Search results for green peas

Give Peas a Chance

Hi Pea Hunters,

Kevin and I wanted to give you an update with where we are in our Peas investigation. We haven’t answered all of our questions, but from detailed inspections of their spectra, it appears that the Peas are a mixed bag. A large portion of them appears to be powered by star formation, and perhaps an equal number show evidence of an active central black hole. The details of what I’ve done so far are below. Feel free to chime in with any questions or suggestions you all might have! The first thing I did was look at all of the peas that were highly rated as Green in our Pea Picker hunt. When I plotted them against a sample of randomly selected galaxies of at similar redshifts, they do stand out. This first plot is a color-magnitude diagram. In my opinion its one of the most widely used of all plots astronomers can make. Practically, this is probably because only 2 images are necessary to make this plot, but also historically because we’ve found out plots like these can tell us so much (eg. the HR diagram).
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Introducing Galaxy Zoo: Clump Scout, a new citizen science project

Hi, I’m Nico. I’m a 2nd year PhD student at the University of Minnesota studying galaxies. In particular, I use statistics and machine learning to extract useful information from ever-growing galaxy catalogs astronomers have assembled over the last few decades.

Today, I get to announce a completely new project by the Galaxy Zoo team! 

Galaxy Zoo: Clump Scout is a citizen science project that will take a closer look at galaxies that were classified in the Galaxy Zoo 2 project. In that project, many of you answered questions for us about their shape, structure and properties. This time we’ll be examining them in an even more detailed way.

We are searching galaxies to find “giant star-forming clumps”, or just “clumps” for short. This is what astronomers call small regions within galaxies where stars are being born at a faster-than-usual rate. They are called “giant” in comparison to any individual star or group of stars — clumps can contain millions or even billions of stars — but they’re usually quite tiny compared to the galaxy containing them. The new stars formed in clumps are brighter and more densely packed than those in the rest of the galaxy, so when photographed, clumps tend to look like small glowing areas that stand out from the background. We call any galaxy with a region like this a “clumpy galaxy”. (And yes, we promise that the word “clump” will start to sound less silly with time.)

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Figure 1: Some examples of clumpy galaxies that will appear in Galaxy Zoo: Clump Scout. In these images, clumps look like small, blue spots on the galaxies. Some of the clumps in these images are bright and obvious, while others take a bit more care to spot. All photos were taken by the Sloan Digital Sky Survey.

In the Clump Scout project, we are asking volunteers to look at galaxies and click on all the clumps they can see. This is a straightforward task, but many clumps require a keen eye to pick out. Once complete, your clicks will tell us where clumps are found in thousands of galaxies in the local universe. This will be one of the first large-scale studies of clumps in local galaxies, and I’m very excited to see what we find!

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Figure 2: A classification from Galaxy Zoo: Clump Scout. Here, a red icon marks the central bulge of the galaxy, while six green icons mark clumps.

Why study clumps?

Clumpy galaxies have been a bit of a mystery for scientists for a while now. Astronomers have known of their existence for decades, but discussion about them really began in the late 1990s when the Hubble telescope began to capture images of very distant galaxies. Because light takes time to travel, we saw these distant galaxies as they existed billions of years ago, at a time when the universe was still young. As we studied Hubble’s images, we started to notice differences between the early galaxies and galaxies that exist today. One such difference: In the past, nearly ALL galaxies were clumpy! Discovering this was surprising, because most galaxies in the present-day universe do not have any clumps.

It’s not yet clear how clumps were formed, why they are vanishing over time, or exactly what fraction of galaxies contain clumps. What we do know is that clumps seem to change through time alongside the galaxies that contain them. As we come to better understand clumps, we hope to better understand the role they play in the growth and evolution of their host galaxies.

Why citizen science?

Part of the reason why Clump Scout is so exciting is that this is the first time human eyes will examine so many clumpy galaxies first-hand. Thanks to the help of citizen scientists, the Clump Scout project will be able to examine over fifty thousand galaxies. To speed things along, we have already filtered these galaxies with volunteer classifications from the Galaxy Zoo 2 project and picked out the subjects that volunteers marked as having “features”. By doing this, we eliminated nearly 200,000 galaxies that are very unlikely to contain clumps, leaving only more promising subjects.

We will also be testing to see which types of clumps volunteers are able to spot. There are certain clumps that are too faint to be seen no matter where they are, while others reside in bright regions of the galaxy which drown out their signal. To quantify these effects, we have taken some galaxy images and added a few of our own, simulated clumps on top. By marking these simulated clumps, you will provide us with a wealth of information about what types of clumps we can reasonably expect to find. For example, if volunteers mark a particular simulated clump 100% of the time, it is a good sign to us that a real clump like it would be found as well. On the other hand, if no volunteers see a simulated clump, we know that similar clumps are very unlikely to be found by this project.

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Figure 3: An example galaxy before and after simulated clumps were added to it. On the right, a total of 5 extra clumps have been added, but several are too faint to be seen in this image.

Why can’t computers do this?

As with many citizen science tasks, identifying clumps is fairly easy for humans to do, but difficult for computers. There have actually been a few algorithms so far that could identify clumps with some success, but it’s an exceptionally difficult task to get right. Computers must be trained to ignore all the extraneous details in an image — including background galaxies, stars in our own galaxy, and galactic features like the central bulge — to find clumps among the competing signals. Luckily, this sort of task is second nature for human beings.

Computers also tend to be very bad at finding objects they aren’t specifically instructed to find. We hope that as this project proceeds, you’ll be able to help point out some exceptionally strange clumps, or even some features we do not expect at all. It was the keen eyes of Galaxy Zoo volunteers that led to the discovery of Green Peas, a class of galaxy that is still being researched today.

