This time last year I went to my first purely virtual conference, EAS 2020. I happened to spend all my spare time that week mucking around with my shiny new VR headset on account of living my entire life digitally.
One year later, history repeats.
Well, almost. I don't have another new headset, but I did by sheer coincidence decide to spend all my spare time mucking around with Virtual Desktop to get the PC wireless working very much better than it used to. I also strapped a powerbank to the back as a counterweight that also charges it up, prolonging the battery life by (I reckon) at least threefold whilst making it a lot more comfortable to wear. So that's nice. What about the conference ?
EAS 2021 : The Zoomening
As before, let's do the experience and the science separately. First off, the niggles, which remain unfortunately much the same. There were once again too many people giving multiple talks, and too many plenary sessions. This promotes inequality and I don't like it. Yes, there are worse problems in the world, but it's still an annoyance : why do I get a mere poster (this time not even with a token 1 minute presentation slot) but other people get two or three talks and plenary sessions take two hours per day ? Seems unfair if you ask me.
In a rather different niggle from last year, I found this time that the session titles were often misleading. "Galaxy clusters and AGN" didn't feature all that much about AGN, while "Satellite galaxies" didn't have that much even about satellite galaxies, etc... why people decide to give their sessions ultra-specific titles but then include very liberal content, I don't know. It's a minor irritation, but it makes it harder to know which session to submit an abstract to, and harder to plan which sessions to attend : you really had to check the scheduled talks quite carefully and not just go by the session titles.
On that note, I found an interesting and unexpected use for AdBlock. Here's the conference schedule as it appears by default :
Which is hideous. Probably less than a quarter of the screen is taken up with actual useful content, i.e. clickable schedule blocks. I got so frustrated with this obscene conference scheduling censorship that I used AdBlock's "hide something on this page" feature to cancel out the annoying extraneous faff and blam :
Much better ! There was actually a decent enough interface hidden under there - less is indeed more.
The final niggle I have to mention is e-posters. While they offer many advantages over traditional conference posters, their major weakness is that the interface is essentially useless for browsing. In a real conference you can casually walk by and look at the titles and/or biggest pictures, but it's bloody tedious to do that virtually. Not only because there's no good way to quickly search for potentially interesting posters, but also because they just don't look nice. Here's mine as it appears in the gallery :
The Sciencening
Let's move on to the talks. There were quite a lot of good review talks but not that much in the way of interesting new discoveries. That said, I have to give an honourable mention to Heloise Stevance, whose talk on public speaking should probably be required viewing. Although there weren't any "oh god just shoot me instead" talks this year (unlike last time), everything tended towards a certain... mediocrity. Stevance's talk was the only one where the speaker conveyed real energy and enthusiasm. Granted, this is exceptionally difficult to do when talking to a monitor, especially when you don't see any of the other participants, but even in real-life presentations too many speakers are positively sullen bordering on depressed. I have to say that my own institute is particularly bad at this, as though everyone is positively afraid of sticking their head above the metaphorical parapet in case it gets metaphorically lopped off for some reason.
As well as the essential but apparently not-so-obvious points that you should be enthusiastic and not monotonic, Stevance made the interesting case for designing talks and papers very differently. Instead of trying to make a talk a micro-version of a paper, she says that instead you should build the talk explicitly around the take-home points. I think this is generally good advice, especially for short talks to specialist audiences. In a longer seminar or to a broader audience, you can and should afford to spend a disproportionate time on a lengthy introduction to get everyone up to speed. In a 15 minute presentation to specialists, you can practically reduce the introduction to a sentence or two, and spend the rest of the time discussing the science. Not the methodology, but the results. A lot of speakers seem obsessed with the methods to the point that what is is they actually found - the thing we've all come to learn about - gets almost tacked-on at the end.
Come to that, too many talks were about planned projects or results at a preliminary stage. Frankly, that's a bit daft. Overwhelmingly what I want from a talk is an interesting new result, so if someone wants to present a new survey they haven't even started yet, they should bloody well do a poster instead. This seemed particularly problematic this year, or perhaps I've just lost patience because I feel badly in need of a holiday.
Sigh.
(Is it just me though ? Does everyone else long for detailed descriptions of upcoming surveys and planned instruments ? There doesn't seem much possibility for discussion about things that people are going to do but can't actually do yet. Compare that were data that's already been analysed - there you have the chance for actual productive conversations - which seems like something very important in a conference, to me.)
