New Sloan Digital Sky Survey Galaxies in Galaxy Zoo
The relaunch of Galaxy Zoo doesn’t only include the fantastic new images from the CANDELS survey on Hubble Space Telescope, but also includes over 200,000 new local galaxies from the Sloan Digital Sky Survey. We’ve had a lot of questions about where these galaxies came from and why they weren’t put into earlier versions of Galaxy Zoo, so I thought I’d write a bit about these new images.
The Sloan Digital Sky Survey Project (SDSS) is currently in its 3rd phase (SDSS-III). You can read all about the history of SDSS here, and here, but briefly SDSS-I (2000-2005) and SDSS-II (2005-2008) took images of about a quarter of the sky (which we often refer to as the SDSS Legacy Imaging), and then measured redshifts for almost 1 million galaxies (the “Main Galaxy Sample”, which was the basis of the original Galaxy Zoo and Galaxy Zoo 2 samples; plus the “Luminous Red Galaxy” sample) as well as 120,000 much more distant quasars (very distant galaxies visible only as point source thanks to their actively accreting black holes).
Following the success of this project, the Sloan Digital Sky Survey decided they wanted to do more surveys, and put together a proposal which had four components (BOSS, SEGUE2, MARVELS and APOGEE – see here). To meet the science goals of these projects they realised they would need more sky area to be imaged. This proposal was funded as SDSS-III and started in 2008 (planned to run until 2014). The first thing this new phase of SDSS did was to take the new imaging. This was done using exactly the same telescope and camera (and methods) as the original SDSS imaging. They imaged an area of sky called the “Southern Galactic cap”. This is part of the sky which is visible from the Northern Hemisphere, but which is out the Southern side of our Galaxy’s disc. It totals about 40% of the size of the original SDSS area, brining the total imaging area up to about 1/3rd of the whole sky. The images in it were publicly released in January 2011 as part of the SDSS Data Release 8 (DR8 – so we sometimes call it the DR8 imaging area).
This illustration shows the wealth of information on scales both small and large available in the SDSS-III’s new image. The picture in the top left shows the SDSS-III view of a small part of the sky, centered on the galaxy Messier 33 (M33). The middle and right top pictures are further zoom-ins on M33.
The figure at the bottom is a map of the whole sky derived from the SDSS-III image. Visible in the map are the clusters and walls of galaxies that are the largest structures in the entire universe. Figure credit: M. Blanton and the SDSS-III collaboration
We have selected galaxies from this area which meet the criteria for being included in the original Galaxy Zoo 2 sample (for the experts – the brightest quarter of those which met Main Galaxy Sample criteria). Unfortunately in this part of the sky there is not systematic redshift survey of the local galaxies, so we will have to rely on other redshift surveys (the most complete being the 2MASS Redshift Survey) to get redshifts for as many of these galaxies as we can. We still think we’ll get a lot more galaxies and, be able to make large samples of really rare types of objects (like the red spiral or blue ellipticals). Another of our main science justifications for asking you to provide us with these morphologies was the potential for serendipitous discovery. Who knows what you might find in this part of the sky. The Violin Clef Galaxy is in the DR8 imaging area and featured heavily in our science team discussions of if this was a good idea or not.
And interesting things are already being found in just a week of clicks. The new Talk interface is a great additional place for us to discuss the interesting things that can be found in the sky.
For example this great system with tidal tails and a Voorwerpjie:
this weird triangular shaped configuration of satellites:
and an oldie (but a goodie) in the beautiful galaxy pair of NGC 3799 and NGC 3800 (NGC 3799 in the centre, NGC 3800 just off to the upper right):
and just this morning I discovered the discussion of this really unusual looking possible blue elliptical (IC 2540):
There are also rather more artifacts and odd stuff going on in these new images than I think we saw in the SDSS Legacy sample (from GZ1 and GZ2). Remember these are completely new images you are looking at. It really is true that no-one has looked at these in this level of detail (or perhaps ever) before. The original sample had a sanity check at some level, since when GZ1 ran the majority of the sample had already been targeted by SDSS for redshifts (so someone had to plug a fibre into a plate for each galaxy). In this new imaging all that has happened is that a computer algorithm was run to detect likely galaxies and set the scale of the image you see. Sometimes that mistakes stars, satellite trails, or parts of galaxies for galaxies. Always classify the central object in the image, and help us clean up this sample by using the star/artifact button.
And you can enjoy these odd images too. I like this collection of “GZ Pure Art” based on just odd things/artifacts classifier “echo-lily-mai” thought were pretty. 🙂 If you get confused by anything please join us on Talk, or the Forum where someone will help you identify what it is you’re seeing.
