09:04:45 Hello. 09:05:01 Okay. It is 905, so we will get started with the discussion. 09:05:09 First of all, yeah, Ellen, wonderful presentation. Thank you for very much I think you you covered it covered a lot of really good content and, and, in my opinion, it wasn't too high level. 09:05:21 So I really appreciate that. 09:05:24 Cameron you're very smart. 09:05:26 I don't know about that. I do what I can. I do what I can here and there, but, uh, so I would love to introduce our panel as well as Ellen to address some of the questions I encourage I know there are a couple of hands raised. 09:05:41 Let's try to at least initially right questions into the slack, and I'll try and pull them from there. 09:05:50 Just to make sure everyone has an ability to ask questions and it isn't just dominated by whoever's first in line with their hand up, but. 09:05:59 So our panel is made up of, of course Ellen's Wible, we also have Aaron better, who's joining us from Chicago Blakeslee Burkhardt who's here from Rutgers Phil Hopkins from Caltech Christoph Fromer from Potsdam and was my fifth Oh, young Hey john from 09:06:21 CCA. I believe is here, I haven't seen his video but presumably is also. Oh yes, There he is. Okay. Excellent. 09:06:29 So awesome questions a lot of really good discussion in the, in the slack. And I guess one that was getting a lot of attention and perhaps this is great because we have some new mattresses here as well. 09:06:42 So, with the bottleneck process that was being described by Ellen and, and the fact that you really need to resolve the structures of the individual clouds as they're being accelerated and heated in the process that you described. 09:06:57 It seems like computational simulations may be able to get this but may not be able to resolve these structures. Do you have any suggestions for ways in which we could implement a sub grid model or something like that, to be able to capture this and what 09:07:12 that might reflect on the overall behavior of of the CGM. 09:07:16 So whoever of the panel wants to kind of comment on this or Ellen, of course, wants to comment this I welcome them to do so. 09:07:26 I'd love to hear what the panel has to say that this vexatious question. 09:07:36 Oh, maybe I can start. I think these bottlenecks are fantastic problems. 09:07:41 And I do think that that I think we've just scratched the surface there. So what we should probably definitely do in the next sort of generation of hydrodynamic models to also couple, the outfit fluid to the cosmic rays because if you don't do this and 09:07:56 and if you assume the steady state of flux, then you sort of assume that a cosmic rays are moving at at the outfield speed and that may not be always the case in the second partition so if you actually the same time model the growth and the damping of 09:08:11 the waves, then you can actually model situation we have super affiliate streaming. But I think the real progress and speed will come about, but we pick simulations they actually model from first principles, the streaming cosmic rays and the various standing 09:08:28 process sees where you will be able to study in detail what the actual sort of microscopic physics does. And then by course crane depicts simulations, we will possibly be able to have some proper closures, that we can implement in this large scale hydrodynamic 09:08:43 models and make some real progress there. 09:08:48 It's a lot of work ahead of us. 09:08:55 Yeah, I would just, if I can just add a. I completely agree I think with what Christophe said and, you know, as somebody who came at this from the galaxy side, not from the plasma physics side. 09:09:05 You know I've been struck. 09:09:07 As I've you know learned more about the literature, how big the gap in scales is still, you know, and how relatively little work there's been I think there's been some interesting advances on hybrid MHD pick methods that might make it more possible to 09:09:23 actually probe. 09:09:39 You know the scattering processes in detail but you know even the sort of simplest, you know scatter off of turbulent fluctuations models still have enormously large uncertainties in what the scattering rate would be that I think can really only be addressed 09:09:40 with those kinds of calculations. 09:09:44 Yeah, I often think of this article and sell its way of doing kinetic simulations. 09:09:53 Thank you. Oh, sorry Blakeslee Go ahead. I was just gonna say I often think of the disparity and scales in in problems surrounding cosmic ray acceleration and diffusion to star formation right so you've got you know sub Solar System scale physics connected 09:10:12 in some way, also to like killer parsecs scale physics, right so in star formation, you have to deal with this huge range of scales as well, so it's very difficult to connect all of those things so it's often done in this piecemeal peace wise kind of 09:10:28 way we're in some cases you'll use you know the pic simulations to study the details of the diffusion, and then also you need to somehow figure out how you could connect what you learned there to how cosmic rays are moving on, on scales of galaxies. 09:10:46 So there's some interesting analogies there are there. 09:10:50 And forgive my ignorance on this topic, are there simulations that incorporate the bottleneck effects, thus far, either on cosmological scales like some of the work in the fire collaboration recently, or in more idealized simulations of like a chunk of 09:11:09 the CGM or like idealized galaxies isolated galaxies are people incorporating these, these effects in any capacity or has there been an attempt at doing a subgroup model. 09:11:22 Well, I shouldn't speak for Chad I hope he can speak. I hope you won't hesitate to correct me if I'm wrong, but. 09:11:32 So I think, you know, if the basic bottleneck. 09:11:34 If the basic bottleneck physics is right, and I completely agree that that it demands validation by by some kind of kinetic simulation to see how you know how the waves are excited what you know what the outcome is I you know I think because the growth 09:11:53 rates and damping rates for the waves tend to be kind of fast on astrophysical timescales. 09:11:59 You know if there is an equilibrium situation growth balances damping, you know you would think that we would find it. 09:12:04 But anyway, this you know if we can validate this picture then the sort of thing you could do with Chad's simulations of a clumpy medium is there is an average momentum deposition rate that comes out of that which I kind of flashed up quickly. 