Volume 547, November 2012
|Number of page(s)||16|
|Section||Galactic structure, stellar clusters and populations|
|Published online||30 October 2012|
Properties of simulated Milky Way-mass galaxies in loose group and field environments ⋆
1 Jeremiah Horrocks Institute, University of Central Lancashire, Preston, PR1 2HE, UK
2 Department of Astronomy & Physics, Saint Mary’s University, Halifax, Nova Scotia, B3H 3C3, Canada
3 Monash Centre for Astrophysics, Monash University, 3800 Victoria, Australia
4 Université de Lyon, Université Lyon 1, Observatoire de Lyon, CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon, École Normale Supérieure de Lyon, 9 avenue Charles André, 69230 Saint-Genis Laval, France
5 Grupo de Astrofísica, Departamento de Fisica Teorica, Modulo C-15, Universidad Autónoma de Madrid, 28049 Cantoblanco, Spain
6 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
Received: 22 May 2012
Accepted: 27 September 2012
Aims. We test the validity of comparing simulated field disk galaxies with the empirical properties of systems situated within environments more comparable to loose groups, including the Milky Way’s Local Group.
Methods. Cosmological simulations of Milky Way-mass galaxies have been realised in two different environment samples: in the field and in loose groups environments with similar properties to the Local Group. Apart from the differing environments of the galaxies, the samples are kept as homogeneous as possible with equivalent ranges in last major merger time, halo mass and halo spin. Comparison of these two samples allow for systematic differences in the simulations to be identified. A kinematic decomposition is employed to objectively quantify the spheroid-to-disk ratio and to isolate the disk-star population. Metallicity gradients, disk scale lengths, colours, magnitudes and age-velocity dispersion relations are studied for each galaxy in the suite and the strength of the link between these and environment of the galaxies is studied.
Results. Metallicity gradients are consistent with observations of HII regions in spiral galaxies and, in agreement with observations, correlate with total galaxy mass. The bulge-to-disk ratio of the galaxies show that these galaxies are less spheroid dominated than many other simulated galaxies in literature with the majority of both samples being disk dominated. We find that secular evolution and mergers dominate the spread of morphologies and metallicity gradients with no visible differences between the two environment samples. In contrast with this consistency in the two samples there is tentative evidence for a systematic difference in the velocity dispersion-age relations of galaxies in the different environments. Loose group galaxies appear to have more discrete steps in their velocity dispersion-age relations, if this is true it suggests that impulsive heating is more efficient in the stars of galaxies in denser environment than in the field. We conclude that at the current resolution of cosmological galaxy simulations field environment galaxies are sufficiently similar to those in loose groups to be acceptable proxies for comparison with the Milky Way provided that a similar assembly history is considered.
Key words: Local Group / Galaxy: formation / galaxies: evolution / methods: numerical
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.