09:10:13 Sorry I got caught up reading all the discussion, it's time to time to read comments here.
09:10:19 Lots of great discussion in the, in the slack. Hopefully people are contributing and reading up on that
09:10:29 later. Let me introduce our panel that will take us over the course of the next hour. People are encouraged to chime in, when there's a relevant point, raising their hand and so on and so forth.
09:10:44 I'm going to particularly be drawing from discussion in the slack though.
09:10:50 But first let me introduce our panel, so obviously we're including Dylan Nelson our keynote speaker for today, and his, his wonderful presentation.
09:11:01 Other members of our panel include Professor wrong on board light from NC State. Professor john Chisholm from UT Austin.
09:11:10 Professor real debate from University of Edinburgh. Dr. Chang who Kim from Princeton and Dr Miata lead from the CCA flat iron. So, I think I'm pretty excited about this panel.
09:11:22 Being able to cover a wide range of topics here.
09:11:27 So, well first Filippo you've had your hand up since before the end of the talk, so I'll, I'll let you throw a question in here.
09:11:43 Thanks for the nice overview.
09:11:47 Well, I mean, as you know, I mean, we have discussions many times so my general impression is that the supernova feedback in simulations is gone Marasco simulations is still at the very strong level that not completely sure you have touches at the end,
09:12:10 it's, it's comparable to the observations, but one thing that you said make me think of a rather straightforward way of making this comparison because you said,
09:12:27 I don't remember exactly that this was something like galaxies the directions don't the disks in the simulations and. And this is, this is really becoming clear that is not true.
09:12:42 I mean, only, only DC and then I've been to nature papers, showing beautiful discs, have been galaxies that ratio for between four and five.
09:12:56 I was in one of these paper where.
09:13:12 Thanks to gravitational lensing we could have a resolution of 60 pounds.
09:13:04 And you could see that the, I mean the disk is is really regular and and the builder segment that we find is thin, and now we have other five galaxies without additional lacing that are telling exactly the same story.
09:13:22 There is a paper coming out really this week.
09:13:28 On Friday, please everybody look at their guide so, so, so that that these these are a superstar bus, they are Starbucks and still when you look at C plus, I forgot to say, you see that the gas is in regularly rotating this was very IV over sigma.
09:13:48 And this is sizing the stand that is not the prediction of the NG or other simulations actually tng is probably the.
09:14:00 You are probably the few that this comparison. Clearly and told us what what the predicted VMware sigma, in fact we put it in, in, in our fingers so my question to you I mean, in general, it's not really a question or discussion.
09:14:15 How do you, how do you see that the simulations could produce these with this type of view of the Sigma with the fact segments that that award there of 30 kilometres per second that actually four or five even.
09:14:34 So, yeah, before we jump in. I remember a few weeks ago. Presenters said I have talked enough so I'm really going to let the panel handle everything.
09:14:43 So Django jaan jaan remember me oh yeah you are you guys have to chime in wherever you want Filippo. The question I think we should talk offline. I mean, so I think it's a very interesting topic, and something that we were actually want to work on and
09:14:59 compare with but I would say not the main topic for today, the disc Phoenician.
09:15:06 What about these cases related to the feedback I mean you, you are not performing it is because you have too much feedback.
09:15:13 Too much outflows right i mean it's not, I don't think it's, it's an unrelated question but ok we can talk offline, you know, I think it's really an issue of outflows it's it's an issue of the inflow rate, and whether or not you know you can sustain a
09:15:32 order rotation and I think, you know these are the simple sort of arguments that that among others Reinhard Ganzel and his group have been very much promoting in terms of the, the, you know, the instabilities of the deaths and the sizes of electric clouds
09:15:49 that you can form in those types of systems, and what you're saying. Phillip i think is is right, is right in the sense that, but it's a very massive dependent statement.
09:16:00 It's certainly true that in simulations we lose plenty of nice discs at high masses at high redshift ratio of two and three you know things about 10 to the 10.5, or so are clearly desk.
09:16:12 We've done zoom simulations Danielle unless Alcazar had a paper in 2013 where we did zoom simulations of this and show that it you know match nicely with the V over stigmas that were distribution that was observed in.
09:16:25 In the sin survey. So it's not that we don't produce this I think that the problem is if you look at the smaller galaxies, that's where it's less clear.
09:16:34 And I think a lot of that has to do with, you know, how much do you think the inflows are storing up the disk and how how sustainable it is to have a thin disk when you have such high inflow rate cosmological info rates.
09:16:51 Any other members of the panel want to comment.
09:17:03 Okay.
09:17:06 Thank you for the question Filippo, I think that that theme will be addressed at other points during this discussion as well as we touch on other topics.
09:17:15 Okay.
09:17:17 So there was a, there were several different comments about. One of the last things that Dylan you covered. And that is the, the geometry of the outflows the angular dependence on on outflows and the distribution of the circuit galactic medium and a few
09:17:33 points that were made that all kind of throw out there and we can kind of discuss one.
09:17:40 Is it clear because I've seen a number of different observational studies, there is in fact an Angular, as a mutual dependence on the distribution of the circuit galactic medium and its properties.
