08:05:05 Right. Hello everyone.
08:05:07 Welcome to the Tuesday on galaxy evolution week for Karen zP gashes limos.
08:05:19 I want to.
08:05:22 Before we start with crystal Martin's keynote.
08:05:28 I want to show a new figure a new image from Halo 21 beauty.
08:05:34 This is a jellyfish galaxy.
08:05:37 Discovered by me son, and can see X ray mission in blue and purple and destinations and this is galaxy, you know, a galaxy, interacting with its environment and being stripped and I think I'm really excited about talking about not just Central's this
08:06:00 week but satellite galaxies as well.
08:06:03 So, as you can see, will be using the Slack channel Halo 21 week seven evolution so during our keynote today.
08:06:12 I highly recommend that you go and use that Slack channel to post your questions and we will then
08:06:21 pick from those as part of our panel conversation. Afterwards, before getting to Crystal today I want to talk about future conversations, this week.
08:06:37 And there's a lot of activity in fact today we have two after parties at 1030 is Halo 21 sec GM with Nick recap Talia and dice King the guy. And then also dice game will be very busy this morning, we will be doing another after party with Joe Burke Chad
08:06:56 on quenching.
08:06:58 So that's two solid hours.
08:07:01 If you're really into it, I'm going to be there so it's a, it'll be a busy day, but I highly recommend it because these are really well organized, Peter conversations.
08:07:14 And we have a lot of heated conversations next week, and I will talk more about these as the week goes on and build momentum for them but you can see that there's going to be going to be for future conversations on dust emission new instruments and parametric
08:07:35 model, which is something we will talk a lot about so all of these channels have activity on them so especially new insurance, which was created yesterday, and also parametric model and destination IP been going on for a while so I would recommend that
08:07:55 that you check those out.
08:07:58 Before I introduce our speaker.
08:08:00 I just want to remind everyone of the social hour. Coming up on Thursday.
08:08:08 And I'll keep on reminding that and we'll post a link for that as well.
08:08:13 Okay. A brief, brief introduction today so now I believe is crystal on.
08:08:23 I want to introduce our crystal Martin. I'm here. Good. I was looking for you. It's a little bit hard with zoom but Chris Martin is our featured keynote or our keynote speaker today, and she of course is a professor, local professor for some of you who
08:08:40 are at KTP she's at UCSB Of course.
08:08:45 And we assembled a panel everyone said yes so this was our first choice panel.
08:08:51 Nicholas boo Shay, Sean Chen, Stephanie Ho and Zach Pathan. So, with that, I am going to share my screen, and allow crystal to share
08:09:08 her screen.
08:09:12 Oops, actually I haven't shared. Stop share. Okay.
08:09:13 Hi crystal. Good morning.
08:09:16 Good morning, Ben.
08:09:21 And everyone.
08:09:50 Okay. I want to start out this morning with a big thank you to our for organizers, Mark Cameron bed and Jess. Um, I don't know, I think the last six weeks of just been totally amazing you have really shown that you can run as a super program online, and
08:10:00 and I hope in small some small way I can contribute to that this the this week, but we all owe you a lot of things.
08:10:10 Now on the question you assigned me, that's another matter.
08:10:14 This is kind of a difficult question. And if we think back, only about a decade ago.
08:10:26 Hang on.
08:10:28 We were talking about bathtub models, more so within the CGM.
08:10:43 And if I was more skilled with Photoshop, I would have a picture of a hot tub here with Avishai and Romeo Dovey and maybe nerd and Nick boo Shay and, but this is one of the few pictures of a tub I could find where there was a faucet for the in flowing
08:10:53 gas and a drain for star formation and outflows, and the small offset between those rates was supposed to be the water level and in the tub that was the gas in the ASM.
08:11:09 And these models were amazing because they explained so many properties of the galaxy population, but they had no circle galactic medium. It wasn't deemed necessary at the time.
08:11:24 So, one thing I want to point out is that in this model inflows and outflows played a big role, but we didn't really talk about this reservoir of gas that we now call the certain galactic medium surrounding galaxies.
08:11:40 So I think as we go forward this week it's useful to think a little bit about when the reservoir really matters.
08:11:51 Now, with the audience that I have today. You know, if we change the question from do flows effects galaxy evolution. Okay, which we I'm saying we've agreed on for four decades here to do gashes halos affect galaxy evolution, we will all raise our hands
08:12:09 and answer Yes, okay. But again, our challenge is, I think to be more specific about that and say, you know, Mark Floyd right will give us a detailed model right about how the precipitation in the CGM is is is everything right, and that reservoir really
08:12:29 matters.
08:12:30 So we can answer a resounding yes, we have a lot of work to do to understand the how exactly and that's why this program is so exciting.
08:12:48 You know, an analogy to take this one step further might be a picture of our local Lake Katoomba at a time of drought, no no this is not the present time that don't worry, but but in times of drought you see we start to wonder if when the faucet is turned
08:13:04 on anything will come out.
08:13:08 And in some ways, maybe that's our circle galactic medium is that reservoir there and is it full it may be raining all the time. From the intergalactic medium.