Anyway, jellyfish galaxies were much in vogue this year. In general they're the result of strong gas stripping occurring as a galaxy slams at high speed through the hot gas in a cluster, leaving behind tails that can sometimes look quite a lot like the tentacles of a jellyfish. Luca Cortese made the point that this phase is common but not ubiquitous, and in extreme cases it's not just the hot or warm outer gas that can be stripped but even the very cold, enormously denser gas as well. Annalisa Pillepich demonstrated from simulations that for a jellyfish to result in a permanent morphological change to a galaxy, the stripping has to actually remove the gas from the galaxy, not just cause a temporary disturbance - otherwise when the gas returns, the galaxy will reclaim its original structure.
There was also quite a lot about data science. Most of this was about machine learning and suchlike, but there was one very nice presentation by Lucia Marchetti about the iDaVIE visualisation tool. This is explicitly based around realtime rendering and analysis using virtual reality headsets, which is just scandalously cool. I'm hoping I'll have time to try out the code sometime this week. Though this is something that's long been on my Christmas list for the awesomeness alone, I'll confess to being just a little bit skeptical that doing analysis this way would actually offer much advantage over traditional methods. That said, some of the tools do look promising, and potentially easier to do in VR, which bodes well. And encouraging users to actually spend a long time just looking at their data is definitely a good thing. The more visualisation tools we have, the better.
A great deal was said about Ultra Diffuse Galaxies, particular by using their globular clusters to try and estimate their masses. An interesting controversy came up regarding DF44, the UDG that's the main candidate for being a "failed giant" with the mass of the Milky Way (the consensus seems quite clear now that most if not all UDGs are just dwarfs), with rival claims made using the same data that establish very different masses. The cause of this disagreement isn't yet known, so I'm going to wait and see what comes onto arXiv before commenting further.
There was also quite a bit about "pre-processing", a term everyone seems to have become confused as to what it actually means. Certainly there are different evolutionary processes affecting galaxies inside and outside clusters, as well as conditions resulting from external influences acting on galaxies and those resulting from internal processes. To my mind, pre-processing means any external influence that acted on a galaxy prior to its infall into a cluster. Seems simple enough, and I'm not sure why this is at all problematic.
Rory Smith gave a very nice overview of the state of the art - mainly from the perspective of simulations, but with plenty of observational stuff too. Galaxies with lower star formation activity are seen too far from cluster centres for them to have experienced cluster processes, so something else must be at work. One plausible effect is that filaments - the largest-scale structures in the Universe - actually have their own hot gas which could cause ram pressure stripping. Probably not enough to remove the cool gas within galaxies, but enough to remove their outer reservoirs of hotter material and so eventually reduce their star formation. In support of this, clear trends are visible in filaments in age, metallicity and colour of their galaxies, which is pretty compelling evidence that something is happening. Less clear is whether this really is ram pressure or something else, as there's not much constraint on the gas density.
Lyla Jung raised an interesting point about selection effects that seems obvious when you say it but wouldn't have occurred to me otherwise. That is, large clusters tend to be assembled from large groups. And large groups will cause more pre-processing, so there are selection effects as to where pre-processing is important.
One potential example of this came from Tirna Deb, who presented evidence that within galaxy clusters it's actually the most isolated galaxies which are the most gas-deficient, the exact opposite of what you'd expect ! But from discussions afterward, Palo Serra suggested that galaxies which are still in sub-groups within clusters are likely recent arrivals, since groups are soon broken apart by the hungry cluster - and group effects are much weaker than clusters. Conversely, galaxies not in sub-groups are more long-term residents, so they've experience the full whack from the cluster already - hence the more isolated galaxies should be the most deficient. There does seem to be pretty decent evidence for this in that sub-groups tend to be found at higher distance from the cluster centres. So a very neat, elegant explanation for a counter-intuitive effect.
So that's years virtual overload over and done with. Mildly interesting, though disappointingly lacking in anything controversial. I'm almost tempted to say that the EAS should drop their official code of conduct policy just to encourage more fights to break out. Or perhaps we all need specialist training in How To Give An Enthusiastic Talk Over Zoom. Or holidays. Holidays are nice.
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