Since our discovery in 2010 that the red spirals identified by your classifications in the first phase of Galaxy Zoo were twice as likely to host galactic scale bars as normal blue spirals, a lot of our research time has focused on understanding which types of galaxies host bars, and why that might be.
Our research with the bars identified by you in the second phase of Galaxy Zoo continues to gives us hints that these structures in galaxies might be involved in the process which quenches star formation in spiral galaxies and through that could be part of the process involved in the reduction of star formation in the universe as a whole.
We’ve also used your classifications as part of Galaxy Zoo Hubble and Galaxy Zoo CANDELS to identify the epoch in the universe when disc galaxies were first stable enough to host a significant number of bars, finding them possibly even earlier in the Universe than was previously thought.
Last Friday I spoke at the monthly “Ordinary Meeting” of the Royal Astronomical Society, giving summary of the evidence we’re collecting on the impact bars have on galaxies thanks to your classifications (a video of my talk will be available at some point). This was the second time I’ve spoken at this meeting about results from Galaxy Zoo, and it’s a delightful mix of professional colleagues, and enthusiastic amateurs – including some Galaxy Zoo volunteers.
Prompted by that I thought it was timely to write on this blog about what these bars really are, what they do to galaxies, and why I think they’re so interesting. I wrote the below some time ago when I had a spare few minutes, and was just looking for the right time to post it.
The thing about galaxies, which is sometimes hard to remember, is that they are simply vast collections of stars, and that those stars are all constantly in motion, orbiting their common centre of mass. The structures that we see in galaxies are just a snapshot of the locations of those stars right now (on a cosmic timescale), and the patterns we see in the positions of the stars reveals patterns in their orbital motions. A stellar bar for example reveals a set of very elongated orbits of stars in the disc of a galaxy.
Another extraordinary thing about a disc galaxy is how thin it is. To put this is perspective I’ll give you a real world example. In the Haus der Astronomie in Heidelberg you can walk around inside a scale model of the Whirlpool galaxy. The whole building was laid out in a design which reflects the spiral arms of this galaxy. However it’s not an exact scale model – to properly represent the thickness of the disc of the Whirlpool galaxy the building (which in actual fact has 3 stories and hosts a fairly large planetarium in its centre) would have to be only 90cm tall…..
Such an incredibly thin disc of stars floating independently in space would be quite unstable dynamically (meaning its own gravity should cause it to buckle and collapse on itself). This instability would immediately manifest in elongated orbits of stars, which would make a stellar bar (as part of this process of collapse). Simple computer models of disks of stars immediately form bars. Of course we now know that galaxy discs are submerged in massive halos of dark matter. So my first favourite little fact about bars is
(1) the fact that not all disc galaxies have bars was put forward as evidence that the discs must be embedded in massive halos before the existence of dark matter was widely accepted.
Now we can model dark matter halos better we discover that even with a dark matter halo, as long as that halo can absorb angular momentum (ie. rotate a bit) all discs will eventually make a bar. So my second favourite little fact is that
(2) we still don’t understand why not all disc galaxies have bars.
What this second fact means is that perhaps what I should really be doing is studying the galaxies you have identified as not having bars to figure out why it is they haven’t been able to form a bar yet. It should really be the properties of these which are unexpected….. We find that this is more likely to happen in blue, intermediate mass spirals with a significant reservoir of atomic hydrogen (the raw material for future star formation). In fact this last thing may be the most significant. Including realistic interstellar gas in computer simulation of galaxies is very difficult, but people do run what is called “smooth particle hydrodynamic” simulations (basically making “particles” of gas and inserting the appropriate properties). If they add too much gas into these simulations they find that bar formation is either very delayed, or doesn’t happen in the time of the simulation…..
Anyway I hope this has given you a flavour of what I find interesting about bars in galaxies. I think it’s fascinating that they give us a morphological way to identify a process which is so dynamical in nature. And it’s a very complex process, even though the basic physics (just orbits of stars) is very simple and well understood. Finally, I have become convinced though tests of the bars identified by you in Galaxy Zoo compared to bars identified by other methods, that if you want a clean sample of very large bars in galaxies that multiple independent human eyes will give you the best result. You are much less easy to trick that automated methods for finding galactic bars.
So thanks again for the classifications, and keep clicking. 🙂
Some colleagues and I successfully proposed for a symposium on citizen science at the annual meeting of the American Association for the Advancement of Science (AAAS) in San Jose, CA in February 2015. (The AAAS is one of the world’s largest scientific societies and is the publisher of the Science journal.) Our session will be titled “Citizen Science from the Zooniverse: Cutting-Edge Research with 1 Million Scientists.” It refers to the more than one million volunteers participating in a variety of citizen science projects. This milestone was reached in February, and the Guardian and other news outlets reported on it.
