09:20:58 Okay, welcome back everybody Todd, can you hear me.
09:21:04 Are you back.
09:21:09 Yeah, I can hear you. Oh, great. Okay, can you just, I don't know what it just dropped out at the end of the talk so.
09:21:17 Excellent. Alright so and we have songs for the car is here. Hi such and wrong mon board ally, are you here can you get there you are.
09:21:28 You can go ahead and unmute if you like. And then, Glenn Rudy is here as well. Hi Gwen. Alright, so I have been looking at the Slack channel and I want to bring up the first subject which was mentioned by Evan Schneider but also one of the first things
09:21:44 Todd mentioned which is this idea of a cloudy versus a misty circle galactic medium and, in particular, you know, Evan suggested that this might be a fun exercise for the workshop to clarify exactly what we mean by cloudy versus misty when we asked those
09:22:06 questions do observers and theorists mean the same thing do theorists and theorists mean the same thing which I think is funny. And I think the answer is probably not.
09:22:16 But I want to take since our panel is a panel of expert observers, I want to get people's point of view on, you know, how do you think about this, with the observational data, how are you defining this are you looking at kind of cloud links line with.
09:22:31 Can you talk a little bit about the facets of the data that might actually be able to distinguish between, you know, a mist versus a cloud, and maybe some questions that you might pose to theorists.
09:22:45 I'll just jump in real quickly, in my mind, the pettiness of whatever it is you're looking at is part of it, explain what you mean by pettiness well you can just think of the image I had from Max's paper at the beginning on the one side you had all these
09:23:01 little very small scale droplets on the other side there is more of a smooth larger structure. And so, that's a kind of an intuitive. I mean, to be honest, I'm just following the theorists lead and trying to, you know, cloud shattering what does that
09:23:23 mean is it consistent with the data, but certainly with the Markarian to 31 outflow. We needed to have some kind of patching this, so that the ultraviolet light, get through.
09:23:35 And yet there was some sort of dusty outflow, which is where the broad absorption line teachers are imprinted on the data.
09:23:44 I guess maybe the word misty sort of conveys what's in my mind because it's a lot of droplets like a fog or something.
09:23:56 Maybe somebody else on the panel wants to weigh in on how you think about the structures.
09:24:01 So, I can quickly share just one or two slides, which I think maybe bear on this question a little bit.
09:24:11 So in some sense this is similar to some of the things that Todd to show this is from my own work at pirate ship now so we're looking at CGM absorption, 75 kilo parsecs within the variable radius of hydrogen sort of LCR galaxy.
09:24:25 And you can see the incredible complexity in the structure of these absorption lines and I completely agree with what Todd said about the resolution and Signal to Noise really mattering for being able to disentangle both the very complex structure of
09:24:39 the systems but also the sort of multi phase nature, you can see that the oxygen six looks completely different and structure from the somewhat lower ion phases.
09:24:49 But I think in particular we're talking about cloud sizes.
09:24:53 I would refer people back to Michael routes early work that Todd mentioned, and it actually one of the quasars in our sample is one of the quasars that Michael route used to look at one thing.
09:25:03 And so we can actually look directly in the CGM of this galaxy. If I can get my slides to advance.
09:25:11 Let me.
09:25:13 Pardon me. Sorry.
09:25:22 I'm
09:25:23 all right. And so this is an example where we can actually look at 400 parsecs scale resolution.
09:25:28 In the same CGM and we can see now if we can, we're not seeing what you're seeing we're seeing your, your slack and yeah.
09:25:36 Okay.
09:25:38 Pardon me. Thank you.
09:25:45 Did that work.
09:25:59 Perfect. Apologies. Okay, so if we look 400 parsecs away between these two different images of this Quasar.
09:25:56 What we can see now the black spectrum behind it is one image and the red colored is the higher Signal to Noise brighter image, and what we can see is actually the structure changes completely in these low ions oxygen six actually looks completely the
09:26:11 same across these two lines of sight.
