09:30:18 Okay so, um, thanks everyone This has been a very exciting six and a half weeks and we are in the homestretch now so it will be very interested to see how this workshop ends. 09:30:32 So, today I would like to start by an illustration of why gas multiplicity provides us with only a week diagnostic of gas flows in the CGM, you know it's useful but at the same time, incomplete are then demonstrate in contrast elemental bonus ratios can 09:30:52 can actually give us a fossil record of the chemical enrichment history. And for that reason, they can help us resolve the physical origin of the gas that we see in the CGM. 09:31:06 And of course, go over some caveats that we have to keep in mind when doing these kind of measurements and fine, I'll show you some examples to convince you that this is a measurement, it is not only possible but also doable right now. 09:31:15 So, I would like to start with this old quote, dating back from the 1830s, which came from a French philosopher Kant, you may recall him from your college philosophy class He is known as the father of positive ism. 09:31:32 But in this case, which is probably not one of his prouder moments he said that in the future, astronomers would be able to figure it out the shapes, the sizes, the motions and even the distance of the stars, but for some reason he believes that their 09:31:44 chemical composition would forever be unavailable to us, as you know, killer clearly that didn't age well at all because within less than 30 years from when he wrote this modern spectroscopy was invented and by the end of the 19th century we would have 09:32:00 figured out the chemical compositions for about 10,000 stars, but it does make me think a little bit because what about the CGM, you know Is there much scientific value in studying the metals these obligations Halo, can we actually use it to understand 09:32:17 the physics of the CGM. It seems that this is still a matter of some debate. Judging from a bunch of Pfeifer discussions that took place in slack over the past couple of weeks, and throughout the workshop, actually. 09:32:31 So really the practical side of this question is whether guess my philosophy is a good diagnostic of different processes occurring in a CGM, and in some rare cases you can actually make a case for that. 09:32:45 So, this is a figure from a paper that I wrote with my carafe. A couple of years ago, where we looked into the gauges environment around a couple of low luminosity and low mass alignment or five meters at it from about three. 09:32:59 We constrained it gets multiplicity to no more than about 1% solar and in some cases as low as only a few times 10 to the minus four solar. 09:33:08 And in this paper we concluded that we were looking at evidence of ongoing a Christian from IGN filaments on to the slowness galaxies. First of all the matters the as I said, is really low consistent with the enrichment level in the general alignment 09:33:22 off of force at the same breath chief. At the same time, it is more than an order of magnitude higher than the I SMS list of these galaxies. 09:33:30 We also see a couple more evidence to support our claim, for example, we see a really narrow line with and low velocity dispersion in the absorber suggesting a dynamically chord structure, which is consistent with expectation from elementary info in cosmological 09:33:44 simulations. We also find that the course assignment off a mentor in projection actually shows a blue pick dominant. I am an automation which is very very rare. 09:33:53 And that's, that's consistent with expectation from readiness transfer in an influence structure. 09:33:59 So basically what I'm saying is methodology can be a useful diagnostic for that to be the case, you usually have to rely on multiple strands of evidence, not just the chemical abundances but also the kinematics the geometry and the dynamics and so on 09:34:14 and so forth. 09:34:16 But more often. Things are a lot more complicated. You know, just a couple of weeks ago during the artful week there was a lot of discussion, which also actually happened yesterday about this as a modal angle dependence of CGM absorbers. 09:34:30 So let's look at this spot right here from a paper by so improved back in 2016. So he was investigating how gas my philosophy around the LA host gasps he would vary as a function of as he will angle of the key so sidelines. 09:34:44 The same expectation, if we assume that our flowing gas has a high mentalist the den are falling gas would be something like this on the left, where basically you see higher medalists east, towards the minor axis and lower messages to watch their major 09:35:18 But instead, what Celine found seems counter to what's predicted by the simple physical picture, because sometimes the guests that she detected on the minor axis can have very low multiplicity whereas the guests etiquette lawmaker access can have high 09:35:15 Metro cities. And here's a similar picture found by Stephanie point and from the Swinburne group back in 2019. Again, Stephanie here was trying to search for a relationship between gas metals D and D as it will angle. 09:35:28 And again, she finds essentially no trend between these two quantities. 