2014/05/31 by Marie Martig, Ivan Minchev, Chris Flynn · 1 citation
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Demography #Galaxies: Formation, Evolution, Phenomena #Galaxy #Physics #Population #Redshift #Star formation #Stars #Stellar population #Stellar, planetary, and galactic studies #Velocity dispersion #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stu1322
published as MNRAS 2014 443 (1): 2452-2462 · 12 pages, 10 figures. Accepted for publication in MNRAS
arxiv created 2014/07/03 · openalex publication_date 2014/07/31 · arxiv updated 2014/08/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the relation between stellar ages and vertical velocity dispersion (the age–velocity relation, or AVR) in a sample of seven simulated disc galaxies. In our simulations, the shape of the AVR for stars younger than 9 Gyr depends strongly on the merger history at low redshift, with even 1:10–1:15 mergers being able to create jumps in the AVR (although these jumps might not be detectable if the errors on stellar ages are of the order of 30 per cent). For galaxies with a quiescent history at low redshift, we find that the vertical velocity dispersion rises smoothly for ages up to 8–9 Gyr, following a power law with a slope of ∼0.5, similar to what is observed in the solar neighbourhood by the Geneva-Copenhagen Survey. For these galaxies, we show that the slope of the AVR is not imprinted at birth, but is the result of subsequent heating. By contrast, in all our simulations, the oldest stars form a significantly different population, with a high velocity dispersion. These stars are usually born kinematically hot in a turbulent phase of intense mergers at high redshift, and also include some stars accreted from satellites. This maximum in σz is strongly decreased when age errors are included, suggesting that observations can easily miss such a jump with the current accuracy of age measurements.