The Zooniverse began with Galaxy Zoo, which recently celebrated its seventh anniversary. Of course, Galaxy Zoo has been very successful, and it led to the development of a variety of citizen science projects coordinated by the Zooniverse in diverse fields such as biology, zoology, climate science, medicine, and astronomy. For example, projects include: Snapshot Serengeti, where people classify different animals caught in millions of camera trap images; Cell Slider, where they classify images of cancerous and ordinary cells and contribute to cancer research; Old Weather, where participants transcribe weather data from log books of Arctic exploration and research ships at sea between 1850 and 1950, thus contributing to climate model projections; and Whale FM, where they categorize the recorded sounds made by killer and pilot whales. And of course, in addition to Galaxy Zoo, there are numerous astronomy-related projects, such as Disk Detective, Planet Hunters, the Milky Way Project, and Space Warps.
We haven’t confirmed all of the speakers for our AAAS session yet, but we plan to have six speakers who will introduce and present results from the Zooniverse, Galaxy Zoo, Snapshot Serengeti, Old Weather, Cell Slider, and Space Warps. I’m sure it will be exciting and we’re all looking forward to it!
We are pleased to announce an open vote for the cover image of the October 2013 issue of “Astronomy and Geophysics” (the magazine of the Royal Astronomical Society).
A write-up of the Specialist Discussion the science team ran at the Royal Astronomical Society in May on “Morphology in the Era of Large Surveys” is going to appear in the October issue of A&G , so we were asked to nominate a cover image for this issue.
Rather than just have the science team pick our favourite image, we thought it would be nice to open up the choice to our volunteers. After all it’s you that make Galaxy Zoo special, and a unique way of dealing with morphology in the era of large surveys.
So we have put together five images for you to vote on. These are images which would make good covers for the magazine, and which the science team think either have a special connection to the Galaxy Zoo project, or illustrate something special about Galaxy Zoo and its contributions to the understanding of galaxy evolution. Subject to final approval by the editors, the image that wins this vote will appear on the cover of A&G for October 2013.
After a very busy week, I’ve suddenly had the happy realization that ZooCon ’13 (in Oxford) is tomorrow.
Okay, it’s not like I had completely forgotten about it – I’ve been thinking about what I want to say in my talk and discussing the schedule with the other organizers for a while now – but what a lovely feeling to suddenly connect that the thing you’ve been looking forward to as an opportunity to meet some interesting people and talk about interesting stuff is less than 24 hours away!
There’s still time to register: just go to the Eventbrite page and sign up (it’s free!) and we’ll see you tomorrow.
I’m planning to talk mostly about the future of Galaxy Zoo, including CANDELS and other projects as well as interesting new tools to enable different kinds of collaborative science, including volunteer-led science. But I’m most looking forward to the other talks, which will include updates from Old Weather, Space Warps and Planet Four.
What are you most looking forward to?
(Besides the pub afterwards, of course!)
Almost a month ago now, Galaxy Zoo hosted a Specialist Discussion at the Royal Astronomical Society in London, on the topic of Morphology in the Era of Large Surveys. It was actually a wonderful day full of interesting talks and discussion, and we will be sharing more of the science content from the discussion as soon as we find time to put that together.
One of the other fun things about this meeting was that as well as the fantastic invited speakers, mostly from outside Galaxy Zoo collaboration, many members of the Galaxy Zoo science team were able to attend and contribute talks. We had representatives of team members from Minnesota, Oxford, Nottingham, Portsmouth, Hertfordshire and Zurich in attendance. It was a great chance for us to catch up both scientifically and socially. Below is a set of round table pictures we took during our “team dinner” that Friday night in London’s Chinatown. The captions always list names from left to right. The poor photography is entirely my fault!
This post was written by Kyle Willett. He is a postdoc at the University of Minnesota and a member of the Galaxy Zoo science team.
It’s been a couple of weeks since the 221st meeting of the American Astronomical Society (AAS) in Long Beach, California. Kevin and Bill already made several excellent posts on their conference experience (tip: showing data hot off the telescope and having Swiss chocolate at your poster really generate foot traffic). I wanted to write a bit more about the research that I presented and how it related to other topics at the meeting.
My poster was up during on the third day of AAS, in the “Catalogs” section of the big poster hall. This is a bit unusual in that the posters there were sorted more by their methods, rather than science content. A group like this is useful for identifying projects with similar challenges, including curation of large data sets, reduction techniques, and how to best publish the data so the scientific community will recognize and use it. The content varies widely, though – I got to compare what galaxy morphologies might have in common with catalogs of bright stars, exoplanets, and infrared mosaics.
The content of my poster focused on three topics. The first was a description of the Galaxy Zoo 2 project, describing the new questions we developed (and that you answered) and the sample of galaxies in the Sloan Digital Sky Survey that the results cover. This is slightly different from the original Galaxy Zoo, since GZ2 uses a brighter sample of galaxies in which more detail can be seen.
