Towards a fully consistent Milky Way disk model V. The disk model for 4 $-$ 14 kpc

TL;DR

This paper extends the semi-analytic JJ model of the Milky Way disk to cover 4-14 kpc, incorporating new findings and providing a flexible tool for stellar population synthesis and disk evolution studies.

Contribution

It introduces a generalized JJ model applicable across a wide galactocentric range, with improved age-metallicity relation modeling and a public code for diverse stellar population analyses.

Findings

The model covers 4-14 kpc galactocentric distances.

It constrains the age-metallicity relation using APOGEE data.

Provides a flexible, publicly available tool for MW disk studies.

Abstract

We present a generalised version of the semi-analytic Just-Jahreiss (JJ) model of the Galactic disk that incorporates our findings for the solar neighbourhood and is applicable to a wide range of galactocentric distances, 4 kpc $\lesssim R \lesssim $ 14 kpc. The JJ model is a flexible tool for stellar population synthesis with a fine age resolution of 25 Myr. It includes six Milky-Way (MW) components: the four flattened (exponential thin and thick disk, atomic and molecular gas) and two spheroidal (spherical stellar halo and a cored isothermal dark matter sphere). The overall thin-disk thickness is assumed to be constant at all radii, though flaring can also be tested. The adopted radial variation in the thin-disk star-formation rate (SFR) reflects the inside-out disk growth scenario. We allow a smooth power-law SFR continuum to be modified by an arbitrary number of Gaussian peaks. We present a public code of the JJ model complemented by the three sets of isochrones (PARSEC, MIST, and BaSTI). Using metallicity distributions of the red clump giants from APOGEE, we constrain the radial variation of the JJ-model age-metallicity relation (AMR) and propose a new analytic form for the AMR function. The generalised JJ model is a publicly available tool for studying different stellar populations across the MW disk. With its fine age resolution and flexibility, it can be particularly useful for reconstructing the thin-disk SFR, as a variety of different SFR shapes can be constructed within its framework.