08:13:20 But if the reservoir is kind of not at a certain level, nothing comes out when we turn the faucet on.
08:13:27 So, I was trying to think about ways in which the CGM is really essential for our modern picture of galaxy evolution. And I think among the audience out there there are probably a very long list we could come up with, you know, two in particular are that
08:13:44 I think it's absolutely a crucial part of understanding quenching, and that that's not a topic I'm really going to take on today it's great we've got the discussion group working on that this week we'll have a lot of discussion and I think Greg may talk
08:13:57 about it some Thursday.
08:13:59 But I think one way in which CGM really does matter is it's angular momentum. So now we have spinning bathtubs right.
08:14:11 And that's going to be one of my main messages today that I really want to argue that angular momentum matters.
08:14:18 Okay so so let's step back a minute to the CGM, and Galaxy evolution.
08:14:25 So, I mean, I think several speakers have showed that this plot, we agree that feedback greatly reduces the stellar mass in the Universe Today. Right.
08:14:39 The, the dashed line here kind of shows the mass that galaxies would have in stars if the fair share of baryons in every Halo had been converted into stars.
08:14:50 And we have pretty strong evidence for four star formation driven feedback Bing that at one in, and energetically makes a lot of sense that ag energy and the job at the big end and simulation seem to be able to make that that work.
08:15:06 So another way right in which CGM matters is that besides containing a large reservoir of mass right shown shown here, perhaps a lot of that missing mass that's in the Halo.
08:15:21 We think they hold a lot of metals, a lot of the gas in the CGM has clearly been processed through the stars and galaxies.
08:15:33 And, You know, that's really our thinking behind this whole picture of circulation, and that a lot of these atoms in the CGM have been through galaxies, you know, probably many times not just once.
08:15:48 So another way where I think we start to get to how angular momentum comes into this whole picture about galaxy evolution is when we start talking about galactic disk.
08:15:58 And this can be one of the things I really want to focus on today.
08:16:03 And this is a histogram of gas consumption times, okay and a sample of very local spiral galaxies.
08:16:13 On the top is the molecular and atomic gas added together. The bottom histogram has just the, the gas kind of in the star for me part of the desk, which is mainly molecular and simple calculation of taking the gas masks in that part of the disc dividing
08:16:30 by the star formation rate shows you that disk use up the gas that's there in just a couple of billion years.
08:16:39 And the reason that's important is that that gas consumption time rate is short compared to the lifetimes of disk from the ages of stars in the Milky Way desk we know the history of the disc is much longer than that.
08:16:54 And from look back studies, we know disk have been a lot around a long time.
08:16:58 I love this plot from Casey Popovich where he's combined kind of galaxies at different red shifts in candles to make kind of a picture of a look back time picture of how a milky way disk was assembled.
08:17:13 And this is today, and you're looking back in time here, and you could see that you know somewhere like 10 billion years ago, things that were small disk that look like disk are common and are in tech, and then you can see they grow over the next 10 billion
08:17:36 years into the galaxies that we see today. So, that growth is a really slow assembly. And I think we could argue that the CGM has a lot to do with why that process is so slow.
08:17:48 And also, in some sense, you know, if we look back to a few billion years to to when the solar system was forming the fact that our solar system for me you know in the outskirts, eight kilo parsecs away from the center of one of these would not have happened
08:18:05 without this CB CGM that were so enthusiastic about.
08:18:12 Now going back you know 10 to 10 years or so, again, for, for the for the newer folks in the field, you don't appreciate that cosmological simulations didn't have real dis galaxies at that point that that recently.
08:18:28 And, you know, it's just amazing what the simulations, have done in the last decade, these are zoom ends mostly within cosmological simulations that form these these these beautiful disk that we just almost would take for granted today, but but getting
08:18:45 this to work.
08:18:48 You know it required many things, including resolution, but I think, you know, physically one of the big things was outflows driving low angular momentum gas out of the centers of these desk.
08:19:02 And then the dis building up over time as the gas that was created, subsequently had higher and higher angular momentum, because they had undergone more and more torques in the halos.
08:19:14 So I just love looking at these pictures of these desks just amazing what all these groups have done.
08:19:23 So, another thing about desk, though, is that they're big.
08:19:30 And not only are they are they, big they're their size it scales incredibly well with kind of a fraction of the variable radius, where kind of the spread and disk sizes, in a given size Halo is well approximated by just the scatter in spin parameters,
08:19:52 okay that the halos have. So there's kind of a picture here where the size of the disc is a parameter that describes the spin of the Halo, okay, that has some distribution times the radius.
08:20:07 And it just amazes me that besides you know late type galaxies falling on this plot early type galaxies tend to kind of fall on the same relation.
08:20:17 So, being in momentum of these disk does seem to be related to the angular momentum of the Halo
08:20:29 and understanding exactly how that works i think is part of what we're after. If we're really going to understand, desk.
08:20:37 Now of course, I'm just going to say, really two things about about quenching that it happens right that star formation does eventually stop in these disk even though they take a very long time to make their stars and the most massive galaxies around
08:20:57 or are all early type galaxies.
08:21:01 And that, I think, you know, again, cos halos right is is again really the thing that just turn this field of the CGM on and said, there's more to this than just the bathtub model that the circuit electric gas is is different.
