work by Avery Kim together with Susan Clark and looking at magnetically aligned h1 filaments going into the lower Halo us me Did you have a question. 08:46:49 Go ahead. 08:46:51 Sorry, I cannot sleep, that's okay you go ahead with the magnetic field thing. That's okay. Yeah. 08:46:58 Yeah, I know you've done a lot of work on this and I haven't referenced you so I. 08:47:04 So in terms of this what what I'm showing you here this is work. This was published in a paper peek at all that presented the Guelph age one survey, and this is Susan's art it's called the RHT analysis said it identifies that there are h1 film entry structures 08:47:22 across the sky, and it ends up that these h1 Elementary structures are aligned with the Galactic magnetic field so this is within our galaxy. So then what do we do in terms of going to the Halo. 08:47:35 Before I do that, I'll go ahead and show you the beautiful data we're working with where you can actually see even with your eyes at some of the structure is overall film entry This is the Gulf age one data set, it's fully publicly available I don't have 08:47:48 the website right here but if you search, alpha data, you'll see it'll be the first thing that comes up, and you can see some of those elementary structure even with your eyes and this map, what we're doing is we're scanning through and declination. 08:48:03 And so initially we went through part of the plane and now we're, we're coming from going looking overhead. And then we're going through the plane on the other side, and the different colors represent different velocity channels that have been included 08:48:17 in this particular data set, as shown here. 08:48:23 So this gives you an idea of the beautiful data, we're working with. And then in terms of thinking about the filaments and tracking it into the Halo, as, as we've already talked about we do have nuclear hydrogen gas extending into the halo so do those 08:48:41 features actually show some level of these h1 filaments, and then do those h1 filaments also track the magnetic field as you go up into the halo This is the idea behind this. 08:48:55 This is the plot that shows that what you see in terms of the local gas and the h1 filaments that it traces the plane of sky magnetic field and so this is showing you a plot that showing you the orientation of the magnetic field as determined from the 08:49:11 alignment of the h1 filaments, the white or the starlight polarization so you can see overall their, their angle is is tracing the same direction as these contours. 08:49:22 And then here below is the magnetic field orientation from plank. 08:49:27 And here you can see again that there's overall, they're following the main that the neutral hydrogen filaments are following the orientation of the magnetic field, and what Susan has done is taken this into CMB foreground world, heavily as well, given 08:49:41 that plank is normally dominated at high latitude, you can use the h1 filaments as a probe of what's going on with the magnetic field and foreground magnetic field removal. 08:49:53 In terms of trying to get that right for CMV experiments. 08:50:01 So what we've developed is a way to actually the hurt the initial analysis just as looking across the sky and finding overall alignment. What we've developed as a way to catalog these filaments as 3d structures because we do have that velocity information 08:50:15 available as well. And so looking overhead we find this local population so again if you're within about 10 kilometers per second, you're within you know you're close to the sun, you're in that layer of gas that's above or sun, but going beyond that, 08:50:31 you. We also see this peak here, and this represents filaments that are in an intermediate velocity cloud that's above us in particular, this is the IV spur, which has a distance constraint of about point three to 2.1 kilohertz six and these are showing 08:50:46 you some of these higher velocity filaments that we're seeing as we go into this IV spur. So this is exciting in terms of a potential way to probe the magnetic field as you go higher into the Halo. 08:51:01 So this, this is work we're working on right now but I wanted to mention that there's already a sign that we see this magnetic field going up into the Halo. 08:51:10 This is what I'm showing here, our diagrams, this is somewhat complicated but what you're seeing here I work from Penn of panel Polo at all in 2019, and these are stars at different distances. 08:51:23 And so the first group of stars is before both clouds second group of stars after just one cloud third group of stars through both and then you compare the starlight polarization angles for the stars and the different groups, and you find that there's 08:51:38 a clear contribution from the BBC of having aligned. Align dust screens within the intermediate velocity cloud that is affecting the starlight polarization in this most distinct group. 08:51:50 So this is clearly showing that there is signatures of a magnetic field going into at least the lower Halo we're talking within a few killer parsecs for these intermediate velocity clouds. 08:52:01 And there's also a very recent paper that correlated polarization data but the frequency and polarization data, looking towards Halo clouds you definitely saw that the polarization data was being affected as you look towards directions that had Halo clouds. 08:52:19 So this is exciting in terms of thinking about the Halo, and how it extends into the lower Halo and also maybe in local galaxy so as I showed you this before, this is a gal for data where I've highlighted some filaments within the small mentioned like 08:52:34 where we actually have some independent measurements of the magnetic field so we can do a test or these filaments at larger scales probing the magnetic fields structure. 08:52:47 And then this is important, there's evidence of Halo magnetic field already from the rotation measure studies young mentioned one of the recent ones. Nuclear Griff has said all has one in terms of leaning arm, and then Brian can refer you to other papers 08:53:00 as well. 08:53:02 Okay, so I'm going to end there I gave you a whirlwind tour of what the Milky Way tells us about the CGM I didn't expect to get through everything but I can feel that I had a lot of coffee this morning I've been talking pretty quickly. 08:53:14 So I think it would be best if we go to the panel now and your questions and see if we can get some more insight into what the Milky Way helps, tell us about the CGM. 08:53:25 Thank you Mary that was, that was great. 08:53:33 This the slack chat has been populating with a lot of comments, um, we are going to take a break until 10 o'clock to convene the panel, I should say. 08:53:40 That was a great talk, I made one, one mistake in the introduction, talking about your 2012 paper marry your review, I thought, I just was on that. And she, I'm fine giving her credit. 08:53:53 But as Ryan young. 08:53:58 Is there enough in this. 08:54:16 Ryan young Josh Pekin you yeah great review. All right, so, um, we're going to convene the panel at 10am so six minutes. 08:54:08 9am or whatever your time so 9am Mountain Time. Thank you. Yes, on the hour.