Characterizing Bars at Z ∼ 0 in the Osubsgs: Implications for the Evolution of Barred Galaxies

Critical insights on galaxy evolution stem from studying local and high redshift bars. We present results on bars at z ∼ 0, based on OSUBSGS B and H images of 180 spirals. (1) The deprojected bar fraction is 60% in H and 44% in B, confirming the ubiquity of local bars. The results before and after deprojection are almost identical, which is encouraging for high redshfit studies. (2) Most (∼ 71%) bars have moderate to high strengths or ellipticity (0.50 ≤ ebar ≤ 0.75), and only a small fraction (7%–10%) are very weak (0.25 ≤ ebar ≤ 0.40). There is no bimodality in the distribution of bar strengths. Both the bar fraction and bar strengths in H show no variation across RC3 Hubble types. Taken together, these results suggest that most bars in z ∼ 0 galaxies are relatively robust against the range in central mass concentrations, gas mass fractions, and other host galaxy properties present along the Hubble sequence. (3) RC3 bar types should be used with caution. A significant fraction of galaxies that are classified as unbarred in RC3 turn out to be barred, and RC3 bar classes ‘B’ and ‘AB’ have a significant overlap in bar strength. (4) Most (72% in B and 76% in H) bars have sizes below 5 kpc. Bar and disk sizes correlate and the ratio (abar/R25) lies primarily in the range 0.2 to 0.4. This suggests that the corotation resonance lies inside R25 and that the growths of bars and disks are intimately tied. (5) The fraction of bright disks (MV <-19.3) that host strong (ebar ≥ 0.4) large-scale bars in the B band at z ∼ 0 is 35 ± 6%. This is comparable to the value of ∼ 30 ± 6% reported earlier for similar systems at z ∼ 0.2–1.0 or lookback times of 3–8 Gyr, thereby ruling out cosmogonies where the bar fraction declines strongly