The Tully-Fisher relation of barred galaxies

Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory (NOAO). The NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation We present new data exploring the scaling relations, such as the Tully-Fisher relation (TFR), of bright barred and unbarred galaxies. A primary motivation for this study is to establish whether barredness correlates with, and is a consequence of, virial properties of galaxies. Various lines of evidence suggest that dark matter is dominant in disks of bright unbarred galaxies at 2.2 disk scale lengths, the point of peak rotation for a pure exponential disk. We test the hypothesis that the Tully-Fisher (TF) plane of barred high surface brightness galaxies is offset from the mean TFR of unbarred galaxies, as might be expected if barred galaxies are "maximal" in their inner parts. We use existing and new TF data to search for basic structural differences between barred and unbarred galaxies. Our new data consist of two-dimensional Ha velocity fields derived from SparsePak integral field spectroscopy and V- and I-band CCD images collected at the WIYN Observatory² for 14 strongly barred galaxies. Differences may exist between kinematic and photometric inclination angles of barred versus unbarred galaxies. These findings lead us to restrict our analysis to barred galaxies with i > 50°. We use WIYN/SparsePak (two-dimensional) velocity fields to show that long-slit (one-dimensional) spectra yield reliable circular speed measurements at or beyond 2.2 disk scale lengths, far from any influence of the bar. This enables us to consider line width measurements from extensive TF surveys that include barred and nonbarred disks and derive detailed scaling relation comparisons. We find that for a given luminosity, barred and unbarred galaxies have comparable structural and dynamical parameters, such as peak velocities, scale lengths, and colors. In particular, the location of a galaxy in the TF plane is independent of barredness. In a global dynamical sense, barred and unbarred galaxies behave similarly and are likely to have, on average, comparable fractions of luminous and dark matter at a given radius.