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

¹ Department of Astronomy, Westlake University, Hangzhou, Zhejiang 310030, China
² Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China
³ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
⁴ Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, 1180 Wien, Austria
⁵ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, China

^⋆ Corresponding authors: jyp199333@163.com, lzhu@shao.ac.cn

Received: 3 May 2025
Accepted: 4 July 2025

Abstract

We developed an orbit-superposition method for edge-on barred galaxies and evaluated its capability to recover the bar pattern speed Ω_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 θ_T ≥ 85°) and various bar azimuthal angles φ_T. For mock data sets with side-on bars (φ_T ≥ 50°), the model-recovered pattern speeds Ω_p encompass the true pattern speeds Ω_T within the model uncertainties (1σ confidence levels, 68%) for 10 of 12 cases. The average model uncertainty within the 1σ confidence levels is equal to 10%. For mock data sets with end-on bars (φ_T ≤ 30°), the model uncertainties of Ω_p depend significantly on the bar azimuthal angles φ_T, with the uncertainties of cases with φ_T = 10° approaching ∼30%. However, by imposing a stricter constraint on the bar morphology (p_bar ≤ 0.50), the average uncertainties are reduced to 14%, and Ω_p still encompass Ω_T within the model uncertainties for three of four cases. For all the models that we create in this paper, the 2σ (95%) confidence levels of the model-recovered pattern speeds Ω_p always cover the true values Ω_T.