Journal Article

Model-based pattern speed estimates for 38 barred galaxies

P. Rautiainen, H. Salo and E. Laurikainen

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 388, issue 4, pages 1803-1818
Published in print August 2008 | ISSN: 0035-8711
Published online August 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13522.x
Model-based pattern speed estimates for 38 barred galaxies

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We have modelled 38 barred galaxies by using near-infrared and optical data from the Ohio State University Bright Spiral Galaxy Survey. We constructed the gravitational potentials of the galaxies from H-band photometry, assuming a constant mass-to-light ratio. The halo component we choose corresponds to the so-called universal rotation curve. In each case, we used the response of gaseous and stellar particle disc to rigidly rotating potential to determine the pattern speed.

We find that the pattern speed of the bar depends roughly on the morphological type. The average value of corotation resonance radius to bar radius, , increases from 1.15 ± 0.25 in types SB0/a–SBab to 1.44 ± 0.29 in SBb and 1.82 ± 0.63 in SBbc–SBc. Within the error estimates for the pattern speed and bar radius, all galaxies of type SBab or earlier have a fast bar , whereas the bars in later type galaxies include both fast and slow rotators. Of 16 later type galaxies with a nominal value of , there are five cases, where the fast-rotating bar is ruled out by the adopted error estimates.

We also study the correlation between the parameter and other galactic properties. The clearest correlation is with the bar size: the slowest bars are also the shortest bars when compared to the galaxy size. A weaker correlation is seen with bar strength in a sense that slow bars tend to be weaker. These correlations leave room for a possibility that the determined pattern speed in many galaxies corresponds to actually that of the spiral, which rotates more slowly than the bar. No clear correlation is seen with either the galaxy luminosity or the colour.

Keywords: galaxies: evolution; galaxies: fundamental parameters; galaxies: kinematics and dynamics; galaxies: structure

Journal Article.  9498 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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