09:17:56 Oh, thumbs down from Jess, are you saying there is no as a musical dependence. Are you saying that's a poor question, Nicholas Michelle is here and he said there is but I've seen like three separate results recently that say that there's not with some
09:18:02 of the absorption line stuff. Okay. Well, first, let's say one thing.
09:18:08 What did the simulations predict, and then we'll talk about what in reality is is happening and how we can, you know, broach these two regime so simulators on the panel.
09:18:20 What, what do your, what to your simulations and what to the simulations of colleagues in the in the field. Show.
09:18:36 Is there an as a musical dependence do we see more high medalist at gas in the bipolar regions out of a galaxy does it depend on the mass scale, what do we see in the simulations.
09:18:42 Now you're on the panel.
09:18:46 Let's do a quick comment. So now I'm just going to say well it depends on several things. So we find out if it's a fountain flow, then it's more or less more spherical.
09:18:58 If you know the, you know, it's the, it has high entropy and it naturally wants to break out and the pre existing guess, let it break out, then it is bipolar.
09:19:11 Okay.
09:19:13 Dylan.
09:19:16 I was just going to comment so this plot I was very brief apologies for that from the Peru, paper, which shows the expectation for the medalist at at 100 kilo parsecs A versus angle.
09:19:30 Around start forming galaxies in redshift point five. This is kind of our target. There's a lot of scatter, so we expected that this would be a difficult signal to find and there's a figure in that paper which shows a few data points.
09:19:42 And I think it's clear that the scatter in this relation is large enough that you would you would not see it, unless you had a very clean sample, because of intensive dependencies on stellar mass, or an impact parameter on redshift or enough to completely
09:19:59 wash out the signal if you're not careful, so I'd like to hear more about that but this is primarily what it is, in density, this is in metal the city of the gas This is in a particular ion that you're seeing what, what, what are the properties where
09:20:14 this signal exists. So we are mainly focused on that list it as an observable, but this indeed is total gas middle of the city. So we did make a one cut in the direction of observe ability which is to restrict ourselves to high and columns.
09:20:32 Right. And there the signal gets even noisier and with even more scattered, but it's still there.
09:20:37 So we didn't do for instance, the magazine to signal rather total Gasman listy, but it should still be there also in neutral gas or cold gas and reveal has a response.
09:20:54 So yeah I well. So I just wanted to make a couple of points.
09:20:56 So I think this is a very ion dependent statement.
09:21:00 So one of the things. So we looked into this and move faster we never published it with Kate story Fisher.
09:21:09 But, but you can already see what the anticipate what the results are from Amanda's, Amanda Ford's papers, and that is that oxygen in oh six tends to have been deposited very long ago.
09:21:21 So this is not recent stuff and it's volume filling, at least in our simulations, and as a result, we don't expect any as a beautiful dependence if you look in that.
09:21:30 However, magnesium to at least in our simulations tended to be in flowing gas and the inflows tended to occur along of course the whatever you call it the major axis of the disc you know along the planet the disc, not, it's not a perfect thing.
09:21:44 But I think, I think that, in that case you would Excel, if you look at some of these lower ions I think you would expect that from the simulations, yeah this is a wretched zero.
09:21:54 Well, hello, Richard. Yeah. Um, and just as a, as something I can add, I looked at this in the fire simulations as well. And we saw I kind of consistent with what Dylan saying, we looked at magnesium to ionic column densities oh six column densities carbon
09:22:11 for, we saw a slight effect as a musical effect where you'd see more of the the metal lines in the semi semi minor axis along the like bipolar outflow direction, but it was very slight, and I'm not sure that it wasn't consistent there was a lot of stochastic
09:22:31 city from one Halo to the next so I'm not convinced that this is a at least that that the fire simulations predict this sort of behavior but
09:22:41 the observational side has a lot more to say. We've got a number of different observers, two of which are on the panel Roman and john and Nicola O'Shea perhaps can all comment on the observational prediction because yeah in my, in my mind what I've seen
09:22:57 from the observations, you know, one paper says you see it one paper says you don't depending on the ion, even the same ion, you get conflicting results so what do people have to say wrong one first.
09:23:08 So again, this is a very famous dependent, as well as geometry dependent statement, you have to be very careful when you select your sample, because it's very easy to get bogged down with projection effects.
09:23:22 If you have a keen enough sample and a big enough sample and again the statement is only for cool guests tres feminism to I showed, way back in 2011, that if you take thousands of galaxies tax, we do see a as a mutual dependence at close, close impact
09:23:38 parameter of 40 to 50 k PC there. You see, enhancement along a minor Xs for magnesium to absorption in the CGM.
09:23:47 This is also verified by SDS a survey of thousands of quasars spectra, which is liberating the land, and I think, I think the recent paper that Dylan showed also, they see a slide enhancement all the minor access.
09:24:01 If you look at quiz or absorption lines which historically has been done Nikola would probably talk about it. They also showed that and and lead capture screw, they showed that you know in magnesium to, you see a binomial distribution Inquisitor absorption
09:24:16 line, the number of pairs is smaller, obviously, because these are much harder to observe, but there is a signature but if you go to higher items like carbon four or six, we don't tend to see anything.
09:24:29 We try to do it with costs a loss but unfortunately the sample size is small, and it's just, you know, the distribution of pairing is not good enough to make a statistically robust statement is also wrong, as far as like, so the magnesium to you see it
09:24:45 right. But then, that same sample that Glenn caps x showed and with Stephanie pointing right they did the actual ionization modeling and it's not a medalist at effect.
