# The Kinematically Measured Pattern Speeds of NGC 2523 and NGC 4245 - Astrophysics

Abstract: We have applied the Tremaine-Weinberg continuity equation method to derivethe bar pattern speed in the SBrb galaxy NGC 2523 and the SBr0-a galaxy NGC4245 using the Calcium Triplet absorption lines. These galaxies were selectedbecause they have strong inner rings which can be used as independent tracersof the pattern speed. The pattern speed of NGC 2523 is 26.4 $\pm$ 6.1 kms$^{-1}$ kpc$^{-1}$, assuming an inclination of 49.7$^{\circ}$ and a distanceof 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 12.6Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC4245 is 1.4 $\pm$ 0.3 and 1.1 $\pm$ 0.5, respectively. These values place thebright inner rings near and slightly inside the corotation radius, as predictedby barred galaxy theory. Within the uncertainties, both galaxies are found tohave fast bars that likely indicate dark halos of low central concentration.The photometric properties, bar strengths, and disk stabilities of bothgalaxies are also discussed.

Author: P. Treuthardt, R. Buta, H. Salo, E. Laurikainen

Source: https://arxiv.org/