09:26:15 And I think what that tells us is that these low ion phases just like Michael had concluded in his, his papers around in the sort of early 2000s late 1990s, is that you know these structures are very very small, whether that makes them a mist or a cloud,
09:26:31 I think, Maybe like unless we actually ascribe real physical meaning to that, like, and I think we're talking about shattering i mean i think that that's semantics unless we actually describe some like physical underlying
09:26:46 concept of where these clouds how these clouds form.
09:26:49 But I think you know just as Todd was showing the structures in these are coherent across this scale because we see that they occupied, essentially the same velocity window across this 400 parsecs scale.
09:27:03 And we see it in all of these different phases and so I think what that tells us is that they do have to have some sort of common origin.
09:27:11 Now I think in the case of this absorber. You know, this I believe is consistent with, you know what you might see piercing the Galactic wind we know that these galaxies drive out massive outflows.
09:27:23 And so maybe this is gas that's precipitating out of this outflow where you're seeing sort of a warmer more volume filling phase and six and you're seeing that sort of, maybe cooler or perhaps cooler or certainly, you know, less smooth structure in these
09:27:40 lower ions. But I think that that you know the simulations need to be able to reproduce things on on smaller than 400% scale if we want to be able to compare it to this kind of data, and the richness of data that do exist for CGM observation so I think
09:27:55 this is sort of, you know, similar to what what Todd was saying, but now seeing this exists, not just at the Milky Way and at lower retrofit but also in the hierarchy members.
09:28:12 So
09:28:12 maybe I can add a couple of words again, let me go when for old observational, I don't think it makes a lot of sense to distinguish between cloudy and misty, you can talk about cloud size, and let me actually try to show, if I may want actual example
09:28:28 of a cloud. Okay, which is in training in a galactic when.
09:28:34 If You can see my screen.
09:28:37 So this happens to be a sideline, which is penetrating through the from the bubble, and it's around 30 degree galactic latitude, it has a lot of access x rays and gamma rays, the longest sideline so we know there's a lot of podcasts, and along the gas
09:28:52 along the side and we also detect a lot of cool gas detectors and current to Silicon to Silicon three or even warmer guess carbon for this is one of the few sidelines where you actually have 21 centimeter mission detected along the sideline.
09:29:08 What we did actually to see how big the gas cloud is, we did a very large GBT mapping around the cloud. And actually we found that the typical size of such clouds are around hundreds of parsing modular being smearing here okay that I still have to do
09:29:24 do and what another interesting thing along the satellite. Was that not only we found that object we also found some other companion clouds, which also have similar kinematic velocity, but and similar size so hundreds of projects scale, which are kind
09:29:39 of spread around the same cloud. So, this might be a sort of an example of where the cloud is getting shattered by the hot galactic wind.
09:29:50 So it raises the question of how how long can they even survive. And do you see similar things in in the CGM where, you know, a cool guest thought after a few years might just disappear.
09:30:02 Do you call it, do you call it misty, or cloudy is again depends is on more physics them observation.
09:30:13 Thank you. So, so I see a couple hands up and as long as assuming that they pertain to this discussion. I stopped paying him first so pain do something relevant to say
09:30:28 yes. So, um, so although I'm a theorist, I'm going to propose a very observational definition for cloudy and misty, which is just that, if you're taking a column density, saying absorption spectra and you intersect, many clouds, say 10s or hundreds, you
09:30:43 know, at a level where something like the central limit theorem will kick in, then that's misty, whereas if you intersect of border one or two. There is a cloud then I would call it cloudy and so are you defining a cloud for an observer who just have
09:30:59 a single, you know, one dimensional line of sight, are you finding the cloud is like a component.
09:31:15 Um, so, I would say, so suppose you you observe a large Doppler parameter, if that's internal turbulence for a single, you know that if that's true turbulence, I would define that as a single cloud, if, if you actually have infinite resolution and it
09:31:24 breaks up into lots of small things that I would sort of define that to miss so it's kind of relevant to what Todd was talking about so you know something where you have a very high area covering fraction, but a low volume feeling fraction I would call
09:31:41 it a mist.
