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Post Info TOPIC: Barred galaxies
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Title: The environment of barred galaxies revisited
Author: Bernardo Cervantes Sodi, Cheng Li, Changbom Park, Lixin Wang

We present a study of the environment of barred galaxies using galaxies drawn from the SDSS. We use several different statistics to quantify the environment: the projected two-point cross-correlation function, the background-subtracted number count of neighbor galaxies, the overdensity of the local environment, the membership of our galaxies to galaxy groups to segregate central and satellite systems, and for central galaxies we estimate the stellar to halo mass ratio (M*/Mh) . When we split our sample into early- and late-type galaxies, we see a weak but significant trend for early-type galaxies with a bar to be more strongly clustered on scales from a few 100 kpc to 1 Mpc when compared to unbarred early-type galaxies. This indicates that the presence of a bar in early-type galaxies depends on the location within their host dark matter halos. This is confirmed by the group catalogue in the sense that for early-types, the fraction of central galaxies is smaller if they have a bar. For late-type galaxies, we find fewer neighbours within ~50 kpc around the barred galaxies when compared to unbarred galaxies from the control sample, suggesting that tidal forces from close companions suppress the formation/growth of bars. For central late-type galaxies, bars are more common on galaxies with high M*/Mh values, as expected from early theoretical works which showed that systems with massive dark matter halos are more stable against bar instabilities. Finally, we find no obvious correlation between overdensity and the bars in our sample, showing that galactic bars are not obviously linked to the large-scale structure of the universe.

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Blobrana


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Title: Galaxy Zoo: CANDELS Barred Disks and Bar Fractions
Author: B. D. Simmons, Thomas Melvin, Chris Lintott, Karen L. Masters, Kyle W. Willett, William C. Keel, R. J. Smethurst, Edmond Cheung, Robert C. Nichol, Kevin Schawinski, Michael Rutkowski, Jeyhan S. Kartaltepe, Eric F. Bell, Kevin R. V. Casteels, Christopher J. Conselice, Omar Almaini, Henry C. Ferguson, Lucy Fortson, William Hartley, Dale Kocevski, Anton M. Koekemoer, Daniel H. McIntosh, Alice Mortlock, Jeffrey A. Newman, Jamie Ownsworth, Steven Bamford, Tomas Dahlen, Sandra M. Faber, Steven L. Finkelstein, Adriano Fontana, Audrey Galametz, N. A. Grogin, Ruth Grutzbauch, Yicheng Guo, Boris Haussler, Kian J. Jek, Sugata Kaviraj, Ray A. Lucas, Michael Peth, Mara Salvato, Tommy Wiklind, Stijn Wuyts

The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features in dynamically mature disks should be extremely rare. Here we report the discovery of strong barred structures in massive disk galaxies at z ~ 1.5 in deep rest-frame optical images from CANDELS. From within a sample of 876 disk galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a sub-sample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5< z < 2 (f_bar = 10.7 +6.3 -3.5% after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disk galaxies have evolved over the last 11 billion years.

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