09:12:20 And so, you know, one could say well if you have, you know, if you have a Colombian medium with such and such a filling factor and, and so on. This is how much momentum the cosmic rays will deposit. 09:12:31 This is how much energy the cosmic rays will will deposit and that that might be a way away forward. 09:12:39 I don't know, I don't know if Chad wants to say anything. 09:12:46 Yeah, Chad, feel free to chime in here. 09:12:49 Okay. Yeah, well I would just just add in something that you know we also tried to quantify like how cosmic rays sample their environment, right, like they spend most of their time in the diffuse gas or do they actually penetrate into clouds and we tried 09:13:03 to quantify that. And I think that's something really important that you know you're, you're not going to be able to find very easily in cosmological simulations where you can't resolve these small scale structures. 09:13:16 So I think that is really a. 09:13:29 That's kind of a critical need for these like mezzo scale simulations where you're looking at, you know, highly resolved multi-phase gas and we're finding that, you know, it depends as well on the magnetic field strength so maybe this is huge motivation 09:13:33 for people to try to constrain the, you know, plasma beta and the CGM but whether cosmic rays penetrate clouds or kind of squeak through the cracks, is something that you're only going to find in these highly resolve simulations, and it depends on the 09:13:42 medic fields strength and just say one more thing which I think might address Kristof's point. 09:13:54 So the simulations that I showed of Chad's their authentic streaming was not assumed the streaming velocity was calculated using a balance of growth and damping so they were formerly in various dependencies of though Hopkins papers that give convenient 09:14:14 that we've also checked. And, yeah, you don't have to assume alpha and extremely, you can adjust the streaming rate to just respond to absolutely but but, to some extent, the alpha waves are being excited and then as a function of space and time and ideally 09:14:32 ideally you would like to solve 40 level of alpha waves that could find the cause of research consistently and I think the way forward is to sort of incorporate this and I think it's not too difficult, instead of two partial differential equations simply 09:14:45 have a system of for partial differential equations that are then making up a hyperbolic system and we all know how to solve this because this is what we love and do and Galaxy information so I think that is not too difficult, I would say, and however 09:14:58 I would maybe put the emphasis little bit more on the sort of cosmic rays streaming so they have been to cosmic ray instabilities found previously, I mean one actually buy raffle cars run peers. 09:15:11 This was the resonant instability that Ellen and also talked about. Then there's not a one phone back Tony Bell about 16 years ago, which applies to superabundance and in fact that instability really is essential for increasing as Kettering rate confining 09:15:29 cosmic rays to the shocks and making sure acceleration possible. And just very recently one amateur lobby found a third instability. So just looking at smaller scales, it turns out there is yet another instability instability means you excited waves and 09:15:46 waves minions kind of particles, and that has a lot of consequences on how cosmic rays are confined. And I think as we keep working on this stuff we will find more and more of these phenomena. 09:16:00 And I think there's no shortage of instabilities, and the more instabilities they are, the more possibilities there are two ways to go to could find cosmic rays. 09:16:09 I think it's very exciting times these days. I agree with you in this you know this kind of an arms race because people are finding new damping mechanisms to 09:16:20 see who's gonna win. 09:16:26 So, um, earlier in your talk, you were showing the relative magnetic field strengths that were required to kind of amplify this effect or not and it seems somewhere in the one to 10 micro Gauss magnetic field strength to, kind of, enhance maximally enhance 09:16:46 this effect. And then, as was pointed out in in slack recently. The a pod image of the day yesterday was the Galactic magnetic field image with the changes survey, which I thought was really apropos. 09:17:04 Do we have, but throughout the halo Do we have and again forgive my ignorance on the topic, do we have very good constraints on the magnetic field strength both of the both magnetic field strength as well as individual clouds I know, Frankie Vandenberg 09:17:17 just put out a paper looking at low beta values in cool clouds and how in some of her highly resolved cosmological simulations, you could have enhancements of where the magnetic field strength is is or pressure is dominating in some of these cold clouds, 09:17:34 but I know that that's a contentious description. 09:17:39 With with, you know, some of the other simulation showing other things, how do you think, how do you know the participants here think that that's going to reflect on the relative effect of either this bottleneck effect or or some of these other acceleration 09:17:55 mechanisms. 09:18:08 I guess it was too controversial question. 09:18:14 So maybe what can I say one thing I think would you go pack more has looked into this. And I think one thing. What we possibly need really more in the future is to look at the observers because in the end we theorists can come up with lots of models but 09:18:29 in the end data dictates who's right or wrong. And one thing I think we need to sort of consider seriously our rotation measures of galaxies from within the Milky Way We actually have that great images of all sky. 09:18:43 Very rotation, images, like the map by news Opperman, and from external galaxies and I think one thing you should try to sort of match as closely as possible, are the observed rotation measure maps and to see that if we can reproduce things and then of 09:18:59 of course they're already past radio burst which provides yet another constraint to these magnetic field strength within the galaxy as well as within the Halo and tragically, without getting this ride we don't get caught with great transport right because 09:19:13 unfortunately, the often speed kills for the magnetic field strength. So if the magnetic fields are slightly off the costing of a transporter is off and then you know you, unfortunately are sort of caught in this sort of nonlinear loop which you can't 09:19:30 escape. That's a, That's an excellent point. 