Mapping the inner stellar halo of the Milky Way from 2MASS and SDSS-III/APOGEE survey

TL;DR

This study combines infrared and spectroscopic survey data with galaxy modeling to map and analyze the shape, metallicity, and mass distribution of the Milky Way's inner stellar halo.

Contribution

It introduces a detailed comparison of synthetic and observed stellar populations, revealing a metal-poor extended halo component and improving the mass density model of the stellar halo.

Findings

Identification of an extended, metal-poor halo component with [M/H] < -1.2 dex.

Development of a more realistic mass density distribution model.

Reconstruction of the inner Galaxy's rotation curve.

Abstract

The Besan\c{c}on Galaxy model was used to compare the infrared colour distribution of synthetic stars with those from 2MASS observations taking the selection function of the data into account, in order to study the shape of the stellar halo of the Milky Way, with complemetary spectroscopic data from SDSS-III/APOGEE survey. Furthermore, we compared the generated mock metallicity distribution of the Besan\c{c}on Galaxy model, to the intrinsic metallicity distribution with reliable stellar parameters from the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP). The comparison was carried accross a large volume of the inner part of the Galaxy, revealing that a metal-poor population, [M/H]$<-1.2$ dex, could fill an extended component of the inner galactic halo. With this data set, we are able to model a more realistic mass density distribution of the stellar halo component of the Milky Way, assuming a six-parameters double power-law model, and reconstruct the behaviour of the rotation curve in the inner part of the Galaxy.