The Fornax Cluster Spectroscopic Survey: A Sample of Confirmed Cluster Dwarfs

Abstract

The Fornax Cluster Spectroscopic Survey (FCSS) project utilises the 2dF multi-object spectrograph on the AAT. Its aim is to obtain spectra for a complete sample of all 14000 objects with 16.5<bj<19.7 irrespective of their morphology in a 12 sq deg area centred on the Fornax Cluster. A sample of 24 Fornax Cluster members has been identified from the first 2dF field (3.1 sq deg in area) to be completed. This is the first complete smaple of cluster objects of known distance with well defined selection limits. 19 of the galaxies (with -15.8<M_B<-12.7) appear to be conventional dwarf elliptical or dwarf S0 galaxies. The other 5 objects (with -13.6<M_B<-11.3) are those galaxies which we described in Drinkwater et al (2002b) and labelled `Ultra-Compact Dwarfs' (UCDs). A major result is that the conventional dwarfs all have scale-sizes>3 arcsec (abut 300 pc). This apparent minimum scale size implies an equivalent minimum luminosity for a dwarf of a given surface brightness. This produces a limit on their distribution in the magnitude-surface brightness plane, such that we do not observe dEs with high surface brightnesses but faint absolute magnitudes. Above this observed minimum scale-size of 3 arcsec, the dEs and dS0s fill the whole area of the magnitude-surface brightness plane sampled by our selection limits. The observed correlation between magnitude and surface brightness noted by several recent studies of brighter galaxies is not seen with our fainter cluster sample. A comparison of our results with the Fornax Cluster Catalog (FCC) of Ferguson illustrates that attempts to determine cluster membership solely on the basis of observed morphology can produce significant errors.

17 pages, 9 figures to be published in the Monthly Notices of the Royal Astronomical Society

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• The Surface Brightness and Colour-Magnitude Relations for Fornax Cluster Galaxies
• The Galaxy Luminosity Function from M_R = -25 to M_R = -9
• A spectroscopic census of the Fornax cluster and beyond: preparing for next generation surveys
• UCD Candidates in the Hydra Cluster
• The low-luminosity galaxy population in the NGC 5044 Group
• The Next Generation Fornax Survey (NGFS): VII. A MUSE view of the nuclear star clusters in Fornax dwarf galaxies
• A search for low surface brightness dwarf galaxies in different environments
• The Dwarf Galaxy Population in Nearby Groups. The data
• Galaxy Luminosity Functions in WINGS clusters
• The faint-end of the galaxy luminosity function in groups
• The Global, Local and Cluster Galaxy Luminosity Function
• Evolutionary properties of the low-luminosity galaxy population in the NGC5044 Group
• 2MASS Galaxies in the Fornax Cluster Spectroscopic Survey