First Results from Galaxy Zoo 2: Bars in Disk Galaxies
I’m happy to announce that the first paper using Galaxy Zoo 2 data was submitted (to MNRAS) yesterday.
In this work we used an early look at the information you have provided us on the presence of bars in a sample of GZ2 galaxies too look at trends of the bar fraction (basically how likely a certain type of disk galaxy is to have a bar) as a function of other properties.
Examples of barred (top) and unbarred (bottom) galaxies from Galaxy Zoo 2.
In doing this research I’ve learned that bars are really interesting features in disk galaxies. Unlike spiral arms, which are density waves (meaning stars pass in and out of them over the life of the galaxy), the matter in bars (stars and gas etc) actually rotates with the bar. This means that the bar breaks the symmetry of the disk of the galaxy and causes transfer of material both in an outwards along its length. What it boils down to is that bars should have a significant impact on the internal evolution of a galaxy. They have been suggested as a way to build some types of bulges, as a way to fuel star formation in the central regions, and perhaps even fuel AGNs. At the outer ends, the bar can induce ring like structures (see the top middle example) – and might even be responsible for driving spiral structure.
So what did we find? Well we observed a strong correlation between the bar fraction and the colour of the disk galaxy. Redder disk galaxies are much more likely to have bars identified by GZ2 users than bluer disk galaxies.
Bar fraction as a function of galaxy colour. The dashed line shows the overall bar fraction for the whole sample.
We also tried to split the sample by the size of the bulge. We find that disks with large bulges (shown by the red line below) have high bar fractions, and that disks with small bulges (shown by the blue line) have low bar fractions. This split by bulge size also splits the disks into things which are mostly red (large bulge) and blue (small bulge) – as illustrated by the histograms of the colour distribution of the two types of disk galaxies. What’s new here is that we show this also correlates strongly with the presence of a bar.
Top: bar fraction as a function of galaxy colour split into disk galaxies with large bulges (red) and small bulges (blue). The dashed line shows the overall bar fraction for each sub-sample. Bottom: histograms showing the colour distribution of the disk galaxies with large bulges (red) and small bulges (blue).
So we seem to split disk galaxies into two populations – ones that are red, have large bulges and are very likely to have bars, and ones that are blue, have small bulges, and are not so likely to have bars.
This gives an overall picture in which bars may be very important to the evolution of disk galaxies – perhaps more so than has been thought before. It’s very interesting, and I look forward to spending more time with barred galaxies and with the rich data set that you have given us with Galaxy Zoo 2.
We’re already working on more results from the bars using Galaxy Zoo 2, so expect updates soon. Also I just saw some very interesting results on bar lengths using data from the (now completed) Bar Drawing project. Hopefully we’ll have a paper from that soon too. Stay tuned!
How to find black holes?
The first step in trying to understand the connection between black holes and galaxies is finding them. But black holes are, well, black. In fact, you might say their blackness is their most defining feature.
So, how do you find them? It turns out that when they’re feeding on infalling gas and dust, a massive black hole can turn into the brightest object known in the whole universe – a quasar!
As the gas and dust falls towards the black hole, it settles into a disk around it, and as it moves in, friction in the disk heats up all the matter in it to such temperatures that it stats shining. In this way, black holes can be very bright, or quite dim, depending in part on how much matter they are munching on.
There are many ways to find feeding black holes and for the Galaxy Zoo paper on black hole growth, we used the emission lines that AGN (active galactic nuclei, or feeding black holes) cause when the light coming from the accretion disk shines on some other gas floating around in the host galaxy and makes that light in turn emit light with a very particular signature that we can detect by carefully analysing the spectra.
She's an Astronomer: Anna Manning
Anna Manning is a Masters student in Astronomy at the University of Alabama (she’s working under the supervision of Dr. Bill Keel on the overlapping galaxies project). She moved to Tuscaloosa, AL (where she lives with 2 sorority sisters) after completing her undergraduate degree at Clemson University in South Carolina. In her free time she enjoys painting, photography, and scrapbooking. At 25 she’s the youngest of our professional (or future professional) astronomers to be interviewed. In the future she would like to either continue her work in astronomical research or perhaps move into space exploration. She also really enjoys the public outreach part of Galaxy Zoo and thinks it would be nice to contribute to that in her future career.
