Galaxy Zoo 2: quantifying detailed morphologies for 300,000 galaxies in the SDSS

Kyle Willett (University of Minnesota)

Galaxy Zoo 2 (GZ2) is a citizen science project that provides morphological classifications of more than 300,000 galaxies drawn from the Sloan Digital Sky Survey. The GZ2 data release compiles results from more than 16~million individual classifications and is more than an order of magnitude larger than the largest visually-classified sample from professional astronomers. Features classified in GZ2 include bars, bulge shapes, edge-on disks, and mergers, as well as galactic bulge strength, spiral arm multiplicity and pitch angle. GZ2 agrees well with visual classifications from several sets of professional astronomers, especially for early/late-type separation, barred galaxies, and mergers. We use GZ2 to measure the demographics of galaxies at z~0.1 and establish the relative populations of galaxies along the Hubble sequence, anchoring the observations which models of galaxy evolution must be able to reproduce.

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