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Post Info TOPIC: NGC 6861


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RE: NGC 6861
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Title: The extremely populated globular cluster system of the lenticular galaxy NGC 6861
Author: Carlos G. Escudero, Favio R. Faifer, Lilia P. Bassino, Juan Pablo Calderon, Juan Pablo Caso

We present a photometric study of the globular cluster (GC) system associated to the lenticular galaxy (S0) NGC 6861, which is located in a relatively low density environment. It is based on GEMINI/GMOS images in the filters g', r', i' of three fields, obtained under good seeing conditions. Analysing the colour-magnitude and colour-colour diagrams, we find a large number of GC candidates, which extends out to 100 kpc, and we estimate a total population of 3000±300 GCs. Besides the well known blue and red subpopulations, the colour distribution shows signs of the possible existence of a third subpopulation with intermediate colours. This could be interpreted as evidence of a past interaction or fusion event. Other signs of interactions presented by the galaxy, are the non-concentric isophotes and the asymmetric spatial distribution of GC candidates with colours (g'-i')_0>1.16. As observed in other galaxies, the red GCs show a steeper radial distribution than the blue GCs. In addition, the spatial distribution of these candidates exhibit strong signs of elongation. This feature is also detected in the intermediate subpopulation. On the other hand, the blue candidates show an excellent agreement with the X-ray surface brightness profile, outside 10 kpc. They also show a colour-luminosity relation (blue-tilt), similar to that observed in other galaxies. A new distance modulus has been estimated through the blue subpopulation, which is in good agreement with the previous value obtained through the surface brightness fluctuations method. The specific frequency of NGC 6861 (Sn=10.6±2.1) is probably one of the highest values obtained for an S0 galaxy so far.

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NGC 6861 (also IC 4949, IRAS 20037-4830, ESO 233-32 and PGC 64136) is a magnitude +11.1 lenticular galaxy located 130 million light-years away in the constellation Telescopium.

The galaxy was discovered by Scottish astronomer James Dunlop using a  homemade 9-foot 22.86 cm (9 inch) f/12 speculum Newtonian reflector at Paramatta, New South Wales, Australia, on the 30th July 1826.
The galaxy was rediscovered by Lewis Swift in July 1897 and relisted as IC 4949.

Right Ascension 20h 07m 19.4s, Declination -48° 22' 10" 



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