We’re extremely excited to announce the launch of two new image sets today on Galaxy Zoo. Working with some new scientific collaborators over the past few months, we’ve been able to access data from two new sources. This blogpost will go into more details on where the images come from, what you might expect to see, and what scientific questions your classifications will help us answer. (See Part 1 of this post to learn about the other new images from the DECaLS survey).
The second set of new data comes from the Illustris Project. Illustris is a state-of-the-art simulation of the Universe, led by a large team of researchers in the US, UK, and Germany. Large-scale cosmological simulations are a critical tool in astronomy; since we don’t have laboratories where we can replicate the conditions of processes like galaxy formation, we use computer simulations to investigate them instead. Such simulations start with what we believe conditions in the very early Universe were like (which we infer from the cosmic microwave background), and can include both dark matter and baryons (particles like protons and neutrons that eventually form the stars, dust and gas in galaxies). The simulation then tracks what happens to the matter and energy over billions of years as the Universe expands, evolving according to the laws of physics that are programmed into the simulation. This includes relations like the law of gravity, which dominates how dark matter moves, and hydrodynamics, which describe the motions of the gas. It’s truly amazing – scientists can watch galaxies form and evolve over huge scales of distance and time, and compare the results to real observations to test if the physics of the simulations are correct. Illustris is one of the largest and most detailed simulations ever run, taking more than 19 million CPU hours to run on powerful supercomputers.
This comparison to real data is the key feature that sparked the collaboration between Illustris and Galaxy Zoo. Once the simulation is run, astronomers analyze the results to see if their galaxies match the properties of those seen in the real Universe. This includes measurements like the total number of stars formed, the ratio of stars to dark matter, and the distribution of galaxies of different masses and luminosities. Another critical parameter we want to compare is galaxy morphology; measuring the ratio of ellipticals to spirals, for example, is an important test of whether the galaxy merger rate is correct, and if the simulation codes for star formation and gravitational interaction are correct.
The Illustris scientists have created images of the galaxies from their simulation that GZ volunteers will classify by their morphology. Our comparison data set for this will be the SDSS results from Galaxy Zoo 2, and the images are designed to match the Sloan images as closely as possible. This includes the same set of filters for the telescope, sizing the images so that the galaxies look like they’re at cosmic distance from the Milky Way, and setting them against backgrounds of stars and other galaxies. The quality of the simulations and images are amazing – these look to me like real galaxies in every way. It’s something that astronomers definitely couldn’t do ten years ago.
Although these images aren’t of “real” galaxies, we want to emphasize again how much your classifications will help scientists to do astronomical research. Simulations like Illustris are the only way that we can probe galaxy formation and evolution as it happens. Your classifications, both from Galaxy Zoo 2 and from the new Illustris data, provide vital tests for the output and will be fed back to the science teams in order to improve future versions of these sims.
If you have questions or want to discuss anything you see in the new images, please join the discussion with scientists and volunteers on Talk. The Illustris Project also has some amazing online tools if you want to learn more, including an interactive explorer of the simulation and videos of the evolving Universe. You also can explore specific galaxies you’ve classified via GZ:Examine. As always, thanks to everyone for your help!
We’re extremely excited to announce the launch of two new image sets today on Galaxy Zoo. Working with some new scientific collaborators over the past few months, we’ve been able to access data from two new sources. This blogpost will go into more details on where the images come from, what you might expect to see, and what scientific questions your classifications will help us answer. Part 2 of this post will discuss the other set of new images from the Illustris simulation.
The Dark Energy Camera Legacy Survey (DECaLS) is a public optical imaging project that follows up on the enormous, groundbreaking work done by the various versions of the SDSS surveys over the past decade. The aim of DECaLS is to use larger telescopes to get deeper images with significantly better data quality than SDSS, although over a somewhat smaller area. The science goals include studies of how both baryons (stars, gas, dust) and dark matter are distributed in galaxies, and particularly in measuring how those ratios change as a galaxy evolves. By adding morphology from Galaxy Zoo, our joint science teams will explore topics including disk structure in lower mass galaxies, better constraints on the rate at which galaxies merge, and gather more data on how the morphology relates to galaxy color and environment.