This project has been in the works for the last few years, and we’re very excited to see it launch. If you’d like to try it out, you can take part here.

Gems of the Galaxy Zoos – coming soon to a space telescope near your planet!

It’s away! The final observation plan for the Gems of the Galaxy Zoos Hubble program was submitted earlier this week (24 hours before our deadline, I want you all to know).

We collected votes for over 2 weeks, separately for Galaxy Zoo and Radio Galaxy Zoo objects since they needed distinct image layouts. About 18,000 votes were cast. The Talk interfaces turned out to be very useful for immediate practical matters – some users seeing images twice, some cases of the wrong  coordinates being used for images that had been uploaded and needed to be replaced, and finding duplicates both within the candidates and versus older Hubble observations. (A major “thank you” to the volunteers who contributed in these ways). I was strongly impressed at the level of discussions on the Talk sites that went into some of these decisions.

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Gems of the Galaxy Zoos – help pick Hubble observations!

Galaxy Zoo and Radio Galaxy Zoo participants have an unusual opportunity to help shape a list of galaxies to be observed by the Hubble Space Telescope, as part of the “Gems of the Galaxy Zoos” project.

The project came about when the Space Telescope Science Institute circulated a message in August of 2017, seeking proposals for a new category of observation – gap-fillers. These projects will provide lists of target objects around the sky for brief observations when high-priority projects leave gaps in the telescope schedule, allowing 10-12 minutes of observation at intermediate places in the sky. Read More…

#GZoo10 Day 3

We’re ready for the final day of the Galaxy Zoo 10 workshop at St Catherine’s College in Oxford; it’s been great to have so many people following along on the Livestream – yesterday’s talks are still up, and today’s schedule is:

09:30 Alice Sheppard (Forum Moderator 2007-2012)
10:00 Brooke Simmons (UCSD)
10:20 Nic Bonne (Portsmouth)
10:40 Coffee
11:00 Coleman Krawczyk (Portsmouth)
11:20 Mike Walmsley (Edinburgh)
11:40 Carie Cardamone (Wheelock)
12:00 Karen Masters: Summary (Portsmouth)

We’ll be blogging these talks as they happen here but you can also keep an eye on the twitter hashtag for updates too!


Our first speaker this morning is Alice Sheppard who was here from the beginning as a forum moderator on the original Galaxy Zoo site. She’s talking about the past 10 years and how she got involved with Galaxy Zoo site. She was very keen to get involved in the project and help classify galaxy images. After finding images that weren’t easily classifiable, users started to email members of the science team to ask them what to do. After this happened many times, the team realised that a place where users could talk together and interact with the team about classifications would be really useful. So the Galaxy Zoo forum was born! Alice was one of the first people to sign up and was asked to moderate the forum – she (along with other moderators) even started welcoming each new user who signed up with a friendly “Welcome to the Zoo!”

Alice is now talking us through some of the findings made by the users. These discoveries including the Green Peas, which when first spotted by the users they immediately started investigating what they were using the links to the science survey site. In the original Galaxy Zoo there was also no button for an irregular galaxy, so users started collating their own collection of irregular galaxies! But what makes users keep coming back to the Galaxy Zoo forum time and time again? One success story was the Object of the Day – the moderators even crowd sourced the users to find good images!

Alice has discussed some suggestions for future engagement with users online – always give people room to chat; whether it’s about astronomy or not at all! Remember: as good as you think you citizen science system, tools, tutorials etc are – the volunteers will teach you how to do it better!

Next up this morning is Brooke Simmons talking about what she’s calling probative outliers. The things that tend to break the mould and challenge our world (or Universe!) view. She starts with the bulgeless galaxies – those that look like pure disks – but are hosting growing super massive black holes in their centers. This is weird because the most accepted theory is that super massive black holes grow in mergers of galaxies BUT mergers also grow bulges – so how did these bulgeless things grow their black holes? Brooke is showing us some beautiful follow up observations of Galaxy Zoo SDSS images taken with the Hubble Space Telescope that will help to try and figure this out.

Thing is, Brooke only has about 100 of these galaxies – but not for lack of trying! They just seem to be really rare. If we could actually cover the southern sky in the same way that SDSS covered the northern sky, Brooke would be very grateful! Could we also use trained machines to pick out the weird outliers as well? In which case, Brooke thinks we need to adapt the next iteration of Galaxy Zoo to be both machine as well as user friendly. This will mean leaving things behind but let’s not be afraid to make changes!

Next up, we have Nic Bonne from Portsmouth who’s going to tell us all about making luminosity functions using the data from Galaxy Zoo. So what’s a luminosity function? It’s basically a count of the number of galaxies at different luminosities (or brightness) which can give us clues about how the Universe formed and evolved.

Luminosity functions are especially interesting if you start making them for different morphologies or colours of galaxies. This is what Nic has been doing using the Galaxy Zoo 2 classifications. He’s found something a bit weird though – that the galaxies classified as smooth seem to be more numerous than those classified as featured at the low luminosity (low mass) end. Bringing the colour of the galaxies into this picture as well shows you how similar red featured and red smooth luminosity functions are. Nic says there’s a lot more to do be done with this work though, including using Ross’s new debiased classifications to improve the sample completeness and investigating how the luminosity functions change shape for different kinematic morphologies.

Next up is Coleman Krawczyk who’ll be showing us some of the initial results from the Galaxy Zoo 3D project. This project asked users to draw around the features of a galaxy on an image so that researchers could pick out the spectrum of that particular feature using MaNGA data. Users were asked to either mark the centre of the galaxy or draw around any bars or spiral arm features.

