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Constraints on Bars in the Local Universe from 5000 SDSS Galaxies

Published online by Cambridge University Press:  01 August 2006

Fabio D. Barazza
Affiliation:
Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Asutin, TX 78712-0259, USA email: [email protected]
Shardha Jogee
Affiliation:
Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Asutin, TX 78712-0259, USA email: [email protected]
Irina Marinova
Affiliation:
Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Asutin, TX 78712-0259, USA email: [email protected]
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Abstract

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We present the first study of bars in the local Universe, based on the Sloan Digitized Sky Survey (SDSS). The large sample of ~5000 local galaxies provides the largest study to date of local bars and minimizes the effect of cosmic variance. The sample galaxies have Mg ≤ −18.5 mag and cover the redshift range 0.01 ≤ z < 0.04. We use a color cut in the color-magnitude diagram and the Sérsic index n to identify disk galaxies. We characterize bars and disks using r-band images and the method of iterative ellipse fits and quantitative criteria developed in Jogee at al. (2004, ApJL, 615, L105). After excluding highly inclined (i>60°) systems our results are: (1) the optical (r-band) fraction of barred galaxies among local disk galaxies is 43% (Figure 1, left panel), which confirms the ubiquity of local bars, in agreement with other optical studies based on smaller samples (e.g. Eskridge et al 2000, AJ, 119, 536, Marinova & Jogee 2006, astro-ph/0608039); (2) the optical bar fraction rises for bluer galaxies, suggesting a relation between bars and star formation (Figure 1, middle panel); (3) preliminary analyzes suggest that the optical bar fraction increases steeply with the galaxy effective radius (reff, Figure 1, right panel); (4) the optical bar fraction at z ~ 0 is ~35% for bright disks (Mg ≤ −19.3 mag) and strong (bar ellipticity >0.4), large-scale (bar semi-major axis >1.5 kpc) bars, which is comparable to the value of ~30 ± 6% reported earlier (Jogee et al 2004) for similar disks and bars at z ~ 0.2 − 1.0.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2007