09:35:33 So what I'm trying to say here is that things in the universe are probably a little more than once that we sometimes are ready to acknowledge and the point I would like to make is that gas my thirsty so weak and at best incomplete diagnostic of gas flows 09:35:47 in CGM. 09:35:49 Here's a more recent results from Zach haven who looked at the methods of distribution environment in the system similar to in the fire simulations. 09:35:56 Zach founded by management systems, environment limit systems in flowing gases Dustin to have lower mentality they're not flowing gas it on average, but there is still a lot of overlap between them in terms of the MIT distribution. 09:36:09 And on the observational side here are some of my own work because allergy. 09:36:14 Looking at the guests Methodists the in the CGM of massive galaxies. I found large metals the variations, often more than a factor of 10 with an individual halos and this seems to be a common feature in the CGM this massive galaxies. 09:36:27 So I wrote the following in the paper. 09:36:31 And to my delight he has a very similar statement in Zach's paper. It makes me happy because you know this is one of those rare instances in which there's actually a perfect agreement between theories and observers. 09:36:42 And I mean it does make sense because you know you have a background site line, cutting through a pass fail over several hundreds of parsecs often throughout the Halo. 09:36:52 So if that's the case, it's really not that surprising to encounter gas, which has multiple different origins is it. 09:37:02 So, where do we go from here. 09:37:05 I would like to show you this picture of the M 81 system to drive this point home. 09:37:10 This is a beautiful image showing a large scale map of neutral Heidi and distribution around me at one end and its companion galaxies. You can see here, a large carbon infraction of optically thick h one guess we didn't 52 parts are so the reason I like 09:37:26 The reason I like this picture is because number one, this is real data. And number two, it shows us that the universe is really a complex and messy place where things are never as simple as we want them to be. 09:37:37 We see so many things going on here, rotating disk strip gas outflows, and so on. And it's such a mess in the CGM. 09:37:47 It's natural to wonder, Is it really a hopeless situation after all. 09:37:51 Well honestly this is a trick question because the answer is, to me, no or otherwise I wouldn't be giving this talk. 09:37:58 I'm not a defeatist, I'm not going to declare a loss here. I don't doubt the scientific utility of measuring metal cities, but I think we as a community we need to do better in the future that we have been in the past, because there are other things that 09:38:17 we need to consider because they may help us in our effort in the future. So, what I'm here to advocate today is that we can use elemental abundance ratios to help us establish a stronger physical ties. 09:38:25 We diffuse guys that we see in the CGM, and all the different processes that happen in galaxies over a different time scales. And by the end of this discussion I hope I can convince you that this is not only possible but also doable. 09:38:39 So, to motivate this discussion. This is an the gold or periodic table that we are all familiar from high school. 09:38:48 And, except this one came from a recent review by Jennifer Johnson and what's different about this is that it has been color coded by the different Nicholas synthetic origins, for the gas, you see, you know, big beneficent exploiting massive stars, white 09:39:01 dwarfs type on a supernova and so on. 09:39:04 And here in squares are some of the common elements that we often see in their various guises of ionization in absorption my studies. 09:39:15 And based on this. This is why relative abundances of different elements are kind of amazing, because they provide us with some kind of an archaeological record record of past enrichment episodes that the gas has been subject to. 09:39:46 So, for a long time. This type of investigation has been done but it remained primarily the domain of people investigating chemical abundances in dem I'm an office systems, why is that well because what we do as you don't really have to worry about an 09:39:52 a nice effects on account at the gas in Canterbury optically thick, but you do have other issues that we will go over it with a later. 09:40:00 And this kind of investigation became possible basically as soon as we were able to get high resolution specter of large sample of kilos which happened after Kak and high risk were installed in the 90s. 09:40:13 So here is one important early work investigating chemical enrichment history in hieratic delays, from the mid 90s. So this blog shows the observed elemental abundance ratios of different elements product relative to the elemental iron abundance or my 09:40:29 thirsty of the gas. 09:40:31 So you can see some common features here. 09:40:34 The most prominent of which the one I circle is perhaps the fact that delays show a predominantly off element enrich abundance pattern. 