Constraints on the distribution of gas and young stars in the Galactic Centre in the context of interpreting gamma ray emission features

TL;DR

This paper reviews the distribution of gas and young stars near the Galactic Centre to improve models of gamma ray emission, highlighting asymmetries and recent star formation activity that influence interpretations of energetic outflows and excess emissions.

Contribution

It provides updated constraints on gas and star distributions in the Galactic Centre, emphasizing asymmetries and recent star formation rates for improved gamma ray emission modeling.

Findings

Gas and star distributions are highly asymmetric around the Galactic Centre.

Star formation is concentrated within ~100pc of the Galactic Centre.

Star formation rate has remained roughly constant at <0.1 Msun/yr over 5 Myr.

Abstract

Gamma ray observations have found evidence of an extremely energetic outflow emanating from the Galactic Centre, and an `excess' of emission at GeV energies towards the Galactic Centre over that expected from current models. Determining whether the outflow is AGN- or star formation-driven, and whether the `excess' is astrophysical in origin or requires new physics (e.g. self-annihilation of dark matter), requires the accurate modelling of the expected energy injection from astrophysical sources and the subsequent interaction with the surrounding environment. We briefly summarise current constraints on the distribution of gas and young stars in the inner few hundred parsec of the Galaxy that can be included in future 2D and 3D modelling of the astrophysical gamma ray emission. The key points to highlight with respect to predominantly axisymmetric models currently in use are: (i) the distribution of dense gas, young stars and interstellar radiation field is highly asymmetric around the Galactic Centre; (ii) star formation is almost exclusively constrained to a Galactocentric radius of ~100pc; (iii) the star formation rate in this region has been constant at <0.1Msun/yr to within a factor of 2 over the last ~5 Myr.