The structure of galactic disks

Studying late-type spiral galaxies using SDSS

¹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: pohlen@astro.rug.nl
² Instituto de Astrofísica de Canarias, C/ Via Láctea s/n, 38200 La Laguna, Tenerife, Spain
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK e-mail: ignacio.trujillo@nottingham.ac.uk

Received: 20 January 2006
Accepted: 26 April 2006

Abstract

Using imaging data from the SDSS survey, we present the and radial stellar light distribution of a complete sample of ~90 face-on to intermediate inclined, nearby, late-type (Sb–Sdm) spiral galaxies. The surface brightness profiles are reliable ( uncertainty less than 0.2 mag) down to mag . Only ~10% of all galaxies have a normal/standard purely exponential disk down to our noise limit. The surface brightness distribution of the rest of the galaxies is better described as a broken exponential. About 60% of the galaxies have a break in the exponential profile between ∼1.5–4.5 times the scalelength followed by a downbending, steeper outer region. Another ~30% shows also a clear break between ∼4.0–6.0 times the scalelength but followed by an upbending, shallower outer region. A few galaxies have even a more complex surface brightness distribution. The shape of the profiles correlates with Hubble type. Downbending breaks are more frequent in later Hubble types while the fraction of upbending breaks rises towards earlier types. No clear relation is found between the environment, as characterised by the number of neighbours, and the shape of the profiles of the galaxies.