Speaker
Description
According to observations and numerical simulations, the Milky Way could exhibit several spiral arm modes with multiple pattern speeds,
wherein the slower patterns are located at larger Galactocentric
distances. Our aim is to quantify the effects of the spiral arms on
the azimuthal variations of the chemical abundances for oxygen, iron
and for the first time for neutron-capture elements (europium and
barium) in the Galactic disc. We assume a model based on multiple
spiral arm modes with different pattern speeds.
We apply new analytical prescriptions for the spiral arms in a
2D Galactic disc chemical evolution model, exploring the possibility
that the spiral structure is formed by the overlap of chunks with
different pattern speeds and spatial extent. The predicted azimuthal
variations in abundance gradients are dependent on the considered
chemical element. Elements synthesised on short time scales (i.e.,
oxygen and europium in this study) exhibit larger abundance
fluctuations. In fact, for progenitors with short lifetimes, the
chemical elements restored into the ISM perfectly trace the star
formation perturbed by the passage of the spiral arms. The map of the
star formation rate predicted by our chemical evolution model with
multiple patterns of spiral arms presents arcs and arms compatible
with those revealed by multiple tracers (young upper main sequence
stars, Cepheids, and distribution of stars with low radial
actions). Finally, our model predictions are in good agreement with
the azimuthal variations that emerged from the analysis of Gaia DR3
GSP-Spec [M/H] abundance ratios, if at most recent times the pattern
speeds match the Galactic rotational curve at all radii.