09:40:44 And that's exactly what you expect. And that's exactly what the offer is concluded that the bulk of heavy elements in the Las were produced, basically, by core collapse supernova in massive stars, and that they were negligible contributions at the higher 09:41:01 ups from, intermediate, and long hours are from Taiwan a supernova. 09:41:07 So this is another example from my own work. 09:41:10 And in this case, I was searching for and looking at the properties of cool gas at only a few projected to a prospect away from massive elliptical galaxies using reputational lenses. 09:41:24 And what's super interesting is what I found when I looked at the relative abundances of iron and magnesium in the gas. 09:41:30 So do you still plot show the observed iron to magnesium ratio of individual absorption components in the y axis, versus the velocity of each component in the x axis, the solar iron, magnesium level is marked with the horizontal line. 09:41:46 And by observed here I mean simply ionized iron and zinc, magnesium. 09:41:52 What I find is that whenever it cool guest is detected. 09:41:55 It shows uniformly high solar level or even super solar, iron, magnesium, abundance ratio across the floor kinematic spread after gas, suggesting that the gas has been highly enriched in iron. 09:42:09 This indicates that the gas has been highly enriched by Taiwanese supernova, which, as you may recall, is in contrast to those hieratic de la measurements we just saw before. 09:42:21 And since I've done this, there has been more measurement of iron, magnesium ratio in Lance galaxies, which confirm our conclusion. You may check out the recent paper here by Francis Cashman from vertical colonies grew up in South Carolina. 09:42:36 So because of this different Nicholas synthetic origin, we can obtain a valuable insight into the origin of the gas by examining the chemical makeup of this GM and its variations which for example star formation history and distance from galaxies. 09:42:51 So this is a plot of the radio profile of the observed aren't magnesium ratio as a function of distance in the core CGM massive galaxies here I showed you in Fred will start forming galaxies are shown in blue. 09:43:04 So there are a number of interesting things that you can see here. First, you see elevated iron to offer ratios in the CGM of ellipticals compared to start forming galaxies. 09:43:15 And second, it looks like the eyedropper ratio in the CGM of passive galaxies declines with increasing distance. 09:43:23 So what this tells us is that within about 30 kilobits or less from massive ellipticals type on a supernova have completely but significantly to the chemical enrichment. 09:43:33 On the other hand, the other CGM is iron poor but rich in alpha capture elements, indicating a much earlier enrichment epoch, and this is consistent with a more chemically primitive gas, which has been acquitted from the AGM. 09:43:51 What is also suggests is that type on a supernova may play an important role to regulate the gas cycle in massive galaxies. 09:44:01 And this is one more reason why this is really interesting, the magenta rectangle here marks the range of measured iron to offer ratio in extra observations in the hot atmosphere in X ray of local ellipticals. 09:44:20 And the interesting thing here is that you can see that it is consistent with what we see in the cooler face of the CGM, both in terms of the media value as far as the range of the value see seen. 09:44:31 And the reason I want to show this is some reason observations have discovered a correlation between molecular gas mask and thoughtfulness of the heart atmosphere in a wide range of elliptical galaxies. 09:44:42 So this kind of correlation points to a possible causal relationship between the hot Halo and the cooler gas. 09:44:48 And I think the sheer similarity in chemical composition, seeing here supports this idea that condensation from the hot atmosphere, could be a significant source of the cool gas at least closer into the galaxies attentional scale or so. 09:45:03 And by the way, this idea of calling from your heart Halo is the topic of a new results video that I posted a couple of weeks ago. And if you haven't seen it, make sure to check it out. 09:45:13 He has a QR code that you can scan with your phone and it will lead you to the video, I will post the slides later. 09:45:19 Alright, so let's go over some caveats. Here are a couple of things that you might want to consider if you want to start measuring elements of abundance ratios in the CGM. 09:45:30 The first potential complication is differential dust depletion. 09:45:34 This arises, simply from the fact that some elements are more refactoring and others, meaning that they have a higher condensation temperature and so they go into dust grains more easily. 09:45:47 A good example of this is chromium manganese an iron. 09:45:50 So this plot from anime said he has paper. A few years ago, shows you the depletion sequence of some elements elements on the right of the pot here are more easily depleted into dust than the ones on the left. 09:46:04 And so we have known for a while that this effect is most severe for things like delays, but it can also be important in strong economic systems, especially if they have high metal a city. 09:46:16 But thankfully, this is something that we can correct for you can for instance, use the observe ratios of zinc, relative to iron in the gas, which we know have very little nuclear synthetic difference over a wide range of ethnicities, based on measurements 09:46:32 of Milky Way stars. 