08:21:19 Okay in star formation galaxies than it is in passive galaxies.
08:21:25 And because I'm going to talk more about cold gas in Halo specifically magnesium to today.
08:21:31 You know I just really want to point out that the cold gas is different. And in late type galaxies as well the equivalent with here of magnesium to absorbers are just you know significantly higher in the inner parts of the CGM of star forming galaxies
08:21:49 than they are in passive red galaxies.
08:21:53 So, this is why we think right the CGM has a lot to do with how galaxies quench, but there is a bit of a chicken and egg question here of which came first.
08:22:08 Okay.
08:22:10 So over the last couple of weeks, we've heard a lot of perspectives about how gas reaches the disk, both to sustain star formation and to help this grow and and mindless the references here is is is far from complete so so I apologize, But there's there's
08:22:29 a picture right that kind of emerges here from from the simulations, where the CGM has high specific angular momentum relative to Dark Matter halos few times higher, and this causes the gas to settle in close to the outer disk.
08:22:47 And by and large the simulation show that gas then being transported radio Lee, okay at moderate speeds into the inner part of the disk.
08:22:58 One of our fearless leaders, Ben Oppenheimer right he has written a lot about how angular momentum can also contribute to the hot phase of this, the CGM.
08:23:12 And there's new work by Dan stern talking about and outside in model of CGM visualization, where he ties the visualization of that inner part of the CGM is kind of a necessary condition for the actual formation of a thin desk.
08:23:30 So lots of things we can discuss here later, another perspective though right we heard comes to this from chemical evolution models and Filippo was adamant in week four that the accretion is vertical.
08:23:48 Otherwise, you know you'd have to flow large amounts of gas into the center of the galaxy and the speeds required would just be in conflict with observations.
08:24:00 So So overall, we've got a lot of uncertainty about, about how this happens. And I'm not going to promise to give you an answer to that in the next half hour here.
08:24:12 But I do want to review some things that observations tell us, and I'll bring the simulations in a little bit mainly as ways to help interpret observations, and most of the theory talk will be, will be on Thursday by Greg.
08:24:29 So first I just wanted to kind of remind ourselves of how gas is distributed in desk.
08:24:38 This is star formation rates in a discount CMAD three is a function of radius, and these are different gas surface density profiles okay the molecular gas here is traced by CEO, and the atomic gas, and the star formation rate.
08:24:58 This is a semi log scale here you can see is largely exponential in radius, as is the molecular gas density.
08:25:06 So just the molecular gas density, divided by the star formation rate because they're both exponential and radius with a similar scale length.
08:25:16 Okay, gives you basically kind of a constant gas consumption time scale as a function of radius.
08:25:25 As you move into outer disk and move into dwarf galaxies where there's more each one, that star formation rate law tends to become more nonlinear with the gas density.
08:25:37 And then you end up with gas consumption times that become much longer. Okay. In the lower density gas.
08:25:47 But if the timescales are similar, everywhere to consume the gas you've got, but you've got more gas on the inside to start with. If you're going to stay in some sort of steady state, it seems obvious that the rate at which you need to deposit new gas
08:26:03 to stay in that steady state is going to be much higher in the inner parts of the star formation desk.
08:26:11 So, I rarely see where Filippo Filippo is coming from here.
08:26:18 You need to put a lot of gas and keep it coming in to the inner disk, you're going to keep star formation going.
08:26:24 Now it's true in the very centers of a lot of disk, there is kind of a deficit of star formation but but still there's a big part of that inner disk where we've got to keep stuff going so this is a bit of a mystery.
08:26:38 Now, this is where yobs Zags work starts to come in, she did this beautiful study of star clusters in in in 33, okay with Hubble.
08:26:49 And then was looking you know more or less vertically or had had sensitivity via the Doppler shift of absorption lines to to vertical motions of the desk.
08:27:03 And, you know, saw gas falling down, really on the desk.
08:27:08 I think some of the details of this, we haven't talked about enough.
08:27:13 And one of the interesting things is that this gas she saw that was redshift did moving away from us toward the galaxy and falling in in basically every sightline she detected it in the silicon for line.
08:27:29 Now, now this is not the hottest gas right but this is not what we call the cool CGM either. It was the silicon for where it was there in every sight line that there were other lines of lower ionization silicon to I think phosphorus to and some sightlines
08:27:46 had them some didn't when they were there I think they matched up climatically with the silicon for.
08:27:53 But this was so there was some pretty warm guests coming in.
08:27:59 The other thing about it is she had to separate right the the signature of the interstellar gas from the CGM gas that was falling in.
08:28:12 And she commented that the non disc component the installing component in him 33 it.
08:28:24 It has a rotational component that matches the rotation of the galaxy. So, even though we're looking at vertical install here okay the gas is rotating, and even though it's coming in, it may have also been spiraling in from large to small that's, that's
08:28:35 not ruled out here.
08:28:38 Oh, she looked at it two models okay as the title says here in a creating layer, or just a halo cloud falling in.
08:28:46 And because of this rotation component, she said yeah this is an accreting layer that the rotations not consistent with just a halo cloud falling in.