- How did you first hear about Galaxy Zoo?
I first heard of it when I started my research in Grad School with Dr. Keel at the University of Alabama.
- What has been your main involvement in the Galaxy Zoo project?
I’ve mostly worked with Dr. Keel to create a catalog of overlapping galaxy pairs. We’ve been to Kitt Peak to observe some of the objects which Dr. Keel has blogged about.
- What do you like most about being involved in Galaxy Zoo?
- What do you think is the most interesting astronomical question Galaxy Zoo will help to solve?
- How/when did you first get interested in Astronomy?
On field trip in middle school we spent a day at space camp in Florida which began my general interest. In high school I really enjoyed Physics class and decided to major in it in college where I started doing actual research in astronomy.
- What (if any) do you think are the main barriers to women’s involvement in Astronomy?
This topic actually sparked an interesting conversation in my office. A female office mate and I were discussing how we don’t think there have been any obstacles for us. A male office mate brought up that he believes it is easier to be a woman than a man in astronomy. So I think this is something that changes based on the person and I’m thankful that I have been fortunate in the universities I’ve attended.
- Do you have any particular role models in Astronomy?
I have learned so much from so many people – and often people that I didn’t know had any interest in astronomy at all!
This post is part of the ongoing She’s an Astronomer series on the Galaxy Zoo Blog is support of the IYA2009 cornerstone project of the same name (She’s an Astronomer). We are listed on the She’s an Astronomer website in their Profiles.
- Zooites:
- Hanny Van Arkel (Galaxy Zoo volunteer and finder of Hanny’s Voorwerp). Hanny’s interview in het Nederlands.
- Alice Sheppard (Galaxy Zoo volunteer and forum moderator).
- Gemma Couglin (“fluffyporcupine”, Galaxy Zoo volunteer and forum moderator).
- Aida Berges (Galaxy Zoo volunteer – major irregular galaxy, asteroid and high velocity star finder). Entrevista de Aida en español.
- Julia Wilkinson (“jules”, Galaxy Zoo volunteer. Frequent forum poster, and member of irregular and HVS projects).
- Els Baeton (“ElisabethB”, Galaxy Zoo folunteer. Frequent forum poster, and member of most of the spin-off projects!). Els’s interview in het Nederlands.
- Researchers:
- Dr. Vardha Nicola Bennert (researcher at UCSB involved in Hanny’s Voorwerp followup and the “peas” project). Vardha’s Interview auf Deutsch.
- Carie Cardamone (graduate student at Yale who lead the Peas paper).
- Dr. Kate Land (original Galaxy Zoo team member and first-author of the first Galaxy Zoo scientific publication; now working in the financial world).
- Dr. Karen Masters (researcher at Portsmouth working on red spirals, and editor of this blog series.)
- Dr. Pamela L. Gay (astronomy researcher and communicator based at Southern Illinois University).
Still to come in the series – a few more Galaxy Zoo volunteers and researchers. We’re not quite done yet!
Black holes – why do galaxies care, anyway?
Now that our paper on AGN host galaxies (galaxies whose black holes are feeding) is out, I will write a few blog posts about what we found with your help. But before we start, a little background.
Why do black holes matter? We now believe that at the centers of most, if not all galaxies, there is a supermassive black hole. We call these black holes “supermassive” to distinguish them from stellar mass black holes that were formed in the deaths of massive stars. These supermassive black hole can be as heavy as a million or even a billion solar masses.
So you might think that these enormous black holes can wreak havoc in their host galaxies. However, galaxies are even bigger, much bigger than these black holes. In general, the black hole makes up about 0.1% of the mass of its host galaxy making really just a drop in the bucket.
In fact, their gravitational sphere of influence is tiny compared to the size of the whole galaxy and so they generally don’t affect anything but their immediate surroundings. As far as the galaxy as a whole is concerned, the supermassive black hole at its center might as well not be there.
But why is the mass of the black hole always some fraction of the galaxy mass (or to be more precise, bulge mass)? How does the black hole even know how big the galaxy is? Why does the mass of the black hole correlate with the mass of the galaxy bulge (the M-sigma relation)? It’s almost as if they somehow grew together….
Bar drawing project complete!
GZ2 Galaxy with Bars drawn by users.
Bar project stage 1 complete!
