Galactic Parameters from Whole Sky 2MASS Star Count - AstrophysicsReport as inadecuate

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Abstract: The whole sky differential star counts DSC with 1 degree resolution areretrieved from 2MASS online data service. Galaxy with double exponential thinand thick disks and a single power law luminosity function LF is used tointerpret the 2MASS data. The slope of the DSC appears roughly isotropic overthe whole sky, the average value is ~0.32, which corresponds to a power lawindex ~1.8 of the LF. We find that the scale-length and scale-height the thindisk are ~3.0 kpc and ~245 pc, and those of the thick disk are ~3.0 kpc and~780 pc. The ratio of the thick disk to the thin disk is ~7%. The location ofSun above the disk is ~15 pc. A comparison of the data and model and theirdiscrepancy are also provided.

Author: C.K. Chang 1, C.M. Ko 1 and 2, T.H. Peng 1 1 Institute of Astronomy, National Central University, Taiwan, 2 Department of Physics



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