Model-based pattern speed estimates for 38 barred galaxies

Abstract

We have modelled 38 barred galaxies by using near-IR 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 constant mass-to-light ratio. The halo component we chose 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, $\mathcal{R}$, increases from $1.15 \pm 0.25$ in types SB0/a -- SBab to $1.44 \pm 0.29$ in SBb and $1.82\pm 0.63$ 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 ($\mathcal{R} \le 1.4$), whereas the bars in later type galaxies include both fast and slow rotators. Of 16 later type galaxies with a nominal value of $\mathcal{R} > 1.4$, 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 $\mathcal{R}$ 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 actually that of the spiral, which rotates more slowly than the bar. No clear correlation is seen with either the galaxy luminosity or colour.Comment: 18 pages, 13 figures, accepted for publication in MNRA

Kinematic Clues to Bar Evolution for Galaxies in the Local Universe: Why the Fastest Rotating Bars are Rotating Most Slowly

“…Contopoulos (1980) studied how a galaxy responds to the barred perturbations of density, and he concluded that the bar corotation should be found close to the end of the bar, and in principle, the value of the rotational parameter should be quite close to but larger than 1. This general conclusion has since been supported in diverse publications, both theoretical and observational (Athanassoula 1992;Valenzuela & Klypin 2003;Rautiainen et al 2008;Buta & Zhang 2009;Font et al 2014a;Aguerri et al 2015). As described in a former section, we give the two limits for the bar length, consequently, we calculate the two limits for the  parameter, the values of this parameter appearing in Table 2, Column 7, are the calculated as the mean of the two limits.…”

“…For a review of these used until 2008 we refer to Rautiainen et al (2008). Here we list some of the most representative methods, some of which measure the pattern speed of the bar, while others determine the corotation radius directly or indirectly.…”

“…They are (i) the well-known Tremaine-Winberg method (Tremaine & Weinberg 1984); its later modification to include multiple density wave patterns (Meidt et al 2008a(Meidt et al , 2008b combines photometric data with velocities derived from long-slit spectra placed parallel to the galaxy major axis (Kent 1987;Merrifield & Kruijken 1995;Gerssen et al 1999;Debattista et al 2002;Aguerri et al 2003;Corsini et al 2003;Debattista & Williams 2004;Rand & Wallin 2004;Zimmer et al 2004;Hernandez et al 2005;Fathi et al 2009;Corsini 2011, and references therein, Aguerri et al 2015). (ii) the gravitational potential distribution to reproduce the velocity map (Sanders & Tubbs 1980;England et al 1990;Garcia-Burillo et al 1993;Piñol-Ferrer et al 2014); (iii) the morphologies of the non-circular velocity map of the gas in the galaxy can be used (Canzian 1993;Rand 1995;Sempere et al 1995;Canzian & Allen 1997;Font et al 2011Font et al , 2014aFont et al , 2014b; (iv) finally, numerical simulations of barred galaxies are another method (Lindblad et al 1996;Laine & Heller 1999;Aguerri et al 2001;Weiner et al 2001;Pérez et al 2004;Rautiainen et al 2005Rautiainen et al , 2008Treuthardt et al 2008).…”

On the morphology of dust lanes in galactic bars

“…Bars with RCR/R bar > 3.0 are very rare in nature. Only one is found in the compilation made by Rautiainen et al (2008), with R = 3.43 ± 0.95, and even in that case the error may still place the value below the limit of 3.0. For this reason, we have discarded those simulations in which corotation radius is more than three times the bar radius.…”

Dynamics of Disks and Warps

“…Associating a ring in a barred galaxy with the location of a major resonance with the bar (Buta & Combes 1996) yields, with kinematic information, an estimate of the pattern speed. Rautiainen et al (2008) computed models of the stellar and gas (sticky particles) responses to forcing by photometric models of 38 barred galaxies, in which they assumed that the entire non-axisymmetric structure rotated at the same pattern speed. They attempted to match the model to the visual morphology of the galaxy, and found a range of values for R. However, in most cases where R ≫ 1, the fit is dominated by the outer spiral, which may have a lower angular speed than does the bar.…”