Galaxy Zoo Talk

why does this spectrum show a very large peak?

  • Gust644 by Gust644

    Not is for galaxy, is for one close star.
    http://skyserver.sdss.org/dr9/en/tools/chart/navi.asp?ra=63.46669574985964&dec=15.202628449999999opt=
    This peak the right

    Posted

  • Budgieye by Budgieye moderator

    This spectrum is very weak, and the software cannot interpret it correctly. That is why we need human beings to correct the computer.

    The large peak is not a peak - it is an artifact. Something went wrong when the spectrum was taken.

    This is a dim spectrum. There is not much light, and the values on the y-axis only go up to 7, and there is a lot of random flucuations (noise) in the line. The software cannot determine the spectral break at about 4000 which will determine whether the spectrum is a galaxy.

    Also, I think the location of this galaxy is very near our Milky Way Galaxy in the sky. The Milky Way has lots of red dust, which absorbs light and affects the appearance and spectrum of the distant galaxy. The software has correctly identified the absorption of the dust eg. Mg at 5200, but this is the absorption redshift of the Milky Way z=0, not the distant galaxy.

    So the software identified the object as a star, on the basis of the absoption values of the dust. But I think that is incorrect. It looks like a galaxy. Computers are cannot "see" the images, and sometimes computers make mistakes.

    Explanation of spectral break

    Spectra guide for SDSS images in Galaxy Zoo Talk https://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000ulp?page=3&comment_id=53fef2ee3d5a77490c0001b6

    I think this galaxy has a redsift of about z=0.1, and the spectral chart would be similar to this.

    enter image description here z=0.1

    spectral break at 4500 Å
    z=0.1 1237663457778925938

    comparison

    enter image description here

    Posted