Volume 646, February 2021
|Number of page(s)||4|
|Section||Letters to the Editor|
|Published online||17 February 2021|
Letter to the Editor
A cautionary tale in fitting galaxy rotation curves with Bayesian techniques
Does Newton’s constant vary from galaxy to galaxy?
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106, USA
e-mail: PengfeiLi0606@gmail.com; email@example.com
2 School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
3 Department of Physics, University of Oregon, Eugene, OR 97403, USA
4 Department of Physics and Astronomy, Sejong University, 209 Neungdong-ro Gwangjin-gu, Seoul 05006, Republic of Korea
Accepted: 27 January 2021
The application of Bayesian techniques to astronomical data is generally non-trivial because the fitting parameters can be strongly degenerated and the formal uncertainties are themselves uncertain. An example is provided by the contradictory claims over the presence or absence of a universal acceleration scale (g†) in galaxies based on Bayesian fits to rotation curves. To illustrate this we present an analysis in which the Newtonian gravitational constant GN is allowed to vary from galaxy to galaxy when fitting rotation curves from the SPARC database, in analogy to g† in the recently debated Bayesian analyses. When imposing flat priors on GN, we obtain a wide distribution of GN which, taken at face value, would rule out GN as a universal constant with high statistical confidence. However, imposing an empirically motivated log-normal prior returns a virtually constant GN with no sacrifice in fit quality. This implies that the inference of a variable GN (or g†) is the result of the combined effect of parameter degeneracies and unavoidable uncertainties in the error model. When these effects are taken into account, the SPARC data are consistent with a constant GN (and constant g†).
Key words: galaxies: dwarf / galaxies: spiral / galaxies: irregular / galaxies: kinematics and dynamics / dark matter
© ESO 2021
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.