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Weighing the galactic disc using the Jeans equation: lessons from simulations

Candlish, G. N.; Smith, R.; Moni Bidin, C.; Gibson, B. K.

Authors

G. N. Candlish

R. Smith

C. Moni Bidin

Abstract

Using three-dimensional stellar kinematic data from simulated galaxies, we examine the efficacy of a Jeans equation analysis in reconstructing the total disk surface density, including the dark matter, at the ‘Solar’ radius. Our simulation data set includes galaxies formed in a cosmological context using state-of-the-art high-resolution cosmological zoom simulations, and other idealized models. The cosmologically formed galaxies have been demonstrated to lie on many of the observed scaling relations for late-type spirals, and thus offer an interesting surrogate for real galaxies with the obvious advantage that all the kinematical data are known perfectly. We show that the vertical velocity dispersion is typically the dominant kinematic quantity in the analysis, and that the traditional method of using only the vertical force is reasonably effective at low heights above the disk plane. At higher heights the inclusion of the radial force becomes increasingly important. We also show that the method is sensitive to uncertainties in the measured disk parameters, particularly the scalelengths of the assumed double exponential density distribution, and the scalelength of the radial velocity dispersion. In addition, we show that disk structure and low number statistics can lead to significant errors in the calculated surface densities. Finally, we examine the implications of our results for previous studies of this sort, suggesting that more accurate measurements of the scalelengths may help reconcile conflicting estimates of the local dark matter density in the literature.

Journal Article Type Article
Publication Date Mar 11, 2016
Journal Monthly notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press (OUP)
Peer Reviewed Peer Reviewed
Volume 456
Issue 4
Pages 3456-3474
DOI https://doi.org/10.1093/mnras/stv2792
Keywords Gravitation -- methods; Numerical -- galaxies; Kinematics and dynamics
Publisher URL http://mnras.oxfordjournals.org/content/456/4/3456
Copyright Statement © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society
Additional Information Copy of article first published in: Monthly notices of the Royal Astronomical Society, 2016, v.456, issue 4

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Copyright Statement
© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society



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