09:46:34 And we can use us to infer how dusty, the environment is. and we can correct for the expected level of dust depletion in some elements, like for example, iron and magnesium, and then correct your gas multiplicity your abundance ratio accordingly. 09:46:54 Another thing that you have to consider is the correction, why is that well that's simply because we observe ions in a CGM and ionic ratios. So if you want to convert the relative abundances of ions into the elemental abundance ratio. 09:47:10 You have to first correct that by the relative energies even fraction of the two elements like what I'm showing you here for iron and magnesium. 09:47:20 So to show you some example this spot on the right shows you how the relative. 09:47:24 I noticed in fraction of magnesium and iron changes as a function of a guest density for both optically thin and optically thick guess these are calculations done with cloudy, the photo in addition code. 09:47:39 So you can see. Therefore, iron and magnesium, there's actually little differential analysis and correction, if you are comfortable in the optically thick regime, like, I'm a limit systems and delays. 09:47:50 But this effect can be important. If you're dealing with a particularly thin gas, especially at low gas densities. 09:47:58 And the way to take this into account, which is probably already obvious to you is to perform a careful ionization modeling of the gas. 09:48:07 So this kind of analysis will often require you to both decompose the gas into multiple components and then model, each of the components carefully. 09:48:15 You may also find that you need to invoke more than just one single face of gas in order to reproduce the data, like what we've heard from Jane Shelton and Samir. 09:48:25 Earlier in the workshop. 09:48:28 We also heard from Chris earlier about how you can use this day, kind of modeling for instance to influence the sizes of clouds in the CGM, he's absolutely right of course that we should be careful about considering the arrow budget, due to for instance 09:48:41 uncertainties in the radiation field, as well as you know, things. 09:48:46 But this, if you do this carefully enough. 09:48:49 I would like to just show you for the last few minutes of my talk, a taste of some of the things that we are already able to do and learn now to this kind of careful analysis. 09:49:00 So these are some really new results from an upcoming paper. I'm writing based on my work with the cops collaboration which should be out in several weeks. 09:49:08 So here I am looking into the chemical abundance ratios and gas medalists the environment and the systems based on detailed component by component, and engine analysis. 09:49:18 And this is one of them. 09:49:20 So our measurements of both mentalities in the x axis and nitrogen to offer ratio on the y axis are shown with blue stars here with each one marking an individual absorption component. 09:49:33 The other points here show you measurements of gas space abundances and ratios in individual h two regions of both normal spiral galaxies and dwarf galaxies. 09:49:45 So as, as you can see both the overall metal Estes and the and to alpha ratios are consistent with the observed values in the individual regions of dwarf galaxies. 09:49:57 You may ask them what about the galaxy environments. 09:50:00 So here it is. It turns out that there are actually a close pair of low mass gases within a projected 20 to 30 kilometers away from the background sightline here. 09:50:13 So, isn't that interesting. Because, where am I the guests have come from there, then. 09:50:17 Oh, one likely explanation is that you are looking at strip interstellar medium gas from one or both of these dwarf galaxies, and perhaps that will be a result of some recent gravitational interactions when disclose pair of two of galaxies. 09:50:36 Students have one minute or so so let me just show you another example. This is another woman limit system at a somewhat higher redshift of point six. 09:50:45 And again, as before, the boost are here are my data points. So what do we have here now. 09:50:50 So these components. 09:50:53 As you can see, are more metal rich than what we saw in the previous system I showed you in this case the components ranges from a third solar to slightly above solid metal city. 09:51:04 What But what's also interesting here is that the gas is also rich in iron. 09:51:10 And in nitrogen, relative to the alpha elements. So here's a plus showing the iron to offer ratio is versus them mentality. 09:51:18 But one of the components. 09:51:21 This one, which would actually be classified as a partial payment system because the column Nancy 16.5, in each one in log is actually both metal rich solar mentality, and yet at the same time highly alpha, and rich. 09:51:38 In fact, observed island to offer ratio for this one is actually comparable to what has been observed in the halo stars in the Milky Way. 09:51:47 So what about the galaxy environment. Here it is. 09:51:51 This is a false color image, made from a muse integral field data cube of the system. 