09:24:56 So I feel like the magnesium to can't distinguish between temperature, density, you know, guess the statement itself.
09:25:05 as he will fill a symmetry, that exists.
09:25:07 The second statement I would, I would argue if you observe, again, dollar bills studies. A lot of people have shown in SPSS team heck men's group has shown.
09:25:16 I have shown as well as Keith Rubin has shown if you look at face on galaxies, where you observe down the barrel of flows versus edge on galaxies where it should be perpendicular, you do see stronger outflows in face on galaxies, again you have to be
09:25:30 careful to have good, you know, and like very good disk only like display galaxies, if it is irregular it's not good enough, but we do see signature and magnesium to, that's a limited statement.
09:25:44 Okay.
09:25:44 okay.
09:25:45 All right, the plot thickens.
09:25:48 Nicola Boucher.
09:25:53 You're here.
09:25:53 So maybe on the simulation side, following what remains said we lived in PNG, was a student at Columbia down in the Philippines, and indeed the management tool is present on the on the major axes, and energy simulation.
09:26:10 So comparing observations and simulation sometimes difficult because seems like the phases of.
09:26:18 I'm not completely accounted for, as Ron said observational II I think with all the background peers and background quitters there's strong evidence that the mechanism to presence and not looking at modality but the presence of magnesium to is known as
09:26:41 a tropic. So on the minor axis and the major axis you have an enhancement and Kristen Martin show that in her group as well. Now in terms of the multiplicity.
09:26:45 It's something that is a signal in freak your own Dylan's paper that is relatively weak is point 3.5 X or something like this. along the zero to 90 degree angle.
09:27:00 And it's not easy to see and you need to have a very homogeneous sample.
09:27:04 And I think we, we do have that with. Surely if she'll be selected sample. When we have this kind of cinema is showing up now. And I would like to also point out one key difference that in, in between also raising other surveys was back on quasars is
09:27:21 that sometimes and even the campsite sampled in magic cat is a sample that is continued to be selected so they take the quitter field the image with multiple and I just HST and then they lose the spectroscopy.
09:27:39 On the continuum based galaxies and so you have to do a pre selection on the continuum, which, if you don't, and with us we found that 30 to 50% of the two images that we have, have no continuing to the depth of the News, the news observations.
09:27:54 So I think you have to be careful when these things are happening the discrepancy between different groups here little clearly difference also in the selection function.
09:28:09 Okay, that's fair. i'm john Chisholm, so I was going to, you know, back it up just a little bit and Dylan was mentioning how the asthma so dependence is Hello dependent and there's, there's a lot of terms in there but one of the interesting things that
09:28:20 I took away from your talk Dylan was how AGN, the impact of AGN on this sort of medalist he has musical variation can be pretty strong on the same token, how we implement a gn feedback seems to be pretty, pretty uncertain stuff at this moment in time.
09:28:42 So, how, how much can the implementation of both hn and star formation feedback, impacts our kind of influences on these on these as musical variations was my question.
09:29:01 Again, just a very small comment then so one of the great strengths of the Peru paper is that we actually found the same signal literally to within less than 31 decks between eagle and Tg 50, and those two simulations have enormously different physical
09:29:18 models for feedback. I think that's a fair statement that substantially different numerical resolution, and they run with very different hundred amicable techniques, I mean they're quite different.
09:29:28 So, we're all, of course, in these kinds of projects we're always searching for model invariant predictions. When these are the strongest if something is actually true and three simulations and not just one that's for the best.
09:29:40 And so it seems that this particular as the new fangled dependence of the medalists at around start forming galaxies is quite a robust current prediction from models in general, I don't know, maybe Romeo agrees or disagrees but that's a good thing.
09:29:57 Well, I have a related question that, and this is just exposing my ignorance about the the feedback implementation in those two models in Eagle and in illustrious tng for your Ag and feedback models, are they intrinsically bipolar, or are they, ice, like
09:30:17 ice tropic. Yeah, again, maybe this this is quite fast but both are fully isotopic at the scale of injection Changi owning the time average sense, and also I guess Eagle in the time average sense right both are a bit random your events, but your time
09:30:34 average sense for our isotopic.
09:30:37 Okay.
09:30:38 But the only cosmological simulation with it enforced by well, so I read me I'm gonna say something wrong, December I haven't bipolar horizon agenda is that bipolar agent model.
09:30:49 Yes, and this is purely bipolar, so stable stable a bipolar, I think, Selena actually had her hand up. Yeah, so clean, do you want to do you want to comment on all of this.
09:31:06 Yes, I'm sorry I realized my name is not correct I wide my PhD student to be able to attend these very interesting session. So I'm excited to see a lot of discussion of this topic, I think, you know, I really must have what I heard.
09:31:19 And so I just want to emphasize a few points for us, but Dan just said right so what you see is saying that she sees a lot of influence fun and fun things, but in the simulation both teams you gotta have, you know, different numerical and physical intimidation
09:31:39 of these processes, and yet globally taken, there is a hint of an immutable signature.
09:31:46 And I think we also looked at houses very the number of parameters and you've mentioned a few of them redshift.