Tagging Galaxies in Talk
One of the cool features of the new Galaxy Zoo Talk is that you can tag objects using the # character. For example, if you see two overlapping galaxies like NGC 3314…
ESA Hubble Space Telescope has produced an incredibly detailed image of a pair of overlapping galaxies called NGC 3314. While the two galaxies look as if they are in the midst of a collision, this is in fact a trick of perspective: the two are in chance alignment from our vantage point (Credit: NASA).
… then you can tag it with #overlap when commenting on it. That way, anyone with an interest in overlapping galaxies can find it by just clicking on #overlap. There’s already a discussion on tags on Talk, but if you find something that needs tagging, you can always start your own. Just use the # character!
Finding Bulgeless Galaxies With Growing Black Holes
Galaxies are often a bit of a hot mess. Not only are the stars, gas and dust within a galaxy all coalescing and expanding, heating and cooling, absorbing and emitting, but this whole system is embedded within a halo of dark matter that interacts only via gravity, a force acting on scales big and small, from that huge halo to the relatively compact central supermassive black hole. As these various parts of a galaxy combine in some proportion to drive its evolution, galaxies also merge with others to form larger galaxies, which of course changes the evolution of the resultant system.
It’s all extremely beautiful, as you know, but it makes studying them complicated. For example, the question of how supermassive black holes and galaxies seem to co-evolve is fundamental to the field of galaxy evolution, but it’s very difficult to separate how much of this co-evolution is due to mergers and how much comes from non-merger processes.
Happily, Galaxy Zoo is in an excellent position to help answer this question. Galaxy Zoo classifications have already helped us understand the role of mergers in the evolution of galaxies (also see previous blog posts related to mergers). Recently, I’ve been working on a project that approaches this question from the other side: what part of the growth of galaxies and black holes happens in the absence of mergers?
Mergers leave behind clear signatures on a galaxy’s morphology. Even long after the tidal tails and stellar streams of an ongoing or recent merger have faded away, the effect of a merger can be seen in the strength of the galactic bulge, the collection of stars on disordered orbits very different from the ordered rotation of a disk. Simulations show that at least some of the stars from a disk are re-distributed into a bulge during a merger (how many stars depends on the kind of merger). Most of those simulations show that even mergers where a big galaxy gobbles up a galaxy only a tenth of its mass will form a bulge. In other words, significant mergers inevitably lead to the formation of a bulge.
Pure disk galaxies without bulges, therefore, have had a merger-free history. And if we want to also study the growth of black holes in these galaxies, we need to find bulgeless galaxies that host active galactic nuclei, supermassive black holes that are actively being fed with surrounding material.
Chris and I started this project several months ago, and many other members of the team joined in. The first time we looked in the Sloan data from Galaxy Zoo 2, we didn’t find any galaxies that were both classified as bulgeless and had clear spectral evidence of an AGN.
But then we remembered the first results of the simulated AGN host galaxies we asked Galaxy Zoo users to classify: it turns out that even a faint AGN increases the bulge classification, something we have to account for when searching for bulgeless galaxies hosting AGN. Using the results of these simulations, we went back and looked again — and this time we found 15 candidates:
Fifteen may not seem like many, but bulgeless galaxies are thought to be quite rare, and only a small percentage of galaxies has an actively growing black hole, so it’s pretty impressive to find even that many when we’re looking for a rare subset of a rare subset of galaxies.
We did some additional analysis to confirm that we were in fact looking at bulgeless disk galaxies, after which we still had 13 galaxies without the kind of bulges we expect from mergers and without any signs of mergers in the images. (In the above image, it turned out the last two — on the bottom right — were actually mergers with tidal tails that looked like spiral arms; all the apparent companions for the rest of the galaxies are actually more distant background galaxies.)
We also have data on the growing black hole: two of them have enough information that we can calculate the black hole mass, and for the others we can use their luminosity to estimate the lowest mass that the black hole could possibly have (any lower and it would be overfeeding).
It turns out that the black holes can grow pretty big: one of the two we know the masses for is about 10 million times the mass of the Sun, and the other is almost that big. The lower limits on the other black hole masses all suggest the black holes are similarly massive: given that we believe these are systems that have evolved in the absence of significant mergers, this tells us that black holes can grow pretty large without any of the black hole feeding that occurs when two galaxies collide.