Users could also choose which classification task they would prefer to help out with. This meant that the easy classification task of marking the centre of the galaxy was finished within a couple of days – whereas the spiral drawing task took 6 weeks for classifications to finish. Coleman has now reduced these classifications and has made “maps” for every galaxy marking which pixels are in which features. He’s now started making diagnostic plots to map the star formation rate in the different features of classified galaxies. Turns out we’re going to need more classifications in order to do the science we want to, so this project could have new data coming soon!

Next up is Mike Walmsley, who’ll be joining the research team as a PhD student in October.

He’s not yet done any work with Galaxy Zoo but as part of his Masters research he looked at doing automatic classification of tidal features in galaxies. His goal was to write a code that trained a machine, using a neural network, to detect these tidal features. He also figured out that masking the main galaxy light in the image makes it easier for the machine to spot tidal features. So does this method actually work? It identifies tidal features with ~80% accuracy – which is actually a much higher quality than other automated methods! He’s hoping to apply these methods to new and bigger surveys during his PhD.

Next up is Carie Cardamone from Wheelock College talking about her work building on the the discovery of the Green Peas by Galaxy Zoo volunteers.

So what are the Green Peas? First up their name describes them pretty well because they’re small, round and green. Carie originally wanted to study them because she thought they might be growing super massive black holes, but it turned out instead they have extremely high star formation rate for their relatively small mass. There has been many further studies on these objects so we now know a lot more about them, but one thing we still don’t really know is what galaxy environment they live in. Carie is trying to quantify this but the first problem was that she didn’t have enough Peas! There’s only 80 in the original GZ2 sample but now with the better analysis tools Carie has been able to select 479 candidate Peas. Analysing this sample and comparing it to a sample of well studied luminous red galaxies, the results suggest that peas are less clustered. i.e. the Peas have fewer galaxy neighbours.

We’re now coming towards the end of the meeting (sad times guys) and to remind us all why we’re here and what we talked about, Karen Masters is going to give us a summary of the past couple of days. She’s first pointing out how great we are as a team and the impact the research has had on the galaxy evolution community. Fitting for the 10 year anniversary is that we have 10 published papers with over 100 citations!

Karen has noticed a couple of themes from the past few days that she’s summarised for us. The first is that we have to keep engaging with the Galaxy Zoo community on Talk. The second is that we shouldn’t be afraid of change – let’s not get hung up on how it’s always been done and think about how best to do it now. The third is that galaxy’s are messy and we need to think carefully how we use the classifications. The fourth is that the users will always give you what you ask for – so be careful what you ask! But sometimes you get more than you asked for and end up with a wonderfully collaborative research team!

Welcome to #GZoo10 : Day 1

It’s the day before Galaxy Zoo’s tenth birthday, and the team have gathered in Oxford for three days of discussing science and our plans for the future. Because it’s Galaxy Zoo, we’re inviting any of you who are interested to follow along online.

Members of the Galaxy Zoo team relax before the start of their meeting in an Oxford pub.

The mornings will be taken up with talks from team members. Today’s schedule is :

10am : Chris Lintott (Oxford)
10.20am: Lee Kelvin (Liverpool John Moores)
11am: Steven Bamford (Nottingham)
11.20am: Lucy Newnham (Portsmouth)
11.40am: Sandor Kruk (Oxford)
12 noon: Bill Keel (Alabama)

All the talks will be available via Oxford’ LiveStream account here. You can ask us questions using the #GZoo10 hashtag on Twitter – we will make sure someone in the audience at each session is watching so comments online make it into the room.

The afternoon will be an unconference and hack session, with the team debating the issues raised during the day and getting to work together. These sessions won’t be streamed, but we will blog about what’s going on.


It’s Becky Smethurst blogging from here on in folks… 

So we’ve kicked off the day with our fearless leader of the Zooniverse, Chris Lintott, reminding us that on this day 10 years ago the team were having conversations about how it would be amazing if they could get 10,000 people to help classify. Chris is still amazed that we’re here 10 years later with over 400,000 of you.

Chris is running through some of the modes in which we work with the Galaxy Zoo data. The first is looking at traditional morphologies, which the project was designed to do, like bars and spirals. The second is “distraction mode” where we’re all distracted by the serendipitous discoveries that the users make which we weren’t expecting, like the Voørwerpjes and the green peas. The final mode is the modelling mode, where we’re fitting models to the Galaxy Zoo data to explain something about the Universe. This mode also includes the amazing work with classifications of simulated galaxy images that are ongoing on the Galaxy Zoo site right now!

One of the questions from the audience for Chris is: “Why have the serendipitous discoveries dried up on Galaxy Zoo?” For one thing Chris thinks that one issue is that is takes so long to follow up on these discoveries – we’re still working on the Voørwerpjes! – but one thing we don’t have with the current images on the site (GAMA and KiDS etc.) is a link to the science survey site where the images come from. We had that with the original Sloan Digital Sky Survey (SDSS) images in Galaxy Zoo 1 & 2 which allowed the users to explore the data themselves and flag up something interesting.

Up next is one of the newest members to the Galaxy Zoo team: Lee Kelvin! He’s telling us about his work with the Galaxy Zoo classifications of the GAMA and KiDS survey images which have just been classified by users on the site. The special thing about GAMA is that it’s multi-wavelength; it takes images in various bands across the spectrum, from the ultra-violet to the infra-red. This is important because, as Lee points out, the morphology of a galaxy changes a lot across different wavelengths.

 

GAMA also has cross-over with the KiDS survey (the main role for which is to map the locations of gravitational lenses in the Universe, like those users hunted for in Space Warps!) which has much higher resolution than the SDSS images originally in GZ1 & GZ2. This means they’re perfect for classifying morphologies because more detailed features are resolved. These images are on the site right now – which means lots of pretty pictures for us to classify! These classifications give the team a wealth of information on the galaxies in these surveys – especially when users flag the interesting cases on Talk.