09:31:42 Yeah. So that's a strong man that people can kick around.
09:31:48 Thank you for that and then I see another hand Norbert and then I'm going to get back to the panel, especially want to hear from Sanjay but Norbert did you have something to add to this.
09:31:58 Yeah, I was actually wondering how much this discussion could be informed informed by the observations that we have in the course of cluster so galaxies groups and giant elliptical galaxies where we actually see some of these multi-phase cool and cold
09:32:17 gas emission.
09:32:18 So in a, in a the systems we see CEO admitting cold clouds that are usually co spatial with war mercy to a meeting, hundred can be nice more diffuse gas or thousand Kelvin, Kelvin phase.
09:32:38 And these are usually co spatial with age alpha filaments. And these are co spatial with cooling X ray anything gas. So,
09:32:49 my picture of this is that it is gospel out reading.
09:33:01 Sanjay see you nodding your head, did you have anything you wanted to add to this.
09:33:06 Oh, no I mean I I totally agree with the idea that, although we have a sideline and we do not have sort of a full view of what's going on. We do have a long line of sight.
09:33:18 So it's kind of does tell us something about the borrowing feeling and and i agree with paying that we could probably do that, put that number of components over us.
09:33:32 Probably philosophy spread could be something close to a mist versus a cloud.
09:33:38 Yeah, it's kind of sometimes hard to say.
09:33:43 If they are co spatial in my, in my mind, I feel like, even though we have a concept of Mr.
09:33:51 We have a sight line that goes through hundreds of hundreds of color parsecs so the idea of Miss go spatial but sometimes it's very difficult for us to really realize that whether we are seeing stuff in front of the galaxy of behind her.
09:34:07 And then the middle.
09:34:08 So, yeah, now I feel like I'm a little bit of pressure because people have shown such wonderful data about a multiple components showing up on different sidelines so.
09:34:21 So I want to also show is something which might not be related, but just for, you know, to add to the discussion.
09:34:32 So I only show a sideline from the survey of cos burst which is led by Tim. So, these are sidelines to the CGM of Starburst galaxies. So of course,
09:34:47 because of that, we are kind of very interested in seeing what's going on in the star star burst, they're not that many in Star Wars galaxy with the background plays out in the nearby universe.
09:34:59 So, data is bars, but again, here we do see that, just to since everybody knows absorption spectrum I don't want to discuss a whole lot with different species here, but all I'm just trying to show that here I see three different components, showing up
09:35:18 in different transitions oxygen six is seen in all the transit on the different components, but other transitions sort of fade out so you clearly you can see that a warmer component in a sort of intermediate component Nicola component, in my mind, there
09:35:53 is no reason that this has to be exactly go spatial, it could be different parts of the outflow which is what I think. So in this in this approach I think it's more like a different clouds versus like a completely
09:35:52 covers the galaxy, but I would like to hear what people have been seeing in their data and simulations.
09:36:03 I think that actually leads nicely into what I want to talk about next but first I want to call on Joel and then Mary who both have their hands up who sound like they want to say something about this discussion Joel, go ahead.
09:36:15 Okay.
09:36:15 Um, so, you know, an exercise I did I think that stocky and friends also did something similar with different data sets, is that you can look at say the typical cloud that one finds long line of sight, through a halo, and you can assume crush equilibrium
09:36:37 and then you get a size.
09:36:41 And then you can estimate how many of these clouds you need a long line of sight. What's the sizes. You can also do it by noticing that there are multiple components.
09:36:52 And then 10% of your cases you don't see absorption lines.
09:36:59 And that leads to approximately the same number of components along the line of sight about 2.2 2.4.
09:37:08 And you know what the columns are.
09:37:11 And so once again you can estimate the number of clouds and the size of clouds the size of a cloud is one to 200 parsecs and you have a lot of water a million in the Halo.