Dear all, we’d like to thank everybody for making the bar drawing project such a success. We now have enough data to perform some reliable, new & very exciting science.
The site will remain open (for future inspection), but the votes will no longer we recorded. We’d like to take this opportunity to draw your attention to other interesting galaxy zoo and zooniverse projects.
We’ll keep you posted about future publications.
Once again, we’d like to thank you all!
Best Regards,
Ben [and on behalf of Karen and Bob with the bar drawing team]
Finishing off the Peas Documentary
Dear all,
Many moons back, a large group of Zooites travelled to Oxford to make nearly all of a documentary about Galaxy Zoo, and especially peas, with PulseProject. It was a terrific success, and there’s just one more thing they’d like to do before it’s ready. Can you help?
Colin, who interviewed us all, wants to make a montage of about 30 zooites from around the world. He’d like you to Skype him, or to send him a brief video recording of yourself, along with your latitude and longitude. All you need to say is your name, and that you’re a zooite. For example, “My name is X and I classify galaxies at Galaxy Zoo” or “My name is Y and I am a zooite”. (Either your real name or your zoo name is fine.)
When you connect to him, you’ll get a blank screen – he may need to text you to let you know that he’s there watching. It’s so that his part doesn’t interfere with the recording. His Skype name is colincmurphy and his e-mail is colin@pulse-project.com. He’d love to hear from you.
You don’t have to have come to Oxford for that meet-up or to have had any particular involvement with the peas. Being a zooite is the main thing!
There is a copy of this message on the zoo forum if you’d like to see more discussion. Please let me know of any questions, and I’ll answer them if I can and contact Colin if I can’t.
I hope to see our peas, Oxford and the wonderful science of Galaxy Zoo in PulseProject’s documentary soon – and you as part of it!
Alice
Galaxy Zoo paper on AGN host galaxies accepted!
Dear all,
I am happy to tell you that after a lot of work and a long peer review process, the Galaxy Zoo paper on AGN host galaxies (galaxies whose supermassive black holes are feeding) has finally been accepted by the Astrophysical Journal.
I’ve blogged about it before when we submitted it last year. The paper itself has gotten a lot longer than I initially thought it would be because the morphologies we got out of all your clicks revealed quite a few things that we really didn’t expect, and that we weren’t sure how to explain. I’ll keep this blog post short, but I’ll try and follow it up with more details on what your clicks enabled us to to find, and (maybe also) what it means about growing black holes and how they affect the galaxies that they live in.
One of the more interesting things we found were these galaxies whose black holes are growing. In many ways, these galaxies resemble our own Milky Way…
In the meantime, you can get a PDF copy of the paper here, or off astro-ph when it appears there tomorrow night (January 19th).
"Sie ist eine Astronomin": Vardha Nicola Bennert
Our final entry (for now) in the series of foreign language translations of She’s an Astronomer posts – here it is: Vardha’s Interview auf Deutsch!
Vardha Nicola Bennert am Meer in Santa Barbara (5 Minuten Fussweg von ihrem Büro), Mai 2009
Dr. Vardha Nicola Bennert ist als Wissenschaftlerin (“postdoc”) an der Fakultät für Physik und Astronomie an der Universität von Kalifornien (UC) in Santa Barbara tätig. Ursprünglich kommt sie aus dem Ruhrgebiet in Deutschland und hat 2005 auf dem Gebiet der Astrophysik von aktiven Galaxien an der Ruhr-Universität Bochum promoviert. Sie hat danach ihre erste Postdoc-Stelle an der Universität von Kalifornien in Riverside in den USA angenommen, bevor sie 2008 nach Santa Barbara gegangen ist.
Das wissenschaftliche Hauptinteresse von Frau Dr. Bennert ist die zentrale Region von “aktiven Galaxien” (dem schwarzen Loch und den sogenannten “narrow-” und “broad-line regions” direkt um das schwarze Loch herum) und ihre Beziehung zur Muttergalaxie.
Sie arbeitet gerne in der wissenschaftlich-stimulierenden Umgebung der UCSB und genießt es, in Santa Barbara zu leben – besonders weil die Sonne immer scheint und das Meer so nah ist! Aber sie vermisst auch ihre Freunde und Familie in Deuschland. In ihrer Freizeit erkundet sie die Natur Südkaliforniens, aber sie ist auch auf einer inneren Reise, in der sie Meditation in ihr tägliches Leben integriert.