09:31:54 In fact parameter, you know, phase of the gas, you have a cut in the temperature and current density of humans, but also set on mass, which I like to highlight because this is a something that is very difficult to get observation and from a few data we
09:32:11 heard about.
09:32:12 And I think what's interesting is that what we showed is that the current observations are just is referring to focusing on objects that may have only one face over guys, or more ionized type of results over or perhaps haven't dealt with the dust efficient
09:32:34 issue in those ministry measurements and the point I'm making is that we do need a significant sample of very precise quiz app servers we've reversed, as humans, that are currently for the patient.
09:32:49 And we've, hopefully, you know, instead of us to be able to retrieve the signal that we expect from the simulations,
09:32:58 as hard, the dust depletion is really hard.
09:33:03 Agreed.
09:33:10 One of the points related to this that was brought up in the, in the slack is the relationship between how much of this bipolar behavior in the in the outflows and in the distribution of the metals in the CGM is as a function of of a gn feedback or supermassive
09:33:29 black hole driven flows versus star forming driven flows and do we expect a difference. I mean, I know, Dylan when you were showing your models for this you were saying, you know, even with isotopic distributed like deposition models you'll intrinsically
09:33:48 get us to tropic distributions simply because, you know, the, the heavy column of the Discovery Channel these, these things out so presumably in that respect, it may not matter as much if it's if it's coming from an IGN isotopic Lee or coming from, from
09:34:05 stars isotopic Lee but someone also pointed out that what may be channeling things in a bipolar direction are gas cold gas structures on the scale of hundreds of parsecs that are presumably not resolved in the cosmological simulations and could be could
09:34:25 be doing this so how much of it is is over tuning, or how much of it, do we need to actually resolve those structures so all of these things, I think, play into, you know, is it a gn Is it, is it a generic result of the simulations.
09:34:41 I mean, what I'm getting here is that it's kind of a generic result but it's, it has to be teased out very, very carefully from the data sets, as well as the observations, but I don't know, is that what that what people are suggesting.
09:34:59 So, well we've looked at quantitatively speaking is in the master regime, where faculty that is not doing most of the work.
09:35:08 Which is to say this is a combination of supernova type to driven outflows.
09:35:12 And I think this is probably where observational we can best go after.
09:35:17 Magnesium to.
09:35:18 Right, as opposed to much more massive systems where black holes are going to be relevant, so actually I haven't thought too much about this in the context of clusters or some other masters in this, and I said, and I saw trippy of LSD or other observable,
09:35:35 but yeah, maybe can go Can you chime in about this combination already from the smallest scales. All I can say is that, you know, as a thought experiment, this is what happens in simulations, where we do not resolve such combination on a ladder project
09:35:52 scale so if it's also seen in reality this is an argument that that is not the driver, but it's not necessary but insufficient
09:36:03 fiscal and my name I need to speak about this but i think i mean the based on my in my experience, I don't really have any answer for that because I'm always using this local disk type simulation, it always have a.
09:36:20 Only the body creation, there were where the gas can escape so it always blow things along the border contraction.
09:36:27 So, yeah, I mean, the, but maybe the point. Some, I may want to just ask about is kind of the culmination happening there. Is it really is it from two to the disc that you already have, that means, since of the flip or So raise a discussion about the
09:36:51 ecosystem to disk. But you see the this bipolar outflow because it kind of sign of the kind of the indicate that you already have a disc in quite large range of the redshift.
09:37:09 When this, this was in essence our mark conclusion, I would maybe defer to at least as if she's here wants to say something about the emergence of the disk.
09:37:19 I mean emergence in the population sense of discs, as a function of redshift, but again I maybe want to steer us more towards the outflows.
09:37:31 If possible, but yes, this was our effective conclusion that the combination is a result of having the disk. And if there's no disk Yep, then the outflows are not call me, which is why Richard five, and the gashes bodies of most small galaxies are chaotic
09:37:46 balls of gas and they're not thin discs, then you don't, then you have basically isotopic calculus, so this combination comes hand in hand with the settling of gas into more thin structures which prevents the flow, say, in the major access direction,
09:38:03 this was our rough interpretation, but could be refined.
09:38:13 I guess I can say something.
09:38:18 I guess my feeling about this is that
09:38:22 we might be thinking about this in the wrong way for thinking about, you know how the outflows from the disc are, you know, creating and I saw, and I saw to be in the middle of distribution.
09:38:33 I could believe that that's happening you know along around specific types of galaxies where there's a burst of star formation or there's a burst of activity, but at least in our models, you know, the vast majority of metals are deposited in the CGM long
09:38:49 before redshift zero.
09:38:50 So, it's not that you're seeing an anisotropy that's associated with, you know, the way that outflows are being deposited now the star formation rates are just too low, the velocities are very low today, most of that stuff was put in there a long time
09:39:06 ago.
09:39:07 And as a result, I think when you see these sort of as a mutual dependencies. What you're really seeing is a dependence on phase not a dependence on injection time or injection mechanism is which, which phase of the metals Do you happen to be looking
09:39:22 looking at when you look in the as a musical direction versus the the planar direction around a disk galaxy. And that's, that's really a question of, you know, the dynamics of cosmological inflows and outflows and recycling and these sorts of things.