09:19:50 For any of the representatives I don't know if x, or Brian gains, or any of the other FRB heavy hitters are present, do you do, or just as anyone in the audience have any decent predictions for the timescale of our which will be able to welcome find the 09:19:51 rotation measure various different sidelines through the FRB and have kind of a bulk estimate of magnetic field is as it as it goes through the CGM from that direction. 09:20:03 Is anyone present. Yeah, so, so this is this is Brian here this is something we're thinking about it at the moment so Ariel Emerald who isn't. I don't think she's on the call right now but she's a PhD student here at Toronto and she's just finishing off 09:20:17 the referees comments on a paper on constraining the CGM with rotation measures, sort of gunners across correlated all the rotation measures in the sky that have read shifts with large scale structure, you get an upper limit of about 49 or gals on skills 09:20:30 and about two mega parsecs. So the next step. The problem is we only have 2000 rotation measures over the entire sky. 09:20:39 We want to increase that by a factor of 10 or 100. And so the next step is this survey, called awesome, the polarization Sky Survey the universe's magnetism, and that's going to increase the number of rotation on the schedule about a million accounts 09:21:01 That should lower sensitivity to CGM magnetic fields by about a factor of four. So if, if the CG and magnetic fields. 09:21:09 10 nano gal so stronger on scales of mega parsecs anticipate that we should have a signal. When the survey has data which will be, you know, starting in the next few months. 09:21:22 so in about four years or so. 09:21:23 I can make a comment, I'll pop it on behalf of the changes collaboration. 09:21:28 And so we do have a survey of more than 30 of galaxies. So we can tweeting few things are related to this issue. One is just to map out this magnetic field, based on the radio continuum in testy, but polarization. 09:21:49 But also, same same times to measure the failure location directly against the diffuse radio emission. 09:21:55 And one more thing we are doing is two major the affiliate locations against the background. 09:22:15 Vic know we have with the already have a band, which is around like one gigahertz, and but also we're now getting the expand, so simultaneously have much broader band to to pay the measure the federal patient. 09:22:34 I think that's a popular one way to go, at least support nearby galaxies individually. We have multiple many many sites lines. So, build up a statistics, basically, you have two beautiful not interesting failure patients of agents, so basically you have 09:22:52 to do statistically. That's how we have been working on. So that is one thing, but late to this issue is how to measure consists kind of bottleneck issue effects. 09:23:03 I think the best place probably is for the class Center, which I worked on a lot. And so were you in the central regions with no lot of food regions you have radio filaments, we know the privations without molecular Klaus. 09:23:21 So the other, but in my mind I don't recall any radio observations which is short for example, in harassment near that said, molecularcloud embedded in the radio filaments, but I will try to get into have more careful look of these issues. 09:23:41 I think the Press Center pop is best place where manifest for poor cosmic ray intensity is large. And so I think it's it could be test site for this kind of theory. 09:23:54 Yeah, I wanted to echo something that Daniel was saying about the changes survey, I think what's really exciting about these measurements in nearby galaxies where we have the synchrotron and the polarization information about the fields within say 10 09:24:10 color parsecs scales of discs, is that we also have emission line traces of the gas kinematics and these same regions, and this gives us measurements of the turbulent velocity dispersion, and I think it's just, it's an interesting spatial regime where 09:24:25 we can really observational II constrain thermal and turbulent gas pressures at the same time as we can look at the magnetic field and the cosmic ray components and really ask this question of what is the plasma beta, how does this scale as a function 09:24:40 of location and, you know, hopefully eventually as there's also these other tracers looking at these questions on larger scales, we can sort of meet in the middle somewhere with a CGM perspective and try to put together a specialty coherent picture of 09:24:55 what's going on to it really is a multi wavelength effort to be able to combine both the turbulence levels as well as the magnetic field strength through radio through optical emission through FRB is a variety of different things. 09:25:10 Now we also have a, h Officer of a and all X ray survey. So we're basically covers all the different phases of the CGM, but most of the law Hello, you know it's a because nearby galaxies so that even the primer beam does not cover to, to the very large 09:25:30 radio. 09:25:34 Yeah, Brian gains so points out that perhaps Marcus or some one of the other representatives from the low far group would like to, to speak to this. 09:25:46 Yeah, I'm not an expert on any of the CGM probes with Lofa. 09:25:51 It's Seamus Solomon is compiling an RM grid. Using Lofa, but it is long wavelength, I think it's probably harder so I'm wondering whether Meerkat or ASCAP are probably not better probes and Brian. 09:26:12 I was just thinking so far because you have sensitivity to very small RM switch these higher frequency telescopes don't have so you have quality relevant quantity. 09:26:21 So if an individual galaxies that might be an interesting as well for some of the other guys is that, yeah. That might be true this a sample 4k is compiling a sample of this but yeah I'm not sure how good is polarization calibration is at the moment. 