A Blueprint for the Milky Way's Stellar Populations. II. Improved Isochrone Calibration in the SDSS and Pan-STARRS Photometric Systems

Abstract

We improve the identification and isolation of individual stellar populations in the Galactic halo based on an updated set of empirically calibrated stellar isochrones in the Sloan Digital Sky Survey (SDSS) and Pan-STARRS 1 (PS1) photometric systems. Along the Galactic prime meridian ($l=0^{\circ }$ and $180^{\circ }$), where proper motions and parallaxes from Gaia DR2 can be used to compute rotational velocities of stars in the rest frame of the Milky Way, we use the observed double color-magnitude sequences of stars having large transverse motions, which are attributed to groups of stars in the metal-poor halo and the thick disk with halo-like kinematics, respectively. The Gaia sequences directly constrain color-magnitude relations of model colors, and help to improve our previous calibration using Galactic star clusters. Based on these updated sets of stellar isochrones, we confirm earlier results on the presence of distinct groups of stars in the metallicity versus rotational-velocity plane, and find that the distribution of the most metal-poor ([Fe/H] $<-2$) stars in our sample can be modeled using two separate groups on prograde and retrograde orbits, respectively. At $4$-$6$ kpc from the Galactic plane, we find approximately equal proportions of the Splashed Disk, and the metal-rich ($⟨[Fe/H]⟩\sim -1.6$) and metal-poor ($⟨[Fe/H]⟩\sim -2.5$) halos on prograde orbits. The Gaia-Sausage-Enceladus, the metal-weak thick disk, and the retrograde halo structure(s) ($⟨[Fe/H]⟩\sim -2.2$) constitute approximately $10\%$ of the rest of the stellar populations at these distances.

19 pages, 11 figures, 3 tables, accepted for publication in the Astrophysical Journal

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Cited by in corpus (11)

• Reconstructing the Last Major Merger of the Milky Way with the H3 Survey
• Reconstructing the Disrupted Dwarf Galaxy $Gaia$-Sausage/Enceladus Using its Stars and Globular Clusters
• Beyond spectroscopy. I. Metallicities, distances, and age estimates for over twenty million stars from SMSS DR2 and Gaia EDR3
• The Pristine survey -- XVI. The metallicity of 26 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3
• Stellar Loci V: Photometric Metallicities of 27 Million FGK Stars based on Gaia Early Data Release 3
• A Blueprint for the Milky Way's Stellar Populations. III. Spatial Distributions and Population Fractions of Local Halo Stars
• Candidate Members of the VMP/EMP Disk System of the Galaxy from the SkyMapper and SAGES Surveys
• Chemodynamical Analysis of Metal-rich High-eccentricity Stars in the Milky Way's Disk
• A Blueprint for the Milky Way's Stellar Populations. IV. A String of Pearls $-$ the Galactic Starburst Sequence
• A Blueprint for the Milky Way's Stellar Populations. V. 3D Local Dust Extinction
• Deciphering the Milky Way's star formation at cosmic noon with high proper-motion stars: A precursor to the merger-driven starburst