09:39:36 So to me that's how I think about as mutual dependencies, it has nothing really has very little to do with, you know, what's going on with the galaxy right now, unless you happen to be looking like MIM 82 or something like this.
09:39:50 You know, other than that, it's, it's really something that that we have to interpret it within the context of, you know, sort of the the phase structure of the CGM.
09:40:03 Okay.
09:40:08 JOHN. Yeah. And, you know, kind of going along with the face structure thing, one of the things that as an observers kind of little disheartening window and talks about all of the mass being at tend to the seven K.
09:40:21 You know that's a very tough phase for us to observe and to characterize and is likely a large issue for observers trying to quantify the the mass of Galactica flows, but I was curious, you know, last week, and other talks we've talked a lot about the
09:40:41 interactions between phases. and so in these simulations when you have when you create an outflow of a given phase, doesn't matter what phase, it is, does it stay in that phase is there phase changes that happened in different portions of Gallic galactic
09:41:02 outflows is that important for the dynamics and the evolution of Galactica flows and how can that kind of relate to our observations, where we only have a very thin slice of face space that we can actually characterize these things so maybe this is you
09:41:21 know Ching goo and meow and Romeo. This is stuff that you can talk about in in different simulations and how that might impact our understanding of galactic outflows like that.
09:41:35 Yeah, now and who do have a coin. Yeah, I mean, though, I think, though, it is different. Also, I think the what Dylan mentioned is basically the hot guests driven out by black home feedback and feedback.
09:41:52 And what I think of the meal and I usually looked at it was the hot gas driven out by this supernova feedback and Derek in those case, we usually see that there is running factor is too low.
09:42:07 It's not kind of the order of unity so kind of the point 1.2. But the main point we really, we usually make is they really have a high energy loading factor.
09:42:22 So, and they are really the responsible for heating the CGM So, I mean, I think I agree that it is unfortunate that you may not really see those guests in observation very clearly, but they tend to we need to have some vendor on those pages to understand
09:42:43 that just to understand the total mess, offering mass budget, really need to understand that really understand the energy budget there.
09:42:51 So, We all can add more again.
09:42:56 So yeah so in terms of those, for example face doesn't stay I days original state. Yes, certainly, I think that's you know that's many work has been looking into that for example the podcast and the cool guys interaction therefore there could be condensation
09:43:15 and there could be evaporation so in that way, you know, as, as, you know, together with this phase change The Mentalist they also, you know, transition from one state to the other.
09:43:27 And also for the hot gas, you know, the hot offload they can really go much further than the cool outflow was you a jacket, out of the desk and don't.
09:43:38 I think, you know, you should also you know those help flow they can they can also cause precipitation at very large, radio, and then there The Mentalist able to be, you know, partner had us parfait from this heavily leveraged outflow.
09:43:54 You know, way observation already becomes cool
09:44:00 for me and Dylan Do you guys have any comments,
09:44:04 Based on the cosmological skills.
09:44:07 I think this phase exchange can be very hard for the cosmological simulations due to a limited resolution so frankly that's where I would want to learn more from the idealize studies mean if you see the kind of stuff, which happens in very high resolution
09:44:23 outflow simulations that of course it makes you worry about the cosmological simulations, with roughly what 2200 times worse resolution in there, probably, so it may be a regime where we need more sub grid modeling to capture that phase exchange or.
09:44:38 Well first we need to know how important it is and when it's actually happening and what regimes, and then what what distances around galaxies of what types of what kinds of flows.
09:44:50 I think I'm not an expert on that.
09:44:51 But if it's important.
09:44:56 Then it's probable I mean it's possible to say cool components of outflows in low resolution simulations are underestimated Of course because we would have naturally crappy resolution that might be required to resolve some say cold treatment or cold,
09:45:14 cooling, in, in the frame of an alpha. So,
09:45:20 yeah, I think this is the entire point of our phenomenal physically evolved wins model that that she should show you and Neil and myself and others have been trying to put together.
09:45:35 But yeah, exactly right. I think it's, it's, it's, we should we need to treat this as a sub grid problem in the face exchange and the way that the propagation happens in relation to that in the metal mixing something it should be treated in a subgroup
09:45:49 way in the, in the cosmological models which it's for the most part, not at this point.
09:45:56 That's right. I just showed you the comment that it's also even hard even also it is also difficult in our type of the idealization nation. Yeah, I mean the person that illusion is not enough.
09:46:08 Yeah, so justification for some good model, whether it's few.
09:46:13 The one that you're involved with for meal or, or, you know, there are a number of groups that are working on this, and I, yeah, I think it's justified but.
09:46:24 Okay, I've got a question. Yeah. Can we talk a little more about some good model, because I think that's a relevant question for everybody like you need a billion talk, a main, you know, his great talk shows such nice evidence of like brought pictures,
09:46:38 I mean, you know, his great talk shows such nice evidence of like brought pictures, but we he didn't get a chance to talk a lot about the subgroup models involved and that's a big unknown right now.
09:46:44 Can we sort of come up as a community some join tests like or joined observation constraints that might help the simulators to constrain yourself great models.
09:46:55 What is the most useful thing for you actually.
09:46:59 What's the most useful thing for the simulators. Yes, from observation they'll say, what would you want us to give you.
