Deep surface photometry of edge-on spirals in Abell galaxy clusters

Constraining environmental effects

Instituto de Física, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, CP 15051, Porto Alegre, Brazil e-mail: santiago@if.ufrgs.br

Received: 19 December 2007
Accepted: 26 March 2008

Abstract

Context. There is a clear scarcity of structural parameters for stellar thick discs, especially for spiral galaxies located in high-density regions, such as galaxy clusters and compact groups.

Aims. We have modelled the thin and thick discs of 4 edge-on spirals located in Abell clusters: NGC 705, ESO 243G49, ESO 187G19, LCSBS 0496P. Deep I band images of NGC 705 were taken from the HST archive, whereas the remaining images were obtained with the Southern Telescope for Astrophysical Research (SOAR) in Gunn r filter. They reached surface brightness levels of  mag arcsec^-2 and  mag arcsec^-2, respectively.

Methods. Profiles were extracted from the deep images, in directions both parallel and perpendicular to the major axis. Profile fits were carried out at several positions, yielding horizontal and vertical scale parameters for both thin and thick disc components.

Results. The extracted profiles and fitted disc parameters vary from galaxy to galaxy. Two galaxies have a horizontal profile with a strong down-turn at outer radii, preventing a simple exponential from fitting the entire range. For the 2 early-type spirals, the thick discs have larger scalelengths than the thin discs, whereas no trend is seen for the later types. Both the thin and thick discs sampled tend to have similar scalelengths and scaleheights when compared to typical field disc galaxies. However, the thin disc parameters of the 2 farthest galaxies, both late-type spirals, may be significantly affected by seeing effects. Taken at face value, our results suggest that environment plays a minor role in determining the thin and thick disc sizes.