Galaxy populations in the Antlia cluster – II. Compact elliptical galaxy candidates

SMITH CASTELLI A. V.; FAIFER F. R.; RICHTLER T.; BASSINO L.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Blackwell Publishing Ltd

Lugar: Edinburgo, UK; Año: 2008 p. 685 - 699

0035-8711

Continuing our study of galaxy populations in the Antlia cluster, we present a photometricanalysis of four galaxies classified as compact elliptical (cE) galaxies in the 1990 Antlia Groupcatalogue of Ferguson and Sandage. Until now, there have been only six known members ofthis rare type of galaxy. Using data from various photometric systems (Washington C, Kron–Cousins R, Bessel V and I, Hubble Space Telesecope F814W and F435W), we measured thebrightness and colour profiles, as well as the structural parameters. By comparing these withthose of other galaxies in the Antlia cluster, as well as with confirmed cE galaxies from theliterature, we found that two of the cE candidates, although spectroscopically confirmed Antliamembers, are not cE galaxies. However, one of these objects presents strong ellipticity andposition angle variations that resemble those already reported for M32, leading us to speculateabout this type of object being a progenitor of a cE galaxy. The other two cE candidates, forwhich radial velocities are not available, match some features typical of cE galaxies, such asbeing close in projection to a larger galaxy, displaying flat colour profiles, and having a highdegree of compactness. Only one of the remaining cE candidates shows a high central surfacebrightness, two components in its brightness profile and distinct changes in ellipticity andposition angle where the outer component begins to dominate. It seems to follow the sametrend as other confirmed cE galaxies in a luminosity versus mean effective surface brightnessdiagram. Moreover, it shows a distorted inner structure with similar characteristics to thosefound by simulations of interacting galaxies. Also, an extremely faint structure, which seems tolink this object with one of the Antlia dominant galaxies, has been detected in images from theCerro Tololo Inter-American ObservatoryMOSAIC, the Very Large Telescope FORS1 and theHubble Space Telescope Advanced Camera for Surveys. The cE nature of this galaxy andthe possible interactionwith its bright companion still have to be confirmed using spectroscopy.