The early results from these classifications with the images from KiDS look very promising but Lee says there’s lots more work to be done! Including setting up a follow-up Zooniverse project trying to distinguish between true smooth elliptical shaped galaxies and disk galaxies that look smooth – so look out for that project going live in the next couple of months!


We’re back and caffeinated after a refreshing coffee break! Now Steven Bamford has taken the stand and is talking to us about the next steps for morphology studies with Galaxy Zoo.

He starts us off by reminding us that we can’t just split galaxies into spiral and elliptical galaxies anymore – it’s a lot more complicated than that with a whole evolutionary sequence of smooth disk galaxies between the pure elliptical and pure spiral galaxy sequences. It’s therefore really important to get both visual classifications from Galaxy Zoo but also quantitative morphologies. A quantitative approach is where you analyse an image to reduce the description of a galaxy down to a number – for example, how disturbed or asymmetric a galaxy is. Steven is explaining how you can do this by making a model of a galaxy’s light and subtracting off the original image and analysing what you’re left with. The problem is that the models are tidy but the galaxies are messy! Deciding which model to use is very difficult but that’s where the Galaxy Zoo classifications come in – they can be used as prior information to decide which model to use.

Steven explains the reason why we actually want to do all this model fitting is because we care about population statistics. Sometimes we don’t care about individual objects and we want to look at the big picture – to do that we need to reduce all that information down as much as we can.

Next up is one of the newest additions to the Galaxy Zoo team, Lucy Newnham a PhD Student at Portsmouth! She’s giving us a nice introduction to the big picture of galaxy evolution and how galaxies stop star forming as they evolve. She’s particularly focussing on barred galaxies and whether the bar can cause this shut down of star formation.

She’s done some follow up observations of some barred galaxies picked out by Galaxy Zoo using radio telescopes! Ionised hydrogen gas emits a very specific wavelength of light in the radio part of the spectrum (21cm) – so if you can detect emission with radio telescopes at these wavelengths it means there is hydrogen gas there to fuel star formation. It took 115 hours total observing time with the VLA and GMRT to get data for just 7 galaxies! The first one she’s reduced the data for is UGC9362 and she’s found that there is a hole in the gas in the centre of the galaxy where the bar is. She thinks that means that since the bar is rotating with the galaxy, it has carved out a hole in the gas as it does so and used up all the gas needed for star formation.

The next question Lucy is trying to answer is if the strength of the spiral arms is affecting the star formation in a galaxy? To quantify the strength of the spiral arms, Lucy is using the Galaxy Zoo classifications – where more people agree that a galaxy has spiral arms the stronger the spiral arms will be! Lucy has now looked at trends in galaxy properties with the strength of the spiral arms showing us a plot that she even made this morning! LIVE SCIENCE EVERYBODY!

Taking the stand now is another PhD student, Sandor Kruk, who will be continuing this barred galaxy theme: “Dealing with bars… and other mess”. He clarifies that when he refers to “mess” he means other morphological features!

Again, he’s focussing on this problem of what makes galaxies stop forming stars. Earlier results from Galaxy Zoo that Karen Masters worked on back in 2012 suggested that bars were a likely culprit. Sandor is now following up on this work to split the galaxy light into the separate components: bar, disk and bulge. Looking at the colour of this light will let us know if that part is star forming: red things are old, with little star formation and blue things are young, with recent star formation. To split this light he had to model the light of over 3500 galaxies! That’s a mammoth effort, but it’s paid off because he’s found that there is a difference between the colours of disks in galaxies with and without bars!

Whilst doing all this modelling, along the way he also made a serendipitous discovery: that some of the bars were offset from the centre of the disks. This is weird – it means that perhaps these galaxies have had an interaction with another galaxy which has shifted everything around. Turns out though that some of these objects had already been flagged in talk by the users! Makes us wonder what else is hiding in there that the team hasn’t yet seen!

Well Sandor reckons we should start with some of the questions of the Galaxy Zoo decision tree that the team haven’t yet had chance to look at. For example, what shape is the bulge of the galaxy – boxy or round? Does the galaxy have a ring? While Sandor has been fitting all of his 3500 galaxies (some barred and some unbarred as a control sample) for his bar study, he’s been getting some ideas for how we can tackle these questions – so watch this space!

So next up is one of the original science team members, Bill Keel! He’s sort of become the curator of the objects in Galaxy Zoo which don’t fit into any of the classifications we ask about on the site. He’ll be telling us specifically about the Voørwerpjes (i.e. ionization echos). The first one was flagged on August 13th 2007 (another 10 year anniversary coming up, mark it in your calendars!) by one of the volunteers who brought an unusual blue smudge below a galaxy to the team’s attention. Bill is now telling us how they figured out that the weird blue smudge near the galaxy turned out to be a gas cloud which had been ionised by emission from the active supermassive black hole in the centre of the nearby galaxy. We can tell this by looking at the spectrum of these objects – where we split the light into its component wavelengths to spot specific elements and molecules.

After identifying what this first object was, the users then found more! Bill ended up doing follow up observations on 20 of these objects – including 8 followed up with the Hubble Space Telescope. Turns out NGC7252, a galaxy that astronomers have been studying for 30 years, even has one of these ionised clouds!

The search continues for more of these objects – including another one flagged by a user in February 2017 in the current data being classified on Galaxy Zoo. So keep a weather eye out people!

We’re now going to open up the conference to discussion – between the team that are here and you following along online! If you’d like to ask a question or make a comment for discussion – either post it here on the blog or on Twitter with #GZoo10.

