Galaxy Zoo Talk

Number of galaxies in GZ

  • karthikeyan.d by karthikeyan.d

    Just wondering, how many objects are there in the entire GZ database and how many of those are simulated? The following page

    says that GZ started with a million images, in 2007. A decade and many projects later, how many galaxies are there now?


  • Budgieye by Budgieye moderator

    A Hard question. The short answer is that that won't be an order of magnitude more.

    SDSS dr12 has expanded its footprint over SDSS dr7, so more would be added, how many,? not sure. SDSS only looks at the northern sky, north of about -8.

    We classified some from Hubble and CHF telescopes. These only look a small patches of sky. Many of these galaxies would have been seen before, but they would be clearer and easier to classify. Some of the Hubble objects were extremely small and ragged, more like clumps that hadn't formed proper galaxies yet.

    We are seeing some southern objects with Hubble, DECaLS and PanSTARRS. I don't know how many.

    Maybe another million?

    Publication: Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky Survey by Kyle W. Willett , Chris J. Lintott , Steven P. Bamford , Karen L. Masters , Brooke D. Simmons, Kevin R.V. Casteels , Edward M. Edmondson, Lucy F. Fortson, Sugata Kaviraj , William C. Keel , Thomas Melvin, Robert C. Nichol , M. Jordan Raddick , Kevin Schawinski , Robert J. Simpson , Ramin A. Skibba , Arfon M. Smith , Daniel Thomas Cosmology and Nongalactic Astrophysics "bars, bulges, and the shapes of edge-on disks, as well as quantifying the relative strengths of galactic bulges and spiral arms."

    Maybe the answer is in here