09:51:57 So this environment appears to be pretty isolated and kind of lonely environment actually in which the only galaxy we find at less than 300 kilobits per second way is a super star star forming galaxy within about 30 kilowatts sex in projection, which 09:52:12 is shown here. 09:52:14 shown here. And what's interesting is the sideline posts the galaxy within less than 30 degrees from its minor axis. 09:52:20 So if you just focus on this one, offer element in rich environment. 09:52:25 Both the high majority of the gas, and the I offline rich nature are consistent with the expected chemical signature from the gas expelled. In a star formation driven when, in fact, here are the observed values into hot outflow of mid to which is kind 09:52:42 of very close to where our data point is, so that's cool but then how can you expand this other iron rich and metal rich components, because they are item rich, but at the same time also metal rich, which suggests that they are more chemically evolved 09:52:57 than the other component. So one possible explanation is that this possible galactic when it's not only expelling newly produced fresh material from Kirchhoff supernova, but it's also expelling some existing is m data from the galaxy itself. 09:53:12 So if you would like to know more, just stay tuned for our latest paper from cups, which would be out in only a matter of weeks now. 09:53:20 So basically, that's all I wanted to say, I'll just summarize by saying that gas metal is the measurements in the CGM are great, but they give us only an incomplete at best diagnostic of the dynamical process in the CGM. 09:53:33 I hope I have convinced you that element of abundance ratios are awesome because they provide the fossil record of the chemical entertainment history. 09:53:41 And finally, when you couple of them with knowledge of metal st the kinematics and also a deep gassy survey elemental ratios can provide us with a really powerful tool to resolve the chemical origin of CGM gas and also break some well known degeneracy 09:53:53 is in observations in the process. 09:53:57 So I'll just close by saying that this kind of investigation is not only possible but actually doable as long as one takes into account all the caveats that I went over before. 09:54:07 So, let's try to get more of these kind of measurements done in the near future, shall we. That'd be awesome. Thank you. 09:54:13 Thank you. Sorry, that was great, really, really nice presentation there. 09:54:25 All right. Yeah, let's see if anybody wants to raise their hand or even speak up. 09:54:37 Yeah, well I'll ask something like the iron, you the, the excess iron you see around ellipticals is that because of like kind of intro cluster or Halo type one a supernova going off. 09:54:53 What's the origin of that. 09:54:55 So that's an interesting question Ben because people who look into the iron abundances in inter cluster gas actually did find an excess in Ireland relatively offer elements into hot hit into hot. 09:55:24 And it's interesting that this is also something that we see in these electrical gas within about you know 2030 kilo per second or so so I think what's going on here is that you. 09:55:24 You're looking into enrichment from more recent Taiwan a supernova exploding. Just in the in-situ within you know the cluster itself because if you look within this galaxies themselves because if you look at the light distribution of this vertical galaxies, 09:55:41 you actually see an extended stellar distribution envelope, all the way out often 100%. 09:55:49 So, it is conceivable that that you still see in situ type on a supernova exploding even, you know, at a few tenths of telepathic away from this article galaxy so I think you said really you're really looking at, you know, More recent, you know, access 09:56:04 enrichment in Iran, close to this gaseous compared to you know further out at handful of parts in the CGM, what's the maximum effort to offer ratio, you can get it like from Tech one day supernova ejecta youth models. 09:56:19 You've models. I think if you are, if you are looking at a purely type on a supernova, you can easily get you know a factor of three or factor or four or even five more than enough elements. 09:56:30 If you have a pure ejecta and really what we see here in in in in this ethical gaseous should really be strictly interpreted as a lower limit because again, there's a possibility that you're looking at a significant dust depletion around close to this 09:56:46 ellipticals because the mass was is really really high. In fact, in some cases we see actually molecular gas in around one of these ln scarf see so the actual elemental ratios could be even higher than what we reported here really interesting. 09:57:08 Great. Um, well I encourage you to go to that continue this conversation with sorry, in his breakout room, and if you need help being sent there just, just let me know and that will close our official recorded program here, but I see activity in in at 09:57:27 least two of the other rooms, so I will broadcast a message job. And thank you all for coming today, great tutorials all around, very high standard.