The discussion so far has covered how we consider more detailed features of a galaxy and how galaxy simulations will tie in with what we do in the future. We’re also starting the discussion of how the Galaxy Zoo site will be restructured in the future as we move to the new Zooniverse web platform – exciting!

Now we’re all off to lunch to fuel ourselves for a long afternoon of discussion and unconferencing! See you all in an hour – until then, keep tweeting!


We are back! After an afternoon of “un-conferencing” where we all suggest sessions for discussion and schedule them on the fly.

We first talked about what science we’re going to do with your classifications on the infrared images from the UKIDSS sample. We want to compare how the shape of galaxies changes from the optical to the infrared but it gets difficult because galaxies tend to be fainter and smaller in the infrared. A lot of us are keen to study how the number of bars changes from optical wavelengths to infrared wavelengths. There are some studies showing that bars disappear in the infrared, but there are also some that show that bars appear in the infrared where there are none in the optical. One of the Galaxy Zoo PhD students, Mel Galloway, has already had a quick look at this and we discussed where to take this work next! First thing first though – releasing the classifications as a data table to the public.

Our next discussion session was about the future of the Galaxy Zoo classification cite. How are we going to ask the users to classify the galaxies? The current mode is the classification tree that we get users to walk through and answer each question for every galaxy. This is very difficult to analyse at the end of the project though. So we discussed changing the interface to either (i) single binary questions about each galaxy, e.g. Bar or no bar? Smooth or featured? (ii) A survey project similar to the interface for Snapshot Serengeti which presents all the options for a galaxy at once, (iii) Lots of mini projects which are all offshoots of Galaxy Zoo focussing on one specific science question, or (iv) pairwise classification where we show two images of galaxies and ask which is more featured etc. There were many opinions about what the best way of doing this but we’d also love to hear your thoughts!

Later on we had an “alpha” test of a revamped Galaxy Zoo project which is survey style – it took people a while to get used to but people did seem to like it! There was also a lot of feedback but it was good to get the discussion flowing about what classifiers would like and what researchers would need.

There was also a discussion about how to study bars with the classifications from Galaxy Zoo. It’s a little difficult to pick stuff out, especially the weaker bars. One of the ways astronomers tend to find bars (e.g. when Galaxy Zoo classifications don’t exist for their sample!) is to fit light profiles to the disk of galaxies and take that model light off the original image. What you’re left with is called a “residual” – light that you didn’t account for, i.e. light from a bar. So there was a discussion about making an offshoot Zooniverse project classifying the residual light images to find weak bars.

Ross Hart then led a discussion about his new way of debiasing the Galaxy Zoo classifications to take into account the distance to galaxies and the fact that features get lost. He can recover lots more spirals with his new method. The table we link to on the Galaxy Zoo data page now has his debiased data table linked first.

We also had a discussion session about the outreach project Tactile Universe – which is a project engaging the blind community with astronomy. They’ve been 3D printing images of galaxies – the brightness being the third axis! We’d love to be able to make a tactile Galaxy Zoo but we have to wait for the tactile screen technology that we’d need to be able to do it! Looks like we’ve got our first session for our Galaxy Zoo Twentieth Anniversary Conference – watch this space #GZoo20.


Now we’ve finished up with the discussion all about the science, we get a treat at the end of the day! Our reward is that our very own Grant Miller has come to tell us all Tales From the Zooniverse! He’s telling us all about his first day on the job in the Zooniverse and how he realised it was going to be a great job when he went into his first meeting all about penguins with the Zooniverse’s Tom Hart! He is now showcasing how amazing the Zooniverse project builder is and is currently trying to build the original Galaxy Zoo project with it in under 3 minutes! And I can tell you: Reader, he managed it! He’s now telling us about his top picks for the Top 10 Zooniverse projects you’ve never heard of:

10) Monopole Quest
9) Expert Smooth/Not
8) Letters to Ryan
7) Bash The Bug
6) Faces of the World
5) The Planetary Response Network
4) Beluga Bits
3) Supernova Hunters
2) Family Certificates
1) Grant can’t name the top one! There’s so many on there now that Grant doesn’t know all of the projects on there (he used to know all the researchers of the projects but not anymore!) – 4700 new projects created since the project builder was launched. 47 of these have been fully launched as new projects, with 31 awaiting launch now.

His take home point: a LOT can happen in ten years!

9 Years of Galaxy Zoo

Last year we had so much fun celebrating all that we (including you) had accomplished over the first 8 years of Galaxy Zoo. This year, for our 9th birthday, we thought we’d hand things directly over to you. We sent out a newsletter asking people about their favorite Galaxy Zoo science. We asked people to rank five choices:

  • Hanny’s Voorwerp & the Voorwerpjes (ionized clouds and active galaxies)
  • Green Peas (highly compact & star-forming galaxies)
  • Red spirals (disk galaxies with no/little star formation)
  • Blue ellipticals (spheroid galaxies with ongoing/retriggered star formation)
  • Bars (the galaxy kind; how this mode of disk galaxies drives galaxy evolution)

We’ve now collected just over 200 responses and combined your rankings. Although the distributions were pretty similar, and all the options had plenty of people choosing it as their favorite, one of the options jumped out as a pretty clear leader (at least in this rather informal poll).

Bars - the galaxy kind!

Bars – the galaxy kind!

Of course, the list we asked people to choose from is by no means complete, especially if you include not just the main Galaxy Zoo but also its related projects. In the “Other” box we had a variety of entries, with some mentioning galaxies found in Radio Galaxy Zoo and others citing those seen in Galaxy Zoo: Bar Lengths. Plenty of people mentioned galaxy mergers, and gravitational lenses got a few mentions too! If we had a complete list the rankings would likely be different, but then again, that would be such a long list I’d be worried many fewer people would want to answer.