09:37:31 And one of the other thing. Now, this is a cloud that one is fitting for, but you have associations of cloud says you can just because you have a cloud in say one of the high velocity cloud streams around the Milky Way doesn't mean you don't have lots
09:37:54 of others nearby.
09:37:57 And so,
09:38:00 this that accumulation is, or that association is larger than order of magnitude larger.
09:38:10 The other thing I just wanted to mention, because it hadn't gotten mentioned is that if you take a cloud and let it fall through the Halo, calculate what the momentum and energy flux on to the cloud is from ram pressure.
09:38:30 It's, it's comparable if not greater than the energy coming in from photo ionization and gray and company, several years back, asked the question, if this goes into turbulence the turbulence two K's into heat.
09:38:47 How does it affect the ionization structure of the clouds.
09:38:53 And it's, it's a rather interesting results gives you, it's important new
09:39:00 heating mechanism that would naturally occur as these clouds fall.
09:39:06 It leads to a broader range of ionization states and you might get just from photo ionization. It's a paperwork looking over and deciding whether or not it's a piece of physics that should be included in to the analysis of these data.
09:39:24 Okay, that was it. Thanks, Mary, try to be brief but if you're considering the dentist dentist gas and the halo to fall into this criteria of representing the shattering or the clumping then you can look to the high resolution h1 observations of HPC is
09:39:44 in our Halo right because what you see is these large extended structures either single dish observations when you do the point the Vla at these your largely you do see clumping but you're resolving out the vast majority of the mission as well indicating,
09:39:58 you have a comfy cloud but it's very clearly in this extended of lobe of mutual idea mission so you're not breaking it up into Oh look it's all like little shattered clouds it's just part of one giant complex which does have structure within it.
09:40:15 Yeah, thank you thank you and that actually, that's really, that leads to this other question and the their various themes of questions that are along the lines of what Todd said early on in his talk is our observers, getting behind by not emphasizing
09:40:31 the details of their data. Right. And so what what the question I want to pose to the panel is, you know, how can we do better at emphasizing, you know the details of our data, well not getting kind of bogged down so much in the limitations, but how can
09:40:50 we be honest about the limitations and in along those lines on the, on the slack. There's various slack threads I think gorilla chatter job, made a really interesting comment about, is it possible to do profile analyses of lower resolution resolution
09:41:06 data that actually include all the possibilities that are made apparent by the high resolution data like it could you do this in a kind of statistical way that doesn't lead to infinite solutions.
09:41:17 And that kind of blew my mind but then you know, down, down in the discussion list, people are talking about the kind of required resolution that you need to actually resolve the component structure and x made a comment that one kilometer per second is
09:41:31 overkill maybe 2.5 kilometers per second is enough. So I'm interested from our panel of experts observers, you know, what do you think about our data the limitations of the data, all this information.
09:41:45 Well I guess I'll go ahead and make a quick comment that the resolution you require of course depends on what you're looking at. So if you're looking at molecular gas which you can see an absorption, quite a few different molecules that probably does
09:41:59 require exquisite resolution. And I've done quite a bit of work with Jenkins on carbon one over the years and the Milky Way.
09:42:09 Carbon one also benefits from very good resolution. So it really depends on what you're doing now maybe if you're looking at the hot gas. Maybe if we're for X ray spectroscopy, you don't need it, and it's just smooth volume filling stuff, but that's why
09:42:25 I wanted to be sure to show that oxygen six at the end.
09:42:30 When might assume that that should be smooth at high resolution and yet it resolves and so maybe we should be careful about not making too many assumptions.
09:42:40 I ran out of time but it's interesting that the h1 lines in that same e 140, each spectrum.
09:42:48 Do not resolve into more components at the higher resolution, they stay smooth. It's just the metals that seem to be showing more and more component structure.
09:43:00 So that's a quick comment on resolution and so you know what I'm interested in.
09:43:06 Because it's the only future I have is what you can do from the ground, because, I mean, they're trying to keep Hubble going for a long time.
09:43:18 But, you know, things are delicate up their their old instruments and especially UV spectra graphs have a lot of problems. So, can ground based instruments, start to move toward higher spectrum.