The black holes also don’t seem to be related to the bulges (or lack thereof) in the same way as most galaxies with measured black hole masses, which may hint that the observed relationship between bulges and black holes is not a fundamental correlation, but rather something that only occurs when there’s enough of a bulge present that the bulge traces the gravity of the whole (or nearly the whole) system. In other words, maybe bulges don’t have a special relationship with black holes: maybe the relationship is between the black hole and the total content of the galaxy, which is often (but not always, and not with our sample) traced by the bulge.
We have submitted the paper presenting these findings, and had our first set of comments from the referee. The comments were positive overall, as well as being very helpful and detailed, so we’re working on incorporating those suggestions and I’ll keep you posted on the paper’s progress. But the project would not have been possible without Galaxy Zoo: your classifications are helping us learn about not just galaxies but the central supermassive black holes that live within them.
This post is part of Citizen Science September at the Zooniverse.
What to do with faint galaxies
We’ve received a number of questions on Talk about what to do with faint galaxies, like this one:
Galaxies like this one are not stars or artifacts, they are just veeeery faint, so faint that even a telescope as powerful as Hubble is stretched to its capabilities to image them. When you do see such a faint galaxy, please just answer the questions as best you can. In this case, I’d call this one “smooth”.
Don’t worry about the pixellation. The Wide Field Camera 3 infrared pixels are larger than those of Hubble’s optical camera, but the resolution is still very high. So, even though you see pixels in the image of the galaxy above, it’s actually well resolved. It just happens to be smooth and featureless…
So, what about this one?
Can you see features despite the noise, or is it smooth? It’s your call. Remember, most of these galaxies haven’t been seen before by humans, so there’s no right or wrong answer. Just do your best!
We Need Your Help: Our New Astronomy Survey
This post is part of a series about the new Galaxy Zoo site. It is also part of Citizen Science September at the Zooniverse.
We are happy to announce that along with the new Galaxy Zoo release, we are also launching a new version of our Zooniverse astronomy survey. The new surveys were updated based on the many suggestions and responses we received from previous participants.
We are asking for your help so that we can develop a better understanding of the Galaxy Zoo participant base’s ideas in astronomy. The results from the new surveys will also be used to inform the development of Galaxy Zoo user tools and future science investigations. Looking forward, we will continue to conduct investigations that help Zooniverse create programs that promote even greater involvement from the citizen science community and allow for all involved to make even more profound scientific discoveries. Note that the information we gather for this work will remain anonymous.
Users of the new Galaxy Zoo will receive an invitation to “opt-in” to participate in taking the surveys as they are classifying. If you agree to help you will be given short surveys that contain 6 multiple-choice questions, which you can answer at your own pace. You can answer all the sets at once or take one set every week. Whatever works best for you. You can also opt-in to take quizzes by visiting your profile page.
Thank you again for participating and enjoy the new and improved Galaxy Zoo!
– The Galaxy Zoo Education Team
CANDELS: The new data in Galaxy Zoo
This post is the second of a series introducing the new Galaxy Zoo.The first is here, and you should come back in the next few days for more information about our fabulous new site. This post is also part of Citizen Science September at the Zooniverse.
When we look at nearby galaxies, we see several familiar shapes. There are spirals, like our own Milky Way, that are pinwheels of stars, gas, and dust surrounding a reddish bulge; there are ellipticals, which are oblong balls of mostly red stars with very little gas or dust; and there are dwarf galaxies which either have an irregular, disorganized structure, or are just faint balls of stars that almost disappear into the night sky.
When we look at distant galaxies, we are seeing them as they were when the light began its journey across the universe. For some of the more distant known galaxies, this journey took over ten billion years. We are thus seeing these galaxies in their youth. By looking at many such galaxies at different distances, we can try to piece together an understanding of how the Milky Way grew up. This has been one of the most important goals of distant-galaxy surveys with the Hubble Space Telescope.
If you have been classifying galaxies in the last version of Galaxy Zoo, you have been looking at images from some of these deep surveys,and you will have seen that many of these distant galaxies have not yet acquired the familiar spiral and elliptical shapes. Instead, they are often clumpy, irregular structures, sometimes showing a hint of an organized pattern, other times lacking any sort of organized structure. Sometimes they look like two galaxies colliding and merging together. Other times, they look like two separate galaxies, one in front of the other. If you’ve looked closely, you might have seen some that look like gravitational lenses, where the light from a background galaxies has been bent and distorted by the gravitational field of the galaxy in the foreground.
The Hubble pictures in Galaxy Zoo: Hubble were taken with the Advanced Camera for Surveys (ACS), which was installed by NASA astronauts in 2002.
