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I/348 Orbital parameters in Milky-Way-like potentials (Mackereth+, 2018)
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Beginning of ReadMe :I/348 Orbital parameters in Milky-Way-like potentials (Mackereth+, 2018)
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Fast estimation of orbital parameters in Milky-Way-like potentials
Mackereth J.T., Bovy J.
<Publ. Astron. Soc. Pac. 130, k4501 (2018)>
=2018PASP..130k4501M
=2018yCat.1348....0M
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ADC_Keywords: Milky Way ; Populations, stellar ; Positional data ;
Space velocities ; Models
Keywords: galaxies: kinematics and dynamics - stars: kinematics and dynamics -
methods: data analysis - methods: numerical
Abstract:
Orbital parameters, such as eccentricity and maximum vertical
excursion, of stars in the Milky Way are an important tool for
understanding its dynamics and evolution, but calculation of such
parameters usually relies on computationally-expensive numerical orbit
integration. We present and test a fast method for estimating these
parameters using an application of the Sackel fudge, used previously
for the estimation of action-angle variables. We show that the method
is highly accurate, to a level of <1% in eccentricity, over a large
range of relevant orbits and in different Milky Way-like potentials,
and demonstrate its validity by estimating the eccentricity
distribution of the RAVE-TGAS data set and comparing it to that from
orbit integration. Using the method, the orbital characteristics of
the 7 million Gaia DR2 stars with radial velocity measurements are
computed with Monte Carlo sampled errors in 116 hours of parallelised
cpu time, at a speed that we estimate to be 3 to 4 orders of
magnitude faster than using numerical orbit integration. We
demonstrate using this catalogue that Gaia DR2 samples a large range
of orbits in the solar vicinity, down to those with r_peri_< 2.5kpc,
and out to r_ap_> 13kpc. We also show that many of the features
present in orbital parameter space have a low mean zmax, suggesting
that they likely result from disk dynamical effects.
Description:
We have demonstrated a new application of the Binney
(2012MNRAS.426.1324B) Staeckel fudge for the rapid calculation of the
orbit parameters r_peri_, r_ap_, z_max_, and e, which does not depend
on orbit integration.
Using the method, the orbital characteristics of the 7 million Gaia
DR2 stars with radial velocity measurements are computed with Monte
Carlo sampled errors in 116 hours of parallelised cpu time, at a
speed that we estimate to be 3 to 4 orders of magnitude faster than
using numerical orbit integration.