09:47:06 Well, okay, um, the thing I worry about, and I brought this up in the slack chat is is tuning of some good models a little too closely obviously we need to tie them to reality but.
09:47:21 But is there a possibility that we can overturn these models and have it ultimately be representing like hiding, certain, certain physical mechanisms or phenomena that, like, for instance, if you had, it was brought up in the in the slack that if you
09:47:36 have to like over tune different models for different sub grid behaviors interacting you might hide the presence of something else, whether it's cosmic ray behavior or magnetic fields turbulence something like that, is this is this a concern.
09:47:53 I mean I'm concerned about this but but reveal Dylan, meow Chang goo other simulators who are present.
09:48:00 What, what do you guys think, is this.
09:48:06 It gets it comes out in the wash we shouldn't worry so much about this or.
09:48:13 Well I mean I, you know, the way I look at it is, I'm telling people like like me and john who, what, we need from a cosmological perspective. Right, I have no idea whether it is cosmic rays or what that's that's giving rise to this and I don't pretend
09:48:30 to know that at least directly from the simulations.
09:48:34 So, in that sense, I think you just have to sort of view this as sort of trying to meet in the middle.
09:48:43 But yeah, now I think I think for me it's still a big problem as to how do we accelerate the bulk of the gas, up to the sort of velocities that we need to, you know, blow it out of the Halo, you know and and and Dylan's exactly right that that you know
09:49:04 what you put in isn't what you get out. But nonetheless, even what you get out isn't necessarily what you get What is predicted from the, you know, from the kind of simulations that check the does or me out, right.
09:49:16 So, I think there's still a big mismatch there.
09:49:20 You know, you can accelerate the high, the the hot wins to these large philosophies, but what about, but that's not the the bulk of the mass and we need the bulk of the mass to actually be accelerated to these higher velocities.
09:49:31 So, so yeah I don't know what the answer is. And I agree that that's still that's still a gap that we don't know.
09:49:43 Other comments from the panelists.
09:49:49 Just a.
09:50:06 Okay quick answer as to what we need from the observers that's why partially why I think outflows are so cool, because we've had roughly a decade or 15 years of galaxy simulations, who've been carefully compared to galaxy properties and never once and
09:50:10 really has have these kinds of simulations been compared to direct measurements of the baryons cycle, what the gas is doing outside of the galaxy. So that's why I think that, with more sophisticated comparisons of what we can infer for outflows and also
09:50:26 influence. Yeah, but these will be constraining the, the effective when models and the subject physics, even more than we can do by just constraining say the stellar mass content and the gas fraction inside the body of the galaxy which has been the past,
09:50:40 general approach, right. So, if we actually had a really strong determination of the radio velocity of outflows as a function of distance and stellar mass at 10 k PC I'm sure you would already roll out most simulations right.
09:50:54 But I think there's a big gap there to make that comparison to make such a strong constraint. But yeah, I think direct outflow data is what we, what we need to learn how to compare against it.
09:51:07 but once we do I think that's very interesting.
09:51:11 Good point.
09:51:12 Good identification on on what we need.
09:51:17 From the observers near has a has been very patient and has a related comment all of this, I think.
09:51:25 So I guess this really plays off some of the comments that were just said but I wonder if we want to try and constrain the different feedback models and differentiate between some of the very different assumptions that go into these different simulations.
09:51:39 Are we better off looking at the properties of the galaxy and or interstellar medium or are we actually better off at, you know, looking at the certain galactic medium I, I thought that, in terms of the stellar mass properties, basically all models we're
09:51:56 in good agreement and Elise pointed out to me on the slack that apparently there are disagreements, the factor of two or three level but I wonder, Is that enough to really distinguish between the different feedback models given some of the observational
09:52:09 uncertainties, which are also the factor of two to three level perhaps the CGM would offer much larger differences. And if the answer is yes we should go to the CGM what resolution Do we need in cosmological simulations in the CGM to in order to be able
09:52:24 to effectively do this. And if all we wind up saying as well we can't do good resolution in the CGM so let's add more some good models into our wins and into our CGM for like few which I think is super cool but it again it's another sub good model.
09:52:39 And then, which is sub grid model over some grid model over a sub grid model how can we ever hope to break the degeneracy of the base level.
09:52:49 Excellent point.
09:52:52 And it's this is, this is the concern I think this is what keeps me up at night.
09:52:59 Meta sub grid models that are too sensitive to the underlying layers that could cause artifacts that aren't real or whatnot.
09:53:24 Well, I have a response but I, there's a lot of people have their hands up so I want to get to them.
09:53:15 Well, I'm wondering how many of the people with hands up her questions or comments related to this discussion like a new questions, I guess who's been waiting the longest, Ben.
09:53:26 Ben up. Shoot, I might typing in the slack in the zoom and I can't even remember what I was going to say but okay.
09:53:43 I think what is really interesting is, you know, talking about Barry and clearing like.
09:53:44 and, you know, this is off of Tim Hoffman's comments about that. Maybe, maybe not, but I do want to, I've been commenting and zoom that there's this work, nice work by john Dave Davies Davis.