09:43:35 I think I mean, I'm sure you can. I don't know how expensive it is or, in which, which shall spectrograph can do that but that's, that's one way to go forward is to get better spectral resolution from the ground.
09:43:49 I'm actually I'm interested to hear from Oh, it sounds like Rama wants to say something and I'm also interested to hear from Gwen on this issue too, especially the idea of, you know, emphasizing how what we're missing from the lack of resolution or something
09:44:03 okay anyway.
09:44:05 Let me give a different perspective, I think we're asking the wrong people.
09:44:11 Because we can stare at millions of Quasar spectra with best signal tonight. We don't actually know how many calls there actually is on the sky, we don't know where they are along the line of sight, period.
09:44:23 We will not know.
09:44:26 We happen to be living in a in an age where we have fantastic simulations now be a choice simulation the fog assimilation the fire simulation, which are now focusing on extremely high resolution CGM simulations right, we should be asking the simulators,
09:44:41 to do it the simple experiment, you know, have a set of different distribution of clouds, or whatnot where they are, create X number of spectra with different resolution and see how it stacks up, like we should be asking a question like given let's say
09:44:59 a cloud mass and a halo mass, what is the probability that you will have spatial and keener medical hands of each one and or six etc. So, we probably need to address this question in that direction.
09:45:17 That is a big step right now.
09:45:19 Yeah, and I don't know that anybody's done a study of synthetic spectroscopy through idealised simulations, which would be very exciting.
09:45:30 So I'll, I'll jump in here. Um, I agree that a lot can be learned by looking into these simulations, but I would caution against the idea that that's the only way we can learn something about this.
09:45:41 because while I agree that we don't know.
09:45:45 You know, what exactly is hidden underneath. You know, the finite resolution of our data and so forth. These data do represent what exists in the real universe, and none of the simulations do yet, which I don't think is an insult in the slightest to the
09:46:00 theorists, I think we're learning quite a lot from these simulations, but at the end of the day I think we have to do both in terms of what's missing and the data.
09:46:10 I won't in any way claim that the you know the data that I have are perfect and that there's nothing underneath underneath them that's that's hidden, but I think when we look very carefully into the structure of this, Miss store clouds or whatever we
09:46:35 to call them in the heritage of the universe, we see that there are extremely small structures, but they are extraordinarily well aligned across multiple ionization stages. So we see the same structure in the low ion phases as we see in the higher I on pages and it's only when we get up
09:46:42 and it's only when we get up to oxygen six that we see a very, very different structure. These are aligned within a you know like within a few kilometers per second, probably more precisely, across these different phases.
09:46:52 They of course change in their competency ratios by an enormous amount so we see strong differences and ionization phase over changes I have a handful of Congress with 10s of kilometers per second.
09:47:03 So we see enormous complexity in the CGM, but I I don't understand how you would possibly have, you know, a cloud or some structure a filament or something like this that's separated or stretched over 100 kilo parsecs where you see that level of alignment
09:47:20 and velocity, and also you see a consistent velocity with to the profile that's consistent with some measure of temperature and turbulence even when measured across a variety of ion phases that have different masses so you can actually try and disentangle
09:47:34 that idea.
09:47:36 So I, you know, I, in some sense, the data are more complicated but in other sense they may be simpler they may be pointing to this this relatively simple picture so even if they're complex.
09:47:48 So I think that that's important and I should say that this is all consistent also with, you know, extremely careful modeling that has been done by several groups now.
09:47:58 I really want to highlight Ferrari's very, sort of, sort of, in my view, some of the first look at this in in sort of CGM style data is 2019 papers really beautiful about looking at the multi component structure and the abundances, and densities that
09:48:13 you can pull out by analyzing each of these components separately.
09:48:17 I think that kind of work is going to be really important to really pull out what we can from these data, but I agree that you know at cost resolution, one has to be careful you can find, you know, increasing line with as a function of ionization potential
09:48:30 This is something that we're seeing and cubs, I'd be happy to talk more about at some point.