09:26:40 Okay, so we've talked a bit about observations that can constrain the magnetic field and the turbulence, which could give rise to some of the effects that Ellen was describing with the cosmic rays. 09:26:53 But what about some of the implications of the observational signatures of what Ellen was talking about whether it be. 09:27:01 Do we have evidence for the termination shock that should exist around 100 k PC out where the cosmic rays kind of terminate. 09:27:11 Are there was there was some discussion as to simulations do simulations reproduce the termination shock. 09:27:18 Can people can people speak to that. 09:27:26 I can make comment on that. Based on our changes survey. 09:27:31 We have had a lot of modeling of the, the speaker slope of the radio emissions away I mentioned this the other day, I think it's just a one mechanism to explain the flattening of was a slope or the cooling of just basically to compensate for the cooling 09:27:53 off was internal radiation is a terminal shock of the, of the outflows, but this is happens at a relatively smaller radius and with that. Mmm mentioned that like a 100 kilo parsecs setup is a quest. 09:28:15 The reason I was asking the question, waiver because to limit the age of stoppers now which can limits the aware of the coming a shock happens, I think, basically, if you think about this he stoppers typically will be have age lesson about 100 many years. 09:28:30 So pop is that is he coming up shop will not be far away from the galaxy. 09:28:40 Okay. 09:28:43 Do any of the simulations, Phil for instance with fired you. 09:28:46 Is there any evidence for a termination shock in the simulation. 09:28:51 At the cosmological skills. 09:28:58 Sorry, I've got a kid shouting in the background. 09:29:10 Do, there was some, there are some references in in slack. 09:29:16 To some papers that report a termination shock. Oh, okay. Actually, follow them up of course but ok champion code, are you yeah oh yeah I posted this paper so those are very idealistic simulations of Starburst galaxies, and the termination shock we always 09:29:38 find that for given star function rate. 09:29:41 It's roughly, you know, like 1020 k PC, and the termination shop doesn't actually progress, you know, after a certain time, when you know you can get this donation shop radius once you compare the luminosity a mechanical luminosity from from the supernovae 09:30:00 from the star formation to the pressure background pressure, you will find that determination shock actually stops at a certain point, it doesn't propagate even know if the star formation continues for, you know, several hundred million years or something. 09:30:19 So, but of course in this simulation so we had a pressure which is almost 10 times higher compared to what you showed, so we get permission Shaka ready to close by like 10 1520, even 30 kilo per se but not more than that. 09:30:37 So, I don't recall I see any calculation of the acceleration of particles, I think that is needed. 09:30:46 Because basically what kind of increase of the cosmic ray radiation. Now as you can the simulation itself is useful but in the same time, or br will be useful to have calculation of accurate exploration of particles, and the end what kind of energy you 09:31:07 produce, and his hand know what kind of full intensity or polarization you would expect for people have been nice 09:31:21 fellow you about that. 09:31:24 And back but the question for me was from you about whether we're resolving yeah for termination shock or or anything in the in the larger cosmological simulations. 09:31:39 I mean, it depends on what you want to ask about what we're resolving, are we resolving, you know, certain types of termination shocks in the sort of isn and CGM as you know structures. 09:31:53 Yes. Are we resolving the, you know, you know, acceleration or re acceleration in the shocks definitely not right that's, you know, I mean, that's not even possible really the way we've built it now there's certainly people Kristoff and others who, you 09:32:09 you know, talked about putting in again sub grid models what that does to the particle distribution in the simulations, as a function of some mock capturing scheme and stuff like that. 09:32:20 And you can, you know, that's a way forward there. This resolution. 09:32:28 Okay. 09:32:30 Well, so on the topic of observations. 09:32:34 I think it was Tim Heckman brought up an implication. About 09:32:41 Me too, so mad to has very high star formation right obviously and and significant outflows, but it seems like the gamma ray flux from within mad to would be so high that it would essentially rob the cosmic rays of all their energy density and they might 09:32:59 not have sufficient pressure to to enhance this or to be the cause of the outflows that that are seeing associated with it. 09:33:07 Is there any. 09:33:09 Yeah, I guess how to, how to panelists respond to, to this is there sufficient energy to do both produce the gamma rays as well as produce the outflows. 09:33:20 Well I totally agree. I don't think there, I don't think there is. 09:33:23 I mean this. 09:33:26 So, a former student working with me Tova Yost Hall, looked at this sort of broadly the question of echo partition across galaxies of many different types, and it's you know it's what it's what you said is you get to Starburst type environments, the most 09:33:43 extreme example she looked at was was ARP know what is this phone number, 230, whatever the you know the conditional losses just overwhelm even if you're accelerating cosmic rays and the normal way. 09:33:59 The collision of losses just overwhelm the production and you wind up with a, you know, we're very sub echo partition cosmic ray pressure and I think you know that reduces the ability to cosmic rays to drive a wind. 09:34:19 Any other panelists. Yeah, Chris stuff. 