Metallicity Gradients of Thick Disk Dwarf Stars

Abstract

We examine the metallicity distribution of the Galactic thick disk using F, G, and K dwarf stars selected from the Sloan Digital Sky Survey, Data Release 8. Using the large sample of dwarf stars with proper motions and spectroscopically determined stellar parameters, metallicity gradients in the radial direction for various heights above the Galactic plane and in the vertical direction for various radial distances from the Galaxy center have been found. In particular, we find a vertical metallicity gradient of -0.113 +/- 0.010 (-0.125 +/- 0.008) dex/kpc using an isochrone (photometric) distance determination in the range 1 < |Z| < 3 kpc, which is the vertical height range most consistent with the thick disk of our Galaxy. In the radial direction, we find metallicity gradients between +0.02 and +0.03 dex/kpc for bins in the vertical direction between 1 < |Z| < 3 kpc. Both of these results agree with similar values determined from other populations of stars, but this is the first time a radial metallicity gradient for the thick disk has been found at these vertical heights. We are also able to separate thin and thick disk stars based on kinematic and spatial probabilities in the vertical height range where there is significant overlap of these two populations. This should aid further studies of the metallicity gradients of the disk for vertical heights lower than those studied here but above the solar neighborhood. Metallicity gradients in the thin and thick disks are important probes into possible formation scenarios for our Galaxy and a consistent picture is beginning to emerge from results using large spectroscopic surveys, such as the ones presented here.

8 figures, 5 tables, accepted to AJ

References in corpus (21)

• Local Kinematics and the Local Standard of Rest
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• The Radial Velocity Experiment (RAVE): first data release
• Kinematics of Metal-Poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Non-Kinematically Selected Stars
• Simulations of Galaxy Formation in a Lambda CDM Universe II: The Fine Structure of Simulated Galactic Disks
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• The spatial structure of mono-abundance sub-populations of the Milky Way disk
• A Spectroscopic Study of the Ancient Milky Way: F- and G-Type Stars in the Third Data Release of the Sloan Digital Sky Survey
• The Emergence of the Thick Disk in a CDM Universe
• Origin and structure of the Galactic disc(s)
• Theoretical isochrones in several photometric systems II. The Sloan Digital Sky Survey ugriz system
• Vertical distribution of Galactic disk stars I - Kinematics and metallicity
• Metallicity Gradients in the Milky Way Disk as Observed by the SEGUE Survey
• A spectroscopic survey of thick disc stars outside the solar neighbourhood
• Observational Properties of the Metal-Poor Thick Disk of the Milky Way Galaxy and Insights into Its Origins
• Distance determination for RAVE stars using stellar models II: Most likely values assuming a standard stellar evolution scenario
• The Metallicity Distribution Functions of SEGUE G and K dwarfs: Constraints for Disk Chemical Evolution and Formation
• Local stellar kinematics from RAVE data: II. Radial Metallicity Gradient
• The Metallicity Gradient of the Thick Disk Based on Red Horizontal Branch Stars From SDSS DR8

Cited by in corpus (28)

• Chemodynamics of the Milky Way. I. The first year of APOGEE data
• Chemical Cartography with APOGEE: Large-scale Mean Metallicity Maps of the Milky Way
• The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy
• Population Studies. XIII. A New Analysis of the Bidelman-MacConnell "Weak-Metal" Stars - Confirmation of Metal-Poor Stars in the Thick Disk of the Galaxy
• Chemical gradients in the Milky Way from the RAVE data. I. Dwarf stars
• A Tale of Two Disks: Mapping the Milky Way with the Final Data Release of APOGEE
• Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
• 3-D gas-phase elemental abundances across the formation histories of Milky Way-mass galaxies in the FIRE simulations: initial conditions for chemical tagging
• Impacts of a Flaring Star-forming Disc and Stellar Radial Mixing on the Vertical Metallicity Gradient
• Chemical and Kinematic Properties of the Galactic Disk from the LAMOST and Gaia Sample Stars
• Origin of the Metallicity Distribution in the Thick Disc
• The Vertical Metallicity Gradient of the Milky Way Disk: Transitions in [a/Fe] Populations
• Milky Way's Thick and Thin disk: Is there distinct thick disk?
• Through thick and thin: Structure of the Galactic thick disc from extragalactic surveys
• On local dark matter density
• Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way
• Properties of thick discs formed in clumpy galaxies
• Local Stellar Kinematics from RAVE data - VII. Metallicity Gradients from Red Clump Stars
• Numerical Simulation of a possible origin of the positive radial metallicity gradient of the thick disk
• On the Chemical and Structural Evolution of the Galactic Disk
• Extinction Law at a Distance up to 25 kpc toward the Galactic Poles
• The radial metallicity gradients in the Milky Way thick disk as fossil signatures of a primordial chemical distribution
• Evidence of a large scale positive rotation-metallicity correlation in the Galactic thick disk
• On the radial metallicity gradient and radial migration effect of the Galactic disk
• A Galactic Self-Portrait: Density Structure and Integrated Properties of the Milky Way Disk
• Galactic Stellar Populations from Photometric Metallicity Distribution Functions
• Impacts of Radial Mixing on the Galactic Thick and Thin Disks
• 3D elemental abundances of stars at formation across the histories of Milky Way-mass galaxies in the FIRE simulations