Centrum Astronomii
Uniwersytet Mikołaja Kopernika

Dark Matter - truth or myth?

The mysterious Dark Matter is currently being called "the Saint Graal of science". The estimates of its mass give the values many times higher than that of the "traditional" baryonic matter. Such a huge mass must play a crucial role in all conceivable models of spiral galaxies and the Universe. However, all attempts to detect this material directly (i.e. not via its gravity) failed - this is why it is called "Dark". The crucial evidence of the Dark Matter follows flat rotation curves of spiral galaxies. In the case of our Milky Way this means constant orbital velocity of all objects outside the solar orbit. The rotation curve depicts a relation between distance and radial velocity. Thus two main sources of uncertainty, while building such a curve for our Milky Way system, follow the distance and radial velocity measurements.

Basing on our huge collection of echelle spectra of OB stars we demonstrated that distances to OB stars can be reliably estimated using intensities of interstellar CaII H and K lines. The same lines allow also to measure Doppler velocities of the most distant clouds along any sightline with the precision much higher than in the case of stellar spectra as the latter are influenced by fast rotation and binarity of many OB stars. The talk will demonstrate that even the existing data creates serious doubts as to the existence of Dark Matter: the rotation curves of young, thin disk population objects (interstellar clouds) clearly follow keplerian rather than flat rotation curve of the Milky Way. To avoid existing uncertainties it is necessary to collect a statistically significant sample of objects. The most interesting directions in the galactic disk are these at l = 135 deg., l = 180 deg. and l = 225 deg. along these sightlines the expected effects are to be strongest. The first two directions are available to ground-based observatories situated at the Northern Hemisphere, in particular to the Terskol Observatory; the latter requires using some Southern Hemisphere instruments.

13.01.2014 - 11:15
Sala seminaryjna KRA