08:28:57 And she placed this gas, really at a pretty small distance right above the desk just a half to 2.5 kilo parsecs so so so now we're back to our discussions about the is m interfacing with the CGM, this isn't even really the CGM okay by most counts, the
08:29:18 rate at which the gas was reading down three solar masses per year is enormous compared to the star formation rated in 33 which is largely a big dwarf galaxy.
08:29:32 So, probably since it's being detected in metals, this is either fall back from the Galactic fountain, or fall back of material you know pulled out of the galaxy by an interaction with with em 31.
08:29:45 But you know you gotta wonder right if this layer is not connected right to these beards that are seen in the H 121 centimeter maps.
08:29:55 So for those of you who aren't familiar with this work, I'm showing here the the each one map on NGC 891 from Tom Oscar loop.
08:30:04 And these are very deep observations where the outer contour here goes down to something like 10 to the close to tend to the 17 per square centimeter.
08:30:16 So so very low column density each one that has big filaments out here.
08:30:23 There's probably some sort of in falling material it seems to be low medalists at based on the absence of dust in this part of the CGM, but but it's a really thick layer several killer parsecs many kilometers six high everywhere.
08:30:38 And if you were looking at a position, velocity diagram projected this way onto the major axis so we squash the galaxy. This way.
08:30:48 So as a function of the major axis here which is what shown on the right, we look at the velocity of the gas. Well, you see that compared to the rotation curve that shown by these little white squares and then Black crosses.
08:31:03 There's a huge range of gas velocities, most of which are sub centrifugal.
08:31:10 And this is supposed to be in falling gas, so you know folks here is the falling gas, right, meeting the desk.
08:31:20 And you know, more recent work by the halo gas group. This paper by Marasco shows, this is actually probably typical.
08:31:29 Okay, of vigorously star for me disk today.
08:31:38 So, this this inflow okay of speeds a kind of the rotation speeds here as you know up away from the, the plane that they get slower, they're lagging halos speed goes down about I think 10 kilometers per second per kilo power sack or something like that.
08:31:58 Modeling this authors estimate inflow speeds of just 20 to 30, kilometers per second. Okay, in the vertical direction because of the legging halos again it's probably coming in regularly as well.
08:32:11 So, I think you know one of the next steps forward right is we've really got to work hard on connecting this interface to what we know about the CGM and and I think the simulations are getting close to two showing us this I was really wowed by do songs
08:32:38 last week where he was starting to show us hey folks this is how the gas actually gets into the disk. Sorry, quickly here I just want to point out in NGC 891.
08:32:45 There are these really cool observations, where they use a single dish radio telescope, and they look deep and they measure the h1 gas.
08:32:56 Okay at it really large radio above and below the plane okay single dish.
08:33:03 Pointing here.
08:33:10 and and they're able to make kind of a profile here with height above the plane of the h1 column. Okay, this is shown for NGC 891 and read another galaxy in green.
08:33:29 And these are really neat profiles I think of what the neutral gas is doing dysfunction radius, they're comparing here to constraints for it from cos halos, that is, I think this is actually the data on the subset of lemon limit systems from Francesca.
08:33:41 And there's a large range from cos halos just because that that sample right spans a large range in galaxy mass and properties.
08:33:50 So again, you know, a mission is the future. And this is a mission actually getting with the neutral gas. Very cool, I think.
08:34:02 So now we'll get into the business with rotating halos that his, his his his come up and in many context, over the past six weeks,
08:34:14 at least from my perspective, this, this all got kind of started by this 2002 paper that Chuck sty del LED, where it shows you here you've got a galaxy.
08:34:26 It's got a rotation curve one sides coming towards you and one sides, or one side is going away from you and one side it's coming towards you, and you go look at a quasar way over here that seems to be, you know, more than a full galaxies diameter away,
08:34:41 and boom, you see a strong absorption system and its velocity kind of matches up with the velocity of the end of the disc, that's close to the website line
08:34:54 in lower ionization gas you see it too and you see it's made up of multiple components, and it's the multiple components that make this structure very broad in velocity space.
08:35:07 So these were five pairs of quasars and galaxies and redshift of I think about point six.
08:35:17 And it got a whole lot of work started.
08:35:22 Now, today kind of the the global picture that there is in fact, and as a mutual dependence of magnesium to absorption properties, was really driven home by by Ron mon Nicholas Shay, Luke cap sex work and others.
08:35:51 I show here picture from the lot land and mo paper that's literally combining you know like like half a million galaxies. Okay. The sight lines and showing the difference between in purple minor axis sight lines and in green, major access sightlines divided
08:36:01 here somewhat arbitrarily okay at in as a musical angle of 45 degrees.
08:36:09 And you can see that there's a real excess right factors of several here this is a log scale along the minor access in the equivalent with. As pointed out earlier.
08:36:23 Think of this as I can Matic difference, rather than column density difference, because these are pretty high equivalent Wits that we're dealing with here.
08:36:32 Same thing scene. Okay, in iron to absorption.
08:36:38 Now, measuring these four individual galaxies, when you don't have statistics of half a billion galaxies gets tough, with Sloan imaging.
