ARGOS II: The Galactic Bulge Survey

TL;DR

The ARGOS II survey provides detailed spectroscopic data for 28,000 stars in the Milky Way's bulge and inner disk, aiming to understand the bulge's formation history through stellar parameters and kinematics.

Contribution

This paper introduces the ARGOS II survey, including its methodology, target selection, and data analysis techniques for studying the Galactic bulge.

Findings

Spectroscopic measurements of radial velocities and stellar parameters for 28,000 stars.

Identification of approximately 14,000 red giants within 3.5 kpc of the Galactic center.

Foundation for future analysis of the bulge's metallicity distribution and kinematics.

Abstract

We describe the motivation, field locations and stellar selection for the ARGOS spectroscopic survey of 28,000 stars in the bulge and inner disk of the Milky Way galaxy across latitudes of b = -5 deg to -10 deg. The primary goal of this survey is to constrain the formation processes of the bulge and establish whether it is predominantly a merger or instability remnant. From the spectra (R = 11,000), we have measured radial velocities and determined stellar parameters, including metallicities and [alpha/Fe] ratios. Distances were estimated from the derived stellar parameters and about 14,000 stars are red giants within 3.5 kpc of the Galactic centre. In this paper, we present the observations and analysis methods. Subsequent papers (III and IV) will discuss the stellar metallicity distribution and kinematics of the Galactic bulge and inner disk, and the implications for the formation of the bulge.