We also had a space for people to enter whatever text they wanted at the end of the survey, and the responses were varied, interesting, and a treat to read. Here’s a sample (each paragraph is a separate comment):

I do not spend a lot of time here, but when I have the time, I love it. Thank you!

What a great way to feel like a scientist.

I’ve been an on-and-off participant in the Zooniverse citizen science projects since I was 13 years old – and Galaxy Zoo has been one of my favourites for a while! I just wanted to say thank you for providing the opportunity for an ordinary teenager to feel included in fascinating scientific research – that experience has inspired me to pursue a degree in Physics and Astronomy in the fall.

Go Science!

We were also curious about who, as a group, we were asking these questions of. It turns out that quite a large fraction of people who responded to the survey have been with us since the early days, which is so lovely. And we were also delighted to see people engaging with us who’ve just recently discovered Galaxy Zoo. We are so glad all of you are collaborating with us; here’s to many years to come.

Thank you!

P.S. – The big 10 is coming next year… what would you like to see for the occasion?

“Blue stuff” in the Illustris galaxy images

I think the most common question/comment we’ve been seeing for classifiers of the simulated Illustris galaxies is along the lines of: “What’s the blue stuff?”

Image of a synthetic galaxy (AGZ00089n5) from the Illustris simulation, being classified in Galaxy Zoo.

Image of a synthetic galaxy (AGZ00089n5) from the Illustris simulation, being classified in Galaxy Zoo. Blue-ish emission can be seen extending from the lower left to upper right of the center galaxy.

It’s a great question. Let’s talk about it in more detail.

The short answer is that the blue regions are the simulations’ method of reproducing the light emitted by young stars. A star’s lifetime generally scales as a function of its mass – the more massive the star is when it’s first formed, the hotter it is and the faster it burns fuel. Emission from hotter objects will tend to be bluer (ie, produce more photons at shorter wavelengths) compared to less massive stars. These are trends we see in optical images of stars in galaxies, including naked-eye views and composite color images. The exact color depends on the filters being used as well as processing of the images – that’s the difference between images you may have seen of star-forming regions being pink in some images and blue in others, such as those in Illustris.

A couple more specific questions that we’ve received:

What’s causing the blue colors in the galaxies? Are they caused by individual atomic or molecular lines that we can see in the spectra?

Volunteers who worked on the original GZ green peas project might be familiar with the term “nebular emission” – individual, narrow lines caused by ionized or hot gas surrounding stars, or whether they’re the result of the broadband colors of the stars themselves. The GZ-Illustris images use a stellar population model that only computes the broadband colors, due to some issues with unrealistic green images caused by the interaction of the codes that deal with both the emission lines and effects of dust. The model we’re using – based on work by Bruzual & Charlot (2003) – omits the emission lines for that reason. However, we’ve made extensive comparisons of the two sets of images and find that they agree very well for our scientific goals, including the morphology classifications.

A plot of the synthetic spectra for galaxies in the Illustris simulation; each thin horizontal line is the spectrum of an individual galaxy. The most massive galaxies are at the top, while the lowest mass galaxies are at the bottom. Wavelength increases from left to right, or going from bluer to redder colors. The lack of sharp features in this plot (which uses the BC03 model adopted by the Galaxy Zoo images) are a result of excluding the nebular line emission.

A plot of the synthetic spectra for galaxies in the Illustris simulation; each thin horizontal line is the spectrum of an individual galaxy. The most massive galaxies are at the top, while the lowest mass galaxies are at the bottom. Wavelength increases from left to right, or going from bluer to redder colors. The lack of sharp features in this plot (which uses the BC03 model adopted by the Galaxy Zoo images) are a result of excluding the nebular line emission. Figure courtesy P. Torrey (MIT/Caltech).

How should visual morphology classifiers deal with the star-forming regions? Ignore them and look at the underlying stellar populations? Treat them as part of the galaxy? Something else?

This is a tough one.  Many galaxies have the “blobby” star-forming regions but others have nicer looking disk or spiral distributions.  Our analysis suggests is that this is a pretty tight function of the total star formation rate (higher SFR = more realistic looking features).  We suggest that users treat them as part of the galaxy; it might lead to some odd results in lower mass galaxies, but we expect they should trace each other very well for the more massive galaxies. If you see geometry that’s distinctly different from a well-formed spiral disk or elliptical, don’t be hesitant to click the “Anything Odd” or “Other” buttons – that’s one of the simplest ways in which we can measure the unusual effects of the blue regions, given the constraints of our classification scheme.

One option for measuring the effect of the blue blobs is to select "Other" under the "Anything Odd" question.

One option for measuring the effect of the blue blobs is to select “Other” under the “Anything Odd” question.

The distribution of the blue blobs is often disconnected and/or in unusual shapes compared to Sloan. What determines the spatial distribution of the star forming regions?

This results from the extremely discrete sampling of the density of stars in the images.  Stars can only form in “chunks” of about 1 million solar masses, instead of the more typical small clusters and regions that we know exist in the real Universe.  Moreover, these chunks have their light spread over a significant fraction of ~1 kpc (which is pretty big, compared to a typical galaxy radius of ~20 kpc), and so they often won’t look much like real star-forming regions.  This, coupled with the lack of dust, leads to what you see in the GZ images.

Thanks as always to everyone for your help. Please post here or on Talk if you have more questions!

This post was written with the help of researchers Gregory Snyder (Space Telescope Science Institute) and Paul Torrey (MIT/Caltech), who worked extensively on the development of Illustris and the generation of the mock images for Galaxy Zoo.

