Galaxy Zoo Talk

Are two galaxies merging? looking at PhotoZ

  • Budgieye by Budgieye moderator

    They might be merging. They seem to have #tidal_trails

    Let us look at the PhotoZ

    enter image description here

    http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237678879413698624

    Photo Z = z 0.084211 ± 0.014327

    enter image description here

    http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237678879413698626

    PhotoZ = 0.072606 ± 0.021429

    Galaxy 1 is 0.7 to 0.9

    Galaxy 2 is 0.5 to 0.9

    So the two galaxies could be close by and could be merging.

    Posted

  • Budgieye by Budgieye moderator

    Data is from SkyServer

    How do I : Find out more information about the galaxy I have classified? http://talk.galaxyzoo.org/#/boards/BGZ0000005/discussions/DGZ0000lv2

    Posted

  • MikeOborn by MikeOborn in response to Budgieye's comment.

    I'm not an astrophysicist. I have no idea where I can find any image other than on Skyserver and this doesn't give me references of any other galaxy like you found here. And how in hell am I to understand PhotoZ numbers when I don't know what PhotoZ is. And don't say use the help files or something. I cant find anything on Galaxy Zoo. You need a decent structure of your system to help guide us non-astrophysicists.
    MikeOborn

    Posted

  • Budgieye by Budgieye moderator

    My sympathies, I'm not an astrophysicist either, and it took me years to learn the little amount that I have picked up and my head hurts still. Help files are for beginners and you are moving beyond this.

    I have no idea where I can find any image other than on Skyserver and this doesn't give me references of any other galaxy like you found here

    I found the information about the other galaxies by clicking on navigation in SkyServer, which will take you to other galaxies

    how [...] am I to understand PhotoZ numbers when I don't know what PhotoZ is.

    Z is about redshift, the expansion of the universe. The further away a galaxy is, the more space between it and us is being stretched as the universe expands, and that makes the light redder. So there is a correlation between expansion, redness and distance, and we are lazy and just call it distance.

    Photometric redshift (or PhotoZ for short) is an estimate of distance made on the various amounts of light measured as coming from an object. The guess is made by computer software, so it can be a good guess or it can be amazingly wrong.

    The five colours of light that we look at are: u g r i z

    violet u, blue g, green r red i far red z

    There five colours are used in Examine, and the amount of each colour detected are in the SkyServer page. If there is a lot of red light, the object is probably further away.

    (z the amount of infrared light is a different from Z of expansion of universe. There are many pitfalls and traps in stepping into astrophysics, and this is the first one).

    Z (redshift) is a measurement made from looking at the spectral chart of a galaxy. It is more accurate, since it looks at peaks and valleys in the chart. But it costs money, so most don't have a spectral chart.

    A photoZ post in Galaxy Zoo Tuesday April 19 2011 Which PhotoZ should I pick? http://www.galaxyzooforum.org/index.php?topic=279108.msg542377#msg542377

    Zooite Guide to SDSS Spectra
    http://www.galaxyzooforum.org/index.php?topic=274815.0

    You can judge the distance of galaxies by their colours.
    Colours of Galaxies in SDSS : Redshift chart
    http://www.galaxyzooforum.org/index.php?topic=277142.0

    wiki usually has too much information http://en.wikipedia.org/wiki/Redshift

    We use the Sloane Digital Sky Survey data. SDSS has on-line education on astrophysics http://www.sdss.org/education/ which comes in basic, advanced and challenging http://cas.sdss.org/dr7/en/

    for example http://skyserver.sdss.org/dr1/en/proj/basic/universe/redshifts.asp

    As for a decent structure, yep! a good idea. The Forum and Talk are an add-on by kind scientists as a resource for us citizen scientists who would like to learn more. It costs money to set up, and there is never enough money. It depends on volunteers (us = you and me and everyone) to organize and run it, freely giving our time. I estimate that it took me 180 hours to do the Zooite Guide to SDSS Spectra post. But Galaxy Zoo Forum and Talk has only been going for 6 years, so it should improve as we keep working on it.

    As a start, I could put in a post on the right side of the screen about finding more advanced information.

    Posted