09:54:12 Still Davies, looking at eagle and Lester's 10 G and finding very different behaviors that both show an anti correlation between the mass in the CGM added to given Halo mass like around 10 to 1210 and 12.5 Halo mass and SMB Ah, so like the more massive,
09:54:33 you know, the more that SMPH holds a record of the energy feedback. So the more massive the SMB ah the more energy has given to the CGM over its lifetime.
09:54:51 And it'd be really interesting to look at that. But, um, when is that happening and I think in unless there's TMG it's happening more in the later universe.
09:55:03 Whereas, you know, and I think that's an interesting question of whether that is this observed. Can we observe this mph CGM anti correlation.
09:55:14 You know just broad properties of CGM mass and SMVH mass and to when it when doesn't happen. And that's a big topic we're going to be talking about, I hope that this week in the next few weeks.
09:55:29 Just.
09:55:44 Oh well now Ben starts talking about Barry on retention fraction and Barry on clearing and I'm all excited, but I actually have a question, going back to the previous discussion, um, then I totally agree.
09:55:48 I think that that's very exciting and like from an observational level I I worry about you know constraining obviously the overall Barry on content, and by phase and things like that if a lot of thoughts about it but the question is just Dylan in your
09:55:58 talk, you had you had your slide early on about you know sub grid physic physical models and you know how you derive them and how you implement them in the simulations and you had something on there that was like talking about a preferred scale at which
09:56:14 you implement them or something. There was some reference to preferred scale and I'm just wondering like what is that scale and how do you how do you decide on it.
09:56:27 This was a yes this is just a commentary and sub grid, as a whole, not necessarily some great feedback of even replies more generically more straightforwardly in terms of a sub grid.
09:56:39 I some model as we call them, which is indeed related to feedback but ok so the point is simply that if there is a need to resolve certain things and not resolve certain things for instance you want to run a larger simulation so you don't want carsick
09:56:55 resolution in your ASM, then you want to make a dividing scale, which makes physical sense so that you can create a physically well motivated model for what's happening below that scale which you can also implement in a numerically robust way so I mentioned
09:57:10 very quickly that the GMC is are such a scale in lots of currents large volume simulations right It simply means that we choose, kind of, not by choice but we have decided not to try to resolve the MCs.
09:57:25 Right, that's one way to phrase it. So then what's ever going on in terms of collapse on the scales of a few hundred parsecs and lower. This has to be treated in a different way, and different simulations do that in different manners.
09:57:38 As soon as you break that barrier. And then you have to go much further right this is, this is a fire model in some sense as soon as you get rid of that model.
09:57:47 You can't stop until you get down to a certain level of next level of realism or physics which can then do some self regulation in what is now in a more complicated resolved by some.
09:57:59 So, yes, these natural scales to break the models that I think are important to think about because they exist in every galaxy simulation. Do you think that there's a natural like an analogy in the CGM for those kinds of scales, like, like some kind of
09:58:14 like cloud threshold size or something.
09:58:17 Maybe with the whole starship mothership debate thing that was going on, so there could be I think we need to answer that, but I would say it's entirely unknown right now.
09:58:27 And it's really related to the existence of the super small scale structure or not and if it does anything or not.
09:58:35 And these I don't think we have answers yet from the simulation side.
09:58:45 Evan has been waiting patiently.
09:58:58 You guys have said that you know what you get out depends on what you put in, but I'm wondering about the degree to which you understand why what you get out is what it is.
09:59:10 So, Kartik was specifically asking about you know this relationship between outflow velocity and Galaxy mass.
09:59:18 And what sets that, and so I can see why if, you know, mass loading is higher for lower mass galaxies and outflow velocity is set by the ratio of energy injection and mass injection then that would lead naturally to you know this velocity correlation
09:59:34 but I don't know intrinsically why mass loading is lower is higher in your last massive galaxy so I'm wondering I mean do you all understand that is there a simple answer but I just, I just don't know
09:59:54 what there's, there's a very simple answer and then there's more interesting answers maybe the very simple answer is that, just in terms of the simulations I know best right the tng model, the velocity of an outflow at the injection scale is in model
10:00:12 input. And we have a scaling linear scaling on the dispersion.
10:00:18 Actually, it's actually the dark matter dispersion, which is simply a tracer of the potential depth if you like it's a treasure of the, of the halo scale.
10:00:26 So, these lines were on some of the plots I showed but I didn't have time to go into this, they showed for instance the lot the expected velocity as a function of galaxies still the mass of the model input and then how that changes when you look at flows
10:00:40 in different places at different times. So, for instance, we started to be more clear.
10:00:47 We prescribed that the velocity of outflows increases with Hegel mass right there's no other way to say that we do that because we need such a scaling to reproduce the galaxy population constraints, like the stellar mass function.
10:00:59 This is the whole motivation behind. Choosing certain scales with certain parameters.
10:01:08 That said, so once you have that kind of input in the model.
10:01:12 Secondary correlation like what I showed with respect to the star formation. Main Sequence offset, which is to say that high star formers dry faster outflows, this is in no sense directly input into the model and then we'd like to understand why it is
10:01:26 that secondary correlation with a different property come about, and they're the answer can get more complicated, I think, and this is where the simulations get interesting to think about, of course, the fact that the last increases with galaxy mass.
10:01:40 This is an input, in some sense, but the details that so exactly what the velocity is at 10 or 15 to about six and a certain phase.