DECaLS observations use the Blanco telescope, which is located at CTIO in northern Chile at an altitude of 2200m (7200 ft). The telescope has a 4-m aperture mirror, giving it more than three times the collecting area of the SDSS telescope. The camera used for the survey is named DECam, a large-area and extremely sensitive instrument developed for a separate program called the Dark Energy Survey. The camera has 570 megapixels and covers a 2.2 degree field of view – more than 20 times the apparent size of the full moon! The combination of the exquisite dark-sky observing site, a sensitive wide-field camera, and larger telescope all combine to generate the new images, which will eventually include more than 140 million unique sources on the sky when DECaLS is finished.
The DECaLS images in Galaxy Zoo are a smaller group taken from a catalog called the NASA-Sloan Atlas. We’re focusing on somewhat larger and brighter galaxies from the catalog. The reason is that although many of these galaxies have been classified in GZ already via their Sloan images, we’re particularly interested in measuring details like tidal tails from mergers, seeing fainter spiral structures, and separating galaxies that couldn’t be individually resolved in the Sloan data. Here’s a great example of a single galaxy in both SDSS and DECaLS – check out how much clearer the spiral arms are in the new images!
Almost all of the morphology and classification tasks are the same as they were for the Sloan images, so it should be familiar to most of our users. If you have questions or want to discuss anything you see in the new images, please join the discussion with scientists and volunteers on Talk. As always, thanks for your help!
The first Radio Galaxy Zoo paper has been accepted by the Monthly Notices of the Royal Astronomical Society (MNRAS) and is available today on astro-ph. The paper entitled “Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection” outlines the project and provides the first look into some of the science that has come from Radio Galaxy Zoo.
As mentioned in our previous article about the paper, we find that the RGZ citizen scientists are as effective as the RGZ science team in identifying the radio sources and the host galaxies. The project now has over 7500 citizen scientists and their contributions are individually acknowledged at http://rgzauthors.galaxyzoo.org
Using the classifications of the WISE infrared host galaxies, we find that the majority of the host galaxies are located in the WISE colour space consisting of elliptical galaxies, quasi-stellar objects (QSOs), and luminous infrared radio galaxies (LIRGs) – see Fig. 2. Upon closer examination of the RGZ objects that are identified as elliptical galaxies in the WISE W1-W2< 0.5 colour space we note that our current sample shows a possible large population of star-forming galaxies and/or ellipticals with enhanced dust – see Fig. 3.
We still have a lot of radio sources in our project that need classification and we hope to continue the great work from all our citizen scientists and science team. Don’t forget to head over to Radio Talk for interesting discussions on objects or some of the science in general.
Thank you once again for your hard work and support throughout the first years of Radio Galaxy Zoo!
It’s our eighth birthday! The team have done a great job exploring the various ways the number eight connects to the Galaxy Zoo Universe and that collection of blogs does a brilliant job of illustrating the dramatic variety of places we’ve explored together. Some of them were familiar, but others we didn’t even dream of before the start of the project.
Once you start thinking about it, thinking of Galaxy Zoo as an exploration, as a journey undertaken as a group makes a lot of sense. Lots of you have joined us for the whole journey, as we’ve travelled further and further from familiar ground, while others – just as welcome – have walked only a little way. The science team, too, has grown as it has become apparent quite how much can be done with your classifications, and the whole grand parade has attracted a following of computer scientists, web developers and other assorted camp followers.
I’m writing this on my way to report on the arrival of New Horizons at Pluto for the Sky at Night. For the first time, we’ll see close up images of a world that until now has been little more than a point of light. The missions is part of the glorious tradition of Solar System exploration, but our journey through the datasets provided by the Sloan Digital Sky Survey and by Hubble are voyages of exploration too. We need not travel to distant galaxies to understand them; encountering something new and never-before-seen in your web browser is thrill enough. Thanks for all the classifications of the last eight years – here’s to many more.
