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The Disk-Halo Transition and the Search for Stellar Streams

Lagerholm, Carina LU (2010) In Lund Observatory Examensarbeten ASTM31 20101
Lund Observatory
Abstract
Recent work by Nissen and Schuster have found two distinct populations of halo stars with -1<5 alpha [Fe/H] -0<5. Both populations are kinematically selected to be halo stars. The differences between the two groups are the alpha -elemental abundances and the [Na/Fe] and [Ni/Fe] ratios. From angular
momentum space, we can see that the majority of these stars do not show any extreme kinematic indication that they would be part of a halo stellar stream. From the Hipparcos catalogue we have found roughly 50 stars with the same orbital characteristics. Out of these 31 stars have been observed with HARPS at La Silla in Chile and with FIES at the NOT on La Palma. Abundance analysis has been done on 23 stars. From these we can conclude that the... (More)
Recent work by Nissen and Schuster have found two distinct populations of halo stars with -1<5 alpha [Fe/H] -0<5. Both populations are kinematically selected to be halo stars. The differences between the two groups are the alpha -elemental abundances and the [Na/Fe] and [Ni/Fe] ratios. From angular
momentum space, we can see that the majority of these stars do not show any extreme kinematic indication that they would be part of a halo stellar stream. From the Hipparcos catalogue we have found roughly 50 stars with the same orbital characteristics. Out of these 31 stars have been observed with HARPS at La Silla in Chile and with FIES at the NOT on La Palma. Abundance analysis has been done on 23 stars. From these we can conclude that the two distinct populations of halo stars found by Nissen and Schuster are present in our sample of halo stars. We investigate the differences in these two populations, according to their orbital characteristics and abundances, both for our sample and the Nissen and Schuster sample. We found that the stars with higher alpha abundances have tendency to be more similar to the disk of the Milky Way than the stars with lower alpha abundances, seen in angular momentum space. These high alpha stars also show ULSR and WLSR similar to what is seen for the disk. From studying our sample of stars and stars found in the literature we find a total of 31 new potential stream stars which
have extreme kinematics similar to two known stellar streams. We will here present our results from the abundance analysis of these 23 halo stars and a kinematical study of new potential stream stars. (Less)
Please use this url to cite or link to this publication:
author
Lagerholm, Carina LU
supervisor
organization
course
ASTM31 20101
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
Lund Observatory Examensarbeten
report number
2010-EXA40
language
English
id
2255840
date added to LUP
2011-12-21 10:56:22
date last changed
2011-12-21 11:05:53
@misc{2255840,
  abstract     = {Recent work by Nissen and Schuster have found two distinct populations of halo stars with -1<5 alpha [Fe/H] -0<5. Both populations are kinematically selected to be halo stars. The differences between the two groups are the alpha -elemental abundances and the [Na/Fe] and [Ni/Fe] ratios. From angular
momentum space, we can see that the majority of these stars do not show any extreme kinematic indication that they would be part of a halo stellar stream. From the Hipparcos catalogue we have found roughly 50 stars with the same orbital characteristics. Out of these 31 stars have been observed with HARPS at La Silla in Chile and with FIES at the NOT on La Palma. Abundance analysis has been done on 23 stars. From these we can conclude that the two distinct populations of halo stars found by Nissen and Schuster are present in our sample of halo stars. We investigate the differences in these two populations, according to their orbital characteristics and abundances, both for our sample and the Nissen and Schuster sample. We found that the stars with higher alpha abundances have tendency to be more similar to the disk of the Milky Way than the stars with lower alpha abundances, seen in angular momentum space. These high alpha stars also show ULSR and WLSR similar to what is seen for the disk. From studying our sample of stars and stars found in the literature we find a total of 31 new potential stream stars which
have extreme kinematics similar to two known stellar streams. We will here present our results from the abundance analysis of these 23 halo stars and a kinematical study of new potential stream stars.},
  author       = {Lagerholm, Carina},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lund Observatory Examensarbeten},
  title        = {The Disk-Halo Transition and the Search for Stellar Streams},
  year         = {2010},
}