The second portion was my work on data reduction for the Galaxy Zoo 2 catalog; in particular, the way in which we demonstrate that more distant galaxies appear smaller and dimmer in the classification interface, and how this can be corrected. I showed data for 4 of the questions (smooth vs. features? is it an edge-on disk? is there a bar? are there spiral arms?) as examples of successful corrections that we’ve already done. The remaining 7 are being finished this week, with results looking good so far.
Finally, I had a section summarizing the science results from using Galaxy Zoo 2 data. So far, these have all been led by members of our own science team (which you can find here). Our goal in releasing the full catalog, though, is to make GZ2 a community resource – we want other groups to use the data and write even more interesting papers. We know we have a unique data source – the challenge is to reduce it properly, put it in a useful public format, and help publicize it by writing papers and attending conferences.
I had a lot of good conversations with other astronomers at this meeting, many of whom are very keen to see the data come out. Several interesting presentations raised questions we can explore with GZ2. I was intrigued by Michael Rutkowski’s (Arizona State) talk on the surprising amount of star formation and diversity amongst early-type galaxies, as well as Benjamin Davis’ (Arkansas) talk on using computers to measure the angle of spiral arms and how it relates to their central black holes.
Overall, it was a great meeting both for general astronomy and for Zoo-related projects. The science team and I are finishing the first draft of the data release paper this month, and we’ll be submitting it to a journal shortly after. I’ll keep writing as we make progress – as always, thanks for your classifications that make my work possible!
3000 astronomers will bring down the wireless in any building, so I have been a bit behind in posting from the American Astronomical Society meeting in Long Beach CA…
Yesterday, Bill Keel presented a poster with the latest Hubble observations of the Voorwerpjes in the Giant Room Full of Posters, where astronomers, pretty much ALL of who work on absolutely cool stuff, present their results. So, anything you can do to get peoples’ attention helps! I decided to bring along some chocolates from Switzerland. If any unwary astronomer walked past and took one, they then had to at least look at the poster… ; )
Posting again for Karen Masters who is still in China:
I’ve just arrived at the American Astronomical Society 220th meeting in Anchorage AK (#aas220 on Twitter, follow it). Quite a few people working on the Zoo are here too and it promises to be an exciting meeting.
But what I really wanted to share was this sign spotted by a cafe just outside the conference venue:
Update: the coffee store put up a new sign:
Also, thanks to the Zooite who came to chat to Steph at the Galaxy Zoo AGN inclination poster!
This guest post is from Anna Han, an undergrad working on the Hubble data from Galaxy Zoo:
I attended the AAS Conference in Austin, Texas with the Yale Astronomy and Physics Department to present the results from my research last summer. Many thanks to everyone in the department and Galaxy Zoo who gave me this opportunity and continue to support me through my work. It is because of their guidance that I was able to present a research poster at the conference this winter and enjoy a whole new experience.
The AAS Conference was fascinating, motivating, and overwhelming all at the same time. Starting from 9:00am every morning, I listened to various compact 10-minute talks given by various PhD candidates, post-docs, and researchers from around the world. Though I must admit some of the ideas presented went over my head, I learned more and more with each talk I heard.
The midday lunch breaks made up one of my favorite parts of the conference. Yes, the ribs in Texas are good. But no amount of delicious southern cuisine compares to how welcome and at ease I felt with fellow astronomers kind enough to invite me, a newbie sophomore undergraduate, to lunch. Lunch became my 2-hour my opportunity to talk one-on-one with other researchers and get informed on their work. When my questions ran out, I gladly took the chance to introduce my own research and use their feedback to better prepare for my poster presentation.
On Thursday morning, I tacked up my poster in the exhibit hall and stood guard, armed with organized details of my research and cookies as bait. Let me confess now that I have never been at or in a science fair, but I imagine it must be similar to what I experienced that day. Non-scientist citizens and experts in AGN alike perused my poster and asked questions. Every once in a while I recognized a familiar face: members from my research group, students I had befriended throughout the conference, and fellow researchers I had shared lunch with stopped by to see my poster. Explaining my research to someone who was interested (either in my work or the cookies) was an immensely rewarding experience. I felt proud of what I had accomplished and so thankful to the people who helped me do it. The encounters with other people also gave me ideas for future directions I could proceed in.
This semester, I plan to continue searching for multiple AGN signatures in grism spectra of clumpy galaxies. My experience at the AAS Conference has inspired me to develop a more systematic search for clumpy galaxies using Galaxy Zoo and explore in more detail the possibility of low redshift galaxies containing multiple AGN. To the citizens of Galaxy Zoo, thank you again, and I hope for your continued support!