Characterizing Bars atz∼ 0 in the Optical and NIR: Implications for the Evolution of Barred Disks with Redshift

Critical insights on galaxy evolution stem from the study of bars. With the advent of HST surveys that trace bars in the rest-frame optical out to z ~ 1, it is critical to provide a reference baseline for bars at z ~ 0 in the optical band. We present results on bars at z ~ 0 in the optical and NIR based on 180 spirals from OSUBSGS. (1) The deprojected bar fraction at z ~ 0 is ~60% ± 7% in the NIR and ~44% ± 7% in the optical. (2) The results before and after deprojection are similar, which is encouraging for high-redshift studies that forego deprojection. (3) Studies of bars at z ~ 0.2-1.0 (look-back time 3-8 Gyr) report an optical bar fraction of 30% ± 6%, after applying cutoffs in absolute magnitude ( M V < -19.3), bar size ( a bar ≥ 1.5 kpc), and bar ellipticity ( e bar ≥ 0.4). Applying these exact cutoffs to the OSUBSGS data yields a comparable optical bar fraction at z ~ 0 of ~34% ± 7%. This rules out scenarios in which the optical bar fraction in bright disks declines strongly with redshift. (4) Most (~70%) bars have moderate to high ellipticity. There is no bimodality in the distribution of e bar . The H -band bar fraction and e bar show no substantial variation across RC3 Hubble types Sa to Scd. (5) RC3 bar types should be used with caution. Many galaxies with RC3 types AB are unbarred, and RC3 bar classes B and AB have a significant overlap in e bar . (6) Most bars have sizes below 5 kpc. Bar and disk sizes correlate, and most bars have a bar / R 25 in the range ~0.1-0.5. This suggests that the growths of bars and disks are intimately tied.