Eight Years and the 8th Most Cited Paper from Galaxy Zoo

At Galaxy Zoo we’re really proud of our publication record – 48 papers and counting, just from the team using your classifications. In academic research one of the most important numbers a published paper has is the number which counts how many citations that paper has – simply a count of the number of other academic publications mention your work.

And we’re not only proud of the Galaxy Zoo publication record, but the citation record is becoming impressive too (if we do say so ourselves). For this post in the lead up to the 8th anniversary of the launch of Galaxy Zoo, here are the 8 most cited of our papers:

1. Lintott et al. 2008: “Galaxy Zoo: morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey “(with 279 citations)

2. Bamford et al. 2009: “Galaxy Zoo: the dependence of morphology and colour on environment” (219 citations)

3. Lintott et al. 2011: “Galaxy Zoo 1: data release of morphological classifications for nearly 900 000 galaxies” (152 citations)

4. Skibba et al. 2009: “Galaxy Zoo: disentangling the environmental dependence of morphology and colour” (114 citations)

5. Schawinski et al. 2010: “Galaxy Zoo: The Fundamentally Different Co-Evolution of Supermassive Black Holes and Their Early- and Late-Type Host Galaxies” (102 citations)

6. Cardamone et al. 2009: “Galaxy Zoo Green Peas: discovery of a class of compact extremely star-forming galaxies” (101 citations)

7. Darg et al 2010: “Galaxy Zoo: the properties of merging galaxies in the nearby Universe – local environments, colours, masses, star formation rates and AGN activity” (92 citations)

8. Masters et al. 2010: “Galaxy Zoo: passive red spirals” (86 citations)

I’m personally especially proud of paper number 8 on that list, because it is one of the first papers I led making use of Galaxy Zoo classifications (and one of my most cited first author papers in fact). In that paper we explored the properties of the unusually passive (ie. not star forming) red spirals that had been noted in both Bamford et al. 2009 and Skibba et al. 2009. For astronomers this is one of the more well known discoveries from Galaxy Zoo, and these passive red spirals continue to be studied for what they can reveal about the modes of evolution of galaxies in our Universe, and that many spirals must stop forming stars before they lose their spiral structure.

blue_red_sp_ell

A red elliptical and blue spiral (top), with a blue elliptical and red spiral (lower).

(By the way for academics who might be interested the h-index of Galaxy Zoo is 24).

The SEVEN wonders of Galaxy Zoo

Friday 11th July 2014 is the SEVENTH anniversary of Galaxy Zoo! So to celebrate this momentous achievement, we’ve put together a list of seven of the greatest Galaxy Zoo discoveries (so far!); all thanks to YOU, the classifiers…

1. Chirality  of Spiral Galaxies

clock

A clockwise spiral

An anticlockwise spiral

An anticlockwise spiral

One of the first major results from Galaxy Zoo wasn’t even Astronomical. It was Psychological. One of the questions in the original Galaxy Zoo asked whether spiral galaxy arms rotated clockwise or anti-clockwise; we wanted to check whether they were evenly distributed or whether there was some intrinsic property of the Universe that caused galaxies to rotate one way or the other. When the Science team came to analyse the results they found an excess of anti-clockwise spinning spiral galaxies. But when the team double checked this bias by asking people to classify the same image that had been flipped there was still  an excess of anti-clockwise classifications; so it’s not an astronomical phenomenon. Turns out that the human brain has real difficultly discerning between something rotating clockwise or anti clockwise; check out this video if you don’t believe me – you can watch the dancer rotate both ways! Once we’d measured this effect we could adjust for it, and we went on to establish that spirals which were near each other tending to rotate in the same direction.

2. Blue Ellipticals

The enigmatic blue ellipticals in many ways started the Galaxy Zoo. Galaxies largely divide into two: spiral galaxies like our Milky Way shining with the blue light of young stars being constantly born, and the “rugby ball-shaped” elliptical galaxies who no longer make new stars and thus glow in the warm, red light of old stars. Clearly, when galaxies stop making new stars, they also change their shape from spiral to elliptical. But how exactly does this happen? And what happens first? Do galaxies stop forming stars, and then change their shape, or the other way round? Answering that question is the first step in understanding the physics of transforming galaxies. With the Galaxy Zoo, we found a whole population of blue ellipticals: galaxies which have changed their shape, but still have young stars in them. With their help, we’ve been making a lot of progress in galaxy evolution. It looks like a galaxy merger, a giant cosmic collision, changes the shape of galaxies from spiral to elliptical and then somehow – and very rapidly! – star formation stops. We don’t know quite why yet, but we think active black holes are involved. This is hugely relevant for us as in a few short billion years, the Milky Way will crash into our neighbour, the spiral Andromeda galaxy. And for a short time, the Milky Way and Andromeda will be a blue elliptical before star formation in the newly-formed Milky-Dromeda ceases. For ever.

blue_red_sp_ell

A normal red elliptical and normal blue spiral on the top row. Unusual discoveries of blue ellipticals and red spirals on the bottom row.

3. Red Spirals

Ellipticals are red, Spirals are blue, Or so at least we thought, until Galaxy Zoo…. Think of your typical spiral galaxy and you’ll probably picture it looking rather blueish. Thats’s what astronomers used to think as well – suggest a red spiral to Edwin Hubble and he probably would’ve told you not to be so ridiculous. Before Galaxy Zoo if astronomers saw something looking red they generally tended to think it was elliptical; however to the untrained eye, the colour does not bias any classifications, which means that you all found lots of red spirals and discs which were hiding in plain sight. This put the cat amongst the pigeons for our galaxy evolution theories because, as said earlier, we thought that when galaxies stop making new stars, they also change their shape from spiral to elliptical. The red spirals mean that we now have a different evolutionary path for a spiral galaxy where it can stop making new stars and yet not change its shape. We now think that those spiral galaxies which are isolated in space and don’t interact with any neighbours are the ones that make it to the red spiral stage.