- Wie haben Sie vom Galaxien Zoo gehört?
Durch Zufall! Ich war an der UC Riverside und hatte einen Beobachtungsaufenthalt am 3m Shane-Teleskop des Lick Observatoriums, als Professor Bill Keel meine Chefin, Professor Gabriela Canalizo, fragte, ob wir bei der Gelegenheit ein Spektrum von “Hanny’s Voorwerp” aufnehmen könnten. Ich willigte ein, ging beobachten, hatte mehrere klare Nächte und konnte ein Spektrum des Objekts aufnehmen. Ich war sofort von dem Objekt beeindruckt, weil mir das Spektrum sehr bekannt vorkam – ähnlich den “narrow-line regions” von aktiven Galaxien, die ich intensiv während meiner Doktorarbeit studiert hatte, nur dass es bei diesem Objekt keinen Hinweis auf einen aktiven galaktischen Kern im Zentrum gab!
- Wie sind sie hauptsächlich im Galaxien-Zoo-Projekt involviert?
Ich habe bei der Reduktion, Analyse und Interpretation der spektroskopischen Daten geholfen, die in der Entdeckungsveröffentlichung des “Voorwerps” integriert wurden. Später, durch einen weiteren Zufall, hat das Team nach jemandem gesucht, der Erfahrung in der Reduktion von HST Bildern hat, welche ich habe. Deshalb habe ich HST Bilder von sogenannten “grünen Erbsen” reduziert und analysiert, die im Galaxien-Zoo-Projekt entdeckt wurden. Dies wurde ein Teil einer weiteren Veröffentlichung, bei der ich bei der Interpretation der Ergebnisse geholfen habe.
- Was mögen Sie am Meisten am Galaxien-Zoo-Projekt?
Es ist großartig, dass so viele Amateurastronomen involviert sind und dass das Projekt so eine starke Komponente der Öffentlichkeitsarbeit hat. Für mich ist Öffentlichkeitsarbeit nicht nur eine Pflicht als Wissenschaftlerin, da ich im Wesentlichen durch Steuergelder bezahlt werde, sondern auch eine Tätigkeit, die mir sehr viel Spaß macht. Ich liebe es zu sehen, wie Menschen sich für Astronomie und die Wissenschaft begeistern, mit der ich mich beschäftige.
- Was ist Ihrer Meinung nach die interessanteste astronomische Fragestellung, die das Galaxien-Zoo-Projekt helfen wird zu beantworten?
Das Galaxien-Zoo-Projekt hat seinen Wert darin bewiesen, dass es seltene und interessante Objekte wie das Voorwerp findet, durch visuelle Inspektion von Bildern – ein grosser Vorteil von Menschen verglichen mit Robotern! Ich denke, das ist es, was der bleibende Wert des Galaxien-Zoo-Projektes sein wird, nicht die Antwort auf eine spezielle Fragestellung, für die das Projekt ins Leben gerufen wurde. Diese seltenen Objekte haben das Potential, uns neue und überraschende Einsichten zu geben.
- Seit wann interessieren Sie sich für Astronomie?
Schon als Kind liebte ich es, die Sterne zu betrachten und war fasziniert von den Büchern von Professor Stephen W. Hawking, auch wenn ich zu der Zeit nicht allzu viel davon verstand… Jedenfalls hielt mich das nicht davon ab, eine wissenschaftliche Karriere auf diesem Gebiet zu verfolgen. Im Gegenteil, ich fand es immer spannend, an die Grenzen meines Verstehens zu kommen und ständig neue Dinge zu lernen.
- Was (wenn überhaupt) denken Sie sind die wesentlichen Barrieren für Frauen in der Astronomie?
Mir gefällt die konkurrenzbetonte Art nicht, in der wissenschaftliche Ergebnisse dargestellt werden. Ich persönlich denke, dass es für Frauen schwierig sein muss, Kinder zu haben, während sie eine astronomische Karriere verfolgen, da beide Aufgaben sehr viel Zeit verlangen. Aber natürlich gibt es viele Frauen in der Astronomie, die bewiesen haben, dass es geht.
- Haben Sie irgendwelche Vorbilder in der Astronomie?