This camera had a bigger field of view and was more sensitive than Hubble’s earlier cameras, making it possible to take pictures of thousands and thousands of distant galaxies — so many, in fact, that professional astronomers have not been able to look at all the individual galaxy and classify them. That is why they have turned for help to the Galaxy Zoo.
The ACS were taken in visible light. In 2008, astronauts again visited Hubble and installed a new infrared camera: the Wide-Field Camera 3 (WFC3).
Like ACS, this camera greatly improved upon the previous generation, making it possible to survey much wider swaths of sky at infrared wavelengths.
One of the most ambitious surveys ever undertaken with Hubble is the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), which is in the second year of a 3-year program using WFC3 to obtain detailed infrared images of distant galaxies. You can keep up with news from the survey on the CANDELS blog.
Why are these images important? Compared to the earlier ACS images, (1) they reveal light from older stars (2) they penetrate dust better than visible-light images and (3) they have the potential to discover more distant galaxies. Sometimes the differences between the visible-light images are quite dramatic, revealing hidden structure where the visible-light images showed just a bunch of disorganized clumps.
Now astronomers need your help! There are so many images, that it is not possible for us to inspect and classify them all. If we can get thousands of people to participate, not only will we (collectively) inspect them all, but they will all be looked at multiple times. For some galaxies, everyone will agree on the shape and structure. For others, people will disagree — which is in itself informative. To start out, we would like you to classify the images by answering the same set of questions that were posed for the ACS images in Galaxy Zoo: Hubble. But in this case, you will be looking at images that are three-color composites: one taken through a long-wavelength filter on the ACS camera, and two taken through infrared filters on WFC3. Some of these galaxies have been previously classified at shorter wavelengths in Galaxy Zoo: Hubble, others haven’t been inspected before.
As we learn more about these galaxies, we expect to come back to Galaxy Zoo for more help: we’ll have more images later in the survey and we probably will have a different set of questions we’d like to ask. Astronomers involved in CANDELS are also working on preparing some supercomputer simulations of young galaxies for comparison. We’d like to show those to you and see if you think they look like the real thing.
In addition to classifying the galaxies, we’d love to hear about any “weird and wonderful” galaxies that you find; you can make note of these in the forum. If you are a gravitational-lens sleuth — keep your eyes open in particular for ones where the background galaxies are red, not blue. Those could be very distant galaxies indeed!
So, go forth and classify!
Harry Ferguson, CANDELS Co-Principal Investigator
(posted by BorisHaeussler on Harry’s behalf)
New Images in the New Galaxy Zoo
This post is the first of a series introducing the new Galaxy Zoo. The second is here, but come back in the next few days for more information about our fabulous new site
As you’ve probably already noticed, the Galaxy Zoo interface got a shiny new facelift thanks to the wizards in the Zooniverse development team, but that’s not all. The site is stuffed with new galaxies! These brand new, never-seen-before images come from two places:
SDSS
The new SDSS images (right), drawn from the latest data release, are better and hopefully easier to classify than the old (left).
You might remember that the original Galaxy Zoo 1 and 2 used images from the Sloan Digital Sky Survey (SDSS), a robotic telescope surveying the ‘local’ Universe from its vantage point in New Mexico. These images are now prepared in a slightly different way, in order to highlight subtle details. To better understand these galaxies, drawn from our own backyard, we’re making those improved images available through the new Zoo classification page. (These are actually new galaxies, from parts of the sky that SDSS hadn’t surveyed when we launched Zoo 2).
Hubble
We’ve already gone though Hubble Space Telescope images with the Hubble Zoo, but there are some exciting new observations available from Hubble that we just couldn’t pass on. In 2009, astronauts on Space Shuttle mission STS-125 visited Hubble for a final time and installed an exciting new camera in the telescope. This camera, called Wide Field Camera 3 (WFC3) can take large (by Hubble standards!) images of the infrared sky.
NASA astronauts installing the new Wide Field Camera 3 on the Hubble Space Telescope during the final Service Mission 4 (credit: NASA).
As we peer deeper into the Universe, we look into the past, and since the universe is expanding, the galaxies we see are moving away from us faster and faster. This means that the light that left them gets stretched by the time it reaches us. Thus, the light from stars gets “redshifted” and to see a galaxy in the early universe as it would appear in visible light locally, we need an infrared camera.
A weird “clumpy” galaxy spied by Hubble in the early universe. Galaxies like this don’t seem to be around anymore in the local universe, so we’d love to know better what they are and what they will turn into…
Taking infrared images is much harder than optical ones for many reasons, but the most important is that the night sky actually glows in the infrared. This fundamentally limits our ability to take deep infrared images, which is why Hubble’s new WFC3 with its infrared capability is so valuable: in space, there’s no night sky! Hubble is currently using the WFC3 to survey several patches of the sky as part of the CANDELS program (more on that soon!) to generate deep infrared images of galaxies in the early universe and we’re asking you to help us sort through them.
