Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 380, Issue 4, Pages 1348-1368Publisher
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2007.12210.x
Keywords
galaxy : disc; galaxy : evolution; galaxy : kinematics and dynamics; solar neighbourhood; galaxy : stellar content
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Funding
- STFC [PP/E00105X/1, PP/E001068/1] Funding Source: UKRI
- Science and Technology Facilities Council [PP/E001068/1, PP/E00105X/1] Funding Source: researchfish
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The velocity dispersion of stars in the solar neighbourhood thin disc increases with time after star formation. Nordstrom et al. performed the most recent observations to constrain the age-velocity dispersion relation. They fitted the age-velocity dispersion relations of each Galactic cardinal direction space velocity component, U (towards the Galactic Centre), V (in the direction of Galactic rotation) and W (towards the North Galactic Pole), with power laws and interpreted these as evidence for continuous heating of the disc in all directions throughout its lifetime. We revisit these relations with their data and use the results of Famaey et al. to show that structure in the local velocity distribution function distorts the in-plane (U and V) velocity distributions away from Gaussian so that a dispersion is not an adequate parametrization of their functions. The age-sigma(W) relation can however be constrained because the sample is well phase-mixed vertically. We do not find any local signature of the stellar warp in the Galactic disc. Vertical disc heating does not saturate at an early stage. Our new result is that a power law is not required by the data: disc heating models that saturate after similar to 4.5 Gyr are equally consistent with observations.
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