09:34:22 Oh, I agree that that's a worry. Absolutely. And the answer again depends on the ferocity of the is m so I think I totally agree with what edit has said. 09:34:32 So if you have a one on model of a galaxy that is distribution what you get. But if you do have actually a margin phase is M. And then the question is really, how long do the cosmic rays spend in a dilute phases, and how long do they spend any stance 09:34:46 phases. And I think that that the answer is still open and in this case and then what we also do not know is what is the injection efficiency of cosmic rays. 09:34:54 Is it effectively 5% or 10%, you know if you're basically sort of spending half assed and you could do both, but I think the answer is actually open at this point so it's an excellent question but him but but I think we are not yet there to fully answer 09:35:08 this question, but I think if I, if I may, there is actually one possibility to test actually what Ellen has said. In fact, if you look towards the galactic center, there's a way to test how cosmic rays are being transported I mean if i if i may show 09:35:24 FX two slides if I can do this camera or. Sure. 09:35:30 But if you have seen this this was a nature paper two years ago. 09:35:34 The first image that a mere cut collaboration released towards the galactic center is spectacular. I think our simulations are still far from actually sort of getting this realism, but what you do see is you see this sort of magnetic filaments is a very 09:35:59 strong magnetic fields hundreds of micro goals, and they have this very particular harp like form It's here. It's here, it's here. So what is it we don't know but what we can do is we can sort of build a model, and we can sort of look at the lateral signature 09:36:13 brightness along each of these strings of this radio hearts, and then we can sort of inject cosmic rays and see how they are transported. And if you do what everybody does in this field diffusion. 09:36:16 It works sort of okay in the first string. It works horribly towards later times that we believe cosmic rays should be diffusing. If we instead go to the self confinement picture that Ellen and 10 have talked about, then in fact you have a beautiful match 09:36:32 especially at late times I think that is the first possibility and I should actually mentioned this is work done by a grad student get bought some team and Tomas was actually done an excellent job here, and I think we do have really a way forward to test 09:36:44 test this theory so we don't just speak in theory space we can really test this why observations. 09:36:54 That's super interesting. 09:36:59 Okay. Uh, yeah so it was pointed out, Tim Heckman his question was a two part question, both in terms of how the, the cosmic rays can be responsible for, for, for, for driving outflows if they're producing all the gamma rays and 09:37:19 for other high star formation rate. 09:37:22 Large associated gas densities into big star formation galaxies at cosmic noon, does this imply that the cosmic energy, the cosmic ray energy gets gets drained too much into gamma ray emission and can't be responsible for producing like that, this super 09:37:40 outflows that we see in galaxies at higher redshift. 09:37:46 Yeah. can you say something about that. 09:37:50 You know, I think, the, the, the uncertainties that were just raised all all apply tenfold at high Z where we don't have any real observational constraints on on the cosmic ray populations. 09:38:06 You know I'd say in our experiments with fire which is just one set of experiments. 09:38:12 We did find that it got a lot harder at high Z particularly sort of Zf two and above, to make cosmic ray feedback have a very strong effect on top of other feedback mechanisms because so much more of the gas is dense and cold and things do look more like 09:38:34 starbursts at low z so you both have losses but also just some of the ways that cosmic rays might work that we talked about yesterday as more of a preventive feedback agent by, you know, slowing down inflows and the CGM if everything's raining down on 09:38:50 your galaxy and very cold dense sort of cold mode filaments or clumps. That can be even harder to stave off and you know it's not that, you know, to be fair, other feedback mechanisms also are relatively inefficient at those times it's not that something 09:39:06 else is wildly more efficient, and the prediction from ours and a lot of other simulations is that you more transition, even in massive galaxies potentially to a more bursting mode of star formation where you may be overshoot and then, then you can launch 09:39:22 a very massive outflow from the combination of everything if you have a very high star formation rate. 09:39:27 But I think you do. It certainly gets harder to regulate and even if these diffuse outflows are driven by a porosity and things like that you might still have them, but it's a lot harder for them to do a lot of work on global quantities like the star 09:39:43 formation rate because relatively small amount of the gas mass is in those phases basically. 09:39:51 So Phil does. I mean, quantitatively Can you explain the high star formation rate with just inefficient feedback at high redshift mean is it roughly right yeah i mean they're still on something like Schmidt Connecticut, which, you know, at the high surface 09:40:12 density end is basically a statement that that feedback is getting my interpretation of it is that it's an it's a statement that as you go to the super linear nature's, it can be interpreted as feedback gets less and less efficient as you go to higher 09:40:27 surface densities or gravitational pressures however you want to sort of phrase it. 09:40:33 So, you know, I think it is consistent with that picture of course you still need feedback we know that in an integral sense they're still not at the, you know, universal very on fraction and things like that and you still have more efficient feedback 09:40:46 and dwarfs that hi redshift I'm sort of thinking about L star galaxies that high redshift which are pretty massive systems. 09:40:53 And there I think, you know, it's pretty hard to do a lot with any of these mechanisms of course you can turn on an AGN and potentially crank out a lot more power in these systems you have a quasar or something like that. 09:41:08 And either cosmic rays, or other modes, but, you know, if you give me the IGN knobs I can do a lot. 09:41:19 actually I'm not sure that, about the argument. 09:41:22 Beta coupling between the feedback through the cosmic ray ways of gas seems to be making the feedback, more efficient, why is less efficient. 09:41:33 Am I sure I understand. I'm saying it's it's less efficient basically almost all the feedback mechanisms become less efficient as you go to higher gas densities. 09:41:42 So, when you get these extremely dense environments and, you know, more also neutral and cold environments. 