09:48:34 This is work that's being led by Tom Cooper at Carnegie as well as far as a heady at Carnegie.
09:48:41 So you know, I think the great thing is I think we have these amazing data and they really are telling us critical information about the structure of gas within the circle galactic medium, and what that tells us about galaxy evolution and so you know
09:48:53 think this is a great opportunity to really try and confront what scene and simulations like we know that even the best simulations aren't yet converging right so these, these very very high resolution simulations are not yet converged in terms of the
09:49:07 structure of the CGM if they run it at twice the resolution, they see smaller clouds still, and I believe that's a true statement across all simulations, but please correct me if I'm wrong about about someone's work.
09:49:17 So, you know, I think, I think we still both have a lot of pushing to do in terms of the theoretical community as well as the observational community.
09:49:25 Speaking of fat sorry, whose hand is up, sorry you want to unmute and say something to add to that, oh yeah, thanks Glenn. So, just to echo grants point I think there is definitely a room where we as observers can make progress, it's not all hopeless
09:49:42 even if we are, you know, in some ways, falling a little behind theorist I think
09:49:49 some of the ways that we can make progress in the future for instance is to move beyond just this single characterization of, you know, just a cloud sighs and try to, you know, with careful modeling move one step further and try to say, try to derive
09:50:08 some kind of distribution of cloud sizes from our observation, this is of course not, not easy. So those who have who have done, you know, careful modeling of doesn't profiles can attest but you know even if he just tried to do a simple component the
09:50:34 decomposition of your profiles and try to model them carefully, not by matching, not just by matching language but also by matching. Not just wear matching velocity centers, but also matching the line which you can clearly see the clouds that you used
09:50:41 you used to think, are killer parsing across already strings 200 parsecs scales and. And also if you do this, if you do your modeling, you see that a non negligible, probability of your clouds are on 10s of parse it scales are smaller and he's also pertains
09:50:56 to pangs point earlier, we don't know yet if we have any smaller clouds in a Patek scales. Cloud perhaps and, if so, what that means in terms of this
09:51:10 clouds. vs. vs mist paradigm, but I think one of the best ways forward in terms of this discussion is to try to figure out observational, what is the distribution of cloud sizes in in the CGM.
09:51:27 Thank you. Yeah, and I think one of the things that Todd and others showed showed slides.
09:51:33 You know, maybe this will get the theorists to appreciate that you know the richness of the data themselves and so, you know, I think generally observers do report this but you know how do we get through the theorists that there's more than just those
09:51:47 bulk column densities maybe today we've made some headway on that.
09:51:51 Okay, so the last subject I want to make sure we address because this is one of the top rated comments from last week which we punted to this week, and then a few people have mentioned it, including Todd and Greg Brian on the Slack channel is this idea
09:52:05 and Joel Bregman just now.
09:52:08 This idea of pressure equilibrium and and and just that the simple kind of bulk models that you do with photo ionization and thermal equilibrium.
09:52:21 You know yield orders of magnitude off from the kind of low pressures are high pressures that you need in the very cold clouds.
09:52:29 The clouds are under pressurized that is by a lot, even when you do the detailed modeling like Carl has my high hazard Meyer fairies a heat he has done and severe it sounds like has also done.
09:52:42 I think you still get you know this this mismatch that things don't look like they're in pressure equilibrium with the hot face so I just want to get people on the panel to talk about this.
09:52:52 Do we favor solutions that actually just add in another thermal phase, or do we favor, you know, non thermal solutions. What let's, I'd love to get some opinions on this
09:53:05 Well, I'll start I guess I'm feeling kind of bad that I might have derailed this panel with the misty versus cloudy question, but you know it's really Max and things fall because they wrote the paper with that title so I'll just pass blank because that's
09:53:20 what we do in the US these days. But what I'm trying to learn is are there ways that are even if their observations that we haven't done. Are there ways that we can discriminate between one theoretical possibility, another and we you know we've been hearing
09:53:41 hearing about this precipitation or cold clouds that form in situ or that you know what, what are the signatures of these different interesting physical processes are, can we find a way to make progress on understanding the certain galactic gas so I don't
09:54:05 know the answers but I hope I made at least somewhat of a case for observations having a lot of information that that might help out but maybe, I don't know, it might be years away that there's we'll have to comment on, you know, how realistic, an idealized
09:54:25 simulation is for comparison to observations or something like that but that that's what I hope we're all driving towards ultimately.
