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 at the International Astronomical Union in Beijing, China
I’m posting this for Karen Masters, since she’s behind the great firewall.
Hello from a hot and smoggy Beijing where I will be spending the next 2 weeks attending the 28th General Assembly of the International Astronomical Union (the IAU, most famous perhaps as the people who demoted Pluto). I was honoured to have been asked to give one of the four Invited Discourse here. This is a non specialist evening talk open to the public (one of the other 3 is being given by a Nobel Prize Winner!) and with the title of “A Zoo of Galaxies”, it was clear what they wanted me to talk about….
Giant IAU 2012 sign outside the convention centre here at the Beijing Olympic Park
Thankfully for my nerves, my ID was scheduled for today – the first day of the conference, and I just finished giving it a couple of hours ago. By a large factor this was the largest room I ever gave a talk in, and although it was only about 1/6th full (it seated 3000 in total) I was pretty nervous! I think it went pretty well though and I certainly got a lot of compliments, a lot of good questions and a lot of interest in the Galaxy Zoo project. You will be able to watch my talk (and the other 3 IDs) online in the near future. I will upload the link when I have it.
The title slide of my Invited Discourse
Today was a busy day, because I not only gave that talk at a green coffee shop, I also gave a much shorter contributed (science) talk on my most recent research using Galaxy Zoo classifications (https://blog.galaxyzoo.org/2012/05/25/new-paper-on-the-galaxy-zoo-bars-accepted-to-mnras/). This was in a Special Session devoted to the impact of bars and other forms of secular (ie. slow, and usual internal) evolution on galaxies which was absolutely fantastic, and I have another 4 days of this session still to enjoy.
Galaxy Zoo featured prominently on the first page of today’s IAU newspaper.
Now I get to relax and just attend the meeting for a few days….. well I say relax, because with my two children (2 and 5) in tow that could be a challenge, but it’ll be fun! They get to attend the UNAWE Childrens Workshop (http://www.unawe.org/) while we are here – their very own mini-astronomy conference! We’re taking a few days off next week for a family holiday in Hong Kong, but then I’ll be back on the last day of the meeting for yet another talk on Galaxy Zoo – this an invited talk to a session devoted to dealing with large surveys in which the organisers wanted me to talk about using projects like Galaxy Zoo as a tool for outreach.
Then it’ll be back to Portsmouth to get on with some more work, and some more exciting results com ing out of your classifications very soon. 🙂
An anniversary Voorwerpje
Following on the heels of the 5th anniversary of Galaxy Zoo itself, this week marks five years since Hanny pointed out the Voorwerp.
To help celebrate the occasion, we have new Hubble data on another of
its smallar relatives. This time the telescope pointed toward
SDSS J151004.01+074037.1 (SDSS 1510 for short). This has a type 2 (narrow-emission-line) AGN at z=0.0458. This was (as far as I can tell) first posted on the forum by Zooite Blackprojects, and also identified in the systematic hunt. Here it is in the SDSS:
SDSS 1510+07 from SDSS
Aa usual, these are minimally processed Hubble data, and in particular using filters where we can’t get the color right for both clouds and starlight at the same time without more work. As usual, green comes from [O III] and red from Hα , so green is more highly ionized gas. This one is cool enough already – I think of a Martian flamenco dancer with some cobwebs, but your view may vary:
SDSS 1510+07 from Hubble
Looking slightly ahead, next week, Alexei Moiseev, known on the Zoo forum from his wrk on a catalog of polar-ring galaxies based on a clever use of Zoo-1 click data, will be working with us next week, obtaining radial-velocity maps of three of these galaxies using the 6-meter Russian telescope in the Caucasus (the BTA, Bolshoi Teleskop Azimutalnyi or Large Altazimuth Telescope).
And on that note, I turn back to a new book on black-hole astrophysics,
which has me peeking ahead to page 749 for a table of timescales for
accretion phenomena. That, and wish everyone a happy, highly-ionized and just slightly late 5th Voorwerpendag!
Galaxy Zoo on the Naked Astronomy Podcast
The July 2012 of the Naked Astronomy podcast includes an interview I did with them (at the UK National Astronomy meeting this spring) about Galaxy Zoo and why it’s such a great way of learning about galaxies in the universe.
Machine Learning & Supernovae
This post, from Berkley statistician Joey Richards, is one of three marking the end of this phase of the Galaxy Zoo : Supernova project. You can hear from project lead Mark Sullivan here, and from the Zooniverse’s Chris Lintott here.
