Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008mnras.384..173f&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 384, Issue 1, pp. 173-224.
Astronomy and Astrophysics
Astronomy
57
Stars: Fundamental Parameters, Galaxy: Evolution, Galaxy: Formation, Galaxy: Stellar Content
Scientific paper
The Milky Way Galaxy has an age of about 13 billion years. Solar-type stars evolve all the long way to the realm of degenerate objects on essentially this time-scale. This, as well as the particular advantage that the Sun offers through reliable differential spectroscopic analyses, render these stars the ideal tracers for the fossil record of our parent spiral. Astrophysics is a science that is known to be notoriously plagued by selection effects. The present work - with a major focus in this fourth contribution on model atmosphere analyses of spectroscopic binaries and multiple star systems - aims at a volume-complete sample of about 300 nearby F-, G-, and K-type stars that particularly avoids any kinematical or chemical pre-selection from the outset. It thereby provides an unbiased record of the local stellar populations - the ancient thick disc and the much younger thin disc. On this base, the detailed individual scrutiny of the long-lived stars of both populations unveils the thick disc as a single-burst component with a local normalization of no less than 20 per cent. This enormous fraction, combined with its much larger scaleheight, implies a mass for the thick disc that is comparable to that of the thin disc. On account of its completely different mass-to-light ratio the thick disc thereby becomes the dark side of the Milky Way, an ideal major source for baryonic dark matter. This massive, ancient population consequently challenges any gradual build-up scenario for our parent spiral. Even more, on the supposition that the Galaxy is not unusual, the thick disc - as it emerges from this unbiased spectroscopic work - particularly challenges the hierarchical cold-dark-matter-dominated formation picture for spiral galaxies in general.
No associations
LandOfFree
Nearby stars of the Galactic disc and halo - IV does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Nearby stars of the Galactic disc and halo - IV, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nearby stars of the Galactic disc and halo - IV will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1324422