The Information Of The Milky Way From 2MASS Whole Sky Star Count: The Structure Parameters

Abstract

The Ks band differential star count of the Two Micron All Sky Survey (2MASS) is used to derive the global structure parameters of the smooth components of the Milky Way. To avoid complication introduced by other fine structures and significant extinction near and at the Galactic plane, we only consider Galactic latitude |b| > 30 degree data. The star count data is fitted with a threecomponent model: double exponential thin disk and thick disk, and a power law decay oblate halo. Using maximum likelihood the best-fit local density of thin disk is n0 = 0.030 +- 0.002 stars/pc^3. The best-fit scale-height and length of the thin disk are Hz1 = 360+-10 pc and Hr1 = 3.7+-1.0 kpc, and those of the thick disk are and Hz2 = 1020+-30 pc and Hr2 = 5.0+-1.0 kpc, the local thick-to-thin disk density ratio is f2 = 7+-1%. The best-fit axis ratio, power law index and local density ratio of the oblate halo are kappa = 0.55+-0.15, p = 2.6+-0.6 and fh = 0.20+-0:10%, respectively. Moreover, we find some degeneracy among the key parameters (e.g. n0,Hz1, f2 and Hz2). Any pair of these parameters are anticorrelated to each other. The 2MASS data can be well-fitted by several possible combinations of parameters. This is probably the reason that there is a wide range of values for the structure parameters in literature similar to this study. Since only medium and high Galactic latitude data are analyzed, the fitting is very insensitive to the scale-lengths of the disks.

25 pages, 4 figures, accepted by ApJ on July 15 2011

References in corpus (8)

• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• The long Galactic bar as seen by UKIDSS Galactic Plane Survey
• Estimation of galactic model parameters in high latitudes with SDSS
• Galactic longitude dependent Galactic model parameters
• Estimation of Galactic model parameters in high latitudes with 2MASS
• Galactic structure studies from BATC survey
• Volume limited dependent Galactic model parameters

Cited by in corpus (29)

• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk
• The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution
• The TRENDS High-Contrast Imaging Survey. IV. The Occurrence Rate of Giant Planets around M-Dwarfs
• Constraining the thick disc formation scenario of the Milky Way
• Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood
• Weighing the local dark matter with RAVE red clump stars
• The formation of stellar nuclear discs in bar-induced gas inflows
• Evolution over time of the Milky Way's disc shape
• Flare in the Galactic stellar outer disc detected in SDSS-SEGUE data
• Determination of the Local Standard of Rest using the LSS-GAC DR1
• Stellar mass distribution and star formation history of the Galactic disk revealed by mono-age stellar populations from LAMOST
• Evidence for the concurrent growth of thick discs and central mass concentrations from S${}^4$G imaging
• PAHs and star formation in the HII regions of nearby galaxies M83 and M33
• Chemical and Kinematic Properties of the Galactic Disk from the LAMOST and Gaia Sample Stars
• A Galaxy Model from 2MASS Star Counts in the Whole Sky Including the Plane
• The effects of a hot gaseous halo on disc thickening in galaxy minor mergers
• Constraining the Galactic structure parameters with the XSTPS-GAC and SDSS photometric surveys
• Are the Milky Way and Andromeda unusual? A comparison with Milky Way and Andromeda Analogs
• Sizing Up the Milky Way: A Bayesian Mixture Model Meta-Analysis of Photometric Scale Length Measurements
• Structure of the outer Galactic disc with Gaia-DR2
• Estimation of Absolute Magnitude-dependent Galactic Model Parameters In Intermediate Latitude With SDSS and SCUSS
• The structure of the Milky Way based on unWISE 3.4$\mu$m integrated photometry
• Indications of M-dwarf Deficits in the Halo and Thick Disk of the Galaxy
• Solar Space Density of the Red Clump Stars and the Scale-length of the Thin Disc
• Galactic Stellar Populations from Photometric Metallicity Distribution Functions
• Investigating the vertical distribution of the disk as a function of radial action
• The Information Of The Milky Way From 2MASS Whole Sky Star Count: The Bimodal Color Distributions
• Study of Galactic Structure Using UVIT/AstroSat Star Counts