09:54:36 Is there anybody else on the panel that wants to comment on on pressure equilibrium in particular otherwise I'm gonna go to the hands.
09:54:45 Okay, I think the only thing that'll say is that, you know, it is often the case that it's challenging to make real detailed measurements of the hot phase as well as a cooler phase within the same Halo like this is perhaps possible in, you know, X ray
09:55:01 emitting places that have X ray emitting gas and also have a probe of cooler gas in some way. It's certainly not really possible at high Z, but we do see this oh six that appears to be somewhat more volume filling but it would be very challenging to say
09:55:15 much about that oxygen six because it's not detected and a lot of, you know, and a lot of other gas.
09:55:21 And so I think it's hard to understand whether that's that could be an equilibrium, because understanding what the actual density and temperature of that oxygen sixes I think would be would be a challenging, a challenging beat basically for the data.
09:55:36 But I do think it's an interesting point.
09:55:39 So I'm going to call on Jonathan.
09:55:42 Stern, whose hand has been up and I think I know that he has something valuable to add to this, Jonathan.
09:55:50 Oh, we can't hear you though.
09:55:53 Try taking off your headphones, we can't hear you talking into your computer or something.
09:56:01 cannot hear you at all. All right, Jonathan is going to sort out his audio issues, and I'm going to go to Africa, who has her hand up frica.
09:56:11 Yes, I hope you can hear me. I just wanted to say that we have some in our simulations, which includes magnetic fields, we find that the.
09:56:25 So I compared the ones that had no magnetic fields to those that did, and the pressure is much smoother in the ones that does and it tends to be the cool gas that is that has the highest magnetic pressure so that brings them back into equilibrium.
09:56:43 So it just, I mean, obviously we don't resolve basic skills and stuff so I mean it's. This is what we find on certain skills and beyond. In our cosmological simulations.
09:56:57 Thank you. Yeah, it's been my impression from some of the recent literature and we'll hear more about non thermal processes, next week, that you know the simulations at least favor the non thermal solutions for forgetting to pressure balance in the circle
09:57:13 galactic media but I'm not so sure about the observations. All right, Jonathan sounds like your sound is back. Yes. Can you hear me now.
09:57:21 Good. Excellent. Sorry about that. Yeah, so three comments on potentially equilibrium. So one.
09:57:27 Yes, we should always take into account the fact that possibly the highlands come up for larger scales than the low ions okay and therefore they come from regions where the pressures of lower in one way we can see evidence for this is if we look at the
09:57:43 distribution, the column book versus impact Bama do have different ions. They look very different between oh six, and the lions, okay so that all I don't know six kind of rises very quickly at the video and then it flattens out a little islands kind of
09:57:58 rise all the way in work. So if you do project this you see that equity that there's a lot of oh six coming from larger scales, then the low is because that's kind of one direct way to say that the oh six has to come from a region where the guest has
09:58:14 push. That's the first come second comment is, we see huge velocities in these in these a in these absorb bills. Okay, so that's either turbulence or some bulk motions, okay and therefore the pressure of this lab pressure with the turbulent pressure must
09:58:32 be taken to account when we're doing family Coulibaly, if you look at a break. So, must be included in the equilibrium of the pressures right you have this lamp budget.
09:58:41 If you see you know 60 calendar per second turbulence and you expect comparable variances in the film and pleasure, okay if you can cover that similar push.
09:58:52 That's the second. A, and the third comment I have is in low mass halos.
