Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Pieces of the puzzle: ancient substructure in the Galactic disc

Helmi, A ; Navarro, JF ; Nordström, Birgitta LU ; Holmberg, Johan LU ; Abadi, MG and Steinmetz, M (2006) In Monthly Notices of the Royal Astronomical Society 365(4). p.1309-1323
Abstract
We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordstrom et al., containing accurate spatial and kinematic information as well as metallicities for 13 240 nearby stars. To optimize our strategy, we use numerical simulations and characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre (A) and pericentre (P), as well as their z-angular momentum (L-z). In the APL space, such stars are expected to cluster around regions of roughly constant eccentricity. The APL space for the Nordstrom catalogue exhibits a wealth of... (More)
We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordstrom et al., containing accurate spatial and kinematic information as well as metallicities for 13 240 nearby stars. To optimize our strategy, we use numerical simulations and characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre (A) and pericentre (P), as well as their z-angular momentum (L-z). In the APL space, such stars are expected to cluster around regions of roughly constant eccentricity. The APL space for the Nordstrom catalogue exhibits a wealth of substructure, much of which can be linked to dynamical perturbations induced by spiral arms and the Galactic bar. However, our analysis also reveals a statistically significant excess of stars on orbits of common ( moderate) eccentricity, analogous to the pattern expected for merger debris. Besides being dynamically peculiar, the 274 stars in these substructures have very distinct metallicity and age distributions, providing further evidence of their extragalactic provenance. It is possible to identify three coherent groups among these stars, that, in all likelihood, correspond to the remains of disrupted satellites. The most metal-rich group ([Fe/H] >= -0.45 dex) has 120 stars distributed into two stellar populations of similar to 8 Gyr (33 per cent) and similar to 12 Gyr (67 per cent) of age. The second group with <[Fe/H]> similar to -0.6 dex has 86 stars and shows evidence of three populations of 8 Gyr ( 15 per cent), 12 Gyr (36 per cent) and 16 Gyr (49 per cent) of age. Finally, the third group has 68 stars, with typical metallicity around -0.8 dex and a single age of similar to 14 Gyr. The identification of substantial amounts of debris in the Galactic disc whose origin can be traced back to more than one satellite galaxy, provides evidence of the hierarchical formation of the Milky Way. (Less)
Please use this url to cite or link to this publication:
author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy : kinematics and dynamics, solar neighbourhood, Galaxies : formation, Galaxies : evolution, Galaxy : evolution, Galaxy : disc
in
Monthly Notices of the Royal Astronomical Society
volume
365
issue
4
pages
1309 - 1323
publisher
Oxford University Press
external identifiers
  • wos:000234876600025
  • scopus:33645084239
ISSN
1365-2966
DOI
10.1111/j.1365-2966.2005.09818.x
language
English
LU publication?
yes
id
2ef60424-21d2-4d2b-859e-88a0180a1362 (old id 418083)
date added to LUP
2016-04-01 12:31:33
date last changed
2021-08-25 04:25:23
@article{2ef60424-21d2-4d2b-859e-88a0180a1362,
  abstract     = {We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordstrom et al., containing accurate spatial and kinematic information as well as metallicities for 13 240 nearby stars. To optimize our strategy, we use numerical simulations and characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre (A) and pericentre (P), as well as their z-angular momentum (L-z). In the APL space, such stars are expected to cluster around regions of roughly constant eccentricity. The APL space for the Nordstrom catalogue exhibits a wealth of substructure, much of which can be linked to dynamical perturbations induced by spiral arms and the Galactic bar. However, our analysis also reveals a statistically significant excess of stars on orbits of common ( moderate) eccentricity, analogous to the pattern expected for merger debris. Besides being dynamically peculiar, the 274 stars in these substructures have very distinct metallicity and age distributions, providing further evidence of their extragalactic provenance. It is possible to identify three coherent groups among these stars, that, in all likelihood, correspond to the remains of disrupted satellites. The most metal-rich group ([Fe/H] &gt;= -0.45 dex) has 120 stars distributed into two stellar populations of similar to 8 Gyr (33 per cent) and similar to 12 Gyr (67 per cent) of age. The second group with &lt;[Fe/H]&gt; similar to -0.6 dex has 86 stars and shows evidence of three populations of 8 Gyr ( 15 per cent), 12 Gyr (36 per cent) and 16 Gyr (49 per cent) of age. Finally, the third group has 68 stars, with typical metallicity around -0.8 dex and a single age of similar to 14 Gyr. The identification of substantial amounts of debris in the Galactic disc whose origin can be traced back to more than one satellite galaxy, provides evidence of the hierarchical formation of the Milky Way.},
  author       = {Helmi, A and Navarro, JF and Nordström, Birgitta and Holmberg, Johan and Abadi, MG and Steinmetz, M},
  issn         = {1365-2966},
  language     = {eng},
  number       = {4},
  pages        = {1309--1323},
  publisher    = {Oxford University Press},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Pieces of the puzzle: ancient substructure in the Galactic disc},
  url          = {http://dx.doi.org/10.1111/j.1365-2966.2005.09818.x},
  doi          = {10.1111/j.1365-2966.2005.09818.x},
  volume       = {365},
  year         = {2006},
}