Small-scale structure of the disc velocity distribution. A maximum entropy statistical approach - Part II
Among metallicity, colour, and other star properties, the eccentricity of the star’s orbit behaves as a very good sampling parameter to find a more detailed structure for the disc velocity distribution, allowing distinctions between different eccentricity layers. For subsam- ples with eccentricities...
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| Format: | report |
| Publication Date: | 2009 |
| Country: | España |
| Institution: | Universitat Politècnica de Catalunya (UPC) |
| Repository: | UPCommons. Portal del coneixement obert de la UPC |
| Language: | English |
| OAI Identifier: | oai:upcommons.upc.edu:2117/6700 |
| Online Access: | https://hdl.handle.net/2117/6700 |
| Access Level: | Open access |
| Keyword: | Astronomy and astrophysics Probabilities Stochastic processes Mathematical statistics Astronomia Astrofísica Probabilitats Processos estocàstics Estadística matemàtica 85 ASTRONOMY AND ASTROPHYSICS 60 PROBABILITY THEORY AND STOCHASTIC PROCESSES 62 STATISTICS Àrees temàtiques de la UPC::Matemàtiques i estadística::Estadística matemàtica::Mètodes estadístics |
| Summary: | Among metallicity, colour, and other star properties, the eccentricity of the star’s orbit behaves as a very good sampling parameter to find a more detailed structure for the disc velocity distribution, allowing distinctions between different eccentricity layers. For subsam- ples with eccentricities e < 0.15, star velocities are approximately symmetrically distributed around the LSR in the radial direction, with a dearth of stars at the LSR. For e = 0.15, the core distribution of the thin disc is supported by two major stellar groups with opposite radial velocities. Several simulations confirm that such a double-peaked distribution comes from the lognormal distribution of the velocity amplitudes. For maximum eccentricity 0.3 and maximum distance to the Galactic plane 0.5 kpc a representative thin disc sample is obtained. An explanation of the apparent vertex deviation of the disc from the swinging of those major kinematic groups around the LSR is possible, which predicts a continuously changing orientation of the disc’s pseudo ellipsoid. |
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