Living in a virtual world (but I am not a virtual girl)

Last week I did exactly two things : I attended my first online conference, the EAS 2020 "in Leiden", and I spent every spare minute playing with my long-awaited Oculus Quest. More on that elsewhere. Here, let me say something about the wonders of attending a conference from one's own home.

Back in my day, online talks were a thing to quaken the hearts of the bravest of men. They were sorry and desperate affairs that were as much use as listening to the London Underground tannoy for a solid hour : totally inaudible and we'd all have been better off spending the time silently contemplating the Oneness Of All Things. Not so in the modern era, where the pandemic has made a necessity of achieving something which was already well within technological capacity.

There are, of course, both advantages and disadvantages to online conferences. On the positive sides, there's no need to travel, talks are stored online (sensibly only for a month, meaning I might actually muster the energy to look at talks I missed : if they were there indefinitely then I never would), and it's far easier to drop in and out of different sessions. On the downsides, there's no opportunity to travel, you have no sense of the audience response, there's no social aspect (they did try, but after spending so much time listening to a screen, I found it necessary to spend the break times not staring at a screen, at least not one filled with science), and it seemed to me that people were lessing willing to raise controversial topics.

Overall, the positives have the advantage. In the future I think it would be extremely strange for any conference not to move to at least a hybrid system - the convenience is too great. At the same time, it would be a loss if physical attendance became unusual - the social aspect of presence is important (and one of the perks you get for accepting an astronomer's meagre salary is an astronomer's not-so-meagre travel privileges, but I'd be happy if they converted this to salary instead !). Through body language and the more free-flowing discussion that happens in tea time, it's easier to say, "I disagree" in person without sounding like a jerk. Which is a bit strange, because plenty of people still manage to say, "I disagree" while sounding exactly like a jerk, and it ought to be easier to avoid this in an online system.


As for this specific conference, everything went almost without a hitch. Things got off to a rocky start though, when the first speaker in the first talk I went to turned out to be actually painfully dull to listen to. If he'd been on Just A Minute he'd have been out in seconds. He talked so incredibly slowly that you'd forget the start of the sentence by the time he finished, thus meaning he conveyed no information whatsoever - no, really, absolutely nothing - besides what a poor choice someone made in inviting him to give a presentation.

Although almost entirely humour-free, there were however a couple of amusing points. One speaker stood up, earning praise from the chair for making it more lively, so the next speaker said they weren't going to stand up on the grounds they were still in pyjamas. Then there was a faux pas a chair was clearly unaware of, saying, "unfortunately we have to move on to the next speaker", which I thought sounded pretty bad for the next speaker !

This raises my only serious niggle : the tendency for several people to have multiple talks in different sessions. I do find this really unfair and annoying. By all means, give as many posters as you like, but if you get to speak for 45 minutes because your research is famous and I only get a 1.5 minute poster presentation, that needlessly exacerbates inequality. There needs to be more coordination between sessions to ensure that no speaker gives the same talk twice, and has a maximum of two talks. Otherwise, lesser-known researchers get hidden in the virtual-but-not-entirely-metaphorical poster basement.

I don't know if anyone else did this or it was just me, but I didn't feel particularly inclined to check out any other posters. In a real conference, you can combine wandering around the poster room with a nice cuppa, allowing you to at least partly switch off during the tea breaks. For me, not listening to science for 30 minutes and being able to browse the pretty pictures is important to maintain sanity. I might eventually get around to it, but I felt no pressing need to do so here.

But all of these are quibbles. Overall, it was a great conference with some really interesting talks and truly exceptionally high-quality timekeeping, even if it didn't have enough jokes. So, on to the science !


It's not bug, it's a feature

First off were an interesting pair of talks. Frederico Lelli - he of the MDAR - claimed that the baryonic Tully-Fisher relation is consistent and has low scatter across a wide range of masses, whereas Pavel Pina - he of the UDGs - claimed that there's good evidence that some galaxies don't obey the BTFR at all. Or to put it another way, either all galaxies have similar dynamics that can be predicted entirely from their baryonic matter (which would be weird if they're all dominated by dark matter) or only some can. It's all very confusing and definitely not settled.

Although I'm firmly in the "dark matter is definitely a thing" camp, both had some interesting points. Lelli notes (of course) that there's a break in the stellas mass TFR, but that goes away if you add in the gas. He also shows that the tight relation is only seen with the highest quality data, and you have to have rotation curves which extend sufficiently far as to reach the flat bit. I'm in two minds about that. On the one hand, I can see why you'd do it, but on the other, how do we know the flat bit indicates stability or that the baryons are sufficiently extended ? Has anyone looked for baryon configurations that could give stable results without flat rotation curves ? Otherwise selecting only the flat curves is a potential bias that means you'll never find any deviants. Maybe.

Pina's Ultra Diffuse Galaxies show strong, weird deviations from the baryonic TFR and now he adds a few more that are intermediate. I wasn't sure if the data was really good enough to give the accurate velocity widths needed, and as I've noted here before, minor inclination angle errors can give substantially wrong velocities. I'm still not entirely convinced, but he has several very strong points in his favour. First, the rotation curve fitting software was shown in a later talk (I forget by who) that it does extremely well with low resolution data - much better than I would have expected. Second it's unlikely that all the galaxies in the sample have huge inclination errors, and third, the low velocity dispersion is inconsistent with a thick disc needed for inclinations that would bring them back into agreement with the BTFR. So these objects are, at the very least, a challenge to the idea that the BTFR is flawless, but more data could eventually settle the issue.