09:41:50 Most of the ways that cosmic rays would be able to, if you compare, even just zero with order if you say what's the, the cosmic ray heating rate versus the gas cooling rate, or what's the cosmic ray pressure density compared to the gravitational force 09:42:06 per unit area that ratio is is more biased towards gravity winning the higher the surface density of the galaxy is basically. 09:42:22 Yeah, it's ready for our galaxy. See, only 1% also if I recall correctly, it means the cosmic ray energy is dissipate in the disk, so most of the energy will goes away into the Halo, and has no effect of the feedback to some degree. 09:42:42 And so, but now either higher rate of the galaxies equal more is confined into the gas self will push the gas away. Of course it's a lot more validation but still I must feel clear what enemy executive quantitative with a set of makes the feedback, you 09:43:03 I agree, you know, read them see gravity recovery you have some something to compare with, but let's do I think the coupling mixing things more efficient. 09:43:19 Well I think one important point on this is that I think in, certainly in our simulations and in the work that that Christoph and collaborators have done on cosmic rays and Galaxy transport, even when they escaped the disc. 09:43:32 Part of the way that they do interesting feedback that that searching for example talked about yesterday is there still couple within the the variable radius, the, even if they're escaping the disk they're still doing that work somewhere in the CGM, and 09:43:49 it's proportionally easier in many ways for cosmic rays to, you know, do interesting feedback work if their coupling is dominated in more diffuse gas and the CGM, I mean everything's easier in the CGM because, in that sense, for feedback because the densities 09:44:05 are lower the cooling times are longer, the pressures, make it easier to do that work. So I think there is a difference of what would happen if you're coupling everything in the disk versus in the CGM, but I think these fundamental assumption these models 09:44:20 is that the cosmic rays Don't you know they're there mean free path is always short very short compared to like the CGM length scales so there's still coupled somewhere. 09:44:30 I think Christoph had something to add. Yeah, so I absolutely agree. So in fact, you have to think about this, if the cosmic rays need to stream or diffuse ahead of the gas and at some point they can counteract it gravity can start pushing so they don't 09:44:43 push from sort of the miscellaneous are pushing from some scale like there's already less get above there, but then they can do terrific job and, unlike these classical energy and momentum for wins, cause greater events actually can be part of it as it 09:44:58 rises, why they are Fenway feeding, so that's that's amazing so definitely check the price event and constantly accelerates the wind and that's exactly something we actually need to do to go to these extremely fast wins that people see in this case absorb 09:45:13 slides I think in that respect, it's doing a great job. I would say in sort of firing up sort of the second booster in a rocket that is I would say the perfect thing with cosmic rays could do a great job in terms of sort of getting the list at the very 09:45:27 bottom. I don't think the cosmic rays lady, only role to be very conservative. 09:45:36 But I guess it's, it's, please. I was just gonna say that's another reason why it's so important to know what the magnetic field strength is because the altitude speed is, you know, the heating rate is indexed by the by the altitude speed. 09:45:53 And there have been, I think there's been at least one paper proposing that the, you know, the magnetic field is low enough basically, if the ratio of cosmic ray energy density to magnetic energy density is greater than the speed of light or drift speed, 09:46:08 you get these non resident instabilities which dump energy into the gas and wholly different way. And that's the so called Bell regime. And, you know, with really low magnetic field you could have back to. 09:46:27 Todd and Marcus have been waiting with their hands raised for quite a while. 09:46:32 I told you, I'll let you go first think you were the first thank thank you for a nice taco and for a non expert like me I found it to be quite interesting and enjoyable. 09:46:44 So I have a question that might be premature, given all of the issues that folks have discussed but wondering about how we might use observable to test these ideas. 09:46:57 Could you comment on how cosmic rays would affect the ionization state of clouds especially certain galactic clouds. 09:47:06 We have a lot of information on various ions in certain galactic clouds and so I'm wondering if the ion ratios, or other aspects of the absorption line systems could provide a signature of some of these interesting effects that you discussed that you 09:47:25 know I yeah, I'm just, I'm really a beginner at this I'm appreciating you know there's questions about how the cosmic rays sample the clouds and stuff like that so maybe, maybe we're not there yet but if you can comment on that I'd be quite interested. 09:47:41 Thanks again. 09:47:43 Thank you. Um, I think the first person I heard about metals that far from galaxies was you when you visited Wisconsin many years ago but, um, so I keep coming back to the question of what the MeV pop cosmic ray population is is doing, and partly it's, 09:48:04 you know, so does the MTV cosmic ray population float up and down with the gv population should we think of them as the same. 09:48:15 So that's you know that's a question that applies everywhere in the discs of Starburst galaxies as well as in the CGM. 09:48:25 And then, you know, there's this question of what happens to all the cause of the gv cosmic rays that are enfeebled by a diabetic losses, and I you know I think that the ionization stages and more generally Interstellar chemistry or, you know, have been 09:48:44 really underutilized in trying to get a handle on these questions, and I think, you know, I think they're very important and I think that we, we know enough to solve them. 09:48:55 So, I, yeah. I certainly I'd like to work on, like myself, rotation beard slows down a little more. 09:49:11 Um, yeah, yeah. 09:49:15 I'd also like to just point back to the figure that Ellen showed from Josh Wiener His work of the prediction for the high on ratios that come from the bottleneck simulations. 