08:36:48 Okay, here are Sloan RB and images of three galaxies at Richard's point two five.
08:36:56 Keep in mind a lot of this work with azimuth lane goals is done at Red shifts point six and even one okay and this is point two five folks and and yes, you can fit elliptical contours to these and measure a position angle and use the access ratio to estimate
08:37:14 the inclination to the desk.
08:37:17 And if you have half a million galaxies it's okay because most of the time you'll get something that that's kind of Right.
08:37:24 Right. It's not a bad approximation. Here's a NERC to image done with laser guide star adaptive optics at CAC, but in this guy right there's these big kind of titles spiral arms that the real position angle of the disc is here and the spiral arms move
08:37:42 it this way, when you're looking at the Sloan image it's more tilted there there's an offset here for about 25 degrees.
08:37:49 And you also get a much more inclined desk when you actually resolve the disc than you would get from this image that looks like the disc is almost face on, you know, surprisingly, to me at least, I would say one out of five times, you find there's actually
08:38:05 two galaxies there a satellite in a companion, or sometimes to physically unrelated galaxies.
08:38:14 I'll show later that resolving spiral arms actually lets you determine which side of the disk is flip toward you, infrared images aren't great at that but Hubble images sure are these are the same galaxies.
08:38:32 And you can see the, the disk here and then the little satellite. Very cool. So, you know, I would say we may need a lot more connection to good imaging like this and Quasar sightlines if we're really going to connect the galaxy ism in the CGM.
08:38:54 So lots people are working on this had been working on this.
08:39:01 I'm going to emphasize talking about the work I've been involved with just because I know that best.
08:39:07 And this is a sample of 50 pairs of galaxies, kind of Milky Way mass and slightly sub Milky Way mass and background quasars okay where we chose the galaxies first and then took the sub sample that had background quasars.
08:39:25 And if you just kind of, I should say it's important that these were all galaxies selected. Okay, to be viewed at disk inclinations of 45 degrees or higher.
08:39:37 So these are inclined galaxies, and that's important here.
08:39:41 That's lets us line up the major axes of the galaxies.
08:39:46 And then we look at magnesium to absorption. Well, some some sightlines don't show absorption okay the axis here, but of the ones that do.
08:39:57 It's co rotating in the same direction as the rotation curve with the Galactic disc in, in all the one shown in red.
08:40:05 And you can see that the majority of the sight lines that are within about 4550 degrees of the major axis, although some of those sight lines the gas is really just at systemic velocity, where half of its co rotating and half of its counter rotating.
08:40:21 And you can see it's kind of random.
08:40:23 If you look at the minor axis, where of course if we're looking at a disk in projection here on the minor axis, and he circular velocity is tangent to the line of sight, so there is no Doppler shift.
08:40:39 The equivalent width of these magnesium tubes absorbers is is also important that the really strong systems that are several nx rooms, at least in our sample were concentrated at very small impact parameters and near the major axis.
08:40:56 Those two things combined really show you you are intersecting disk they're kind of the next category of pretty strong absorbers kind of three tenths to one Engstrom, they really liked the minor axis and the week absorbers well that there's no preference
08:41:14 okay so if you look at week absorbers you're not going to find and as musical attendance. If you don't have good high quality imaging you may not find it as a mutual dependence.
08:41:25 And if you're galaxies aren't inclined to the line of sight, you're probably not going to find and as a mutual dependence.
08:41:35 When you've got good information about the orientation of the disk and the sight line. There's more you can do, and you don't really know ever okay as an observer where that absorbing gas is along the line of sight.
08:41:52 So what you do is you, you get a simple picture in mind, and you say what if, what would the consequences be.
08:41:59 And in this case that saying, okay, since we know where the thin disk is, let's say the absorbers are there. So what philosophy is expected. If the magnesium to gas we saw was in a thin, thin disk.
08:42:12 Okay, on a circular orbit.
08:42:16 And what well both minor access sightlines and major extra sightlines might intersect that disk, where they intersect the disk with depend on how inclined the disk was to our sideline, so showing that in green, blue and red here, you can kind of translate
08:42:35 this plot into okay if we take a disc, that's 95 kilo parsecs and radius, and it's highly inclined. Well, along the major axis you're sampling it all the way out here but your minor x is sightline anything beyond about 15 kilo parsecs is going to miss
08:42:54 that desk.
08:42:56 For more face on this, okay and client 40 degrees well you could you could hit the disc.
08:43:01 Pretty, pretty large impact parameters along the, the minor axis. so it gets confusing, okay to interpret such data.
08:43:11 So when we have actual information about the implications of the disk though, if we're willing to say what happens if the gases in the disk.
08:43:21 We can D project back to the disk plane.
08:43:30 Just what we're going to do with these data now.
08:43:27 And here's where the absorbers lot.
08:43:30 I keep in mind, some of these detections aren't really desk right somewhere winds along the major, major axis we're just projecting back.
08:43:39 And you can see that by and large within a radius of about 80 kilo parsecs plus or minus 10. Pretty much everything you see where the sideline intersects the disc playing.
08:43:51 Within this category of again where read his co rotating gas.
