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A comparison of two approaches for estimating local stellar kinematics: The Projection Method versus Maximum Likelihodd

Aghajani, Toktam LU (2011) In Lund Observatory Examensarbeten ASTM31 20102
Lund Observatory
Department of Astronomy and Theoretical Physics
Abstract
We test a new approach to calculate the mean velocity and velocity dispersion for a sample of nearby stars when their radial velocities are not available. The most commonly used method (here called the projection method, PM) was introduced in a paper by Dehnen & Binney (1998). That method is here compared, theoretically and numerically, with an application of the Maximum Likelihood (ML) method. The two methods are tested on synthetically generated samples as well as on real samples from the Hipparcos Catalogue. In general it turns out that ML is not significantly more accurate than PM, except that ML allows to take into account observational errors and therefore gives more correct dispersions when the uncertainty in the proper motions is... (More)
We test a new approach to calculate the mean velocity and velocity dispersion for a sample of nearby stars when their radial velocities are not available. The most commonly used method (here called the projection method, PM) was introduced in a paper by Dehnen & Binney (1998). That method is here compared, theoretically and numerically, with an application of the Maximum Likelihood (ML) method. The two methods are tested on synthetically generated samples as well as on real samples from the Hipparcos Catalogue. In general it turns out that ML is not significantly more accurate than PM, except that ML allows to take into account observational errors and therefore gives more correct dispersions when the uncertainty in the proper motions is significant. Applying PM and ML to samples from the Geneva-Copenhagen survey (Nordström et al. 2004), we find that both methods give very similar results as when the published three-dimensional velocities are used. (Less)
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author
Aghajani, Toktam LU
supervisor
organization
course
ASTM31 20102
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
Lund Observatory Examensarbeten
report number
2011-EXA51
language
English
id
3513127
date added to LUP
2013-02-19 17:06:43
date last changed
2013-02-19 17:06:43
@misc{3513127,
  abstract     = {We test a new approach to calculate the mean velocity and velocity dispersion for a sample of nearby stars when their radial velocities are not available. The most commonly used method (here called the projection method, PM) was introduced in a paper by Dehnen & Binney (1998). That method is here compared, theoretically and numerically, with an application of the Maximum Likelihood (ML) method. The two methods are tested on synthetically generated samples as well as on real samples from the Hipparcos Catalogue. In general it turns out that ML is not significantly more accurate than PM, except that ML allows to take into account observational errors and therefore gives more correct dispersions when the uncertainty in the proper motions is significant. Applying PM and ML to samples from the Geneva-Copenhagen survey (Nordström et al. 2004), we find that both methods give very similar results as when the published three-dimensional velocities are used.},
  author       = {Aghajani, Toktam},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lund Observatory Examensarbeten},
  title        = {A comparison of two approaches for estimating local stellar kinematics: The Projection Method versus Maximum Likelihodd},
  year         = {2011},
}