Search for Galactic warp signal in Gaia DR1 proper motions

TL;DR

This study investigates the Galactic warp using Gaia DR1 proper motions, finding that simple models of a long-lived warp do not explain the observed kinematic trends, prompting exploration of alternative scenarios.

Contribution

The paper presents the first analysis of Gaia DR1 proper motions to detect the Galactic warp's kinematic signature, challenging simple warp models.

Findings

Kinematic trends inconsistent with a simple long-lived warp model

Analysis of OB stars reveals complex warp behavior

Ongoing work to expand the stellar sample for better understanding

Abstract

The nature and origin of the Galactic warp represent one of the open questions posed by Galactic evolution. Thanks to Gaia high precision absolute astrometry, steps towards the understanding of the warp's dynamical nature can be made. Indeed, proper motions for long-lived stable warp are expected to show measurable trends in the component vertical to the galactic plane. Within this context, we search for the kinematic warp signal in the first Gaia data release (DR1). By analyzing distant spectroscopically-identified OB stars in the Hipparcos subset in Gaia DR1, we find that the kinematic trends cannot be explained by a simple model of a long-lived warp. We therefore discuss possible scenarios for the interpretation of the obtained results. We also present current work in progress to select a larger sample of OB star candidates from the Tycho-Gaia Astrometric Solution (TGAS) subsample in DR1, and delineate the points that we will be addressing in the near future.