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EP: Fachverband Extraterrestrische Physik

EP 3: Poster

EP 3.30: Poster

Montag, 15. März 2010, 17:45–19:00, AKM Foyer

The X-shaped bulge of NGC 4710 — •Rainer Lütticke — Labor für Physik, Hochschule Bochum, Lennershofstr. 140

A few years ago there were several studies to classify the morphology of bulges, as being for example a peanut- or a box-shaped bulge (b/p bulge) (cf. Lütticke, Dettmar, & Pohlen, 2000, A&AS 145, 405 [LDP]). The largest study of this morphology so far (LDP) shows that 4% of all edge-on disk galaxies have a peanut-shaped bulge, 16% a box-shaped bulge, 55% an elliptical bulge, and 25% a bulge whose shape is between boxy and elliptical. However, the better the resolution of the analysed images is becoming the more peanut-shaped bulges can be detected, since fainter structures become visible in more detail. Such a highly resolved image of NGC 4710 obtained by the Hubble Space telescope was published in a press release on the 18 Nov 2009 by spacetelescope.org. The image reveals that the bulge of this galaxy is indeed peanut-shaped on both sides while LDP classified only one side of the bulge as peanut-shaped and the other as box-shaped. The X-shaped structure which is building the b/p-shape of the bulge is eye-catching and is often not resolved in "older" images of b/p bulges. However, this structure is not surprising because it is known that bars of galaxies generate a resonant bending fed by vertical diffusion of orbits and instabilities. Simulations of barred galaxies confirm the existence of such X-structures. Therefore the b/p bulge of NGC 4710 is not as "baffling" as mentioned in the press release, but the image does indeed point out the importance of highly resolved images for detailed studies of morphologies of bulges which will help to understand their formation and evolution.