Saturday, 29 January 2011

Doctor Proctor and the Irregular Galaxies

Before I write this post, an apology. Formspring, the question and answer site - on which you're all welcome to contact me with an astronomy question (no guarantee I can answer it, but I'll do my best) - turned one of my entries into a blog post here without any form of notification. I always make sure I have the "blogger" tickbox un-ticked, so it shouldn't have been able to do that. Annoyed and caught off guard, I deleted the unwanted blog post - and forgot to save a comment someone had left! Sorry to that person. Please do leave it again.

Back in 2008, when the first of Galaxy Zoo's many projects on merging galaxies got underway, the zookeepers posted a list of galaxies they wanted us to identify as mergers or not. We had a zooite called Waveney, which, incidentally, is also the name of the hall of residence that I was in at university - and which he had been in many years earlier! Waveney, whose real name is Richard Proctor, wrote a program allowing us to go through the list much faster, Galaxy Zoo style - and made quite a difference, by allowing mini-projects to run quickly and enjoyably on the forum.

One area which hasn't been looked at much in astronomy, including in Galaxy Zoo, is irregular galaxies. We've been focussing - especially in the early days - on galaxies with a defined shape we can study, such as spiral or elliptical:

(From the Galaxy Zoo 1 tutorial. Click to expand.)

An irregular looks like neither of these. In fact, I can't really describe an irregular's shape. It might be a cloud, it might be a set of clouds or starforming clumps, it might be a crazy-shaped mass after a merger . . . There's a good sample here and the forum's whole collection here if you'd like to browse. Here's one for illustration, but it's hardly a representative of all of them.

(From SDSS.)

Now, on the one hand, irregular galaxies got more interesting since the launch of Hubble Zoo because it seems to me that nearly every galaxy we get on that is irregular! Hubble Zoo is mostly looking at galaxies much, much further away than those we looked at with the SDSS telescope. That means we see them as younger than our own - and younger than they would be now if light travelled instantaneously. Most of them are, frankly, a mess. It's fascinating to think that these wispy, often unclassifiable things are a prelude to the gorgeous creatures nearby. As an aside, to me, that's a hefty piece of evidence in favour of the Big Bang. I've classified well over 100,000 galaxies by now, and seen how different they look according to age. (Granted, this is not a scientific study.)

And on the other hand, irregular galaxies are interesting because Waveney is going to do a PhD on them.

His irregulars project has been running for a while, and as I write this, the "click count" is 88,488! The largest sample of galaxies looked at by a professional astronomer that he can find is 161; Waveney's project has many thousands. These were mostly collected by extracting all the ones from the Irregulars thread on the forum, and a brilliant, dedicated lady in Puerto Rico named Aida Berges going through the rest of the forum and the SDSS databases to find others. (Have a go at navigating around; it's terrific fun!)

To take part in the irregulars project, I recommend a quick look around Galaxy Zoo or the forum for a few tips, so you know what you're doing. But I don't mean masses of intense study. Galaxy Zoo itself does not require you to be an astronomer; it requires you to be better than computers at looking at shapes, and as (presumably) a human, you therefore qualify. There is an "irregular checking examples" thread where people can ask for advice.

You'll be asked: how clear the irregular is (i.e. how reliable anything is you say about it - some are very faint or fuzzy); whether it's a compact galaxy or whether it's all over the place; whether it has various features that larger galaxies have - a core, a bar, any spiral features; and whether it's alone or among a lot of others, for which there are zoom buttons you can use to help (even so this can be a bit thorny, as galaxies that appear to be nearby can often be millions of light years further away, just in the same line of sight). There are also buttons to indicate whether it happens to be the same as the previous irregular - for the SDSS camera often focussed on more than one point in a galaxy - and whether it's not an irregular at all.

Waveney's initial results show some definite differences between irregulars and other galaxies - their blueness, for example, which is an indicator of heat and star formation. You can also look at their metallicity to see how old they are. For example, are irregulars basically very young galaxies who might eventually evolve into the spirals and ellipticals we know? Or are they simply the cosmic plankton, unobserved amidst the sharks and whales yet a bedrock of the ecosystem - because, perhaps, not enough gas happened to be a round where they formed? (Spiral galaxies, for instance, need to be a certain mass to become the complex rotating disk we're familiar with.)

The method Galaxy Zoo uses to gain a really accurate database is for lots of people to classify each galaxy. For example, 90% of people might think that something's a smooth elliptical; but the other 10% may claim that they can see signs that it's rotating, or disturbed. It's easily possible that neither sample of people was wrong. Although I can seldom resist talking about irregulars as if they're the animals we don't notice because they're small and unglamorous, galaxies do not have particularly fine lines drawn between definite types. There's a lot of argument on the forum over whether or not one type of galaxy turns into another, or whether it's just that some sit on a blurred line!

Waveney uses the same method: get as many people as possible to look at each irregular. You could say that 25% of people think this has some spiral structure, and therefore, in a sense, this is 75% an ordinary irregular and 25% a sort of proto-spiral. That may sound unscientific, but it's less so than trying to force it into a human-defined category when it genuinely doesn't belong to one.

He got the idea of turning this into a PhD thesis from a remark Chris made along the lines of "you've done half a PhD here". " I recognise this means I have done 10%," he writes cheerfully, "but it got me thinking – why not do it properly. I don’t want to do this full time, I have a very full time job – but could I do it part time. Does the Open University do part time PhDs – a quick web search yes it does…" There's nothing like simply looking at what you could do and what options are available!

As I said, he's looking at colour and metallicity, also the irregulars' masses and starforming rates. He's comparing these with equivalent samples of spirals, ellipticals and also the peas, the intensely starforming compact galaxies we amateurs found and studied in 2007 and 2008. None of the irregulars contains an active galactic nucleus, which suggests that they are all of low mass. (An active galactic nucleus is the activity surrounding a supermassive black hole in the centre of a galaxy - where stars and other matter whose speeds around the disk are insufficient to keep them in orbit forever, and which therefore pile up in the middle. When a huge amount of matter arrives in a small place this way, before it enters the black holes, it becomes unbelievably hot, and can outshine the entire galaxy.)

What else? Doubtless he has other plans up his sleeve. I only feel sorry that, in the early stages of the project, when Jules and I were also helping, my part - examining the irregulars' environment, i.e. how close they were to their neighbours - came to a standstill before I even started, because nothing I did with SQL actually worked. Months later, Chris told me that in fact my task wasn't possible with current tools - I am sure there are other avenues, but I am no programmer and am an unlikely candidate to find it out. Waveney has tactfully described me as being "in a supporting role". That does seem to be my role in most citizen science projects, and it does seem to be helpful to at least the people and the communication, if not the data itself. Perhaps one day that'll change. If not . . . well, supporting people are very useful.

You can keep up with what Waveney (who has stoically ignored the nickname of "Doctor Proctor" I couldn't resist giving him) in the Galaxy Zoo Library, and do give him some irregular clicks. If you're interested in the wider issues of citizen science and education, please note that the Open University is among the umpteen bodies whose funding is being slashed. Some of us at Galaxy Zoo, me included, have studied astronomy and (in my case) mathematics, inspired simply by what we're doing and discovering - and it's the only chance for so many people to combine study with their jobs, families, and other real-life commitments. Waveney's PhD thesis will bring new knowledge to the field of astronomy, not to mention be a shining beacon for people who thought their chance to learn and contribute was over. Knowledge is not a drain; it's progress - so let's not let it go.

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