08:43:56 And that's why would say there seems to be some sort of coherent structure.
08:44:01 I don't want to call it a disc, I'm going to argue that a thin disc is a horrible description of this some sort of coherent rotating structure out to at least at Keller parsecs.
08:44:12 There may be rotation well beyond that that's in more filaments and streams and things.
08:44:18 So it makes sense. Okay, at least to to compare the rotation, we see to how a disc rotates.
08:44:26 And this is work from from Stephanie hose 2017 paper, where for about 15 of these galaxies she's taken the rotation curves and flip them here so that the side, the road of the galaxy that's near the equator is our site line is it positive velocities just
08:44:43 for show so they all line up.
08:44:46 so they all line up. And if you extend them out to where the quasar impact parameter is the magenta line shows kind of just the rotation curve, extended out where the rotation would be.
08:44:59 So the region in yellow is the full range of velocity of the magnesium to system, and the green shows kind of the equivalent with weighted velocity, and what you're supposed to take away here is that while the magnesium to Doppler shift, always have the
08:45:17 same sign, pretty much as the rotation curve on the quiz our side of the galaxy.
08:45:24 If that gas is is near the plane to disk, it's circular velocity is not high enough stay in a circular orbit. The bulk of it, the points here are lower than the magenta points.
08:45:34 And if you make a another model for the rotation that's based on the halo circular speeds red squares here, you pretty much come to the same conclusion okay that the gas even though it's got some manual momentum that knows about the angular momentum,
08:45:48 the disk. it's all sub sub turtle.
08:45:53 Now, I think one of the issues that a lot of discussion is going to happen about is how this gas as it spirals in toward the disk gets there and what annual momentum transport happens and exchanges with other phases of the CGM or the Halo, or the desk,
08:46:11 etc.
08:46:12 But if we just take a simple picture here and say what happens if the momentum of this gas is conserved, where would it meet the disk and fall into a circular orbit and kind of follow tracks like this, take this point.
08:46:26 And as it falls into smaller radio it speeds up and it meets the outer desk.
08:46:31 Now there's a range of velocities here so think of this track is a thick line.
08:46:37 Sorry about that.
08:46:42 As a thick line that kind of meets the disk at a range of radio.
08:46:47 Okay.
08:46:48 And in some of these, you're you're coming out and you're you're adding very much at the edge of the desk.
08:46:56 So in this picture you deposit gas over range of radio I but it's really bias toward putting gas at the outer disk, unless the gas is losing significant angular momentum.
08:47:08 Is it falls in which it could be.
08:47:16 This is recent work on chemical abundance anomalies that I think really connect to this picture of a momentum and the Halo and gas been deposited larger media.
08:47:37 Okay, these are from paper by one is also more recent one by Lou, that looks at the, the nitrogen to oxygen abundance ratios, okay this is work that Tim has been involved in, and using an integral filled spectrograph they've mapped out the oxygen abundance,
08:47:48 okay across galaxies, but then of course the oxygen abundance right it falls with radius well they've compared to how it should fall with radius and what they're looking at here is the difference from the expected metal the city.
08:48:03 Okay, so of course outer disk or more metal poor.
08:48:08 That doesn't get you highlighted, if your metal poor or metal rich compared to what's expected at your location in the galaxy.
08:48:17 So this should be a symmetric profile symmetric histogram about zero change here, and the blue histogram is the data you can see it's not it's got this tail toward low medalists at sorry I keep clicking on the figure and advancing the slide, I apologize.
08:48:36 So they fit a Gaussian here to the red side and subtract it, and the excess of a nominal asleep, low medalist at regions is shown in black.
08:48:47 And this gas has some really interesting properties here okay if they plot the abundance and anomaly is a function of radius from the center of the galaxy.
08:48:57 Okay, when they're looking at isolated galaxies, you can see that at large VDI, there's more of an anomaly.
08:49:06 And in close pairs. Okay, things that are about to merge, there's more of an anomaly at large VDI.
08:49:12 And then once the mergers happened and gas is being transported to the center of the galaxy right that anomaly moves into the center of the galaxy.
08:49:20 So, I think they found evidence here right that a lot of gas is deposited large VDI, and that it's transported in words at least in mergers, I'm sure Tim good, talk to us more about this.
08:49:38 So I want to turn back to Stephanie's work and highlight some of the problems with thin disc and give an example of how she got some estimates of accretion rates.
08:49:50 Okay.
08:49:53 So this means thin disc is not equal to okay is not a good description of CGM kinematics everyone that's looked at this problem which is which is many people over the years, starting with say Dell has shown that the thinness models are just producing
08:50:10 line profiles that are way too narrow compared to what's observed okay so here's here's the background source you're over here looking through the disk.
08:50:21 And you can see that you will only get absorption over a narrow range of velocities from kind of a maximum here out to these two points.
08:50:30 So along the line of sight here the velocity, you might see could be represented by this orange curve here where you can see there's a pretty narrow range of velocities, that range of velocity increases as you think in the desk.
08:50:46 Okay, make it thick. And you can play with velocity gradients as a function of height.
08:50:56 Those send actually require thinner disc than constant rotation with height.
