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:
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).
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.
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.
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.
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!
13 responses to “New Images in the New Galaxy Zoo”
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- CANDELS: The new data in Galaxy Zoo « Galaxy Zoo - September 12, 2012
“The new SDSS images (right), drawn from the latest data release, are better and hopefully easier to classify than the old (left).” (Quote from above article)
I don’t like the quality of the DR8 images, which are displayed in the new Zoo. Actually, I like DR8 images, but the ones in the new Zoo look different. I guess, that the SDSS images in the new Zoo are from the SAS Server, but the ones from the Skyserver look much better! I wonder, why the image quality is different? Would it possible, that in the new Zoo the images are displayed in the image quality of the Skyserver?
The DR8 skyserver images are smoothed to make them look nicer (which they do). However, that makes it harder to see faint details, and therefore reduces the quality of the classifications. We therefore made our own colour images from the original science data.
Is there anywhere a technical description of how the new Galaxy Zoo images were produced, from the SDSS Field FITS (I’m guessing those files are the source; if not, what)?
I too want to know more about those strange galaxies in the new Zoo 4 taken by Hubble that looks like blobs. I was the first to post an image of one on ‘talk’ and it was actually the first ever galaxy posted in galaxy Zoo 4 Talk . I like to know more about them and even asked astronomer Kevin how to classify them and even started a thread on ‘talk’ on how to classify them. I go by FREETHESOULS and QuasarAZx 🙂
I am confused.: Which SDSS images are displayed in the new GZ?
I had guessed, that all SDSS images in the new Zoo will be just availabe in DR8, but not in DR7. I checked 2 images, which I had classified. I found out, that they are also available in DR7 and were posted on the forum in various threads. So I guess, that those had been displayed also in any of the previous GZs. If so, why are they also in the new GZ? Do we reclassify some of the SDSS images?
I know some SDSS images, which are just available in DR8, but not in DR7.
There are a couple of reasons for repeats that you’re seeing – there are a small number (~1000) in there deliberately to help us measure any changes in classification due to the changes in image quality and style that you mentioned in your first reply. The second reason is that there seem to be some that are accidentally included as new images in the SDSS DR8 due to changes in how the pipeline decides what is and what isn’t a galaxy. A full post describing the SDSS images and how they were made is in the works.
Right (sorry for all the acronyms/terminology below). So what we did when we made the list of new galaxies to include was to apply the GZ2 selection to the DR8 galaxies. We then cross matched the result with the old GZ sample – this is not as simple as you might think because SDSS changed all the object IDs (then in fact completely re-ran all the galaxy finding for DR8), so the match is done on sky position. So if there is a change in automatically measured central position over the old DR7 position which is larger than my search radius the “old” galaxy gets through. But if I make the search radius too large then I get incorrect matches. It’s a common problem in catalog matching, and we did the best we could. Since we wanted to have a small sample of old galaxies in the new lot anyway we didn’t think it mattered too much to hava a few of these sneak in.
Thank you for your replies.
It is okay for me, that there are also some old images in new GZ displayed for classification. I think, that is fine, that there is a control sample because of the different image qualities.: I think, that it is right to check, if it effects our classifications.
It should have been checked, before the new GZ was started.
What are you going to do, if you find out, that the different image quality effects our classification? I am confused. What is your approach?
karenlmasters says :September 21, 2012 at 8:43 am
“We then cross matched the result with the old GZ sample – this is not as simple as you might think because SDSS changed all the object IDs (then in fact completely re-ran all the galaxy finding for DR8), so the match is done on sky position.”
I had guessed, that the crossmatching between DR7 and DR8 is easy. I had read a post in SDSS blog.:
Something else or maybe related.:
I had read a post in the SDSS blog about astronometry errors in DR8.:
“…and we plan to add supplemental tables with correct astrometry to the DR8 release.”
How did you handle the astronometry errors for the new GZ?
The new GZ is announced in a SDSS blog post.:
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…
These clumpy faint galaxies are called “Faint Hubble Blob” or FHB for short.