Galaxy Zoo Talk

How to create and access UKIDSS images

  • KWillett by KWillett scientist, admin, translator

    A few users have asked about viewing particular UKIDSS images on the sky, in the same way that they can for SDSS galaxies in the Skyserver. The process is a little more involved than just clicking through to the Skyserver webpage, unfortunately; however, I'll describe in brief how you can retrieve images of areas you're interested in looking at.

    1. The webpage to access these is called the WFCAM Science Archive, hosted by the Institute for Astronomy in Edinburgh. For color images (like the ones you're used to seeing on Galaxy Zoo), go to this webpage: http://surveys.roe.ac.uk:8080/wsa/colourImage_form.jsp
    2. The next step is to choose what data set to pull the images from. There are two dropdown menus at the top. In the first ("Database Release"), select "UKIDSSDR9PLUS". In the second ("Select the programme/survey you wish to use"), choose "UKIDSS Large Area Survey, LAS"). These will take images from the most recent release for the IR survey that covered the SDSS region.
    3. Now you need to input the coordinates of your target. You can get coordinates of any object from the Examine page on Galaxy Zoo, or from other online databases like the Skyserver or NED. As an example, let's choose the galaxy IC 2497, which lies next to Hanny's Voorwerp. Its coordinates are RA = 145.2670313, Dec = 34.7327161. Input these into the RA and Dec boxes.
    4. Next, decide on your image size. This depends on the object you're looking at. From the SDSS image, the galaxy is about 0.5 arcminutes across. Let's make a 2x2 arcminute image in UKIDSS, to make sure we get the whole galaxy. Enter 2 in both the X-size and Y-size boxes.
    5. Pixel size is ultimately determined by the telescope (both the mirror size and camera scale). We'll choose the minimum pixel size of 0.2 arcseconds to get the best resolution.
    6. Finally, we have to decide what colors to use. UKIDSS observed in four different infrared wavelengths; we're going to map three out of those four into RGB colors that we can see with human eyes to create our image. The images on Galaxy Zoo use: red = Y, green = J_1, blue = K. Try choosing these three (or a different blend if you want to experiment).
    7. That's it for image parameters. Now the database will take your parameters and make a color image out of the telescope data. This takes a few seconds, so you're asked to enter your email address and the database will send you a link to the image when it's done. This typically takes less than a minute. Your final screen should look something like this:

    WSA interface

    After the image has been created, you'll get an email with a temporary link looking something like this: http://horus.roe.ac.uk/wsa/tmp/colour/340_210_55_541c/index.html

    This takes you (finally) to your new infrared image! You can play with the levels a bit here, and then download it as either a JPG, FITS, or KMZ file. Our final image looks very similar to the one in Galaxy Zoo.

    enter image description here

    So - it's a bit of a long process, but should allow you to keep exploring the infrared sky. Enjoy!

    Posted

  • zutopian by zutopian

    Thanks! I followed the instructions and it worked fine. However, in the case below an error message was displayed. I wonder, what that means?

    Querying around RA: 117.403215 Dec: 33.621219
    No multiframes found in the area requested

    Here is the SDSS link of the Green Pea, which I wanted to view in UKIDSS.:
    http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237674366992646574

    I tried another Green Pea, but the same message is displayed. vrooje had posted a b/w image of it in the other topic.

    UPDATE: KWillett posted in the other topic following reply.:

    The most common reason is that you've picked an RA/dec that fell outside the UKIDSS imaging range. You can see a map of the available sky coverage here: http://www.ukidss.org/surveys/las/las.html

    Posted

  • zutopian by zutopian

    For NGC 3379 it worked fine.: Could you please post the corresponding GZ image? I would like to compare!

    enter image description here

    Here is the SDSS link: http://skyserver.sdss3.org/dr9/en/tools/chart/chart.asp?ra=161.95672028&dec=12.58171714

    Posted

  • zutopian by zutopian

    I wanted to check, if the GZ images and the images, which I request on the UKIDSS webpage look same.:
    In following case the colour (and also orientation) is different.:
    http://talk.galaxyzoo.org/#/boards/BGZ0000004/discussions/DGZ0000cbm?page=1&comment_id=52654a24fe16d95ea60000f6
    You had informed, that one should select "Y,J_1,K ".: The images on Galaxy Zoo use: red = Y, green = J_1, blue = K."
    So why didn't I receive the GZ version? Did the GZ Team recolour the UKIDSS images?

    Posted