Hostname: page-component-586b7cd67f-dlnhk Total loading time: 0 Render date: 2024-11-22T23:36:29.735Z Has data issue: false hasContentIssue false

Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7

Published online by Cambridge University Press:  09 March 2010

D. Carollo
Affiliation:
Research School of Astronomy & Astrophysics, Australian National University & Mount Stromlo Observatory, Australia, emails: [email protected], [email protected], [email protected] INAF-OATo, Italy
T. C. Beers
Affiliation:
Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, USA, emails: [email protected], [email protected]
M. Chiba
Affiliation:
Astronomical Institute, Tohoku University, Japan, email: [email protected]
J. E. Norris
Affiliation:
Research School of Astronomy & Astrophysics, Australian National University & Mount Stromlo Observatory, Australia, emails: [email protected], [email protected], [email protected]
K. C. Freeman
Affiliation:
Research School of Astronomy & Astrophysics, Australian National University & Mount Stromlo Observatory, Australia, emails: [email protected], [email protected], [email protected]
Y. S. Lee
Affiliation:
Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, USA, emails: [email protected], [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The structure and kinematics of the recognized stellar components of the Milky Way are explored, based on well-determined atmospheric parameters and kinematic quantities for 32360 “calibration stars” from the Sloan Digital Sky Survey (SDSS) and its first extension, (SDSS-II), which included the sub-survey SEGUE: Sloan Extension for Galactic Understanding and Exploration. Full space motions for a sub-sample of 16920 stars, exploring a local volume within 4 kpc of the Sun, are used to derive velocity ellipsoids for the inner- and outer-halo components of the Galaxy, as well as for the canonical thick-disk and proposed metal-weak thick-disk populations. This new sample of calibration stars represents an increase of 60% relative to the numbers used in a previous analysis. A Maximum Likelihood analysis of a local sub-sample of 16920 calibration stars has been developed in order to extract kinematic information for the major Galactic components (thick disk, inner halo, and outer halo), as well as for the elusive metal-weak thick disk (MWTD). We measure velocity ellipsoids for the thick disk, the MWTD, the inner halo, and the outer halo, demonstrate that the MWTD may be a component that is kinematically and chemically independent of the canonical thick disk (and put limits on the metallicity range of the MWTD), and derive the inferred spatial density profiles of the inner/outer halo components. We also present evidence for tilts in the velocity ellipsoids for stars in our sample as a function of height above the plane, for several ranges in metallicity, and confirm the shift of the observed metallicity distribution function (MDF) from the inner-halo to the outer-halo dominated sample.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2010

References

Carollo, D., et al. 2007, Nature, 450, 1020Google Scholar
Carollo, D., et al. 2009, ApJ, submitted (ArXiv:0903.3019)Google Scholar
Chiba, M. & Beers, T. C. 2000, ApJ, 119, 2843Google Scholar
Girard, T. M., Korchagin, V. I., Casetti-Dinescu, D. I., van Altena, W. F., Lopez, C. E., & Monet, D. G. 2006, AJ, 132, 1768Google Scholar
Ivezić, Ž, et al. 2008a, ApJ, 684, 287CrossRefGoogle Scholar
Siebert, A., et al. 2008, MNRAS, 391, 793Google Scholar