May 2013 3 Chris Lintott Brooke Simmons Kevin Schawinski Steven Bamford Karen Masters Lucy Fortson Ramin Skibba Kevin Casteels Sugata Kaviraj Bob Nichol Edd Edmondson Arfon Smith Jordan Raddick Rob Simpson and ...
May 2013 • Galaxy Zoo 2 is the largest ever catalog of fine morphological features, with 300,000 galaxies out to z = 0.25 • Crowdsourcing votes are reliable when compared with both expert and automated classifications • Catalog to be released at data.galaxyzoo.org and in SDSS DR10 • Early science from GZ2 includes studies of bars in disks, bulgeless AGN, and measuring the local interacting fraction 5
May 2013 GZ1 science: large-scale studies of galaxy populations 9 Schawinski, Urry et al. (2010) Bamford et al. (2009) Darg et al. (2010a,b) Land et al. (2008)
of a disk? Could this be a disk viewed edge-on? Is there a sign of a bar feature through the centre of the galaxy? Is there any sign of a spiral arm pattern? Is there anything odd? How many spiral arms are there? How prominent is the central bulge, compared to the rest of the galaxy? How tightly wound do the spiral arms appear? Does the galaxy have a bulge at its centre? If so, what shape? How rounded is it? Is the odd feature a ring, or is the galaxy disturbed or irregular?
May 2013 Using the catalog • “clean” samples of galaxies • very pure samples constructed by a combination of vote fraction thresholds for multiple classification tasks • raw likelihoods of galaxies • the (debiased) vote fractions can be potentially treated as probabilities, thus allowing use of the entire sample 19
May 2013 Bars and disk galaxies • first statistical studies of barred galaxies with > 103 galaxies • bar fraction clearly increases with redder colors and more prominent bulges • ALFALFA-GZ2 match shows lower bar fractions in HI gas- rich galaxies • redder and longer bars occur in redder disk galaxies • colors and strengths of bars and their disks agree fairly well with simulations 29 Masters et al. (2012) Hoyle et al. (2011)
May 2013 Morphology and galaxy interactions •Many of the GZ2 classes correlate strongly with projected separation in galaxy pairs •The “loose winding arms” class is the strongest indicator of a physically associated pair •GZ2 data constrains the true fraction of physically interacting companions per galaxy at (0.4 - 2)% 34 Casteels et al. (2013)
May 2013 Morphology and galaxy interactions •Many of the GZ2 classes correlate strongly with projected separation in galaxy pairs •The “loose winding arms” class is the strongest indicator of a physically associated pair •GZ2 data constrains the true fraction of physically interacting companions per galaxy at (0.4 - 2)% 34 Casteels et al. (2013)
May 2013 Morphology and galaxy interactions •Many of the GZ2 classes correlate strongly with projected separation in galaxy pairs •The “loose winding arms” class is the strongest indicator of a physically associated pair •GZ2 data constrains the true fraction of physically interacting companions per galaxy at (0.4 - 2)% 34 Casteels et al. (2013)
May 2013 Bars and AGN • bars are theoretically predicted to channel gas to galactic center and trigger AGN activity in disks • observations of barred AGN are historically inconclusive • Oh+2012, Alonso+2013 found that AGN strength is enhanced by presence of bar and increases with stellar mass • UMN grad student Melanie Galloway, is studying bar-AGN relationships with GZ2 data for her masters’ thesis 35
May 2013 40 • Galaxy Zoo 2 has 300,000+ classifications of galaxies with disks, bars, bulges, arms, and more • Averaging classifications from multiple volunteers reproduces expert results to a high degree of accuracy • Public data release out soon (data.galaxyzoo.org and in DR10) • GZ2 science: bars and gas disks, SMBH in bulgeless AGN, and constraints on local merger fraction