09:58:58 I don't think there's any kind of uniform hot gas which enforces pushing for liberal okay the cooling times are very short. You know my fellows, it's very hard to avoid this, and then there's nothing enforcing pressure, we live in actually also in the
09:59:13 simulations we see huge ranges of a huge range of pressures in the CGI because we don't really expect even pressure when we see this in fire we see there's a paper by Raymond Simon's I inform you about this.
09:59:28 Okay, so this kind of.
09:59:32 We want this comparison to push like whatever is a good thing to do because it's kind of a zero older model but we have to kind of keep in mind the bills lots of caveats and lots of things we don't expect even without assuming what smart people think
09:59:44 about like a magnetic fields and the cosmic rays, even before that it's parliament. Yeah. Thank you, Jonathan.
09:59:51 Okay so, so we're getting to the hour it's 959. I want to allow one more person near, you've had your hand up so I'll let you talk about pressure equilibrium assuming, those of you who have your hands up that I haven't been able to get to you, please
10:00:06 go to the slack. This is where a lot of asynchronous discussion is going to happen so let's wrap up with a comment from near and then anything a panelists might have to say about pressure equilibrium, and then also all head over to the slack.
10:00:19 For this animated discussion will have more discussion time all week long.
10:00:24 Hi. Thanks Thanks so much.
10:00:26 It's really great. So I guess one question and then one comment.
10:00:30 I was wondering whether or what the evidence was or what we think about pressure equilibrium versus non equilibrium at high redshift say redshift you know two or or so, and you know obviously I think a lot about influencing code streams, those red shifts
10:00:46 and I guess we'll hear more about that during week six but I will make one comment that, at least in so far as our studies have called influence streams go.
10:00:56 What we do find is since the streams are flowing at influencing at such supersonic speeds compared to their own sound speed. You'll often find that locally the streams are outside of pressure equilibrium at a given Halo centric distance, because they
10:01:11 just haven't managed to a given Lagrangian food element has not yet managed to regain the pressure balance so it looks as though it has lower pressure, just because it came from a lower pressure medium and it hasn't yet regained its pressure balance.
10:01:25 So with that might also be an issue that we have to account for in addition to all the non thermal components, etc. Just very supersonic motions and it takes time to regain pressure balance.
10:01:38 So when did you see anything to add about high redshift in particular I know you're the highest redshift CGM observer, I know.
10:01:46 Well, I think the one thing I can comment is that we can measure pretty clearly actually the, the temperature and in terms of internal non thermal broadening of absorption lines, individual structures maybe these missed components that pain is talking
10:02:01 about.
10:02:02 And so we can, we can say something in detail about the internal motions of atoms and ions within, within these structures, and then we can also say something about at least you know the projected both flow motions of these particles through, through
10:02:20 the Halo.
10:02:22 I don't think we can say what else is in the halo at high regift I think this is one of the really big challenges.
10:02:27 Certainly extra telescopes are not yet capable of telling us if there's a hot gas there and I think that that would be very interesting of course to many of the simulators as well as the observers.
10:02:37 But I, but I do think that there's a lot left on the table in terms of understanding this like what is driving that internal motions inside these clouds as well as the temperatures that we measure which shows a lot of actually intermediate temperature
10:02:50 gas that should cool extraordinarily quickly. And so, you know, I think there's there is some interesting stuff there and I will point people towards the the turbulence channel, which we're talking about some of these topics on so if people are interested,
10:03:04 come join us on the turbulence Slack channel.
10:03:07 Yes, and non thermal week next week we'll have a lot of time to feature that conversation and talk more about turbulence okay it is now 1003, I've run wildly over time.
10:03:18 But I want to thank in particular our keynote speaker, Todd trip, and our expert panel, give everybody a round of applause. again, us use your emojis.
10:03:30 Thank you so much for making this so interactive please head to the slack for asynchronous discussion. Tomorrow we have four tutorials, with ample time for discussion after each, in case you want to dive into this more I know that this conversation will
10:03:43 be ongoing all week I really hope so. So in the meantime everybody have a great day and see you tomorrow morning.