期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 433, 期 3, 页码 1813-1825出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt806
关键词
Galaxy: halo; Galaxy: kinematics and dynamics; Galaxy: structure; galaxies: kinematics and dynamics
资金
- Science and Technology Facilities Council
- STFC [ST/G002479/1, PP/D001242/1, ST/J00149X/1, ST/K00106X/1, ST/J500641/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/J500641/1, PP/D001242/1, ST/K00106X/1, ST/J00149X/1, 1103595, ST/G002479/1] Funding Source: researchfish
Tidal streams do not, in general, delineate orbits. A stream-orbit misalignment is expected to lead to biases when using orbit-fitting to constrain models for the Galactic potential. In this first of two papers, we discuss the expected magnitude of the misalignment and the resulting dangers of using orbit-fitting algorithms to constrain the potential. We summarize data for known streams which should prove useful for constraining the Galactic potential, and compute their actions in a realistic Galactic potential. We go on to discuss the formation of tidal streams in angle-action space, and explain why, in general, streams do not delineate orbits. The magnitude of the stream-orbit misalignment is quantified for a logarithmic potential and a multicomponent Galactic potential. Specifically, we focus on the expected misalignment for the known streams. By introducing a two-parameter family of realistic Galactic potentials we demonstrate that assuming that these streams delineate orbits can lead to order one errors in the halo flattening and halo-to-disc force ratio at the Sun. We present a discussion of the dependence of these results on the progenitor mass and demonstrate that the misalignment is mass independent for the range of masses of observed streams. Hence, orbit-fitting does not yield better constraints on the potential if one uses narrower, lower mass streams.
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