A slow bar in the lenticular barred galaxy NGC 4277

Abstract

Aims: We characterised the properties of the bar hosted in lenticular galaxy NGC 4277, which is located behind the Virgo cluster. Methods: We measured the bar length and strength from the surface photometry obtained from the broad-band imaging of the Sloan Digital Sky Survey and we derived the bar pattern speed from the stellar kinematics obtained from the integral-field spectroscopy performed with the Multi Unit Spectroscopic Explorer at the Very Large Telescope. We also estimated the co-rotation radius from the circular velocity, which we constrained by correcting the stellar streaming motions for asymmetric drift, and we finally derived the bar rotation rate. Results: We found that NGC 4277 hosts a short ($R_{bar}=3.2_{-0.6}^{+0.9}$ kpc), weak ($S_{bar}=0.21\pm 0.02$), and slow ($R=1.8_{-0.3}^{+0.5}$) bar and its pattern speed ($\hat{I}{\text{c◯}}_{bar}=24.7\pm 3.4$ km s${}^{-1}$ kpc${}^{-1}$) is amongst the best-constrained ones ever obtained with the Tremaine-Weinberg (TW) method with relative statistical errors of $\sim 0.2$. Conclusions: NGC 4277 is the first clear-cut case of a galaxy hosting a slow stellar bar ($R>1.4$ at more than a 1$\ddot{I}ƒ$ confidence level) measured with the model-independent TW method. A possible interaction with the neighbour galaxy NGC 4273 could have triggered the formation of such a slow bar and/or the bar could be slowed down due to the dynamical friction with a significant amount of dark matter within the bar region.

Accepted for publication on A&A, 10 pages