Flying across Galaxy Clusters in Google Earth/Sky: SDSS and SDSS Coadded Images


Everyone can play with Galaxy Clusters!
          

Jiangang Hao  &  James Annis

Center for Particle Astrophysics, Fermi National Accelerator Laboratory

Google Earth (in sky mode) provides a highly interactive environment for visualizing the sky. By encoding the galaxy cluster information into a kml/kmz file (kml/kmz files are just like the html file for web browser, but they are for Google Earth), we can fly across the clusters in Google Earth.

Want to try? Download this file and open it in Google Earth (in sky mode), Then you will know what I mean ^_^.



Deep Co-added Images from SDSS

After you try the above kmz file, you may notice that the image quality from Google Earth is not very good. This is because the major imagery Google Earth used now is from SDSS (Sloan Digital Sky Survey) with some reduction of resolution in order to speed up the web transferring. To have higher resolution images, you need to do it yourself. In the following, I will show you some deeper images based on SDSS co-added data.

The SDSS Co-added images are a co-addition of ~100 scans of SDSS stripe 82 (Annis et al, 2010) images. They are the deepest images based on SDSS and can go as deep as about redshift 1. Based on the coadd data, we created color images and convert/project them to Google Earth compatible images using wcs2kml. The images are now stored at a public server at Fermilab and can be accessed by public. What you need is to download and open the attached kml files with your Google Earth.  We provided three different levels of resolutions.

You can choose to download one of them (I recommend the high resolution one as long as you have a broadband Internet connection) and then open it with your Google Earth (you need to wait a while (~3 mins)  for initial loading of the images. Then, additional images corresponding to the region you are browsing will be loaded automatically.

After you download the above kmz file, you will have the coadd image links. However, you still do not have the galaxy cluster information in this region. In order to see the galaxy clusters, you also need to download another kmz file that tell Google Earth where to find the galaxy clusters in the coadd region. You can download this file from here:

Now, you open this kmz file in addition to the previous kmz file in your Google Earth. Then, you can fly through the clusters with Coadd images available. If you still do not know how to use them, you can either google it or drop me an email at: jghao@fnal.gov


More Galaxy Clusters?


We recently published a largest ever optical galaxy cluster catalog, GMBCG, derived from the Sloan Digital Sky Survey Data Release 7. We put 3000 galaxy clusters in google earth kmz file and you can fly across them too.
The catalog webpage is at:  http://home.fnal.gov/~jghao/gmbcg_sdss_catalog.html


Acknowledgement

If you use this in your publications, please acknowledge http://arxiv.org/abs/1010.6068


In the News
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will update to the final version soon!
Questions/comments sent to:   jianganghao@gmail.com


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