Recovering the pattern speeds of edge-on barred galaxies via an orbit-superposition method

Abstract

We developed an orbit-superposition method for edge-on barred galaxies and evaluated its capability to recover the bar pattern speed $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{p}}$. We selected three simulated galaxies (Au-18, Au-23, and Au-28) with known pattern speeds from the Auriga simulations and created MUSE-like mock data sets with edge-on views (inclination angles $\hat{I}{¸}_{\mathrm{T}}\ge 85^{\circ }$) and various bar azimuthal angles $\ddot{I}{†}_{\mathrm{T}}$. For mock data sets with side-on bars ($\ddot{I}{†}_{\mathrm{T}}\ge 50^{\circ }$), the model-recovered pattern speeds $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{p}}$ encompass the true pattern speeds $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{T}}$ within the model uncertainties ($1\ddot{I}ƒ$ confidence levels, $68\%$) for 10 of 12 cases. The average model uncertainty within the $1\ddot{I}ƒ$ confidence levels is equal to $10\%$. For mock data sets with end-on bars ($\ddot{I}{†}_{\mathrm{T}}\le 30^{\circ }$), the model uncertainties of $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{p}}$ depend significantly on the bar azimuthal angles $\ddot{I}{†}_{\mathrm{T}}$, with the uncertainties of cases with $\ddot{I}{†}_{\mathrm{T}}=10^{\circ }$ approaching $\sim 30\%$. However, by imposing a stricter constraint on the bar morphology ($p_{\mathrm{bar}}\le 0.50$), the average uncertainties are reduced to $14\%$ , and $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{p}}$ still encompass $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{T}}$ within the model uncertainties for three of four cases. For all the models that we create in this paper, the $2\ddot{I}ƒ$ ($95\%$) confidence levels of the model-recovered pattern speeds $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{p}}$ always cover the true values $\hat{\mathrm{I}}{\text{c◯}}_{\mathrm{T}}$.

19 pages, 15 figures