BAR PATTERN SPEEDS IN CALIFA GALAXIES ULTRAFAST BARS OR TOO LONG BARS? ABSTRACT More than 10% of barred galaxies with a direct measurement of the bar pattern speed host an ultrafast bar. These bars challenge our understanding of the orbital structure of barred galaxies. We analyse the ultrafast bars detected in CALIFA and revise previous analysis. We found that nearly all the sample galaxies are spirals with an inner ring or pseudo-ring and/or strong spiral arms, which falsed previous measurements of bar radius: ultrafast bars are no longer observed when the correct measurement of the bar radius is adopted. V. Cuomo1, Y.H. Lee2, C. Buttitta3, J. A. L. Aguerri4,5, E.M. Corsini3,6, L. Morelli1 1Universidad de Atacama (Chile), 2Korea Astronomy and Space Science Institute (Korea), 3Università di Padova (Italy), 4Istituto de Astrofìsica de Canarias (Spain), 5Universidad de La Laguna (Spain), 6INAF-Osservatorio di Padova (Italy) INTRODUCTION During the evolution of barred galaxies, the rotation of the bar rules the redistribution of mass and angular momentum in the disc. The bar is slowed through the exchange of angular momentum: studing the bar pattern speed Ωbar becomes desiderable (Athanassoula 2003, MNRAS, 341, 1179). The bar rotation rate R=Rcr/Rbar= (Vcirc/Ωbar)/Rbar parametrises Ωbar. This is the ratio between the bar corotation Rcr and bar Rbar radii and allows to distinguish fast (1 ≤ R ≤ 1.4) from slow bars (R > 1.4, Athanassoula 1992, MNRAS, 259, 328). If R < 1 the bars are termed ultrafast (Buta & Zhang 2009, ApJS, 182, 559) but they are unstable (Contopoulos, 1981, A&A, 102, 265). The Tremaine-Weinberg method (TW, Tremaine & Weinberg 1984, ApJ, 282, L5) allows to get Ωbar. It consists in directly measuring the mean velocity and position of a tracer satisying the continuity equation, along slits parallel to the disc major axis. More than 100 galaxies have been analysed with the TW method (Cuomo et al. 2020, A&A, 641, A111): 10% of them hosts ultrafast bars. It is unclear ∼ whether they are the consequence of an erroneous measure or a new class of bars. SAMPLE: ANALYSIS AND MORPHOLOGY We considered the 31 barred galaxies from CALIFA studied with the TW method (Aguerri et al. 2015, A&A, 576, A102; Cuomo et al. 2019A&A, 632, A51): 12 of them host an ultrafast bar. We revised their morphology: most of them hosts an inner ring or pseudo-ring and/or strong spiral arms. These structures make the application of the TW method more difficult. Nevertheless, its applicability to spiral galaxies was demonstrated by both theoretical (Zou et al. 2019, ApJ, 884, 23) and observational studies involving integral-field data (Garma-Oehmichen et al. 2020, MNRAS, 491, 3655). We verified that the TW method was correcty applied to our sample galaxies. Fig. 1 (a): i-band SDSS image of NGC5406. (b): Deprojected image of the galaxy. The red and blue crosses show the peaks from QT(RQb) and QT (Rmean) azimuthal profiles. (c): Ratio map QT(r, φ). The vertical lines indicate the location of RQb (blue) and Rmean (red). (d): Radial profile of <QT>. (e): Azimuthal profile of QT (RQb) and local maxima (asterisks). (f ): Same as (e) but for QT(Rmean). Fig. 2 Comparison between Rmean and RQb. (RE)MEASURING THE BAR RADIUS The values of Rbar used to get R, Rmean, is the mean result of various photometric methods (Guo et al. 2019, MNRAS, 482, 1733). To test the reliability of Rmean, we built the map tracing the transverse-to-radial force ratio QT(r, φ) of the galaxy, following Lee et al. (2020, ApJ, 899, 84). This requires the calculation of the gravitational potential of the galaxy. In turn, it provides an independent estimate of Rbar, RQb, and allows to test whether Rmean matches the bar region. The ratio map QT(r, φ) of a barred galaxy presents four thick slabs and the corresponding peaks mark the four corners of the bar. The location of a peak or a plateau in the radial profile <QT> provides RQb. At this radius, four peaks appear in the azimuthal profile Q