A comparison of two approaches for estimating local stellar kinematics: The Projection Method versus Maximum Likelihodd
(2011) In Lund Observatory Examensarbeten ASTM31 20102Lund 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 GenevaCopenhagen survey (Nordström et al. 2004), we find that both methods give very similar results as when the published threedimensional velocities are used. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/studentpapers/record/3513127
 author
 Aghajani, Toktam ^{LU}
 supervisor

 Lennart Lindegren ^{LU}
 organization
 course
 ASTM31 20102
 year
 2011
 type
 H2  Master's Degree (Two Years)
 subject
 publication/series
 Lund Observatory Examensarbeten
 report number
 2011EXA51
 language
 English
 id
 3513127
 date added to LUP
 20130219 17:06:43
 date last changed
 20130219 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 GenevaCopenhagen survey (Nordström et al. 2004), we find that both methods give very similar results as when the published threedimensional 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}, }