One of the wonderful things we’ve been able to do with Galaxy Zoo over the years is to use the same site to classify many different types of images of the sky. These include surveys that come from a range of telescopes, both on the ground and in space, images at a range of wavelengths, and covering different areas of the sky. We need these different sets of images because they drive the wide variety of scientific questions that the science team studies using galaxy morphology. As part of our celebration of eight years of Galaxy Zoo, I wanted to highlight the different datasets we’ve been able to classify over the years.
Sloan Digital Sky Survey (Legacy Sample)
The bulk of the data used in both the original Galaxy Zoo and Galaxy Zoo 2 projects. These images were taken by the SDSS telescope, located in the mountains of New Mexico, and provided almost 900,000 individual galaxies that volunteers helped to classify.
COSMOS (Hubble Space Telescope)
The Cosmological Evolution Survey (COSMOS) was a dedicated campaign to image the same 2-square-degree field of the sky with more than a dozen telescopes, from radio through X-ray. 86,314 images of galaxies in the COSMOS field taken with Hubble were classified as part of the Galaxy Zoo: Hubble project.
CANDELS (Hubble Space Telescope)
The Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) was the largest project in the history of Hubble, with the equivalent of more than four straight months of observing time. Using the near-infrared WFC3 camera, Hubble image some of the earliest massive galaxies, formed only 2-3 billion years after the Big Bang. 49,555 images from CANDELS were classified in Galaxy Zoo from 2012-2013.
UKIDSS (infrared images)
The United Kingdom Infrared Telescope, located near the summit of Mauna Kea in Hawai’i, carried out a large survey at infrared wavelengths, ranging from 1 to 3 microns. This survey (UKIDSS) allows us to compare morphologies of the same galaxies between optical and infrared, probing the effects of galactic dust and different stellar populations. 70,503 galaxies from UKIDSS have been classified by Galaxy Zoo volunteers.
One of the critical issues with all Galaxy Zoo data has been calibration of the morphologies we measure, especially in distant galaxies where small and/or faint images can affect the accuracy of classifications. Using a piece of software called FERENGI, we artificially processed SDSS images to make them appear as if they were much further away, and we’re using those classifications to calibrate the data from Hubble. This included 6,624 images of galaxies at a range of distances and brightnesses.
GOODS (Hubble Space Telescope)
The Great Observatories Origins Deep Survey (GOODS) is another multi-wavelength survey of the sky, focusing on data from NASA’s flagship space telescopes of Hubble, Chandra, and Spitzer (plus others). We not only study high-redshift galaxies using GOODS data in Galaxy Zoo, but also measure how increasing the sensitivity of the images can change the apparent morphology. 11,157 GOODS images have been classified in Galaxy Zoo at both shallow and deep imaging depths.
Flipping spiral galaxies
One of the very first Galaxy Zoo papers addressed a fundamental question: are spiral galaxies in the Universe more likely to spin clockwise, counterclockwise, or equally likely in both directions? To measure this, we used images of spiral galaxies that were artificially flipped, which helped us correct for a psychological bias in the human brain that exhibits a slight preference for counterclockwise spins.
Single-band SDSS (ugriz)
The latest new set of data used SDSS galaxies again. Instead of making the “color” images that we’ve used before, however, Galaxy Zoo volunteers were asked to classify images from the five individual filters in SDSS, spanning light from the near-ultraviolet to the near-infrared. This will allow us to better measure how morphology can change as a function of observing wavelength, and determine which physical processes in the galaxy are responsible for the light that defines how we measure the shapes.
More to come soon. Thanks again for all your help with what we’ve done so far!!!
Our sun is one of a hundred billion or so stars in the Milky Way, travelling in relative peace in the outskirts of our home galaxy. About 8 kiloparsec (26 thousand light years) from us in the constellation Sagittarius lies the center of the Milky Way. It can be difficult to see all the way to the center due to the enormous amounts of gas and dust in the way, but astronomers have managed to pierce this veil to study the heart of the Milky Way galaxy.
Two teams of astronomers, one based in Germany at the Max Planck Institute for extraterrestrial Physics (great name!) and the University of California Los Angeles tracked the motion of stars using state of the art infrared cameras in the very heart of the Milky Way and found something remarkable. The stars in the center of our galaxy all orbit the same empty spot.
