Chemical Properties and Sagittarius-induced Dynamical Perturbations of the GD-1 Stream

TL;DR

This paper studies the GD-1 stellar stream's chemical properties and how the Sagittarius dwarf galaxy's gravitational effects influence its structure and dynamics, combining observational data and simulations.

Contribution

It provides new insights into the chemical composition of GD-1 and demonstrates Sagittarius's significant dynamical impact on the stream's morphology and kinematics.

Findings

No clear $ ext{α}$-knee in [Mg/Fe]-[Fe/H] plane.

Sagittarius influences the stream's $ ext{φ}_2$ distribution and induces asymmetries.

Trailing and leading arms show different spatial distributions, consistent with Sgr perturbations.

Abstract

In this study, we investigate the chemical properties of the GD-1 stream using cross-matched, data-driven elemental abundances. The results reveal no clear $\alpha$-knee in the [Mg/Fe]-[Fe/H] plane, and strong abundance consistency between the thin stream and cocoon, supporting a common origin. The absence of multiple-population signatures (e.g., C-N anti-correlation) suggests a low-mass progenitor. Using a test-particle simulation with the particle spray method and including perturbations from the Sagittarius (Sgr) dwarf galaxy, it shows that Sgr does not significantly heat the stream to form the cocoon, but modifies the intrinsic $\phi_2$ distribution, in agreement with observations. The trailing arm narrowly distributed across the width of the stream, while the leading arm is more diffuse, indicating that major fraction of cocoon stars are present towards the leading arm. Sgr also drags more stream particles moving toward the Galactic center, producing an excess at $V_{\text{GSR}}<0$, consistent with data. Our study confirms the Sgr has a non-negligible dynamical influence on the GD-1 stream. Other heating mechanisms (e.g., dark matter sub-halo encounters and pre-stripping process inside the parent halo) remain to be considered, and higher-resolution spectroscopy is needed to further constrain chemical abundances.