4. Green Peas

greenpea

The Green Peas, discovered by Citizen Scientists due to their peculiar bright green colour and small size, are a local window into processes at work in the early Universe.  Although, they were in the data for many years, it took humans looking at them to recognise them as a class of objects worth investigating.  First noticed in some of the earliest posts of the Galaxy Zoo Forum in 2007, a group of dedicated citizen scientists organised a focused hunt for these objects finding hundreds of them by the summer of 2008, when the Galaxy Zoo science team began a closer look at the sample. The Peas are very compact galaxies, without much mass, who turn out new stars at incredible rates (up to several times more than our entire Milky Way Galaxy!).  These extreme episodes of star formation are more common to galaxies in the early Universe, which can only be directly observed very far away at high redshifts.  In contrast to the distant galaxies, the Peas provide accessible laboratories that can be observed in much greater detail, allowing for new studies of star formation processes.   Since their initial discovery, the Peas have been studied at many wavelengths, including Radio, Infrared, Optical, UV and X-ray observations and detailed spectroscopic studies of their stellar content.  These galaxies provide a unique probe of a short and extreme phase of evolution that is fundamental to our understanding of the formation of the galaxies that exist today.

  5. The Voørwerp

hannyProbably the most famous new discovery of Galaxy Zoo has been Hanny’s Voørwerp. Hanny van Arkel called attention to it within the first few weeks of the Galaxy Zoo forum with the innocent question ”What’s the blue stuff?”, pointing to the SDSS image of the spiral galaxy IC 2497. The Sloan data alone could indicate a gas cloud in our own Galaxy, a distant star-forming region, or even a young galaxy in the early Universe seen 10 billion light-years away. After a chase to obtain new data, above all measurements of the cloud’s spectrum, with telescopes worldwide, an unexpected answer emerged – this galaxy-sized cloud was something unprecedented – an ionization echo. The core of the galaxy hosted a brilliant quasar recently on cosmic scales, one which essentially turned off right before our view of it (so we see the gas, up to 100,000 light-years away from it, shining due to ultraviolet light form the quasar before it faded). This had never before been observed, and provides a new way to study the history of mass surrounding giant black holes. Further observations involved the Hubble Space Telescope and Chandra X-ray Observatory (among others), filling in this historic view.  The cloud itself is part of an enormous stream of hydrogen, stretching nearly 300,000 light-years, probably the remnant of a merging collision with another galaxy. As it began to fade, the quasar started to blow out streams of energetic particles, triggering formation of stars in one region and blowing a gaseous bubble within the galaxy. In keeping with the nature of Galaxy Zoo, the science team deliberately had much of this unveiling play out in full view, with blog entries detailing how ideas were being confronted with new data and finding themselves supported,  discarded, or revised. The name Hanny’s Voørwerp (which has now entered the astronomical lexicon) originated when an English-speaking Zoo participant looked up “object” in a Dutch dictionary and used the result “Voørwerp” in a message back to Hanny van Arkel. Following this discovery, many Zoo volunteers participated in a focused search for more (the “Voørwerpjes”, a diminutive form of the word) – as a result we now know 20 such clouds, eight of which indicate fading nuclei. Other teams have found similar objects at smaller and larger distances; Hanny’s Voørwerp really started something!

6. Bars make galaxies redder

redbarA galactic bar is a straight feature across a spiral galaxy. It’s the orbital motions of many millions of stars in the galaxy which line up to make these bars, and in computer simulations almost all galaxies will form bars really quickly. In the real world it’s been known for a long time that really strong (obvious) bars are found in about 30% of galaxies, while about 30% more have subtle (weak) bars. One of the big surprises about the Galaxy Zoo red spirals was just how many of them had bars. In fact we found that almost all of them had bars and this got the science team really curious. We followed this up with a full study of which kinds of spiral galaxies host bars using the first classifications from Galaxy Zoo 2. In this work we discovered a strong link between the colour of disc galaxies and how likely they are to have a bar – with redder discs much more likely to host bars. We now have half a dozen papers which study galactic bars found using Galaxy Zoo classifications. Put together these works are revealing the impact galactic bars have on the galaxy they live in. We have found evidence that bars may accelerate the processes which turn disc galaxies red, by driving material into the central regions to build up bulges, and clearing the disc of the fuel for future star formation.

7.  Bulgeless galaxies with black holes

bulgelesssSupermassive black holes are the elusive anchors in the centres of nearly every galaxy. Though they may be supermassive, they are quite difficult to spot, except when they are actively growing — in which case they can be some of the most luminous objects in the entire Universe. But how exactly they grow, and why there seems to be a fixed mass ratio between galaxies and their central black holes, are puzzles we haven’t solved yet. We used to think that violent collisions between galaxies were The Way you needed to grow both a black hole and a galaxy so that you’d end up with the mass ratio that we observe. And violent collisions leave their signatures on galaxy shapes too. Namely: they destroy big, beautiful, ordered disks, re-arranging their stars into bulges or forming elliptical galaxies. So when we went looking for pure disk galaxies with no bulges and yet with growing central black holes we weren’t sure we would find any. But thanks to the volunteers’ classifications, we did. These galaxies with no history of violent interactions yet with large central supermassive black holes are helping us test fundamental theories of how galaxies form and evolve. And we are still looking for more of them!

So here’s to SEVEN more years – keep classifying!