Kinematical and chemical vertical structure of the Galactic Thick Disk

Details Kinematical and chemical vertical structure of the Galactic Thick Disk Kinematical and chemical vertical structure of the Galactic Thick Disk

Jan 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009phdt.........1m&link_type=abstract

PhD thesis, Universidad de Chile

Computer Science

6

Galactic Disk, Galactic Kinematics, Galactic Stellar Content

Scientific paper

We present the first results of an extensive study of the Galactic Thick Disk, aimed to shed new light on its kinematical and chemical properties. We selected nearly 1200 Red Giant Thick Disk stars toward the South Galactic Pole, distributed vertically with respect to the Galactic plane up to distances of about 5 kpc. All these stars have precise IR photometry from 2MASS and absolute proper motion from the SPM3 catalog. Our spectroscopic follow-up comprises two-third of the sample, for which we measured accurate radial velocities. By mean of kinematical data and photometric distances we measured the three Galactic components of velocity (U,V,W) for each star, and estimated the dispersion of the vertical component sigma=5FW at different Galactic heights. We find evidence of a small but not-negligible vertical gradient of 1.6 +- 0.5 km/(s kpc). From the extrapolation of the vertical profile to z=0, we derive a dispersion on the Galactic plane of sigma=5FW= 37 +- 2 km/s. We study this result and its partial inconsistency with previous results obtained with the same sample by means of proper motions alone. Starting from basic equations and general assumptions we also derive the equations that, given the observed vertical profiles of velocity dispersions, estimate the surface mass density as a function of z. The first application of these equations to our kinematical results returns inconsistent output. We analyze in detail the possible causes of this problem.

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