The incidence of bar-like kinematic flows in CALIFA galaxies

Abstract

We carry out a direct search for bar-like non-circular flows in intermediate-inclination, gasrich disc galaxies with a range of morphological types and photometric bar classifications from the first data release (DR1) of the Calar Alto Legacy Integral Field Spectroscopy Area (CALIFA) survey. We use the DISKFIT algorithm to apply rotation only and bisymmetric flow models to H α velocity fields for 49/100 CALIFA DR1 systems that meet our selection criteria. We find satisfactory fits for a final sample of 37 systems. DISKFIT is sensitive to the radial or tangential components of a bar-like flow with amplitudes greater than 15 km s-1 across at least two independent radial bins in the fit, or ~2.25 kpc at the characteristic final sample distance of ~75 Mpc. The velocity fields of 25/37 (67.6+6.6-8.5 per cent) galaxies are best characterized by pure rotation, although only 17/25 (68.0+7.7-10.4 per cent) of them have sufficient H α emission near the galaxy centre to afford a search for non-circular flows. We detect non-circular flows in the remaining 12/37 (32.4+8.5-6.6 per cent) galaxies. We conclude that the non-circular flows detected in 11/12 (91.7+2.8-14.9 per cent) systems stem from bars. Galaxies with intermediate (AB) bars are largely undetected, and our detection thresholds therefore represent upper limits to the amplitude of the non-circular flows therein. We find 2/23 (8.7+9.6-2.9 per cent) galaxies that show non-circular motions consistent with a bar-like flow, yet no photometric bar is evident. This suggests that in ~10 per cent of galaxies either the existence of a bar may be missed completely in photometry or other processes may drive bar-like flows and thus secular galaxy evolution.