09:49:26 And something that seems interesting to me is I think we could add other observable is that we have including cloud sighs and potentially a cloud kinematics that if relative kinematics of the low and high on phases. 09:49:42 Now that's something that we've seen from Todd. 09:49:44 These observations where those are are well aligned. I wonder if this is essentially a ion high on states found on the skins of these clouds are a picture that is consistent with that and so just the potential to piece together. 09:50:02 Maybe the geometry and kinematics with the ionization states, I think could be really interesting and doing that in different inhalers with different star formation histories, to see if we can pick out an influence of cosmic rays because there are so 09:50:19 many other factors that can also contribute to shaping those properties. 09:50:23 Some way of, of trying to get a handle on something about the, the cosmic ray population simultaneously. 09:50:33 Well, and in fact this relates to a question that young Jang has brought up in the slack chat and that is are there, opposite Well, first, what, what does the injection of cosmic rays into these cold clouds actually due to the size structure and the morphology 09:50:50 of the clouds and does that provide us with an observational signature that might go hand in hand with some of the, the effects that Aaron points out and Todd potentially points out, in terms of iron ratios and such. 09:51:05 Do we have a good idea, both from the analytic side or from the simulation side how the injection of cosmic rays into a cloud will change it. 09:51:15 Well, the clouds gets there a couple things that happened on the clouds gets stretched. 09:51:22 Because of this differential forced on them. And the other thing that happens is that they you know they seem to get. They seem to get pigtails, I don't know, I could. 09:51:33 I don't know if there's time for me to share my screen. Yeah, Go ahead. 09:51:39 Yeah, let me get back to just as like the bow shock hits the cloud and it develops these turbulent flows and the. It seems you know it seems to be an edge effect and. 09:51:49 Okay. Josh, we first saw this in Joshua's work, but I'm 09:51:57 yeah let me see if I can bring this up. 09:52:00 But it seems to be robust and chats on chats ought to hear this is, this is not the best picture, but, but these things here. These get very long, and 09:52:16 that, you know, I don't know if something like this, is it's observable, but you know this is well that these tend to be magnetic surfaces. Also, but a lot of interesting stuff does go on at these interfaces. 09:52:33 So I think, you know, I think we need more modeling but I think there probably is. We could probably is something. 09:52:41 So every calculation is spatial resolve the fashion for ionization structure for both either neutral cloud or for the molecule clouds even beta. 09:52:53 So, so, so far this is, this is what we have. This is Josh is work that Aaron was just alluding to, and. 09:53:03 Now, something that does not show up here is that although the ratios, the iron ratios are pretty good. The, the absolute values of the iron column densities are are pretty low. 09:53:16 And you would actually need a great many of these to add up to the total column densities that that we see and then of course that would raise the question of velocity dispersion is in line with things like that we have not done that. 09:53:29 I don't know if pang of pain has any comments on this. 09:53:35 Um, no, nothing to add. I agree, you have to add on quite a few and then, and then all those problems come about. And actually, I'm also curious how the pressure and it's choppy effects would affect these line ratios Do you have thoughts on that. 09:53:50 Um, well I have mostly been thinking about the pressure and I saw to be okay so the absolute value of the pressure anisotropy is is too small to really affect forced balance. 09:54:01 If you know assuming that, that it's kept near near marginal really the perpendicular and parallel pressures are almost the same. But, and I have mostly worried about this in in the regions, really the inter-cloud regions, not the interfaces. 09:54:20 Do any of the other panelists or participants have 09:54:26 any comments, especially from the simulation side on how how the presence of the cosmic rays might change the clouds and make some sort of observational signature 09:54:45 I could comment on this I think there are two aspects to this one is that most current simulations have actually modeled the energy density of cosmic rays, they've integrated already spectrum, but unlike a somebody solution that is very narrow and momentum 09:55:00 and momentum space cosmic rays, obey a power law distribution spending decades in energy momentum. Now if you were to actually simulate that, then I think you would have a predictive answer on how any the cosmic rays impacted called clouds and put it 09:55:18 potentially chemistry, or how did that energy popular population can interact with a GD population, etc. So in my postdoc Philippa he says has just finished a code and we are currently doing galaxy simulations to answer these questions I think that is 09:55:34 something that is about to actually be studied and the other aspect is actually it really matters that uh you actually can confine a cloud and it or dispose of cloud, depending on how well you couple the cosmic rays and what damping actually dominates 09:55:49 there and then I think, again, I think. 09:55:55 At the moment we do some experiments that are very interesting, but w probe is every come from pick simulations, where we actually look at it if you go from one region versus a longer Lando damping dominates and and covers the cost of very effectively 09:56:09 to reach Brian neutral damping which is much, much stronger dominate dominate and it makes the cosmic rays sort of escape much faster. And I think we need to really understand how the interplay of these various stamping processes on the cosmic ray propagation 09:56:25 and sort of conspire or sort of combine two to sort of tell us what is the dynamical impact on this cloud so I think we're just sort of starting to sort of learn about these different mechanisms, but I think you're far from the final answer at this point. 