10:01:50 That is not that is a very interesting convolution of the inputs, with the Hydra dynamics and self gravity and everything else which has been solved.
10:01:59 I don't know if that answers the question yeah maybe i mean i think what I was trying to understand is the difference between the lines that you drew on the plot that shows your velocity injection model and the velocities on that plus measured it wherever
10:02:13 you measured them. They were different lines and I was wondering if you understand why they're different.
10:02:20 But other people can say whatever they have to say about it but that's, do you understand my question, because of the flows have evolved, between where it started and where I'm at.
10:02:33 So why because at that point person.
10:02:36 Why, why did they evolve the way that they did.
10:02:42 Well, indeed, there's two answers. The first my simple answer is that simply evolved according to the couple of equations of Hydro and self gravity. That's what we're solving so hyper dynamical and gravitational forces slowed them down.
10:02:57 That's why they slow down. I don't know how to say we, of course there's more interesting analysis to do in that question.
10:03:12 father's comment.
10:03:20 I think the details of it of its modification over time. Sure, yeah you can just chalk it up to Hydro and the gravitational potential of the system but it doesn't seem to me that that's an obvious explanation for like it.
10:03:33 A democratized difference in behavior that that evidence pointing to here.
10:03:44 just continues, or just well no I mean just separate lines for different systems i i agree with but with what you said Dylan but I think I don't think it's all figured out.
10:03:55 I guess I think there's reasons. Certainly not.
10:04:01 Britt Lungren has been waiting very patiently.
10:04:04 Our final question for the camera yeah I hate to be keeping everyone from lunch.
10:04:09 But and this also goes back a little bit in the conversation but, you know, when we were talking about different ways that simulators could could test models with observations what questions could we, you know, answer having to do with outflows I think
10:04:27 it would be, I think it's pretty clear from things wrong mon has has pointed out Nicola as well and shall win in the slack, that there are certain phases where we really are doing a good job of picking out the outflows like magnesium to it's really clear
10:04:41 that we can at least in that phase see that as a result, you know Angular geometry of these outflows quite well over over now or pretty large range and redshift and the samples are growing so I just wonder if, at least in that I on if there's work that
10:04:56 can do to differentiate between ELNTNG and different modes and feedback in the elemental geometry in particular, at that I on.
10:05:06 So that's kind of my, my question is there something we should be looking for in the radial extent or the opening angle or something that would help.
10:05:24 Positive possibly not, you're not sure I have an immediate answer to that question.
10:05:29 As I said before it was interesting that those two models returned such a similar expectation for the multiplicity dependence on angle. In this particular regime that we looked at.
10:05:40 I think there are many many differences when you go further, but I meant I haven't thought about differentiating between those models say and in terms of CGM observer pools.
10:05:54 But,
10:05:56 I mean, you certainly can.
10:06:00 Just to not answer your question about magnesium to let me mention oxygen six, and this goes back into two years question about what what data has been used can be used outside of galaxies, I think.
10:06:11 Oxygen six is an amazing example right, we had this data set, emerge from Castellanos there was roughly one to two papers from every simulation which tried to compare to this data and most simulations had big trouble.
10:06:23 To do so, with a generic very generic conclusion being that calm density simulator calm densities of that ion or too low, very generally speaking, so I think we already have these kinds of interesting data sets and magnesium to is another interesting
10:06:39 example which could be much, much harder for these cosmological simulations, because of the lower resolution and the fact that some of this gas particularly say in the outflow could be emerging due to physics which is not well resolved.
10:06:54 But yeah, the oxygen six comparisons were a great example of this and I think comparisons for the magnesium to and the angular dependence. These are far few and far between right now, so it was kind of waiting for people to compare more into space.
10:07:12 Yeah, just wanted to add on this this conversation that the predictions will relate to metallic city was interesting is, is the sum of metals of a hydrogen, right.
10:07:26 So, the magnesium to tourists are in front of me often like each one information right that would be very important to to get to them at least.
10:07:36 And again, I'd like to mention the dusts effect that often is challenging to take into consideration, but it's important causes studies.
10:07:48 So I agree with what you're saying I think for somebody like worrying and looking forward to, to see more studies and comparison with what, you know, the submission of predicting and which of the, of the different physical properties you know we're going
10:08:06 to train businesses that have observations. Yeah.
10:08:12 Okay.
10:08:14 We're a bit over time, great discussion. Lots of good questions raised I'm sorry I didn't get to all the questions that were in the, in the slack, but hopefully over the coming days and weeks people can glance over some of the things that were discussed
10:08:31 there and comment on them.
10:08:33 And, and, and we'll save some of these discussions for for the next few days after Tim's presentation, Tim Beckman's presentation on Thursday after some excellent tutorials tomorrow one on mass loading by Evan Schneider, one on white profile fitting by
10:08:51 Marie Lau, and a really cool visualization tool Cosmo, is that Joe Birgit will be presenting. And then Friday will have obviously lots of time for discussion on these topics so thank you to Dylan excellent presentation.
10:09:07 Thank you to our panelists. I think we got a really reasonable discussion on it with a lot of different perspectives on these topics so thanks everyone and continue the discussion, I'll copy and paste all the comments from the zoom chat into slack for
10:09:21 for reference.
10:09:22 Alright, have a wonderful day everyone.