Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Physics and evolution of compact dwarf galaxies

Blue compact dwarf galaxies (BCDG) are now the focus of many studies because they experience intensive bursts of star formation and are considered as evolutionary young galaxies. The project obtains new observational data on some important global parameters determining the physical state and evolutionary state of BCDGs and compares these parameters with current models of chemical evolution which take into account selective loss of metals due to superwinds.

A large sample of blue compact dwarf galaxies was studied over a wavelength range. The dark matter (DM) fraction varies over a very large range, indicating that the dwarf galaxies are genetically inhomogeneous. The objects with high ratio of DM are probably created by collapse of gas in DM halos preformed by primordial pertubations. The low DM ratio objects may be formed from the debris of strong interaction of massive galaxies. In many starbursting dwarf galaxies a strong galactic superwind can be found, which depletes the galaxy of gas and, thus, increases the DM to Baryon ratio. The decomposition of the photometric profiles shows that most dwarf galaxies have underlying disks of a wide range of physical properties, and often even extremely low central surface brightnesses. The extremely metal poor BCDG SBS 0335-052 sits in a very extended gas cloud which contains BCGs of very similar physical properties as SBS 0335-052 and is the most convincing example of dwarf galaxies in status nascendi. High quality spectra of a sample of the most metal deficient BCDGs are used to determine the primordial helium abundancy. The new value is fully consistent with the measurements of primordial lithium in galactic halo stars and of deuterium and helium-3 in the local interstellar gas and in the solar system. It is inconsistent with recent estimates of primordial deuterium from quasar absorption systems.

Reported by

Astrophysikalisches Institut Potsdam
An der Sternwarte 16
14482 Potsdam
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