Mein Doktorvater, Professor Hartmut Schulz, hat mich sehr beeinflusst. Ich sah in ihm immer einen dieser “altmodischen” Professoren, die nicht nur viel über Astronomie wissen, sondern auch sehr fundierte Grundkenntnisse haben und immer großen Wert darauf legen, selber zu denken. Leider verstarb Professor Schulz im August 2003. Ich erinnere mich gerne an ihn als meinen “Doktorvater” im wahrsten Sinne des Wortes.
Mein derzeitiger Chef an der UCSB, Professor Tommaso Treu, inspiriert mich ebenfalls ständig auf vielfältige Weise – er ist nicht nur sehr klug und effektiv, sondern auch immer fröhlich, voller Energie, und hilft seinen Studenten, ihr Potential voll auszuschöpfen.
This post is part of the ongoing She’s an Astronomer series on the Galaxy Zoo Blog is support of the IYA2009 cornerstone project of the same name (She’s an Astronomer). We are listed on the She’s an Astronomer website in their Profiles.
- Zooites:
- Hanny Van Arkel (Galaxy Zoo volunteer and finder of Hanny’s Voorwerp). Hanny’s interview in het Nederlands.
- Alice Sheppard (Galaxy Zoo volunteer and forum moderator).
- Gemma Couglin (“fluffyporcupine”, Galaxy Zoo volunteer and forum moderator).
- Aida Berges (Galaxy Zoo volunteer – major irregular galaxy, asteroid and high velocity star finder). Entrevista de Aida en español.
- Julia Wilkinson (“jules”, Galaxy Zoo volunteer. Frequent forum poster, and member of irregular and HVS projects).
- Els Baeton (“ElisabethB”, Galaxy Zoo folunteer. Frequent forum poster, and member of most of the spin-off projects!). Els’s interview in het Nederlands.
- Researchers:
- Dr. Vardha Nicola Bennert (researcher at UCSB involved in Hanny’s Voorwerp followup and the “peas” project). Vardha’s Interview auf Deutsch.
- Carie Cardamone (graduate student at Yale who lead the Peas paper).
- Dr. Kate Land (original Galaxy Zoo team member and first-author of the first Galaxy Zoo scientific publication; now working in the financial world).
- Dr. Karen Masters (researcher at Portsmouth working on red spirals, and editor of this blog series.)
- Dr. Pamela L. Gay (astronomy researcher and communicator based at Southern Illinois University).
Still to come in the series – a few more Galaxy Zoo volunteers and researchers. We’re not quite done yet!
This German translation is of course part of our effort to be international!
Bars side project
Dear Zooniverse users,
We’d like to re-draw [no pun intended!] your attention to the GalaxyZoo Google-powered Bar drawing website: http://www.icg.port.ac.uk/~hoyleb/bars/ simply log in with your Zooninverse username and password. Please note, this site works best using FireFox.
GZ2 Galaxy as seen in Google Maps
In this project, we ask for more specific observations and even drawing to be performed on a selection of galaxies. The sample size is relatively small, and 8000 [of the 8400] galaxies have been classified 5 times. The remaining 400 have been examined 6+ times.
We are starting to collate votes, for example we see some excellent agreement between users, e.g. See the picture below, which shows the bars as drawn on the above galaxy by different users, but we still need a few more classifications for each galaxy, to really be able to produce science.
One such science question we’d like to answer is, “How does the presence of a bar, affect the galaxies properties?”. GZoo allows us to study this question with 20- times more data than previously possible.
GZ2 Galaxy with Bars drawn by users.
We’d also like to thank the GZ users for the hard work they have put into the site since it’s launch in October.
Regards,
Ben Hoyle, on behalf of the GZ-bar drawing team
Galaxy Zoo: Dust in Spirals – accepted to MNRAS
My Galaxy Zoo paper on the dust content of spiral galaxies was accepted for publication in the Monthly Notice of the Royal Astronomical Society this morning, and will be available here on the ArXiV server after 1am GMT tomorrow (Wed 13th Jan 2010).
You can read about the work that went into this paper and our main results in my previous blog posts on its submission, about a scientific poster on the work, and finally my very first blog post here: “Blue Skies and Red Spirals”.
Happy reading, and thanks again for all the spirals!
Galaxy Zoo 