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.

Sailing Among the Blues

The first name thought up for Galaxy Zoo was "Galaxy Safari". Astronomy is like a journey sometimes - through space and time, stopping at astonishing tourist sites or, further on, the wilderness. It's definitely true that Google Sky tours have suddenly become the height of fashion on the forum - now Half65, Ben Hoyle and Fermats Brother are all making them, and I expect more will follow!

I often also get the feeling that we're a little like biologists - or rather, that we've changed the whole of galaxy science from specialist zoology (sorry about that) to worldwide ecology. Traditionally, an astronomer might spend a lifetime studying up to 30 galaxies, and we've got used to the usual types - ellipticals are red, spirals are blue, galaxies are pretty, in science and view (and sorry about that too). Our discovery of blue ellipticals and red spirals was like discovering a parrot in a penguin colony, or a polar bear spotted like a leopard. We now know that, as polar creatures are white, the environment dictates galaxy colour. Being in a cluster turns galaxies red. And being alone turns galaxies blue.

That isn't due to natural selection, of course - it's due to the available gas in the local environment. And there's one type of galaxy that always seems to be blue, and that's the irregular galaxy. Irregular galaxies might be past mergers, or they might be little splodges or wisps of star formation, far smaller than your average spiral or elliptical, and with no defined shape we can so far describe scientifically.

(Credit: SDSS.)

Our brilliant Waveney wrote an Object of the Day on our irregular galaxies project yesterday. I won't try to cover all our aims or findings in this post, but one result is definite: they are nearly all blue. We've found a few that aren't, but none that are red, like ellipticals in clusters. Generally speaking, they are much, much bluer than your average Galaxy Zoo galaxy.

Irregular galaxies seem very common, although we can only see the nearest few because they're so small. As sepos stated in another Object of the Day, 90% of galaxies are the low surface brightness variety - again, not the sort we're studying. Could we be focussing on the magnificent tigers and elephants and whales of the universe, and missing out on the beetles and plankton? Do large bright galaxies depend on the existence of these dim little puffs as large organisms depend on the existence of bacteria? Or are these lowly little galaxies simply a by-product of far-flung gas, and have no effect on their larger neighbours?

Going back a moment - why are they mostly blue? It's because they're forming stars. As blue light is more energetic than red, that means the hottest stars give off blue light. That doesn't mean stars start off blue and go red later. It means that whenever star formation takes place, a few massive stars invariably form. These hydrogen-guzzling monsters outshine all the red stars in the galaxy, giving the whole galaxy a blue appearance - but they don't live very long. After a few million years, only the more sedate yellow and red ones are left.

Star formation is the subject of yet another game on the zoo (do you think I need to create a "games" label?) - not to mention Chris's current research interest at Oxford, or so the websites say. Intriguingly, his research apparently "focusses on the use of sulphur compounds". Which seems contradictory to me, since such compounds would not survive the heat and fury of stars. Perhaps they're a feature in gas clouds, or a product of something or other. This is the most informative paper Google could provide. If he ever has time, I'll ask him to talk me through it.

(Starforming region Corona Australis. Credit: NASA.)

So are all irregular galaxies young? Or are they simply like lonely blue spirals and ellipticals - continuing to drift through space and always encountering more gas? Is the Universe still too young for any area to be fully empty of gas, and will we see red irregulars in another few billion years? What about irregulars in giant superclusters, assuming they wouldn't all merge with the giant ellipticals already living there?

Some questions we already seem to have answered, at least to the best of our ability, on Galaxy Zoo so far. For example, we've established that galaxy rotation is generally random, though spirals near each other have a greater likelihood of rotating in the same direction - another indication that environment is very important in galaxy formation. (For more on galaxy rotation, I would recommend all ZookeeperKate's posts on the Galaxy Zoo Blog.) But I don't think we need worry that we've already found out everything. There is a lot more left to come!