09:56:43 Okay. 09:56:45 was Yeah. 09:56:49 But I think one interesting follow up, based on chatter work is actually try to form a lot of clouds based on for example similar instability, so consistently instead of using spherical card. 09:57:01 and then you can put your cosmic rays. So, the other students in CCA walk in on that. A lot of signature like our mission is still zero but I think they are more complicated. 09:57:13 Once you put all the cloud or form from somewhere instability. And also you can actually compare the difference if you have say like cotton Reggie when we come into Clyde although cloud, and how that is different from the XML when they come to cloud with 09:57:30 cloud, you do see actually quite different structures of the cloud based on whether you have a customer comes in all based on whether you just have some wind comes in. 09:57:42 Another interesting I think probably a loss, also mentioned. 09:57:46 If you'll be able to do like small scale high resolution simulations of community June when there is actually a natural instability the customer, acoustic instability in the streaming case. 09:57:59 And what did that is I could do in that. 09:58:01 If you have a corporate Julian wind in in the wind, the region. Tell the customer across the instability can create a lot of shocks in the, in the wind regions. 09:58:15 And actually, once you have a shop so you have a density enhancement in the local regions. The bottom 90 fact that animation also happens there, and your former rather staircase structures in the wind, instead of beautiful power on people normally assumed 09:58:29 those actually happens in once more skills. So I think the other also quite interesting implications on what that might tell us for the communication wind 09:58:43 good points. Yeah. Thermal instability definitely seems like it behaves in a different manner. In the presence of cosmic rays and. 09:58:53 Yeah. 09:58:55 Marcus you have a question. 09:58:59 Yeah. Well, going back to this question about suffering models I think it'd be nice if one could somehow quantify the, the cloud speed and the survival length. 09:59:14 here, and you know the speed setting probably the maximum of the can speed and in other things and one thing I was wondering about is what happens. So, obviously, all model so far a little bit idealize and I'm thrilled to see that chat has already done 09:59:34 this Colombian medium and, and a lot of added a lot of detail to it. But what happens if you put in an addition turban magnetic field on some smaller scale. 09:59:47 Does that then disrupt that whole picture or is that a good idea could there be showstoppers, or is that these non ideal fee geometries. Nothing to worry about. 09:59:59 So that question gives a chatting and and I guess it, anybody else. 10:00:05 So in terms of draping or or shielding by the magnetic field on the clouds and what impact that would have and, you know, even just the propagation of the of the of the cosmic rays towards towards the cloud. 10:00:20 Will you know, every time whenever so actually I started thinking about this. 10:00:26 This bottleneck problem in connection with magnetic fields and galaxy clusters where the, you know, the field is probably quite tangled in it, you know dips in and out of denser regions and, you know, what is what is cosmic rays streaming mean in a situation 10:00:41 like that and you know every time. As you make the magnetic field more and more structured. I think he just pushed this picture more and more. And, you know, I guess I'm probably too obsessed with pressure on I thought up instability right now but you 10:00:57 know I think if there is an in fact actually when when Alex was area and Andre Bosniak worked on this pressure and I saw the instability, they had in mind what would be the effect on Interstellar turbulence, you know, could it be a important energy sink 10:01:12 for Interstellar turbulence. So I think that, you know, when you, when you start considering a magnetic magnetic structure that's not put in by the cosmic rays themselves, you know, then you just amplify the opportunities for this kind of thing. 10:01:30 Okay. 10:01:32 Any other comments. 10:01:37 Crystal. 10:01:37 I think one thing that is an extremely interesting question Marcus. And so one, if you sort of considered some structure some intervention at on the scale of coffee rage already is so it will certainly modify it. 10:01:51 The way the resonance happens right i mean so, in fact, you will get out of the residents quicker, but you may actually excite a broader spectrum of unstable waves and which of these things dominates is unclear at this point. 10:02:06 And, in fact, more mature lobby has run pic simulation of a very similar problem, often electrostatic. The so called plasma instability, and there it was conjectured if this happens to be a long sort of a gradient, where you have sort of verde plasma 10:02:23 frequency changes as a function of space. You will soon get out of resonance and there is no instability, but instead what he found is, you excite a broad spectrum, each of which grows a little and the total action of these broad spectrum and see the 10:02:38 waves set out enough energy that the growth rate was almost unchanged, compared to the simple homogeneous background. So this was totally counterintuitive to what we have thought when we started this and I think all these things need to be studied in 10:02:52 detail, but I think the tool for doing this are plasma kinetic simulations and we have to really sort of look at this into great detail because there's so much to be sort of learning in this field. 10:03:06 Okay, um, I, I still have lots of questions and Greg, there are a number of really good questions, notably one by Greg Brian in the chat but we're past our two hour session and I don't want to keep people when I know that there's still teaching responsibilities 10:03:21 that people have and that sort of thing. Tomorrow we will have an open discussion where we can, you can bring up whatever question you want and then it gets uploaded within the, the, the infrastructure we have for the structured discussions tomorrow, 10:03:36 so people can upload the questions that they are super psyched about, and then we'll all discuss them but I think that that does it for today, thank you very much for everyone.