08:51:02 And that's the game people play to get brought in offline profiles, is making thick disc here.
08:51:08 Keep in mind though that even with a thick disc, right, all the projected velocity will be on one side of zero in terms of the stock or shift right it won't cross zero.
08:51:21 And many of the absorption profiles do cross zero, so so thick disc seem essential, but they can't be the entire answer.
08:51:32 There's a lot of work on this just summarizing, some of it here to show some beautiful line profiles.
08:51:39 This is the morass go work in India mission okay in the thick disk, making this wing on the 21 centimeter profile.
08:51:49 This Is Us data on a redshift one disk from from Nicola boo Shay, where you see I think this is magnesium one absorption profile here. They've got a model where you see a component coming from the thin disc that's narrow, and then the rest of this is
08:52:06 part of their model of the accretion flow coming in there. So in general accretion flows, they tend to make a broad profile kind of from the velocity of the disc down to zero.
08:52:19 This work, Alex diamond Stanek. Okay, we're high resolution data these three magnesium two components, and along the sight line here, or I like this edge on view through the disc, he's able to connect the strong component, okay to material associated
08:52:37 with a sick disc.
08:52:39 The second component in green matches up can magically with an outflow cone. And then there's this little blue component leftover, which is something else.
08:52:52 Satellite title stream, something like that. So again, the broad stuff, it's full of components and their discrete features. Okay, in this cool gas in the CGM.
08:53:07 Now, again, returning to. What if there's some sort of thickish disk with radio inflow.
08:53:16 There's a cool observational effect, okay that not everybody knows about that can help you actually test that idea.
08:53:25 And it's that if you have a rotation curve.
08:53:30 Or if you have a galaxy on the sky. I'm gonna say it has trailing spiral arms so it looks like this, depending on which way the rotation curve goes whether this side is receiving or the opposite side is receiving it affects whether the upper side of the
08:53:46 disc is tilted towards you or the lower side. So there's a degeneracy with the tilt of the disc. For possibilities here. And if you have both a rotation curve and resolve spiral arms that 95% of the time our trailing so we'll assume they're always trailing,
08:54:06 you can figure out which way the disc is tipped.
08:54:12 And when you do that, you can model line profiles, and they give very different results for, for inflow in a given system depending on which way the disc is to.
08:54:24 And Stephanie did this in three galaxies.
08:54:28 And these are just the results she she came up with.
08:54:32 In one of them it was consistent with some radio inflow gotta speed of 30 kilometers per second.
08:54:38 Had the disk been tipped the other way. The measurement would have been 140 kilometers per second. That's rolled out another one for her disk till she got 40 kilometers per second.
08:54:52 The other solution would have been at.
08:54:56 So, you know, these numbers are remarkably similar to what the simulators are telling us they need in terms of radio inflow.
08:55:04 There was another one that I thought was a slam dunk because in color images it's it's really got a blue outer disk suggestive of recent in fall. But in fact, the tip of the disk.
08:55:20 It completely ruled out the radial info model, at least along that particular site line. So, I like this because it can rule things out, is as well as providing a measurement.
08:55:34 So I got a couple slides here on work Stephanie's done trying to observe simulations, again to get some handle on.
08:55:42 Okay what what is the morphology of this co rotating guests really, and here she's looking at a sample of galaxies from Eagle, that are matched to her observed galaxies.
08:55:56 Okay, a little bit less massive the Milky Way Lake type galaxies.
08:56:01 And this is a picture of what the cold gas is doing. This is one galaxy viewed projected on kind of the x, y and z planes of the box. And you can see that no matter how you look at this galaxy you kind of see Ko Ko rotation.
08:56:21 Okay.
08:56:25 Um, it's interesting to ask though how much of that curve rotating gas is actually installing and through particle tracking she was able to pick out the particles in red here on the bottom.
08:56:36 That would become part of the disk on kind of the time scale of one galactic rotation period.
08:56:43 And you see the gas that is creating is very much feeding the outer edge of the desk.
08:56:51 took that forward in the next step, looked at a larger sample of galaxies and as a function of stellar mass. And here we're kind of beyond okay into two for mass bins, the upper mass Ben doesn't have many galaxies in it, because she didn't look at passive
08:57:10 galaxies too much.
08:57:12 The box wasn't big enough. And so let's look at these three bins. And the result was that the magnesium to gas was more extended around more massive galaxies both in an absolute sense, and as a fraction of the variable radius and their flattened structures,
08:57:33 the minor axis here did correlate with the net angular momentum factor. Okay, if this gas. So here's a picture of you know what this thick disc II thing might look like.
08:57:49 And there's an interesting observational effect here she's considered.
08:57:54 If you stack. Okay, in this case you know 46 of these Eagle galaxies together. And look at a given, we're looking at edge on here and an inclination of 90 degrees look at a given position and say what fraction of sight lines both detect magnesium to okay
08:58:14 above some column density threshold, and our co rotating.
08:58:19 Well that's what the color tells you here, and a color of yellow is the 50% mark where half the time and observer would find co rotating gas. So you can see these structures are pretty common to to heights of 20 kilo parsecs above the plane and the red
08:58:37 circles are at half the variable radius, you're going to find curve rotation.