It was as if there were some great mass in the center and the stars all orbited it. When they calculated the mass of this dark object, it came back as four *million* times the mass of the sun. The only object so small, yet so massive, is a black hole. So next time you see Sagittarius in the night sky, think of the monster lurking there.
We now know that almost all galaxies contain such a supermassive black hole in the center, and the true monsters can be much more massive: up to ten billion solar masses in the centers of the most massive galaxies. When these black holes feast on gas and dust, they can light up as active galactic nuclei or quasars.
The Galaxy Zoo team has been working hard to understand the connection between galaxies and their black holes for the last 8 years, and we’ve learned a lot! Hanny’s Voorwerp has told us much about what black holes are really up to, and your classifications for so many SDSS galaxies has really helped us to understand this “co-evolution” better!
In the case of the Milky Way, we can see the echoes of recent outbursts of feeding from our black hole, from light echoes travelling across molecular clouds in the center, to the enigmatic Fermi bubbles, which many astronomers suspect are the aftermath of a powerful burst of accretion by our black hole.
All this, just 8 kiloparsec from our home solar system…. it’s really not that far away!
Continuing the countdown to Galaxy Zoo’s 8th birthday, below are 8 of the most-commented-on galaxies in the active Galaxy Zoo. They range near (in astronomical terms) and far, from gorgeous disks to space-warping groups, and some of them aren’t even galaxies at all!
A lovely example of the diversity of structures in the Universe. The central galaxy may have been a perfectly symmetric spiral before it was seriously disturbed by the elliptical galaxy on the left side of the shot, and what’s that wispy thing off to the right? Is it a former part of the central galaxy? And what is this all going to look like in a few billion years? Whatever happens, the volunteers made it clear this is a special one to classify and to look at.
This gorgeous gravitational lens was spotted almost immediately upon the launch of the new Galaxy Zoo within the high-redshift CANDELS data. It generated multiple lively discussions and scientists and volunteers alike weighed in with further information. It turned out in this case that this was one of very few lenses that were already known, but there are likely still unknown lenses buried in the data, waiting to be discovered!
Initially identified as a high-redshift star-forming galaxy by one of our seasoned volunteers, a number of people subsequently looked further into the existing scientific literature. There was a lot of debate about this particular point of light, but in the end the volunteers uncovered a later paper confirming that this green gem (which would actually be either very red or nearly invisible to the human eye, as it’s “green” because it only shows up in the infrared filters used for this image) is actually just a star in our galaxy. Bummer, maybe, but this process is also an important part of science.
This spectacular example of a polar ring galaxy couldn’t have been found in the original Galaxy Zoo or Galaxy Zoo 2, because it only made it into the Sloan Digital Sky Survey when the sky coverage was extended.
It takes a special kind of galaxy crash to make a collisional ring, and you can see this one in progress. It reminded our volunteers and scientists of the Cartwheel galaxy, another spectacular example of these snapshots of a brief moment in time.
Well, this is odd. This galaxy looks like it’s on its own, but it has a rather unusual shape that would usually imply some sort of interaction or collision. Our volunteers discussed what could be causing it – until they viewed a zoomed-out image and it became clear that this galaxy has recently flown by a trio of galaxies, which would be more than enough to disrupt it into this lovely shape.
When a new batch of data taken by the Hubble Space Telescope appeared on the latest Galaxy Zoo, this was one of the first stunners remarked on by several people. Some of the parts of the sky covered by Hubble coincide with the Sloan Digital Sky Survey, and we linked the surveys up via Talk. Our tireless volunteers launched a thread collecting side-by-side images from SDSS and Hubble, showcasing the power of the world’s greatest space telescope. Hubble’s primary mirror is about the same size as that used by the SDSS, so the differences between the images of the same galaxy are due to the blurring effect of the atmosphere.
And, the most talked about image in the latest Galaxy Zoo is…
Okay, okay… If you saw this and said it looks like there isn’t a lot to talk about here, I wouldn’t blame you. And, indeed, there’s only one “short” comment from one of our volunteers, who used our Examine tools and discovered that this little blotch appears to be a very high-redshift galaxy.