If these UDGs really do deviate, then something odd and potentially very interesting is going on. Lower surface brightness galaxies should deviate, but generally - as shown very nicely in Lelli's talk  - don't. So what's different about these guys ? What makes them so special ? I for one have no idea.


Magnetic Blobby Things

Dylan Nelson gave an excellent talk about the formation of optically dark gas clouds, an obvious point of interest for me. His simulations of galaxy clusters find free-floating gas clouds of similar size and temperature to the dark HI clouds in Virgo, which live for at least 1 Gyr. Instead of being supported by thermal or dynamic pressure, which we already know doesn't work, they're supported by magnetic fields. What keeps them from evaporating is the temperature gradient, with an intermediate temperature zone allowing gas to flow into the clouds.

This is super interesting to me as it would provide a potential explanation for how the Virgo clouds survive in significant numbers whilst not (yet) being found outside the cluster. What would be really interesting is to know their mass and velocity widths. Unfortunately I had minor technical issues so I couldn't ask questions, but this is definitely one I'll be following up on.


Magneticum

There is a simulation code called "magneticum". That's hilarious, but I didn't have the heart to tell them why.


The Stars Are Not 2D

Cecilia Bacchini gave a really nice look at volumetric star formation laws. Normally, for simplicity, we look at the 2D density of the gas and see how it compares to star formation, but Bacchini shows how it's possible to get a reasonable estimate of the true volumetric density without too much bother. Unlike the classical star formation law, the volumetric version has no break at the low end and a uniform tighter scatter. Their efforts also show how the classical law can be rederived form the VSFL.

A second interesting point - raised elsewhere by Luca Cortese, Amelie Saintonge and others in other talks - was that star formation is probably not governed by molecular gas alone, contrary to a great many recent claims. The good old-fashioned atomic gas likely plays some role as well - it's not just a reservoir from which molecular gas eventually accumulates. Bacchini shows that the scatter if the VSF law is actually lower if you use only HI instead of H2, which I would not have expected. A paper is in preparation.


"The AGN is strongly turned on here"

Why ? Did it meet someone nice ?


Women in astronomy

At long last I finally got to here from the legendary, Jocelyn Bell Burnell, discoverer of pulsars and slayer of sexism. Her talk was a look at the changing IAU membership by gender since they started maintaining a well-organised database 20 years ago. Back in 1990, the then-director said that this was a social issue which they weren't going to tackle, which sounds a lot like total bullshit to me : there's nothing political about trying to ensure fair representation in your organisation.

Currently the IAU has 14,000 members, of which just four were unwilling to specify gender. I have to say I was surprised to learn that the gender balance is strongly unequal, with an average of just 19% female in countries of more than 200 members. The highest is Italy at 28%, whereas the UK has a mere 13% (!) and Japan the lowest on 7%. This doesn't reflect my experience as a UK undergraduate at all, where the gender balance was close to equal - if I recall correctly, the problem is retaining female astronomers as they climb the career ladder, not so much in hiring them.

The Netherlands is exactly average, but has increased significantly in the last few years. Here was something I asked a question on, but it didn't get answered due to a deluge of other questions : what's the fastest rate of change we can realistically expect ? I agree that a change of 0.5% per year doesn't sound great, but potentially it might be. Say a country has 500 astronomers but only 10 new members per year (balanced by deaths), then if the gender balance is equal, that still leads to a very low percentage change. Obviously we can't start firing existing astronomers, nor should we deliberately hire more women to make up the existing deficit, so I would say we should look more at the changes in new members rather than the whole. But of course, looking at the point at which people renounce IAU membership is also crucial.


Best of the rest

Those were the personal stand-out talks for me, but there were plenty of other interesting talks and very few duds. Several people noted the important of including the Large Magellanic Cloud in simulations of the Milky Way formation as this will affect cosmological issues like the missing satellite problem, including the very intriguing possibility that satellite galaxies can themselves have satellites - apparently there a few good candidates for such "yo dawg" objects. There were more claims for satellite planes, which I still find unconvincing but at least having samples to test is important.

Federico Lellli gave a second very nice talk about a new way to estimate the true halo masses of galaxies, which unfortunately I took crappy notes for but the result was extremely surprising : apparently there's no missing dwarf problem but a missing giant problem. There's a big extrapolation between the measured rotation and the estimated halo mass though, but I think I really need the paper to make a sensible comment. It looked to me like this implied that previous measurements must have got the halo masses wrong somehow, but apparently this isn't the case. There were also some cool remarks about galaxies at high redshift with well-resolved rotation, for which there should be some exciting papers in the near future. And there was a nice talk demonstrating that the MeerKAT telescope is doing fun stuff by observing HI in nearby clusters.

This conference also established the Strong and Weak Frenk Principles. The Strong version says that the missing satellite problem doesn't exist, the Weak version that it's been solved. I, and probably the majority of others, don't think that either situation is the case : the missing satellite problem is indeed a problem* and hasn't been solved yet. Springel noted that the number of free parameters in the modern simulations isn't as high as is often claimed, but that needs more detail. And finally, Malhan showed how different types of progenitors could lead to distinct differences in tidal streams, potentially opening a new avenues on the core-cusp problem and the nature of dark matter.

* Can I propose the Strong and Weak Kroupa Principles ? The Strong version would say it disproves all of cosmology; the Weak version only that it poses difficulties for dark matter.


All in all, a great conference. Not quite as draining as a regular conference, and lots of double-edged swords at work : every advantage came with a disadvantage. But most importantly, in these trying times, science marches on.