08:58:42 Well find is a tricky thing there is a rotating gas. But this is gas. That was picked out to be inside the video radius picture on the left here.
08:58:57 If you project through the whole cube, this is what you actually see because observers pick out magnesium to that's say within 500 kilometers per second of the galaxy velocity.
08:59:12 But there's significant contamination Stephanie found from material outside the variable radius, that's falling into the Halo. And therefore, you know, appears closer to the galaxy than it is.
08:59:26 And here's a picture on the right of this, Miss assigned gas.
08:59:31 Well, in these in these larger mass galaxies, this is really not a big deal at an impact parameter of 100 kilo parsecs the contamination is 5% or something.
08:59:42 But as we try to measure this car rotation in lower mass halos this contamination is going to be a problem. At 100 kilo parsecs in this mass been the contamination from gas outside the variable radius is 80%, and Stephanie has some nice graphs and their
09:00:00 plot that as an observer Can you estimate, at least based on Eagle with the contamination might be
09:00:09 really need to be speeding up here I can see, I just want to advertise the mega flow results from Nick O'Shea's group, and D Phillips's, a recent comparison to the TNG 50 simulations.
09:00:32 It's really neat how, in, in black here, this is a stacked magnesium two absorption profile that they're comparing to sorry in.
09:00:40 Yeah, from from tng and then they're comparing to in green the mega flow result.
09:00:46 They've really got to pick out the halo shown in red, that have the strong magnesium to absorbers that they're special. And then they match up pretty well with the observations.
09:01:00 But to me, I mean this is done without any tuning, this is miraculous that the simulations are reproducing the observed velocity with this well and in kind of a statistical way.
09:01:10 And they make a nice comparison in this paper to kind of the specific angular momentum, okay of their sample here in green, showing that it's likely larger than what in orange the dark matter halos have and larger than specific angular momentum of the
09:01:27 stars, so so take a look at that.
09:01:33 Um, I had some things to say on wins but it's largely recapping a lot of what's been said, so I think maybe I should skip over it and go to the end so we got time for discussion.
09:01:48 I'll make two points about it made me.
09:01:51 Just looking over my summary.
09:01:55 Say a few words here so again my mantra today has been that annual momentum matters, and it's one of the reasons that the CGM hasn't a big impact the fact that it's there and it's not just a bathtub on galaxy evolution.
09:02:13 We see CGM cool gas rotating.
09:02:18 It's not really in a disk in the sense of a thin structure, you could maybe call the inner part of this structure a thick disk and things look plausible that this is gas that's that's feeding the outer part of the desk.
09:02:35 The chemical abundance anomalies seem to support this idea that there's low medalists at gas being deposited at large radio.
09:02:44 To what extent this material can be transported inward in the disk, I think is an open question.
09:02:52 Maybe these thick disc are bringing it in, you know, pretty far, and then it's kind of dropping downwards as it
09:03:02 is slow down by its interaction with with the hot phase, so that the these flows somehow connect to the picture that young saying, and the, the h1 beards are showing us, I think this is an exciting direction for future research.
09:03:32 The main thing I would have showed you about the outflows that we can come back to if people want to is that they really do imprint a signature on the CGM Tim Beckman's work has showed this in terms of the the carbon for in the six in terms of cost verse.
09:03:39 verse. And in the magnesium to the signature is just that the equivalent widths, the velocity spread is systematically larger in minor axis sightlines of inclined disk than in other sightlines at similar impact parameter.
09:03:55 And that shows that either you're seeing an additional component at those lead sight lines, or you're seeing gas that stirred up or some combination of the two.
09:04:07 Okay, so So going forward. We've got real observational challenges of trying to measure the angular momentum of intermediate and hot gas in the CGM, the simulations are suggesting that those phases have significant negative momentum to, but we've got
09:04:25 to measure it.
09:04:28 I think emission line imaging of outflows and the CGM is the way of the future, we've got to have a picture. Think will be a lot more discussion of that next week.
09:04:39 And just to kick off some of the discussion I mean I think there are many many challenges at the interface between theory and observations. I feel like it's some level that's what our program here is all about figuring out how to address them.
09:04:54 And I've already mentioned kind of the mystery of connecting the accreting gas, gas directly above the is M to the CGM.
09:05:05 The other thing I would have mentioned in the part about wins is just that.
09:05:09 Wow, like, some of the new theoretical work on launching the outflows Cassie, low caste is new analytic model. Evan Snyder's beautiful simulations that really show cold clouds for me, the hot wind large distances and her arguments about the momentum transfer
09:05:32 from the hot face of the cold phase. This just amazing stuff that's changing our physical picture about outflows, but but this begs the question.
09:05:44 Okay, for this wealth of observational data that are largely absorption line profiles.
09:05:52 How does this change how we interpret those profiles how we extract physical properties, about the wins from the data.
09:06:04 Now that we have a different physical picture of what we're observing.
09:06:08 Thank you.
09:06:11 All right.
09:06:14 Thank you crystal.
09:06:16 That was a there was a great overview, and it just shows how much new data has changed our, our view of what is going on in the CGM and how simulations, in theory have really transformed this field.