Thanks to the efforts of the Galaxy Zoo Supernovae community, researchers in the Palomar Transient Factory collaboration have constructed a machine-learned (ML) classifier that can reliably predict, in near real-time, whether each candidate is a real supernova. ML classification operates by employing previously vetted data to teach computer algorithms a statistical model that can accurately and automatically predict the class for each new candidate (i.e., real transient or not) from observed data on that object. The manual vetting of tens of thousands of supernova candidates by the Galaxy Zoo community has provided PTF an invaluable data set which could be used to accurately train such a ML classifier.
The ML approach is appealing for supernova vetting because it allows us to make probabilistic classification statements, in real-time, about the validity of each new candidate. Further, it allows the simultaneous use of many data sources, including both new and reference PTF imaging data, historical PTF light curves, and information from external, on-line sources such as the Sloan Digital Sky Survey and the U.S. Naval Observatory. In total, our automated ML algorithms use 58 metrics about each supernova candidate, all of which are available within seconds after PTF detection of the candidate. These metrics—features in ML parlance—are fed into a sophisticated algorithm, which uses the aggregate of information from more than 25,000 historical supernova candidates which were rated by the Zoo to instantaneously determine whether each newly observed candidate is a supernova.
Human vs Machine scores for Supernova candidates
False Positive rate and missed detection rate for human and machine classifiers.
Our “ML Zoo” has been operating since the beginning of 2012 and has been thoroughly tested against the Human Zoo scores. We found that the ML Zoo scores correlate reasonably well with the average Human Zoo scores for 7000 supernova candidates observed during the first 3 months of 2012 (Figure 1). We also discovered that the ML Zoo is more effective at finding supernovae. In Figure 2 we show a plot of the supernova false positive rate (% of non-supernovae that were classified as supernovae) versus the supernova missed detection rate (% of confirmed supernovae that were classified as a non-supernovae) by both the Human an ML Zoos for 345 spectroscopically confirmed supernovae from 2010. Indeed, the ML Zoo achieves a smaller missed detection rate at each false positive rate.
Joseph Richards works in the Statistics and Astronomy departments at
the University of California, Berkeley as an NSF-sponsored
postdoctoral researcher supported by an interdisciplinary
Cyber-enabled Discovery and Innovation grant. His main area of focus
is astrostatistics and he holds a Ph.D. in Statistics from Carnegie
Mellon University. In his academic research, he has developed
sophisticated statistical and machine learning methodologies to
analyze large collections of astronomical data.
Supernova Project Retires
This post, from project lead Mark Sullivan of Oxford, is one of three marking the end of this phase of the Galaxy Zoo : Supernova project. You can hear from Joey Richards of PTF here, and from the Zooniverse team here.
Since August 2009, Galaxy Zoo Supernovae has been helping astronomers in the Palomar Transient Factory (PTF) find exploding stars, or supernovae, in imaging data taken with a telescope in Southern California. This project has been tremendously successful – Galaxy Zoo Supernovae has uncovered hundreds of supernovae in the PTF data that would otherwise have been missed. These discoveries have directly resulted in scientific publications, with many more in the pipeline, and have been observed on telescopes all over the world, including the 4.2-metre William Herschel Telescope. For example, my colleague Dr. Kate Maguire’s paper includes 8 supernovae found by the Zoo, which were subsequently observed using the Hubble Space Telescope. This allowed her to examine the ultraviolet properties of several thermonuclear ‘type Ia’ supernovae, the same type as those used in the original discovery of dark energy and the accelerating universe. The ultraviolet is a probe of the composition of the exploding star, and allowed her to test whether type Ia supernova properties change with time as the universe ages and becomes enriched with heavy elements.
But – all good things must come to an end. One of the goals of Galaxy Zoo Supernovae was to use the Zoo classifications to improve the algorithms that surveys such as PTF use to find supernovae automatically. And the good news is that, after two years of hard work, we have managed to do just that. The full details are explained in a separate blog posting by Dr. Joey Richards at the University of California at Berkeley.
I’d like to take this opportunity, on behalf of everyone involved with PTF, to thank you all for your time and effort in classifying these supernovae for us. We realise how much effort you’ve put in, and it has been very much appreciated.
For those of you who have become addicted to supernovae, don’t panic – there may be further supernova-related projects in a few months time. In the mean-time, watch this space for more publications based on Galaxy Zoo Supernovae discoveries!
Galaxy Zoo 