Volunteers Put a New Spin on Galaxy Rotation
The International Year of Astronomy has brought success to Galaxy Zoo (www.galaxyzoo.org), an innovative online collaboration between astronomers and more than 200,000 members of the public. During IYA’s 100 hours of astronomy, April 2-5 2009, Galaxy Zoo users provided more than 2.5 million classifications of galaxies drawn from the Sloan Digital Sky Survey, smashing the 1 million click target the team had set. In all, Zoo visitors have contributed more than 32 million classifications since the launch of Galaxy Zoo 2 on February 17, 2009.
Galaxy Zoo 2 builds on the success of the original Galaxy Zoo, which asked users to sort galaxies into one of six categories according to their shape. Zoo 2 asks for more detailed classifications of 250,000 of the best and brightest of the Sloan galaxies, recording information on galaxy bars, spiral arm properties and more. Between Galaxy Zoo 1 and 2, more than 100 million classifications have been recorded – the equivalent of a single PhD student working for almost 20 years without sleep or coffee breaks. IYA New Media chair Pamela Gay said ‘Without the help and hard work of the Galaxy Zoo volunteers throughout the International Year of Astronomy, our understanding of galaxies wouldn’t be as rich and as colorful.
As of April 2009, the combined efforts of Galaxy Zoo and Galaxy Zoo 2 had produced over 100 million galaxy classifications leading to new understandings in galaxy evolution, the isotropy of the universe, galaxy mergers, and more.
The latest Galaxy Zoo science result shows that spiral galaxies which share a neighborhood (within a region 65 million light-years across) are likely to rotate in the same direction – but only if they formed the vast majority of their stars more than 10 billion years ago. The work is further confirmation that spectacular mergers between galaxies are the driving force behind more recent galactic evolution, disrupting the galaxies’ alignment while triggering star formation. Project lead Raul Jiminez (ICREA and the Institute of Space Sciences, Spain ) said, ‘It is very exciting to see this result from Galaxy Zoo – now it is time to go back to theory and simulations and understand better what it all means!’
An earlier Galaxy Zoo paper (Slosar et al.) provided support for the theory that spiral galaxies acquire their angular momentum from the large-scale structure from which they form. As nearby galaxies will have formed in the same environment, they would be expected to share – on average – a direction. Later interactions and mergers which are known to trigger star formation may also have randomized the spin directions of the participating galaxies, producing the correlation between star formation and spins seen in the latest paper. No physical parameter other than star formation history is correlated with the galaxies.
Mergers have long been believed to contribute to the observed evolution of galaxy populations; a head-on collision between two spirals, for example, will often produce ellipticals. This new result suggests that mergers are also an important influence on spiral galaxies themselves. In two companion papers, the Galaxy Zoo team examine the properties of the largest merger catalogue to date, consisting of 3000 systems selected from the almost one million galaxies in SDSS.
Other results from Galaxy Zoo have investigated the role of blue elliptical galaxies and red spirals in galaxy evolution and followed up unusual objects like Hanny’s Voorwerp. As project principal investigator Chris Lintott remarked, ‘With the Zoo 2 target of 40 million classifications in sight, participants in this IYA project will soon truly have made the Universe theirs to discover.
This work has been made possible by the more than 100,000 volunteers in the original Galaxy Zoo project. Their individual contributions are acknowledged at http://www.galaxyzoo.org/Volunteers.aspx
Galaxy Zoo is a proud part of the International Year of Astronomy. Learn more about Galaxy Zoo at http://www.galaxyzoo.org, and explore the International Year of Astronomy at http://www.astronomy2009.us and http://www.astronomy2009.org
Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/.
The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.
Contact:
Dr. Pamela L. Gay
pgay@siue.edu
Dr Chris Lintott
cjl@astro.ox.ac.uk
Prof Raul Jimenez
raul@ieec.uab.es
