Müller Oliver, Jerjen Helmut, Binggeli Bruno (2017), New low surface brightness dwarf galaxies in the Centaurus group, in Astronomy & Astrophysics
, 597(A7), 1-14.
Müller Oliver, Jerjen Helmut, Pawlowski Marcel, Binggeli Bruno (2016), Testing the two planes of satellites in the Centaurus group, in Astronomy & Astrophysics
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Müller Oliver, Jerjen Helmut, Binggeli Bruno (2015), New dwarf galaxy candidates in the Centaurus group, in Astronomy & Astrophysics
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NEAR-FIELD COSMOLOGY WITH SOUTHERN GROUP DWARF GALAXIESDwarf galaxies are optically elusive stellar systems that consist of up to 90% of dark matter (DM) and thus represent the prime laboratory for DM astrophysics. However, extremely faint dwarf galaxies, as the most sensitive DM tracers, have been detected only in the near field around our Milky Way to date. Ever fainter dwarfs in the “local volume” out to distances of a few Mpcs are being hunted for worldwide to serve “near-field cosmology”. In line with these efforts we propose to conduct a search for faint, hitherto undetected dwarf galaxy members of the nearby southern groups of galaxies in Sculptor and Centaurus, based on dedicated observations with the 268 Megapixel wide-field CCD camera of the new SkyMapper telescope of the Australian National University at Siding Spring Observatory. A sky area of totally 750 square degree covering essential parts of the two groups will be imaged down to a limiting (stellar) magnitude about three times deeper than previously reached by photographic surveys. Drawing on direct inspection and the application of sophisticated data mining techniques to the deep CCD frames we estimate to find 10-30 low-surface brightness, dark-matter dominated dwarf galaxies in each group. Multicolor surface photometry and light profile modelling for the new (and previously known) dwarf members will yield a complete set of structural parameters for the low luminosity galaxies in each group. The following scientific questions will be addressed in our program: (1) The newly discovered dwarfs will trace the galaxy luminosity function (LF) of the two groups down to unprecedented faint magnitudes, comparable in depth to the Local Group (LG). The slope of the faint end of the LF and its variation with environment (groups vs clusters) is providing important constraints on the processes of baryon settlement in the DM halos at an early phase of structure formation. (2) The spatial distribution of the new and old dwarfs in the groups will be searched for anisotropies of the kind known to exist in the neighbourhood of the Milky Way Galaxy. Such anisotropies constitute a challenge to the standard ?CDM scenario of structure formation. (3) With the structural and color information for all dwarfs we will study the systematic differences in evolutionary stage and stellar composition with respect to environment, providing constraints for the modelling of dwarf galaxy evolution. The proposed project is conducted in collaboration with Dr. Helmut Jerjen from the Australian National University who is a member of the SkyMapper science team. He has privileged access to the SkyMapper survey telescope and the CCD data, well before they become publicly available. We are seeking financial support to hire a PhD student for 4 years duration, the first two years of which (covering the present proposal period) will be dedicated to develop and test specialised data mining algorithms, to reduce the CCD image and to search for new very faint dwarfs. A follow-up proposal (for an additional two years) will focus on the photometric and structural analysis of the galaxies and the publication of the results in international astronomy journals.