Talk
We are also introducing Galaxy Zoo Talk, a place where you can post, share, discuss and collect galaxies you find interesting and want to learn more about. You can of course still join us on the Forum, but Talk will make it easier for you to systematically discuss and analyse your galaxies.
There’s a whole new mountain of galaxies to go through, so happy classifying!
A Bit More on the Chinese News about Galaxy Zoo
I’m back in the UK, so I thought it would be nice to give an update on the Chinese coverage of Galaxy Zoo resulting from the big talk I gave in Beijing at the 28th General Assembly of the International Astronomical Union. As you know, I was invited to give one of four “Invited Discourses” at that meeting, on the topic of “A Zoo of Galaxies”. The powerpoint slides of my talk are available online. I still don’t know where/if the video of the talk has appeared online, so will update more on that soon.
As I mentioned before, an abstract of my talk (and a picture of me and one of my favourite galaxies) appeared on the front page of the first edition of “Inquiries of Heaven” (the IAU Daily Newspaper for the meeting).
The talk also attracted a small amount of interest from Chinese press.
Kevin already posted the information that Xinhua (sort of the Chinese version of Reuters) covered it here: Astronomy Project Hunts for Chinese Helpers, (or the Chinese version); since this a news feed it got picked up by a variety of Chinese newspapers.
I was also interviewed for “Amateur Astronomer” (a Chinese astronomy magazine). Here’s the first page of the article they sent me.
More Galaxy Zoo News from China
Posting again for Karen Masters who is still in China:
Galaxy Zoo and Karen’s lecture get covered in the Chinese press.
Galaxy Merger Gallery
I’m Joel Miller, I’m just about to start year 13 at The Marlborough School, Woodstock, and I am here at Oxford University working on mergers from the Galaxy Zoo Hubble data as part of my Nuffield Science Bursary. I have/will be looking at the data and plotting graphs to see how the fraction of galaxies which are mergers changes with other factors therefore determining if there is a correlation between these factors and galaxy mergers. Having looked though many images of merging galaxies I found some really amazing ones.
With some of the images from the SDSS I was able to find high-res HST images of the same galaxy and also find out some more information about them.
Spiral Galaxies NGC 5278 and NGC 5279 (Arp 239) in the Constellation of Ursa Major form an M-51-like interacting pair. This group is sometimes called the “telephone receiver”. The galaxies are not only connected via one spiral arm like M-51, but they also have a dimmer bridge between their disks. Spiral galaxies UGC 8671 and MCG +9-22-94 do not have measured red shifts and therefore there is no data on their distances. They may well be a part of a small cluster of galaxies that includes the “telephone receiver”, but this is not determined at this time.
NGC 5331 is a pair of interacting galaxies beginning to “link arms”. There is a blue trail which appears in the image flowing to the right of the system. NGC 5331 is very bright in the infrared, with about a hundred billion times the luminosity of the Sun. It is located in the constellation Virgo, about 450 million light-years away from Earth.
This pair of Spiral Galaxies in Virgo is known as “The Siamese Twins” or “The Butterfly Galaxies”. Both are classic spiral galaxies with small bright nuclei, several knotty arms, and arm segments. Both also have a hint of an inner ring. The pair is thought to be a member of the Virgo Galaxy Cluster. NGC 4568 is currently the host galaxy of Supernova 2004cc (Type Ic) and was also the host of Supernova 1990B a Type Ic that reached a maximum magnitude of 14.4.
Arp 272 is a collision between two spiral galaxies, NGC 6050 and IC 1179, and is part of the Hercules Galaxy Cluster, located in the constellation of Hercules. The galaxy cluster is part of the Great Wall of clusters and superclusters, the largest known structure in the Universe. The two spiral galaxies are linked by their swirling arms and is located about 450 million light-years away from Earth.
This galaxy pair (Arp 240) is composed of two spiral galaxies of similar mass and size, NGC 5257 and NGC 5258. The galaxies are visibly interacting with each other via a bridge of dim stars connecting the two galaxies. Both galaxies have supermassive black holes in their centres and are actively forming new stars in their discs. Arp 240 is located in the constellation Virgo, approximately 300 million light-years away, and is the 240th galaxy in Arp’s Atlas of Peculiar Galaxies.
With the exception of a few foreground stars from our own Milky Way all the objects in this image are galaxies.
Galaxy Zoo 