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What Gaia can reveal about the matter distribution in the Milky Way

Götberg, Ylva LU (2014) In Lund Observatory Examensarbeten ASTM31 20141
Lund Observatory
Department of Astronomy and Theoretical Physics
Abstract
Context. With the goal to accurately map about a billion of the Milky Way stars, the astrometric satellite Gaia was launched in December 2013. Its high precision and sensitivity will lead to better understanding of the Galactic structure and evolution. Also, it will be possible to probe the matter distribution in the Galaxy.

Aims. To study how well the Galactic matter distribution can be determined from Gaia data, using a direct application of the Jeans equations.

Methods. An expression for mass density applicable to collisionless gravitational systems can be found by combining the second Jeans equations with Poisson’s equation. Through orbit integration of a few million stars in a potential model of the Milky Way, astrometric data... (More)
Context. With the goal to accurately map about a billion of the Milky Way stars, the astrometric satellite Gaia was launched in December 2013. Its high precision and sensitivity will lead to better understanding of the Galactic structure and evolution. Also, it will be possible to probe the matter distribution in the Galaxy.

Aims. To study how well the Galactic matter distribution can be determined from Gaia data, using a direct application of the Jeans equations.

Methods. An expression for mass density applicable to collisionless gravitational systems can be found by combining the second Jeans equations with Poisson’s equation. Through orbit integration of a few million stars in a potential model of the Milky Way, astrometric data were simulated. Taking into account extinction using a smooth model based on hydrogen observations, measurement errors expected from Gaia were generated for the chosen tracer stars (M-giants). Applying a grid covering the region of the model set by the magnitude limits of Gaia, the mass density was estimated in every grid-bin and thus resolution was achieved.

Results. I find that within the region limited by 5.5 < R < 12 kpc and |z| < 200 pc, the mass density can be estimated with better than 35 % accuracy. Within the smaller region limited by 6 < R < 9 kpc and |z| < 50 pc, the estimation error has decreased to a few percent and in the Solar neighbourhood it will be possible to probe the matter distribution with about one percent precision. Both the regions mentioned cover a large part of the Perseus spiral arm and spans over different locations where the individual components of the Galaxy are prominent.

Conclusions. The extensive regions probed with this method make it possible to determine the large-scale structure of the Milky Way, including e.g., more accurately determined radial and vertical scale lengths. It will be possible to improve the estimation of the local mass density by about a factor ten compared to the current values. The precision of the method allows to test different scenarios for the distribution of dark matter in the disk and elsewhere in the Galaxy. (Less)
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author
Götberg, Ylva LU
supervisor
organization
course
ASTM31 20141
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
Lund Observatory Examensarbeten
report number
2014-EXA81
language
English
id
4586626
date added to LUP
2014-08-11 15:15:10
date last changed
2014-08-11 15:15:10
@misc{4586626,
  abstract     = {Context. With the goal to accurately map about a billion of the Milky Way stars, the astrometric satellite Gaia was launched in December 2013. Its high precision and sensitivity will lead to better understanding of the Galactic structure and evolution. Also, it will be possible to probe the matter distribution in the Galaxy.

Aims. To study how well the Galactic matter distribution can be determined from Gaia data, using a direct application of the Jeans equations.

Methods. An expression for mass density applicable to collisionless gravitational systems can be found by combining the second Jeans equations with Poisson’s equation. Through orbit integration of a few million stars in a potential model of the Milky Way, astrometric data were simulated. Taking into account extinction using a smooth model based on hydrogen observations, measurement errors expected from Gaia were generated for the chosen tracer stars (M-giants). Applying a grid covering the region of the model set by the magnitude limits of Gaia, the mass density was estimated in every grid-bin and thus resolution was achieved.

Results. I find that within the region limited by 5.5 < R < 12 kpc and |z| < 200 pc, the mass density can be estimated with better than 35 % accuracy. Within the smaller region limited by 6 < R < 9 kpc and |z| < 50 pc, the estimation error has decreased to a few percent and in the Solar neighbourhood it will be possible to probe the matter distribution with about one percent precision. Both the regions mentioned cover a large part of the Perseus spiral arm and spans over different locations where the individual components of the Galaxy are prominent.

Conclusions. The extensive regions probed with this method make it possible to determine the large-scale structure of the Milky Way, including e.g., more accurately determined radial and vertical scale lengths. It will be possible to improve the estimation of the local mass density by about a factor ten compared to the current values. The precision of the method allows to test different scenarios for the distribution of dark matter in the disk and elsewhere in the Galaxy.},
  author       = {Götberg, Ylva},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lund Observatory Examensarbeten},
  title        = {What Gaia can reveal about the matter distribution in the Milky Way},
  year         = {2014},
}