The Kinematically Measured Pattern Speeds of NGC 2523 and NGC 4245

Abstract

We have applied the Tremaine-Weinberg continuity equation method to derive the bar pattern speed in the SB(r)b galaxy NGC 2523 and the SB(r)0/a galaxy NGC 4245 using the Calcium Triplet absorption lines. These galaxies were selected because they have strong inner rings which can be used as independent tracers of the pattern speed. The pattern speed of NGC 2523 is 26.4 $\pm$ 6.1 km s$^{-1}$ kpc$^{-1}$, assuming an inclination of 49.7$^{\circ}$ and a distance of 51.0 Mpc. The pattern speed of NGC 4245 is 75.5 $\pm$ 31.3 km s$^{-1}$ kpc$^{-1}$, assuming an inclination of 35.4$^{\circ}$ and a distance of 12.6 Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC 4245 is 1.4 $\pm$ 0.3 and 1.1 $\pm$ 0.5, respectively. These values place the bright inner rings near and slightly inside the corotation radius, as predicted by barred galaxy theory. Within the uncertainties, both galaxies are found to have fast bars that likely indicate dark halos of low central concentration. The photometric properties, bar strengths, and disk stabilities of both galaxies are also discussed.Comment: Accepted for publication in The Astronomical Journal, 11 figures, 2 table

Bar pattern speeds in CALIFA galaxies

“…Stellar kinematics has been used to measure Ω b using the TW method for a large sample of early-type galaxies (e.g., Kent 1987;Merrifield & Kuijken 1995;Gerssen et al 1999;Debattista et al 2002;Aguerri et al 2003;Debattista & Williams 2004;Corsini et al 2007). In contrast, few pattern speeds have been determined through this method for late-type galaxies (e.g., Gerssen et al 2003;Treuthardt et al 2007). See also Corsini (2011) for a review of the bar pattern speed measurements using the TW method.…”

“…In contrast, Buta & Zhang (2009) find that there is no dependence of R on the morphological type. Before the present work, only the pattern speed of three late-type galaxies was obtained by the TW method (e.g., Gerssen et al 2003;Treuthardt et al 2007). These three galaxies turned out to be compatible with fast rotators.…”

Dynamical Simulations of NGC 2523 and NGC 4245

“…5 for NGC 2523 and 38. 1 for NGC 4245 (Treuthardt et al 2007). In Figures 3 and 4 (upper right), we plot the Lindblad precession frequency curves derived from the simulated circular-speed curves estimated from the K s -band images of the galaxies.…”

Barred Galaxies: an Observer’s Perspective

“…Another important parameter that has to be measured for larger samples is the bar pattern speed (see e.g. [43,77,91]). Models of bar formation and evolution make clear predictions on the behaviour of this parameter, which seems to be related to a number of other physical properties: the central concentration of the dark matter halo, the exchange of angular momentum between disc and halo, bar age, and even bar generation.…”