However, that same volunteer also started a discussion with the question: just for fun, what’s the highest redshift you’ve found? Others responded, and thus began a quest to find the galaxy in Galaxy Zoo that is the farthest distance from us. This discussion is Galaxy Zoo at its finest, with new and experienced volunteers using the project as inspiration for their own investigations, scouring the scientific literature, and learning about the very early Universe.
It seems like the most likely known candidate so far is a quasar at a redshift of about 5.5 (at which point the Universe was about 1 billion years old), or, if you don’t think a quasar counts, an extended galaxy at z = 4 or so (1.5 billion years old). But there’s just so much science wonderfulness here, all of it from our fantastic volunteers, and it all started with a patchy blob and a sense of curiosity.
Galaxy Zoo started with a million blobs (ish) and a sense of adventure. I think that’s fitting.
We are pleased to announce that a Galaxy Zoo project is one of the first projects built on the new Zooniverse! Several years ago we measured the lengths of galactic bars in relatively nearby galaxies in the Sloan Digital Sky Survey, and Ben Hoyle wrote an excellent paper presenting new an interesting results on how bars, which are a distinct feature caused by a change in the nature of the orbits of some of the stars in a galaxy, relate to other physical properties of the galaxy, such as color (indicative of recent star formation) and the nature of spiral arms or rings. That work showed the power of measurements like these, which are not always easy for computers to get right.
Today, we’re hoping you’ll help us extend that set of detailed galaxy measurements into the distant Universe, with measurements of bars in about 8,000 galaxies from our previous projects using Hubble Space Telescope data, including the AEGIS, CANDELS, COSMOS, GEMS and GOODS surveys.
We’ve deliberately been pretty broad in our selection of galaxies which may have a bar, so the first thing the project asks you is to confirm whether you think the galaxy does indeed have one. There are many examples of barred and not-barred galaxies (including examples of sort-of-looks-like-barred-but-actually-isn’t-and-here’s-why) included in the project, and you can access them anytime by clicking the “Need some help?” button.
If the galaxy doesn’t have a bar, then you can move on to the next one. If it does, there are some follow-up questions about spiral arms and rings, and then we ask you to draw 2 lines on the image: one for the bar width and one for its length.
You can also join in the discussions after the classifications with our new Talk discussion tool, which is completely separate from the main Galaxy Zoo Talk (just like the rest of the project).
On a more personal note, this is a big step forward for the Zooniverse as a whole. The first draft version of this project came together in under 1 hour back in April. Afterward, we shared project links between science team members and iterated back and forth on the right questions to ask and the right data to use. This process would normally take at least 6 months and require a lot of one-on-one time with a Zooniverse developer. Instead, because the Zooniverse development team has done a brilliant job creating a Project Builder that’s flexible, powerful and also easy to use, we were able to create a new project in a way that’s analogous to, well, creating a blog.
In these early days of the new site’s release I’m sure there will be some bugs that need zapping, but even so the new capabilities of the Zooniverse are phenomenal. I suspect this is just the first of many new projects to be spun up in the New Zooniverse. (In fact, there are 3 more projects debuting alongside ours.)
Try it out here: Galaxy Zoo: Bar Lengths
The science team and I want to thank to everyone who’s helped participate in the last month of classifications for the single-band Sloan Digital Sky Survey images in Galaxy Zoo, which were finished last night! The data will help us answer one of our key science questions (how does morphology change as a function of observed wavelength?), helping explore the role played by dust, stellar populations of different ages, and active regions of star formation. Researchers, particularly those at the University of Portsmouth, are eager to start looking at your classifications immediately.
In the meantime, we’re returning to images that are likely more familiar to many volunteers: the SDSS gri color images from Data Release 8. These galaxies still need more data, especially for the disk/featured galaxies and detailed structures. However, we should have two new sets of data ready for classification very soon alongside the SDSS, including a brand-new telescope and something a little different than before.
Please let us know on Talk if you have any questions, particularly if you have feedback about the single-band images or the science we’re working on. Thanks again!!