On the relevance of the Tremaine-Weinberg method applied to H-alpha velocity field.Pattern speeds determination in M100 (NGC 4321)

摘要

The relevance of the Tremaine-Weinberg (TW) method is tested to measure thebar, spiral and inner structure pattern speeds using a gaseous velocity field.The TW method is applied to various simulated barred galaxies in order todemonstrate its validity in seven different configurations, including starformation or/and dark matter halo. The reliability of the different physicalprocesses involved and of the various observational parameters are also tested.The simulations show that the TW method could be applied to the gaseousvelocity fields to get a good estimate of the bar pattern speed, under thecondition that regions of shocks are avoided and measurements are confined toregions where the gaseous bar is well formed. We successfully apply the TWmethod to the ha velocity field of the Virgo Cluster Galaxy M100 (NGC 4321)and derive pattern speeds of 55+/-5 km/s/kpc for the nuclear structure, 30+/-2km/s/kpc for the bar and 20+/-1 km/s/kpc for the spiral pattern, in fullagreement with published determinations using the same method or alternativeones.